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Interaction between CO2 enrichment and salinity stress in the C4 non‐halophyte Andropogon glomeratus (Walter) BSP
Plant, Cell & Environment
Abstract
Abstract Increasing atmospheric CO2 may result in alleviation of salinity stress in salt-sensitive plants. In order to assess the effect of enriched CO2 on salinity stress in Andropogon glomeratus, a C4 non-halophyte found in the higher regions of salt marshes, plants were grown at 350, 500, and 650 cm3 m−3 CO2 with 0 or 100 mol m−3 NaCl watering treatments. Increases in leaf area and biomass with increasing CO2 were measured in salt-stressed plants, while decreases in these same parameters were measured in non-salt-stressed plants. Tillering increased substantially with increasing CO2 in salt-stressed plants, resulting in the increased biomass. Six weeks following initiation of treatments, there was no difference in photosynthesis on a leaf area basis with increasing CO2 in salt-stressed plants, although short-term increases probably occurred. Stomatal conductance decreased with increasing CO2 in salt-stressed plants, resulting in higher water-use efficiency, and may have improved the diurnal water status of the plants. Concentrations of Na+ and Cl− were higher in salt stressed-plants while the converse was found for K +. There were no differences in leaf ion content between CO2 treatments in the salt-stressed plants. Decreases in photosynthesis in salt-stressed plants occurred primarily as a result of decreased internal (non-stomatal) conductance.
... The authors have hypothesised that any factor that will increase photosynthesis, such as high C02, will alleviate salinity if the mechanism for salt tolerance requires expenditure of photosynthates. Growth enhancement induced by moderately high C02 concentrations (500 to 750 cm3 m-3) has also been demonstrated for salt-stressed C3 and C4 marsh species (Bowman and Strain 1987;Lenssen and Rozema 1990) and mangrove species (Ball and Munns 1992). In addition, growth is generally increased substantially by high C02 under drought (Gifford 1979;Sionit et al. 1980Sionit et al. , 1981Gifford 1984a, 1984b). ...
... Tillering was also increased by high COz, particularly in the salt treatment (Fig. 2, Table 2). A similar increase in tillering under high CO2 has been reported for wheat growing in well-watered and dry soil (Gifford 1977(Gifford , 1979Sionit et al. 1980Sionit et al. , 1981 and for a nonhalophytic marsh species growing in saline solution (Bowman and Strain 1987). Modoc responded less to high COz than Matong, because of a shorter tillering phase associated with faster phenological development. ...
... The improvement in transpiration efficiency caused by high COz was large until day 20, but became smaller thereafter (Table 4). Several authors have argued that increased wateruse efficiency under high COz would result in greater salt tolerance because of reduced water uptake (Baker and Enoch 1983;Pearcy and Bjorkman 1983;Bowman and Strain 1987). However, in our experiment, higher transpiration efficiency did not result in reduced water Elevated COz and Wheat Growth uptake in the high C02 x salt treatment, because of greater leaf area than in the ambient C 0 2 x salt treatment. ...
Wheat plants (Triticum aestivum cv. Matong and T. durum cv. Modoc) were grown at ambient and elevated CO2 (350 cm³ m⁻³ above ambient) in soil with or without 150 mol m⁻³ NaCl for 6 weeks. The increase in dry matter, leaf area and tillering under high CO2 was relatively greater under saline than non-saline conditions for both cultivars. Tillering was the primary component of growth affected by both salinity and high CO2. Salinity greatly reduced tillering and high CO2 partly reversed the effects of salinity. High CO2 increased dry matter accumulation of the salt-sensitive Modoc to a greater extent (+104%) than that of the more salt-tolerant Matong (+73%) in the salt treatment. Transpiration rates were greatly reduced by salinity for both cultivars. Under high CO2, increased leaf areas compensated for reduced transpiration rates per unit leaf area (i.e. greater stomatal closure), and total transpiration was little affected by CO2 level within each treatment. The more salt-tolerant Matong showed greater stomatal closure and higher transpiration efficiencies than the salt-sensitive Modoc under salinity. High CO2 reduced transpiration rate (per unit dry weight) by 40 to 50%, but did not significantly change the rate of sodium accumulation (per unit dry weight), indicating that salt uptake was largely independent of water uptake, and that high CO2 did not increase growth by reducing the salt load. Our results suggest that high CO2 increased growth by stimulating the development of tiller buds that would otherwise have been inhibited.
... There was more variation in the response of C4 species to elevated C0, under control salinity conditions. Growth of two C4 species, Zea mays (Schwarz and Gale 1984) and Spartina anglica (Lenssen and Rozema 1990), was not affected by elevated C02, whereas elevated C02 stimulated growth of Atriplex halimus (Schwarz and Gale 1984) and supressed growth of Andropogon glomeratus (Bowman and Strain 1987). In contrast, most of the species listed in Table 1 grew better under elevated than under ambient C02 concentrations when salinities were excessive. ...
... In contrast, increase in water use efficiency of a C4 non-halophytic species, Andropogon glomeratus, was due to decrease in transpiration rate coupled with increase in growth when the plants were grown in saline soil under elevated C02 (Bowman and Strain 1987). Similar results were reported for a stand of Spartina patens when very hot and dry weather promoted stomatal closure (Drake and Leadley 1991). ...
... Similar results were reported for a stand of Spartina patens when very hot and dry weather promoted stomatal closure (Drake and Leadley 1991). Enhancement of growth in C4 species in response to elevated C02 concentration could be explained if stomatal closure in response to adverse conditions caused the internal C02 concentration to fall below saturating levels under ambient atmospheric C02 concentrations (Bowman and Strain 1987). ...
This review explores effects of elevated CO2 concentrations on growth in relation to water use and salt balance of halophytic and non-halophytic species. Under saline conditions, the uptake and distribution of sodium and chloride must be regulated to protect sensitive metabolic sites from salt toxicity. Salt-tolerant species exclude most of the salt from the transpiration stream, but the salt flux from a highly saline soil is still considerable. To maintain internal ion concentrations within physiologically acceptable levels, the salt influx to leaves must match the capacities of leaves for salt storage and/or salt export by either retranslocation or secretion from glands. Hence the balance between carbon gain and the expenditure of water in association with salt uptake is critical to leaf longevity under saline conditions. Indeed, one of the striking features of halophytic vegetation, such as mangroves, is the maintenance of high water use efficiencies coupled with relatively low rates of water loss and growth. These low evaporation rates are further reduced under elevated CO2 conditions. This, with increased growth, leads to even higher water use efficiency. Leaves of plants grown under elevated CO2 conditions might be expected to contain lower salt concentrations than those grown under ambient CO2 if salt uptake is coupled with water uptake. However, salt concentrations in shoot tissues are similar in plants grown under ambient and elevated CO2 conditions despite major differences in water use efficiency. This phenomenon occurs in C3 halophytes and in both C3 and C2 non-halophytes. These results imply shoot/root communication in regulation of the salt balance to adjust to environmental factors affecting the availability of water and ions at the roots (salinity) and those affecting carbon gain in relation to water loss at the leaves (atmospheric concentrations of water vapour and carbon dioxide).
... Numerous studies have investigated the interaction between elevated [CO 2 ] and drought conditions; however, few have reported on the combined effect of elevated [CO 2 ] and salinity on water relations (Sionit and Patterson, 1985;Rozema et al., 1991;Rozema, 1993;Chen et al., 1999;García-Sánchez and Syvertsen, 2006;Melgar et al., 2008). Additionally, some studies support the hypothesis that CO 2 enrichment stimulates plant growth via increased net photosynthesis and not via improved water relations (Rozema et al., 1991), while other studies focus on improved water relationships to explain the greater growth rate (Bowman and Strain, 1987). Thus, the current knowledge about the interaction between rising [CO 2 ] and salinity remains insufficient for predicting the impact of climate change on plant growth and production; further investigation concerning the mechanisms of this interaction is needed. ...
... On the other hand, under the combined conditions of salt stress and elevated [CO 2 ], the decrease in water potential at midday was lower than at ambient [CO 2 ] and the relative water content and the leaf area (Table 2) were higher along all the salt concentrations. These results are in accord with the ones of Rozema et al. (1991) in Scirpus maritimus and Puccinellia maritima, and Bowman and Strain (1987) in Andropogon glomeratus who analysed the interaction between elevated [CO 2 ] and salinity. Analysing the components of water potential under these conditions, leaf turgor potential was higher but the osmotic potential was the same as at ambient [CO 2 ]. ...
... These results are in accord with the ones of Rozema et al. (1991) in Scirpus maritimus and Puccinellia maritima, and Bowman and Strain (1987) in Andropogon glomeratus who analysed the interaction between elevated [CO 2 ] and salinity. Analysing the components of water potential under these conditions, leaf turgor potential was higher but the osmotic potential was the same as at ambient [CO 2 ]. Bowman and Strain (1987) registered similar osmotic potentials at two different CO 2 concentrations (350 and 650 mol mol −1 ) and proposed that greater vacuolar osmotic regulation could explain the decreased reduction in water potential. In our study, the osmotic adjustment was greater at elevated than at ambient [CO 2 ]. ...
With the changing climate, plants will be facing increasingly harsh environmental conditions marked by elevated salinity in the soils and elevated concentrations of CO2 in the atmosphere. These two factors have opposite effects on water status in plants. Therefore, our objective was to determine the interaction between these two factors and to determine whether elevated [CO2] might alleviate the adverse effects of salt stress on water status in two barley cultivars, Alpha and Iranis, by studying their relative water content and their water potential and its components, transpiration rate, hydraulic conductance, and water use efficiency. Both cultivars maintained their water status under salt stress, increasing water use efficiency and conserving a high relative water content by (1) reducing water potential via passive dehydration and active osmotic adjustment and (2) decreasing transpiration through stomatal closure and reducing hydraulic conductance. Iranis showed a greater capacity to achieve osmotic adjustment than Alpha. Under the combined conditions of salt-stress and elevated [CO2], both cultivars (1) achieved osmotic adjustment to a greater extent than at ambient [CO2], likely due to elevated rates of photosynthesis, and (2) decreased passive dehydration by stomatal closure, thereby maintaining a greater turgor potential, relative water content, and water use efficiency. Therefore, we found an interaction between salt stress and elevated [CO2] with regard to water status in plants and found that elevated [CO2] is associated with improved water status of salt-stressed barley plants.
... In this study, only two species of non-halophytic mesophytes were selected to measure and compare the salt content in leaves. It was considered that measurements from many species are not necessary as the fact that non halophytic plants posses very low salt concentrations (Bowman and Strain, 1986). The results of this study also indicated that the salt content in leaves of the non-halophytic species tested is very low and comparable with values given for other mesophytic species (Bowman and Strain, 1986). ...
... It was considered that measurements from many species are not necessary as the fact that non halophytic plants posses very low salt concentrations (Bowman and Strain, 1986). The results of this study also indicated that the salt content in leaves of the non-halophytic species tested is very low and comparable with values given for other mesophytic species (Bowman and Strain, 1986). That comparability indicates that the measurements received for the Na + concentration in mangrove leaves also in this study are reliable. ...
... In contrast, growth under elevated CO 2 enhanced susceptibility to the necrotrophic pathogen, Botrytis cinerea (Zhang et al., 2015). Atmospheric CO 2 enrichment enhanced photosynthesis rates and increased the growth of several plant species under saline conditions (Bowman and Strain, 1987;Robredo et al., 2007;Del Amor, 2013). High CO 2 -induced salt tolerance is associated with reduced oxidative stress and transpiration rates, and with improved cellular hydration, intracellular Na + /K + homeostasis and water use efficiency (Bowman and Strain., 1987;Maggio et al., 2002;Yu et al., 2015). ...
... Atmospheric CO 2 enrichment enhanced photosynthesis rates and increased the growth of several plant species under saline conditions (Bowman and Strain, 1987;Robredo et al., 2007;Del Amor, 2013). High CO 2 -induced salt tolerance is associated with reduced oxidative stress and transpiration rates, and with improved cellular hydration, intracellular Na + /K + homeostasis and water use efficiency (Bowman and Strain., 1987;Maggio et al., 2002;Yu et al., 2015). However, the mechanisms by which high atmospheric CO 2 levels suppress transpiration and hence decrease the delivery of Na + from roots to shoots remain to be characterized. ...
Plants acclimate rapidly to stressful environmental conditions. Increasing atmospheric CO2 levels are predicted to influence tolerance to stresses such as soil salinity but the mechanisms are poorly understood. To
resolve this issue, tomato (Solanum lycopersicum) plants were grown under ambient (380 μmol mol–1) or high (760 μmol mol–1) CO2 in the absence or presence of sodium chloride (100mM). The higher atmospheric CO2 level induced the expression of RESPIRATORY BURST OXIDASE 1 (SlRBOH1) and enhanced H2O2 accumulation in the vascular cells of roots, stems, leaf petioles, and the leaf apoplast. Plants grown with higher CO2 levels showed improved salt tolerance, together with decreased leaf transpiration rates and lower sodium concentrations in
the xylem sap, vascular tissues, and leaves. Silencing SlRBOH1 abolished high CO2 -induced salt tolerance and increased leaf transpiration rates, as well as enhancing Na+ accumulation in the plants. The higher atmospheric CO2 level increased the abundance of a subset of transcripts involved in Na+ homeostasis in the controls but not in the SlRBOH1-silenced plants. It is concluded that high atmospheric CO2 concentrations increase salt stress tolerance in an apoplastic H2O2 dependent manner, by suppressing transpiration and hence Na+ delivery from the roots to the shoots, leading to decreased leaf Na+ accumulation.
... Plants grown under elevated CO 2 conditions could accumulate lower amounts of Na + due to lower transpiration rate which is the driving force for water uptake (García-Sánchez and Syvertsen, 2006;Maggio et al., 2002). Bowman and Strain (1987), however, found elevated CO 2 had no significant effects on Na + uptake despite increased water use efficiency and reduced water loss in C 4 halophytes. The relative importance of those aforementioned factors involved in elevated CO 2 mitigation of salinity stress may vary with plant species. ...
... The suppression of Na + uptake under salinity stress in plants exposed to elevated CO 2 has been associated with decreased water uptake, as elevated CO 2 causes decreased water loss through transpiration in leaves due to CO 2 -induced stomatal closure (García-Sánchez and Syvertsen, 2006;Maggio et al., 2002). Bowman and Strain (1987), however, found Na + uptake was not affected by elevated CO 2 despite of reduced water loss in C 4 halophytes. In this study, elevated CO 2 concentration did not cause significant reduction in g s and T r during most of the salinity treatment periods and, therefore, the lowered Na + content could not be related to CO 2 effects on water loss rate in Bermudagrass. ...
Salinity stress due to increased use of non-potable water sources for irrigation imposes major limitations on plant growth in salt-affected soils. However, rising atmospheric CO2 concentration may counteract the negative effects of salinity stress. The objective of this study was to determine whether elevated CO2 mitigates salinity stress by influencing physiological activities and/or ion (Na+ and K+) balance in bermudagrass (Cynodon dactylon cv. ‘Tifway’). Plants were exposed to either ambient CO2 concentration (400 μmol · mol−1) or elevated CO2 concentration (800 μmol · mol−1) and maintained well-watered (control) with fresh water or subjected to salinity stress by irrigating plants with NaCl solution (200 mM). Salinity stress caused reduction in turf quality (TQ), leaf relative water content (RWC), leaf net photosynthetic rate (Pn), transpiration rate, stomatal conductance, and cellular membrane stability. Elevated CO2 concentration alleviated the depression of those physiological parameters and promoted osmotic adjustment through accumulation of soluble sugars, proline, and glycine betaine (GB) under salinity stress, but had no significant effects on the ratio of Na+ to K+. Our results demonstrated that elevated CO2 concentration was effective in alleviating physiological damages of salinity stress in bermudagrass, suggesting that C4 grasses may benefit from the rising atmospheric CO2 concentration associated with global climate changes. The positive physiological effects of elevated CO2, as manifested by improved TQ, RWC, Pn and cell membrane stability could be related to the maintenance of cellular hydration associated with osmotic adjustment due to the accumulation of soluble sugars, proline and GB, and the suppression of Na+ accumulation independent of changes in K+ accumulation.
... Some studies have attributed the enhanced plant growth under the combination of salinity and elevated [CO 2 ] -with respect to salt stress alone -to an improvement in water relations (Bowman and Strain, 1987;Pérez-López et al., 2009a), in addition to increased net photosynthesis. However, predictions of climate change impacts on plant water relations depend on the cultivar and additional knowledge is needed about the interaction between enhanced [CO 2 ] and salinity, regarding the mechanisms involved in plant water homeostasis. ...
... However, no differences in « were found in our salinised broccoli plants when comparing both CO 2 level. Similar results were found by Bowman and Strain (1987) and these authors postulated that greater vacuolar osmotic regulation, rather than increased osmotic adjustment, could explain the decreased reduction in « at elevated [CO 2 ]. In fact, the broccoli plants treated with 90 mM NaCl had a greater leaf Na content at elevated [CO 2 ] (1.76 mmol g −1 DW) than at ambient [CO 2 ] (1.59 mmol g −1 DW). ...
In the global change scenario, increased CO2 may favour water use efficiency (WUE) by plants. By contrast, in arid and semiarid areas, salinity may reduce water uptake from soils. However, an elevated WUE does not ensure a reduced water uptake and upon salinity this fact may constitute an advantage for plant tolerance. In this work, we aimed to determine the combined effects of enhanced [CO2] and salinity on the plant water status, in relation to the regulation of PIP aquaporins, in the root and leaf tissues of broccoli plants (Brassica oleracea L. var Italica), under these two environmental factors. Thus, different salinity concentrations (0, 60 and 90 mM NaCl) were applied under ambient (380 ppm) and elevated (800 ppm) [CO2]. Under non-salinised conditions, stomatal conductance (Gs) and transpiration rate (E) decreased with rising [CO2] whereas water potential (Ψω) was maintained stable, which caused a reduction in the root hydraulic conductance (L0). In addition, PIP1 and PIP2 abundance in the roots was decreased compared to ambient [CO2]. Under salinity, the greater stomatal closure observed at elevated [CO2] – compared to that at ambient [CO2] – caused a greater reduction in Gs and E and allowed plants to maintain their water balance. In addition, a lower decrease in L0 under salt stress was observed at elevated [CO2], when comparing with the decrease at ambient [CO2]. Modifications in PIP1 and PIP2 abundance or their functionality in the roots is discussed. In fact, an improved water status of the broccoli plants treated with 90 mM NaCl and elevated [CO2], evidenced by a higher Ψω, was observed together with higher photosynthetic rate and water use efficiency. These factors conferred on the salinised broccoli plants greater leaf area and biomass at elevated [CO2], in comparison with ambient [CO2]. We can conclude that, under elevated [CO2] and salt stress, the water flow is influenced by the tight control of the aquaporins in the roots and leaves of broccoli plants and that increased PIP1 and PIP2 abundance in these organs provides a mechanism of tolerance that maintains the plant water status.
... In this present study, water-stressed conditions in plants might have occurred due to the reduction in the relative water content as salinity increased. Reduced transpiration rates and oxidative stress, with increased water use efficiency, intracellular Na + /K + and cellular hydration are some of the physiological changes observed under salinity stress [30,49]. Elevated CO 2 concentration resulted in an increase in the above-ground biomass, in particular, stem dry weight under low salinity stress. ...
Climate change elements including elevated atmospheric carbon dioxide (CO2) concentration and soil salinity significantly impact weed biology and management. In this study, we evaluated the performance of a highly invasive plant species, parthenium weed (Parthenium hysterophorus L.) grown at various soil salinity levels (ranging from 0 to 16 dS m⁻¹) at two CO2 concentrations (ambient: 400 ppm and elevated: 700 ppm). The CO2 concentration and soil salinity individually affected various early growth attributes of parthenium weed. The interaction between CO2 and salinity was significant for chlorophyll index, stem dry weight and phenolics content. Parthenium weed plants grew taller (13%), achieved greater leaf area (28%) and produced more dry weight (24%) when raised under elevated as compared with the ambient CO2. Soil salinity had a dose-dependent, negative effect on various growth attributes, chlorophyll index, relative water content and phenolics content. Even the modest levels of salinity (4.2 to 4.6 dS m⁻¹) caused 50% reduction in dry weights of leaves, roots and whole plants. Sodium ion (Na⁺) concentration peaked at the highest salinity level (16 dS m⁻¹) as compared with the lower salinity levels (0 to 12 dS m⁻¹). Overall, salinity had a negative effect on different growth variables but elevated CO2 improved growth and phenolics content regardless of the salt stress regime. Hence, parthenium weed could benefit from future atmospheric CO2 concentration and may invade some salt-affected areas.
... Higher temperatures entail a higher evaporative demand. Therefore, the regions with sufficient soil moisture, such as the irrigated lands, it could lead to soil salinization 19 . In tropical monsoon climate, an increase in the number of rainfall events and increase in total precipitation would increase leaching rates in well-drained soils and cause temporary water saturation and hence reduced organic matter decomposition 20 . ...
This study estimates the possible effects of change in climatic factors on the production of major crops in Maharashtra, India. Daily precipitation, and minimum and maximum temperature simulated by a statistically downscaled MPI-ESM-MR model in NEX-GDDP archive have been used in the study. Under RCP4.5, the analysis suggests a significant reduction in the production of three major crops, viz. sugarcane, cotton and rice. This decline is prominent in central and central-east Maharashtra. These findings imply the need to improve and develop new seed varieties that can withstand drastic changes in climate and also give high yield to combat food security of an increasing population.
... However, beneficial effects of high atmospheric CO 2 on the photosynthesis in plants subjected to salt stress are still controversial. In fact, while some studies have reported beneficial effects of high CO 2 pressure on carbon assimilation in plants under salinity (Geissler et al. 2015;Yu et al. 2015;Pérez-López et al. 2014;Yi et al. 2015), others have reported low (Ball et al. 1997) or even no effects on photosynthetic activity (Bowman and Strain 1987). ...
The aim of this study was to evaluate the effects of elevated CO2 concentration on acclimation mechanisms related to gas exchange, photochemical activity, photorespiration, and oxidative protection in cashew plants exposed to salinity. Thirty-day-old cashew plants were irrigated with nutrient solution without (control) or with supplemental NaCl (100 mM) for 2 weeks in the greenhouse. Afterward, control and salt-stressed plants were transferred to the growth chamber and supplied with atmospheric (380 µmol mol⁻¹) or high CO2 (760 µmol mol⁻¹) concentrations for 15 days. The results show that elevated CO2 alone reduced the CO2 net assimilation rate (PN) without affecting stomatal conductance (gS) and transpiration rate (E), whereas salinity and NaCl + high CO2 reduced the PN associated with a decrease in gS and E. The potential quantum yield of photosystem II (Fv/Fm) was not altered, but a slight reduction in electron transport rate and photochemical quenching (qP) in response to high CO2 alone or combined with NaCl occurred. However, non-photochemical quenching increased due to the effects of high CO2 and NaCl alone and by their combination. High CO2 alleviated the toxic effects of Na⁺ favoring the K⁺/Na⁺ ratio under salinity. High CO2 coupled with salinity decreased glycolate oxidase activity and the contents of hydrogen peroxide (H2O2), NH4⁺, and glyoxylate. Furthermore, we observed increase in membrane damage associated with increased thiobarbituric acid-reactive substances levels under high CO2. High CO2 also decreased ascorbate peroxidase activity, but did not affect superoxide dismutase activity. In general, our data suggest that high CO2 could induce acclimation processes in plants independent of salinity, revealing a set of responses that are more associated with acclimation than with protective responses.
... irrigated areas, enhanced evaporative demand could lead to soil salinization if proper water management or irrigation scheduling or drainage is not followed. Some recent experiments by the Salinity Laboratory, Riverside, California, reported the increased salt tolerance of crops under high atmospheric CO 2 conditions (Maas 1986;Bowman and Strain 1987). 4. Transient salinity may increase in sodic soils as capillary rise plays the predominant role bringing salts to the root zone. ...
The increase of greenhouse gas emissions due to anthropogenic activities is continuously changing the climate. The soil is the important factor for the global food production and also responsible for three important greenhouse gases, viz. carbon dioxide, methane and nitrous oxide. These gases are highly contributing in the global warming, which directly affects the soil health. The change in physical, chemical and biological properties of soil system changes the organic carbon content, nitrogen mineralization, availability of essential nutrients and soil hydrological properties, along with the soil aggregate changes. Increased soil temperature is also enhancing the microbial activities in the soil and ultimately causes the decrease in the soil organic carbon and increase the gaseous carbon emission. In the present chapter, the maintenance of the soil health and soil quality in the variable climate are discussed, and the agricultural practices such as maintaining permanent vegetative cover on the soil surface, crop residue incorporation and lowest disturbed soil are recommended to protect the soil surface. These methods also support to mitigate the greenhouse gas emission from the agriculture soil.
... In saline conditions, increased WUE potentially could reduce the salt uptake by plant. Partial stomatal closure under such future environmental conditions could be an ideal mechanism for salt tolerance (Bowman and Strain, 1987;Rozema et al., 1991). Alternatively, high temperature at the plant canopy level will increase transpiration by changing the vapour pressure deficit at the leaf surface, accelerate ageing of the foliage, and also shorten the growing season or grain-filling period which is very critical for the grain yield (Kenny et al., 1993). ...
... Whereas many data are available with regard to the effect of salinity on crop yield, a great deal less is known about the physiological processes during growth. The salinity effect on the water stress of the plant, its gaseous exchanges and its metabolism has been analyzed over short periods (see for example Osmond and Greenway, 1972;Longstreth and Strain, 1977;Albuzio, 1978;Yeo, et al., 1985;West, et al., 1986;Bowman and Strain, 1987). Kaymakanova, and Stoeva, (2008) found the physiological responses of three different bean cultivars plants were treated for 7 days with NaCl and Na 2 SO 4 (100 mM), starting at the appearance of the first trifoliate leaf unfolded. ...
... Higher ATPase abundance and activity is related to improved Na + exclusion from leaves or shoots and Na + transport into the vacuole (Geissler et al., 2010). Some studies found that the positive effects of elevated CO 2 on salinity stress is largely due to the alleviation of osmotic stress and greater WUE under elevated CO 2 (500 or 650 vs. 350 mmol mol -1 ; Baker and Enoch, 1983;Bowman and Strain, 1987;Pearcy and Bjorkman, 1983). The enhanced osmotic adjustment is due to increased accumulation of soluble sugars under elevated CO 2 , which counteracts the osmotic effects of Na + accumulation. ...
Increases in atmospheric CO2 concentration have exerted significant impacts on plant growth. Numerous studies have reported positive effects of elevated CO2 on plant growth and adaptation to various environmental stresses in many plant species. The mechanisms by which CO2 enrichment regulates plant growth and stress adaptation are not completely understood. There have been some recent exciting advances in elucidating the cellular, metabolic, and molecular basis for increased growth under elevated CO2. At the cellular level, cell growth involving both cell division and cell expansion is stimulated by increasing CO2, which has been associated with increased photosynthetic activities and carbohydrate availability, and also with the expression of genes controlling cell division, cycling, and cell expansion. Proteomic profiling studies identified CO2–regulated proteins mainly involved in photosynthesis, carbon metabolism, energy pathways, molecular chaperones, and antioxidant proteins. Transcriptomic analyses identified several hundreds of genes responsive to elevated CO2 levels, which play roles in cell wall loosening, photosynthesis, respiration, water use, and protein synthesis, as well as stress defense. This paper reviews recent progress in the mechanistic understanding of CO2 regulation of plant growth and stress adaptation at the cellular, metabolic, and molecular levels, and addresses research gaps and future research perspective areas.
... In saline conditions, increased WUE potentially could reduce the salt uptake by plant. Partial stomatal closure under such future environmental conditions could be an ideal mechanism for salt tolerance (Bowman and Strain, 1987;Rozema et al., 1991). Alternatively, high temperature at the plant canopy level will increase transpiration by changing the vapour pressure deficit at the leaf surface, accelerate ageing of the foliage, and also shorten the growing season or grain-filling period which is very critical for the grain yield (Kenny et al., 1993). ...
... However, Gale (1982), Schwarz and Gale (1984), Bowman and Strain (1987), Zeroni (1988), Lenssen and Rozema (1990), Cramer et al., 1990), Drew et al (1990) and Nicolas et al (1993) have shown that many species of plants grown in saline water under high CO2 concentration increase growth and productivity. ...
Melon (Cucumis melo L. Cv Parnon) grown in rockwool culture in the greenhouse was CO2 enriched, for 5h every morning, at 400, 800 and 1200μmolmol−1 and trickle-irrigated with nutrient solutions amended with 0, 25 and 50mM NaCl.High CO2 level increased fruit yield, the increase being greater in unsalinated plants than in salinated. With total shoot fresh weight, the increase was greater in salinated plants. CO2 enrichment also increased leaf growth and the chlorophyll content of the measured leaves. Addition of NaCl in the nutrient solution caused significant reduction in total yield, the reduction being greater at higher concentrations of CO2. At 25mM NaCl, the decrease in yield resulted mainly from the smaller fruit size, but at 50mM yield reduction was due both to smaller fruit size and to fewer fruits per plant. Addition of NaCl caused significant reduction in total shoot fresh weight in all cases, the reduction being greater at the lower level of CO2. Salinity also, significantly reduced leaf surface irrespective of CO2 level. Chlorophyll content was reduced by NaCl mainly at the level of 50mM NaCl. A stronger correlation was found between salinity and shoot fresh weight, plant height and leaf surface area, than salinity and yield and other characteristics. Measurements of gas exchange showed that, for the above mentioned CO2 and NaCl concentrations, net assimilation was affected by CO2 to a greater degree than by salinity. Stomatal conductance was most affected by salinity at a concentration of 50mM NaCl.
... In saline conditions, increased WUE potentially could reduce the salt uptake by plant. Partial stomatal closure under such future environmental conditions could be an ideal mechanism for salt tolerance (Bowman and Strain, 1987;Rozema et al., 1991). Alternatively, high temperature at the plant canopy level will increase transpiration by changing the vapour pressure deficit at the leaf surface, accelerate ageing of the foliage, and also shorten the growing season or grain-filling period which is very critical for the grain yield (Kenny et al., 1993). ...
This review addresses possible adaptation strategies in rice production to abiotic stresses that will aggravate under climate change: heat (high temperature and humidity), drought, salinity, and submergence. Each stress is discussed regarding the current state of knowledge on damage mechanism for rice plants as well as possible developments in germplasm and crop management technologies to overcome production losses. Higher temperatures can adversely affect rice yields through two principal pathways, namely (i) high maximum temperatures that cause—in combination with high humidity—spikelet sterility and adversely affect grain quality and (ii) increased nighttime temperatures that may reduce assimilate accumulation. On the other hand, some rice cultivars are grown in extremely hot environments, so that the development of rice germplasm with improved heat resistance can capture an enormous genetic pool for this trait. Likewise, drought is a common phenomenon in many rice growing environments, and agriculture research has achieved considerable progress in terms of germplasm improvement and crop management (i.e., water saving techniques) to cope with the complexity of the drought syndrome. Rice is highly sensitive to salinity. Salinity often coincides with other stresses in rice production, namely drought in inland areas or submergence in coastal areas. Submergence tolerance of rice plants has substantially been improved by introgressing the Sub1 gene into popular rice cultivars in many Asian rice growing areas.
... Influence of soil and foliar application of potash fertilizers (SOP & MOP) on biochemical attributes [ In the present investigation, salt stress significantly reduced the net photosynthesis rate (P n ), stomatal conductance (g s ), internal CO 2 concentration (Ci) and transpiration rate (E) of all wheat cultivars under test. Different factors are responsible for the reduction in CO 2 fixation with the implication of salinity such as reduced stomatal conductance (Tourneux and Peltier, 1995; Kaymakanova and Stoeva, 2008), lower carbon uptake and reduction due to decline in biochemical capacity (Bowman and Strain, 1987; Khan and Panda, 2008), a decline in photochemical capacity (Ball and Anderson, 1986) or a combination of all these factors (Bowman, 1987). Many studies have shown that photosynthetic parameters are adversely affected by increasing salt concentrations (Shabala et al., 1998; Akhtar et al., 2001; Kaymakanova and Stoeva, 2008). ...
Present experiment was conducted to assess the ameliorative effects of soil and foliar application
of potash fertilizers, i.e., sulfate of potash (SOP) and muriate of potash (MOP) on five wheat
cultivars (‘Sitta’, ‘Sehar’, ‘Bhakkar-2006’, ‘PFAU#VEE’, ‘S-24’), subjected to salt stress created by
applying sodium chloride (NaCl; 10 dS m−1) to the growth medium. Different treatments of potash
fertilizers used included: control, SOP (100 kg ha−1) in soil, foliar spray of 1% solution of SOP,
MOP (100 kg ha−1) in soil and foliar spray of 1%solution of MOP. Experiment was carried out in
completely randomized design with three replications. Imposition of salt stress reduced growth, yield,
and related yield attributes, photosynthetic attributes, ionic contents and biochemical activities in
all wheat cultivars. However, application of potash fertilizers in soil as well as in foliar spray
counteracted the adverse effects of salt stress on all wheat cultivars and the application of SOP in
soil and as a foliar spray proved to be more effective in inducing salt stress tolerance. No adverse
effect of chloride on plant growth was observed. Among the cultivars, ‘S-24’ and ‘Sehar’ showed the
maximum growth, yield and biochemical contents and thus could be used in future for obtaining
better yield under saline conditions.
... The elevation of the marsh was measured in 1990 by establishing the height of points in a grid over If elevated CO2 can enhance the water use ef ficiency of Scirpus, then this might improve growth and competitive ability of Scirpus. Salt tolerance of C3 species may be enhanced at elevated CO2 by an increase in available photosynthates and by improved water status (Bowman & Strain 1987;Rozema et al. 1990). During dry years both C3 and C4 species can benefit from reduced evapo transpiration at elevated CO2, and the relative evated CO2 was observed, with Scirpus in the mixed community responding much stronger to elevated CO2 in shoot density, shoot height and biomass (Fig. 2). ...
Elevated atmospheric CO2 is known to stimulate photosynthesis and growth of plants with the C3 pathway but less of plants with the C4 pathway. An increase in the CO2 concentration can therefore be expected to change the competitive interactions between C3 and C4 species. The effect of long term exposure to elevated CO2 (ambient CO2 concentration +340 µmol CO2 mol-1) on a salt marsh vegetation with both C3 and C4 species was investigated. Elevated CO2 increased the biomass of the C3 sedgeScirpus olneyi growing in a pure stand, while the biomass of the C4 grassSpartina patens in a monospecific community was not affected. In the mixed C3/C4 community the C3 sedge showed a very large relative increase in biomass in elevated CO2 while the biomass of the C4 species declined.
The C4 grassSpartina patens dominated the higher areas of the salt marsh, while the C3 sedgeScirpus olneyi was most abundant at the lower elevations, and the mixed community occupied intermediate elevations.Scirpus growth may have been restricted by drought and salt stress at the higher elevations, whileSpartina growth at the lower elevations may be affected by the higher frequency of flooding. Elevated CO2 may affect the species distribution in the salt marsh if it allowsScirpus to grow at higher elevations where it in turn may affect the growth ofSpartina.
... In saline conditions, increased WUE potentially could reduce the salt uptake by plant. Partial stomatal closure under such future environmental conditions could be an ideal mechanism for salt tolerance (Bowman and Strain, 1987;Rozema et al., 1991). Alternatively, high temperature at the plant canopy level will increase transpiration by changing the vapour pressure deficit at the leaf surface, accelerate ageing of the foliage, and also shorten the growing season or grain-filling period which is very critical for the grain yield (Kenny et al., 1993). ...
This review addresses possible adaptation strategies in rice production to abiotic stresses that will aggravate under climate change: heat (high temperature and humidity), drought, salinity, and submergence. Each stress is discussed regarding the current state of knowledge on damage mechanism for rice plants as well as possible developments in germplasm and crop management technologies to overcome production losses. Higher temperatures can adversely affect rice yields through two principal pathways, namely (i) high maximum temperatures that cause—in combination with high humidity—spikelet sterility and adversely affect grain quality and (ii) increased nighttime temperatures that may reduce assimilate accumulation. On the other hand, some rice cultivars are grown in extremely hot environments, so that the development of rice germplasm with improved heat resistance can capture an enormous genetic pool for this trait. Likewise, drought is a common phenomenon in many rice growing environments, and agriculture research has achieved considerable progress in terms of germplasm improvement and crop management (i.e., water saving techniques) to cope with the complexity of the drought syndrome. Rice is highly sensitive to salinity. Salinity often coincides with other stresses in rice production, namely drought in inland areas or submergence in coastal areas. Submergence tolerance of rice plants has substantially been improved by introgressing the Sub1 gene into popular rice cultivars in many Asian rice growing areas.Finally, the review comprises a comparative assessment of the rice versus other crops related to climate change. The rice crop has many unique features in terms of susceptibility and adaptation to climate change impacts due to its semiaquatic phylogenetic origin. The bulk of global rice supply originates from irrigated systems which are to some extent shielded from immediate drought effects. The buffer effect of irrigation against climate change impacts, however, will depend on nature and state of the respective irrigation system. The envisaged propagation of irrigation water saving techniques will entail benefits for the resilience of rice production systems to future droughts. We conclude that there are considerable risks for rice production stemming from climate change, but that the development of necessary adaptation options can capitalize on an enormous variety of rice production systems in very different climates and on encouraging progress in recent research.
... , 1986). Relief from the effects of salinity has been seen in some studies ( Schwarz & Gale, 1984;Bowman & Strain, 1987). In other words, salt tolerance increases as CO2 concentration goes up ( Zeroni & Gale, 1989). ...
Empirical records provide incontestable evidence of global changes: foremost among these changes is the rising concentration of CO(2) in the earth's atmosphere. Plant growth is nearly always stimulated by elevation of CO(2). Photosynthesis increases, more plant biomass accumulates per unit of water consumed, and economic yield is enhanced. The profitable use of supplemental CO(2) over years of greenhouse practice points to the value of CO(2) for plant production. Plant responses to CO(2) are known to interact with other environmental factors, e.g. light, temperature, soil water, and humidity. Important stresses including drought, temperature, salinity, and air pollution have been shown to be ameliorated when CO(2) levels are elevated. In the agricultural context, the growing season has been shortened for some crops with the application of more CO(2); less water use has generally, but not always, been observed and is under further study; experimental studies have shown that economic yield for most crops increases by about 33% for a doubling of ambient CO(2) concentration. However, there are some reports of negligible or negative effects. Plant species respond differently to CO(2) enrichment, therefore, clearly competitive shifts within natural communities could occur. Though of less importance in managed agro-ecosystems, competition between crops and weeds could also be altered. Tissue composition can vary as CO(2) increases (e.g. higher C: N ratios) leading to changes in herbivory, but tests of crop products (consumed by man) from elevated CO(2) experiments have generally not revealed significant differences in their quality. However, any CO(2)-induced change in plant chemical or structural make-up could lead to alterations in the plant's interaction with any number of environmental factors-physicochemical or biological. Host-pathogen relationships, defense against physical stressors, and the capacity to overcome resource shortages could be impacted by rises in CO(2). Root biomass is known to increase but, with few exceptions, detailed studies of root growth and function are lacking. Potential enhancement of root growth could translate into greater rhizodeposition, which, in turn, could lead to shifts in the rhizosphere itself. Some of the direct effects of CO(2) on vegetation have been reasonably well-studied, but for others work has been inadequate. Among these neglected areas are plant roots and the rhizosphere. Therefore, experiments on root and rhizosphere response in plants grown in CO(2)-enriched atmospheres will be reviewed and, where possible, collectively integrated. To this will be added data which have recently been collected by us. Having looked at the available data base, we will offer a series of hypotheses which we consider as priority targets for future research.
Some of the bigger and wider changes in the soil that arise from any global change which are slowly and not visible, particularly the steady decline in soil fertility and physical qualities after increased climatic temperature. Low crop productivity and typically equivalent or moderately high rainfall can cause soil deterioration and nutrient depletion. Expect higher biological activity and occasional soil degradation in addition to larger but less significant changes in the soil. Other climatic changes (temperature and rainfall) are anticipated to have a reasonably positive impact on many soils' mineral composition, organic matter content, or structural stability. With rising, decreasing, or more severe seasonal rainfall, the type of the dominant soil formation may be inferior in some fragile soils. In most cases, changes in the soil through direct human action, on‐site or off‐site, far outweigh the effects of climate change. Soil management measures are designed to improve the soil's productivity and may lead the soil capacity to be sufficient to prevent any reduction of agricultural production through climate change. The land of natural areas, or other lands that have a low intensity of management such as semi‐natural forests used for digging wood and other products, is less easily protected from the effects of climate change. Such soils are also less vulnerable to climate change than they are to human activities, such as pollution from acid accumulation, or excessive nutrient depletion on site, such as very little input agriculture. To disarm the world's soil against any negative impact of climate change, or external nutrient deficiencies or over‐pollution, or drought or high‐intensity rains, The best that can happen to them is: manage their soil by maintaining maximum physical flexibility by maximizing the off‐ground cover through a stable, proportional soaking system. Using an integrated plant nutrient management system to balance nutrient input and offtake during crops or over the years, while maintaining soil nutrient levels substantially and sometimes to minimize losses. Occasionally high demands should be high enough to eliminate them.
The forecasts have shown that yield of the most agricultural crops will be reduced
until 2030 due to different reasons. Climate changes via increase temperature and intensifies evapotranspiration, decrease precipitations and soil leaching and groundwater pollution caused soil salinization especially at higher latitudes. Halophytes are the promising plants for future agriculture of the world in climate change conditions, because these plants are capable to complete their life cycle in higher salt concentrations, and increasing CO2 can enhance more salinity tolerance of C3 halophytes and increasing temperature can enhance the production of C4 halophytes. Different results have been seen on the effect of climate change on halophytes. For example, increasing CO2 enhanced salinity tolerance and reduced oxidative impact in Aster tripolium a C3 halophyte. Or increasing CO2 induced growth of Spartina densiflora a C4 halophyte, which mainly be due to greater leaf area and improved water relations. Enriched CO2 also enhanced the salinity tolerance of Avicennia germinans. Atriplex centralasiatica, a C4 halophyte, showed a higher photosynthesis rate and greater Fv/Fm in higher temperature conditions. In general, it seems that the growth of halophytes in a changed climate consisted of increased salinity, temperature, and CO2 concentration, and decreased water resources will be more than non-halophyte plants. Enriched CO2 also improved the salinity tolerance of halophytes.
Tomato (Solanum lycopersicum L. cv. 'Momotarou') plants were grown in pots inside a greenhouse. The adverse effects of salinity stress under elevated atmospheric CO_2 on biomass production, the apparent photosynthetic rate, and activities of antioxidative enzymes during the vegetative growth period were examined. Although salinity stress severely decreased biomass of all plant organs, this reduction was alleviated by elevated CO_2. The salinity treatment also depressed the apparent photosynthetic rate, but the impact of salinity stress on photosynthesis was alleviated under elevated CO_2. Catalase activity in leaves was increased by the salinity treatment, but was decreased by elevated CO_2. In contrast, APX activity was increased by salinity but was not affected by elevated CO_2. These results suggest that salinity stress suppressed vegetative growth in tomato plants, but that the adverse effect was alleviated under elevated CO_2 due to elevation of source activity in leaves at high source/sink ratios.
Abstract: Computer simulation models are widely applied in various areas of the health care sector, including the spread of
infectious diseases. Patch models involve explicit movements of people between distinct locations. The aim of the present work has
been designed and explored a patch model with population mobility between different patches and between each patch and an
external population. The authors considered a SIR (susceptible-infected-recovered) scheme. The model was explored by computer
simulations. The results show how endemic levels are reached in all patches of the system. Furthermore, the performed explorations
suggest that the people mobility between patches, the immigration from outside the system and the infection rate in each patch, are
factors that may influence the dynamics of epidemics and should be considered in health policy planning.
Key words: Simulation, spread of infectious diseases, population mobility, epidemic patch model, SIR model.
Brassica oilseed species now hold the third position among oilseed crops and are an important source of vegetable oil. The most common Brassica oil-seed crops grown for commercial purposes are rape seeds, (Brassica campestris L. and B. napus L.) and mustards (B. juncea (L.) Czern. & Coss. and B. carinata A.Br.). The other Brassica species such as B. nigra (L.) Koch and B. tournefortii Gouan are grown on a very small scale. Brassica napus, B. juncea, and B. carinata are amphidiploids, whereas B. campestris and B. nigra are diploid. Most of the Brassica species have been categorized as moderately salt tolerant, with the amphidiploid species being the relatively salt tolerant in comparison with the diploid species. Due to the higher salt tolerance of the amphidiploids, it has been suggested that their salt tolerance has been acquired from the A (B. campestris) and C (B. oleracea L.) genomes. However, significant inter- and intraspecific variation for salt tolerance exists within brassicas, which can be exploited through selection and breeding for enhancing salt tolerance of the crops. There are contrasting reports regarding the response of these species to salinity at different plant developmental stages, but in most of them it is evident that they maintain their degree of salt tolerance consistently throughout the plant ontogeny. The pattern of uptake and accumulation of toxic ions (Na and Cl), in tissues of plants subjected to saline conditions appears to be mostly due to mechanism of partial ion exclusion (exclusion of Na and/or Cl) in most of the species, although ion inclusion in some cases at intraspecific levels has also been observed. Maintenance of high tissue K/Na and Ca/Na ratios has been suggested as an important selection criterion for salt-tolerance in brassicas. Osmotic adjustment has also been reported in Brassica plants subjected to saline conditions, but particularly to a large extent in salt-tolerant species or cultivars. The roles of important organic osmotica such as total soluble sugars, free amino acids, and free proline, which are central to osmotic adjustment, have been discussed. In canola, B. napus, no positive relationship has been observed between salt tolerance and erucic acid content of seed oil in different cultivars. Furthermore, glucosinolate content of the seed meal in canola generally increases with an increase in salt level of the growth medium. This review highlights the responses of potential Brassica crops to soil salinity from the whole plant to the molecular level. It also describes the efforts made during the past millennium in uncovering the mechanism(s) of salinity tolerance of these crops both at the whole plant and cellular levels. The important selection criteria, which are used by researchers to enhance the degree of salinity tolerance in brassicas, are summarized. In addition, the vital role of genetic engineering and molecular biology approaches to the improvement of salt tolerance in brassicas is emphasized.
Salinity is one of the most damaging agro-environmental problems limiting plant growth and development in most parts of the world. The problem of salinity existed long before human beings and the start of agricultural practice and today it has become a very serious problem for crop production, particularly in arid and semi-arid regions, which constitute about one third of the world's land surface. The magnitude of genetic variation for salinity tolerance in spring wheat and broad-sense heritabilities has been estimated at different salinity levels. The 68 genotypes responded with different behaviors to increasing salinity levels in the growing medium. Responses of different genotypes to increased salinity levels in reduced growth were found, with those originating from Australia exhibiting a significant increase in salinity tolerance compared with others, originating from Pakistan. Plant vigor and salinity tolerance were found to have no significant correlation as measured by relative growth rates in saline environments. The relative growth rate of various accessions grouped on the basis of different geographic origin and different genes of various stresses also were not different significantly from each other, which suggests that different genes may be controlling the characteristic, from a single major dominant or from recessive genes. Estimated broad-sense heritability indicated that phenotypic variance exceeded that of genotypic by nearly two orders of magnitude. This study was to determine genetic and phenotypic relationships between plant performance in the presence of NaCl at three developmental stages in wheat. These results suggest that improvement in salinity tolerance in spring wheat is possible through selection and breeding.
This paper presents a detailed analysis of several hundred plant carbon exchange rate (CER) and dry weight (DW) responses to atmospheric CO2 enrichment determined over the past 10 years. It demonstrates that the percentage increase in plant growth produced by raising the air's CO2 content is generally not reduced by less than optimal levels of light, water or soil nutrients, nor by high temperatures, salinity or gaseous air pollution. More often than not, in fact, the data show the relative growth-enhancing effects of atmospheric CO2 enrichment to be greatest when resource limitations and environmental stresses are most severe.
Three high marsh communities on the Chesapeake Bay were exposed to a doubling in ambient CO2 concentration for one growing season. Open-top chambers were used to raise CO2 concentrations ca. 340 ppm above ambient over monospecific communities of Scirpus olneyi (C3) and Spartina patens (C4), and a mixed community of S. olneyi, S. patens, and Distichlis spicata (C4). Plant growth and senescence were monitored by serial, nondestructive censuses. Elevated CO2 resulted in increased shoot densities and delayed sensecence in the C3 species. This resulted in an increase in primary productivity in S. olneyi growing in both the pure and mixed communities. There was no effect of CO2 on growth in the C4 species. These results demonstrate that elevated atmospheric CO2 can cause increased aboveground production in a mature, unmanaged ecosystem.
Elymus athericus (Link) Kerguélen, a C3 grass, was grown in a greenhouse experiment to determine the effect of enhanced atmospheric CO2 and elevated UV-B radiation levels on plant growth. Plants were subjected to the following treatments; a) ambient CO2-control UV-B, b) ambient CO2-elevated UV-B, c) double CO2-control UV-B, d) double CO2-elevated UV-B. Elevated CO2 concentrations stimulated plant growth, biomass production was 67% higher than at ambient CO2. Elevated UV-B radiation had a negative effect on growth, biomass production was depressed by 31%. Enhanced CO2 combined with elevated UV-B levels caused a biomass depression of 8% when compared with the control plants. UV-B induced growth depression can be modified by a growth stimulus caused by high CO2 concentrations. Growth analysis has been performed and possible physiological mechanisms behind changing growth parameters are discussed.
It is generally assumed that healthy, natural ecosystems have the potential to sequester carbon under favorable environmental conditions. There is also evidence that CO2 acts as a plant fertilizer. It is of interest to know if these assumptions are valid and how natural systems might respond under future scenarios of CO2 increase and possible climate changes. Few measurements of the effects of CO2 and global climate change have been made on “natural” ecosystems under realistic field conditions. Most measurements have been conducted in the synthetic environments of totally controlled greenhouses and growth chambers. Several lines of evidence indicate that controlled environment studies using plants growing in pots induce experimental artifacts that reduce confidence in the use of results for prediction of future global responses. Open top chambers are being used in several autecological field studies in an attempt to obtain more realistic field environments. A few field microcosm studies have been completed and a system for the free air release of CO2 has been applied in cotton fields. Unfortunately, the requirement of large amounts of CO2 and financial restrictions have precluded the initiation of larger scale field studies in natural vegetation. This paper lists and summarizes the best field studies available but draws heavily on studies from artificial environments and conditions in an attempt to summarize knowledge of global environmental change on forests and other non-agricultural ecosystems. Finally the paper concludes that there is a need for the development and application of equipment for field measurements in several representative natural ecosystems and makes specific recommendation of the creation of a tropical research center.
Two mangrove species, Rhizophora apiculata and R. stylosa, were grown for 14 weeks in a multifactorial combination of salinity (125 and 350 mol m−3 NaCl), humidity (43 and 86% relative humidity at 30°C) and atmospheric CO2 concentration (340 and 700 cm3 m−3). Under ambient [CO2], growth responses to different combinations of salinity and humidity were consistent with interspecific differences in distribution along natural gradients of salinity and aridity in northern Australia. Elevated [CO2] had little effect on relative growth rate when it was limited by salinity but stimulated growth when limited by humidity. Both species benefited most from elevated [CO2] under relatively low salinity conditions in which growth was vigorous, but relative growth rate was enhanced more in the less salt-tolerant and more rapidly growing species, R. apiculata. Changes in both net assimilation rate and leaf area ratio contributed to changes in relative growth rates under elevated [CO2], with leaf area ratio increasing with decrease in humidity. Increase in water use efficiency under elevated [CO2] occurred with increase, decrease or no change in evaporation rates; water use characteristics which depended on both the species and the growth conditions. In summary, elevated [CO2] is unlikely to increase salt tolerance, but could alter competitive rankings of species along salinity × aridity gradients.
Review of literature indicates that many uncertainties and assumptions exist in predicting the impacts of a climate change on forest ecosystems. However, current knowledge is sufficient to encourage any measures that are combating climate change, that is to reduce first and foremost the release of harmful substances to the atmosphere, lithosphere and biosphere.
The growth response of Dutch salt marsh species (C3 and C4) to atmospheric CO2 enrichment was investigated. Tillers of the C3 species Elymus athericus were grown in combinations of 380 and 720 μ11−1 CO2 and low (0) and high (300 mM NaCl) soil salinity. CO2 enrichment increased dry matter produc
The Stroodorpepolder salt marsh (Zeeland, The Netherlands). (Photograph: W. E. van Duin).
tion and leaf area development while both parameters were reduced at high salinity. The relative growth response to CO2 enrichment was higher under saline conditions. Growth increase at elevated CO2 was higher after 34 than 71 days. A lower response to CO2 enrichment after 71 days was associated with a decreased specific leaf area (SLA). In two other experiments the effect of CO2 (380 and 720 μ11−1 ) on growth of the C4 species Spartina anglica was studied. In the first experiment total plant dry weight was reduced by 20% at elevated CO2. SLA also decreased at high CO2. The effect of elevated CO2 was also studied in combination with soil salinity (50 and 400 mM NaCl) and flooding. Again plant weight was reduced (10%) at elevated CO2, except under the combined treatment high salinity/non-flooded. But these effects were not significant. High salinity reduced total plant weight while flooding had no effect. Causes of the sainity-dependent effect of CO2 enrichment on growth and consequences of elevated CO2 for competition between C3 and C4 species are discussed.
In general, C3 plant species are more responsive to atmospheric carbon dioxide (CO2) enrichment than C4-plants. Increased relative growth rate at elevated CO2 primarily relates to increased Net Assimilation Rate (NAR), and enhancement of net photosynthesis and reduced photorespiration. Transpiration and stomatal conductance decrease with elevated CO2, water use efficiency and shoot water potential increase, particularly in plants grown at high soil salinity. Leaf area per plant and leaf area per leaf may increase in an early growth stage with increased CO2, after a period of time Leaf Area Ratio (LAR) and Specific Leaf Area (SLA) generally decrease. Starch may accumulate with time in leaves grown at elevated CO2. Plants grown under salt stress with increased (dark) respiration as a sink for photosynthates, may not show such acclimation to increased atmospheric CO2 levels. Plant growth may be stimulated by atmospheric carbon dioxide enrichment and reduced by enhanced UV-B radiation but the limited data available on the effect of combined elevated CO2 and ultraviolet B (280–320 nm) (UV-B) radiation allow no general conclusion. CO2-induced increase of growth rate can be markedly modified at elevated UV-B radiation. Plant responses to elevated atmospheric CO2 and other environmental factors such as soil salinity and UV-B tend to be species-specific, because plant species differ in sensitivity to salinity and UV-B radiation, as well as to other environmental stress factors (drought, nutrient deficiency). Therefore, the effects of joint elevated atmospheric CO2 and increased soil salinity or elevated CO2 and enhanced UV-B to plants are physiologically complex.
The effect of a doubling in the atmospheric CO2 concentration on the growth of vegetative whole plants was investigated. In a compilation of literature sources, the growth stimulation of 156 plant species was found to be on average 37%. This enhancement is small compared to what could be expected on the basis of CO2-response curves of photosynthesis. The causes for this stimulation being so modest were investigated, partly on the basis of an experiment with 10 wild plant species. Both the source-sink relationship and size constraints on growth can cause the growth-stimulating effect to be transient.Data on the 156 plant species were used to explore interspecific variation in the response of plants to high CO2. The growth stimulation was larger for C3 species than for C4 plants. However the difference in growth stimulation is not as large as expected as C4 plants also significantly increased in weight (41% for C3
vs. 22% for C4). The few investigated CAM species were stimulated less in growth (15%) than the average C4 species. Within the group of C3 species, herbaceous crop plants responded more strongly than herbaceous wild species (58%vs. 35%) and potentially fast-growing wild species increased more in weight than slow-growing species (54%vs. 23%). C3 species capable of symbiosis with N2-fixing organisms had higher growth stimulations compared to other C3 species. A common denominator in these 3 groups of more responsive C3 plants might be their large sink strength. Finally, there was some tendency for herbaceous dicots to show a larger response than monocots. Thus, on the basis of this literature compilation, it is concluded that also within the group of C3 species differences exist in the growth response to high CO2.
Recent progress in improving the salt tolerance of cultivated plants has been slow. Physiologists have been unable to define single genes or even specific metabolic processes that molecular biologists could target, or pinpoint the part of the plant in which such genes for salt tolerance might be expressed. While the physiological might be expressed. While the physiological processes are undoubtedly complex, faster progress on unraveling mechanisms of salt tolerance might be made if there were more effort to test hypotheses rather than to accumulate data, and to integrate cellular and whole plant responses. This article argues that salts taken up by the plant do not directly control plant growth by affecting turgor, photosynthesis or the activity of any one enzyme. Rather, the build-up of salt in old leaves hasten their death, and the loss of these leaves affects the supply of assimilates or hormones to the growing regions and thereby affects growth.
Although there is consensus that water use efficiency increases at elevated concentrations of CO2, there are few studies on the interacting effects of elevated CO2 on plant salt tolerance. The objectives of this study were, (1) to determine the effect of ambient and twice ambient concentrations of CO2 on tomato (Lycopersicon esculentum Mill.) responses to salinity; (2) to compare the salt tolerance threshold values based on the classic root zone salinity [J. Irrig. Div. ASCE 103, (1977) 115], or ion flux to the shoot, a measure recently defined as Salinity Stress Index (SSI) by Dalton et al. [Plant Soil 192 (1997) 307; Plant Soil 219 (2000) 1; Plant Soil 229 (2001) 189]. For all salinities, the water use of the twice ambient CO2 treatment was significantly reduced. The effect of twice ambient CO2 was to increase the root zone salinity threshold value from 32 to 51 mmol dm−3 Cl. The threshold SSI value of 1.05 mmol Cl per g shoot DW for the twice ambient CO2 treatment was almost identical to that of the ambient treatment and to those previously obtained when plant growth was modulated by root temperature (SSI=1.19 and 1.10 at 25 and 18 °C, respectively [Plant Soil 192 (1997) 307]) and photosynthetic photon flux density (PPFD) ((SSI=0.97 and 1.10 at 400 and 600 μmol m−2 s−1 PPFD respectively [Plant Soil 229 (2001) 189]). The twice ambient CO2 treatment showed a slightly lower root/shoot ratio (0.138±0.001) than the ambient CO2 treatment (0.156±0.014). Consistent with the predictions of the SSI, leaf chloride per plant and leaf chloride concentration showed significant reduction for the twice ambient CO2 treatment which follows from the supposition that water and salt uptake are linked. Based on the SSI, it was shown that the intrinsic salt tolerance of tomato is invariant to an increase in atmospheric CO2 as has been previously shown for root temperature and solar radiation, while at the same time, the root zone salinity threshold value is dependent on environmental factors.
Relationships between growth and different gas exchange characteristics of two amphidiploid salt tolerant species, Brassica napus, and B. carinata with respect to their salt sensitive parents, B. oleracea, and B. nigra were investigated. Twenty three-day old plants of these four species along with those of another amphidiploid moderately salt tolerant B. juncea (developed by hybridization of diploids, B. campestris and B. nigra), and a diploid moderately salt tolerant, B. campestris, were subjected for 28 days to salinized sand culture containing 0, 100 or 200 mol NaCl m(-3) in Hoagland's nutrient solution. The species B. napus and B. carinata produced significantly greater shoot fresh and dry matters than their parents under saline conditions. A close association was found between growth, and assimilation rate for all species differing in degree of salt tolerance. Stomatal conductance (g(s)) was reduced due to salt stress in all species but this variable had no significant correlation with assimilation rate (A). However, the amphidiploid salt tolerant species, B. napus and B. carinata had significantly greater photosynthetic rate, water use efficiency (A/E), intrinsic water use efficiency (A/g(s)) than those of their diploid parents. In conclusion, high salt tolerance of the two amphidiploid species, B. napus and B. carinata was associated with a high assimilation rate, water use efficiency and intrinsic water use efficiency but there was little association of the tolerance of these species with stomatal conductance, leaf water potential or transpiration rate (E).
The invasion of African grasses into Neotropical savannas has altered savanna composition, structure and function. The projected increase in atmospheric CO(2) concentration has the potential to further alter the competitive relationship between native and invader grasses. The objective of this study was to quantify the responses of two populations of a widespread native C(4) grass (Trachypogon plumosus) and two African C(4) grass invaders (Hyparrhenia rufa and Melinis minutiflora) to high CO(2) concentration interacting with two primary savanna stressors: drought and herbivory. Elevated CO(2) increased the competitive potential of invader grasses in several ways. Germination and seedling size was promoted in introduced grasses. Under high CO(2), the relative growth rate of young introduced grasses was twice that of native grass (0.58 g g(-1) week(-1) vs 0.25 g g(-1) week(-1)). This initial growth advantage was maintained throughout the course of the study. Well-watered and unstressed African grasses also responded more to high CO(2) than did the native grass (biomass increases of 21-47% compared with decreases of 13-51%). Observed higher water and nitrogen use efficiency of invader grasses may aid their establishment and competitive strength in unfertile sites, specially if the climate becomes drier. In addition, high CO(2) promoted lower leaf N content more in the invader grasses. The more intensive land use, predicted to occur in this region, may interact with high CO(2) to favor the African grasses, as they generally recovered faster after simulated herbivory. The superiority of invader grasses under high CO(2) suggests further increases in their competitive strength and a potential increased rate of displacement of the native savannas in the future by grasslands dominated by introduced African species.
Katerji, N., van Hoorn, J.W., Hamdy, A., Bouzid, N., EI-Sayed Mahrous, and Mastrorilli, M., 1992. Effect of salinity on water stress, growth and yield of broadbeans. Broadbeans were grown on clay in tanks and irrigated with water of three different levels of salinity. During the experiment, soil salinity, determined from the salt balance and soil water samples, showed a gradual increase. The water stress of the broadbeans was determined by measuring the predawn leaf water potential, the stomatal conductance and the differences in radiation temperature between the treatments. Growth was measured as leaf area and dry-matter production and, finally, the yield and its components were determined. The three water stress parameters and the two growth parameters showed good coherence, with all parameters indicating systematic differences between the saline treatments and the control. At increasing salinity water potential of the leaf and the stomatal conductance decreased, the difference in
This paper discusses whole-plant responses to salinity in order to answer the question of what process limits growth of non-halophytes in saline soils. Leaf growth is more sensitive to salinity than root growth, so we focus on the process or processes that might limit leaf expansion. Effects of short-term exposure (days) are considered separately from long-term exposure (weeks to years). The answer in the short term is probably the water status of the root and we suggest that a message from the root is regulating leaf expansion. The answer to what limits growth in the long term may be the maximum salt concentration tolerated by the fully expanded leaves of the shoot; if the rate of leaf death approaches the rate of new leaf expansion, the photosynthetic area will eventually become too low to support continued growth.
The comparative responses of photosynthesis and growth to salinity were investigated for two C3 and one C4 species native to the tidal marshes of the San Francisco Bay-Sacramento River estuary of Northern California. At low salinities (0 or 150 meq l-1), where photosynthetic rates were maximal for all species, the C4 grass Spartina foliosa maintained the highest photosynthetic capacity and the C3 stem-succulent shrub Salicornia virginica the lowest; photosynthetic rates of the C3 sedge Scirpus robustus were intermediate. Differences in photosynthetic responses to intercellular CO2 pressure and temperature were consistent with those generally observed between C3 and C4 plants.
CO2 uptake was reduced at salinities above 150 meq l-1 in Scirpus and 300 meq l-1 in Spartina. In contrast, Salicornia exhibited no inhibition of CO2 uptake even at 450 meq l-1 salinity. Analysis of the responses to intercellular CO2 partial pressures showed that the inhibition of photosynthesis by high salinity in both Spartina and Scirpus is primarily accounted for by reduced photosynthetic capacity of the mesophyll, and secondarily, by reduced leaf conductances.
Species differences in relative growth rate (RGR) almost exactly opposed the differences in photosynthetic rates; the highest RGR was found in Salicornia and the lowest in Spartina. This reversal is accounted for by the greater allocation to photosynthetic shoots in Salicornia, which more than compensated for the lower photosynthetic capacity per unit surface area. RGR was more sensitive to salinity than photosynthetic rate in all three species, but the same relative sensitivities held. For Scirpus, reduced leaf elongation rates and changes in allocation patterns account for the greater limitation by salinity of RGR than of photosynthesis, and may be a primary factor restricting productivity of this species in saline habitats.
Gas exchange characteristics were studied in two mangrove species, Aegiceras corniculatum (L.) Blanco and Avicennia marina (Forstk.) Vierh. var australasica (Walp.) Moldenke, grown under a variety of salinity and humidity conditions. The assimilation rate was measured as a function of the intercellular CO(2) concentration [A(c(i)) curve]. The photosynthetic capacity decreased with increase in salinity from 50 to 500 millimolar NaCl, as shown by decline in both the initial linear slope and the upper plateau of the A(c(i)) curve, with A. corniculatum being the more sensitive species. The decline in photosynthetic capacity was enhanced by increase in the leaf to air vapor pressure difference from 6 to 24 millibars, but this treatment caused a decrease in only the upper plateau of the A(c(i)) curve. Stomatal conductance was such that the intercellular CO(2) concentration obtaining under normal atmospheric conditions occurred near the transition between the lower linear and upper plateau portions of the A(c(i)) curves. Thus, stomatal conductance and photosynthetic capacity together co-limited the assimilation rate, which declined with increasing salinity and decreasing humidity. The marginal water cost of carbon assimilation was similar in most treatments, despite variation in the water loss/carbon gain ratio.
Spinach (Spinacia oleracea) plants were subjected to salt stress by adding NaCl to the nutrient solution in increments of 25 millimolar per day to a final concentration of 200 millimolar. Plants were harvested 3 weeks after starting NaCl treatment. Fresh and dry weight of both shoots and roots was decreased more than 50% compared to control plants but the salt-stressed plants appeared healthy and were still actively growing. The salt-stressed plants had much thicker leaves. The salt-treated plants osmotically adjusted to maintain leaf turgor. Leaf K(+) was decreased but Na(+) and Cl(-) were greatly increased.The potential photosynthetic capacity of the leaves was measured at saturating CO(2) to overcome any stomatal limitation. Photosynthesis of salt-stressed plants varied only by about 10% from the controls when expressed on a leaf area or chlorophyll basis. The yield of variable chlorophyll a fluorescence from leaves was not affected by salt stress. Stomatal conductance decreased 70% in response to salt treatment.Uncoupled rates of electron transport by isolated intact chloroplasts and by thylakoids were only 10 to 20% below those for control plants. CO(2)-dependent O(2) evolution was decreased by 20% in chloroplasts isolated from salt-stressed plants. The concentration of K(+) in the chloroplast decreased by 50% in the salt-stressed plants, Na(+) increased by 70%, and Cl(-) increased by less than 20% despite large increases in leaf Na(+) and Cl(-).It is concluded that, for spinach, salt stress does not result in any major decrease in the photosynthetic potential of the leaf. Actual photosynthesis by the plant may be reduced by other factors such as decreased stomatal conductance and decreased leaf area. Effective compartmentation of ions within the cell may prevent the accumulation of inhibitory levels of Na(+) and Cl(-) in the chloroplast.
The sensitivity of stomatal conductance to changes of CO(2) concentration and leaf-air vapor pressure difference (VPD) was compared between two C(3) and two C(4) grass species. There was no evidence that stomata of the C(4) species were more sensitive to CO(2) than stomata of the C(3) species. The sensitivity of stomatal conductance to CO(2) change was linearly proportional to the magnitude of stomatal conductance, as determined by the VPD, the same slope fitting the data for all four species. Similarly, the sensitivity of stomatal conductance to VPD was linearly proportional to the magnitude of stomatal conductance. At small VPD, the ratio of intercellular to ambient CO(2) concentration, C(i)/C(a), was similar in all species (0.8-0.9) but declined with increasing VPD, so that, at large VPD, C(i)/C(a) was 0.7 and 0.5 (approximately) in C(3) and C(4) species, respectively. Transpiration efficiency (net CO(2) assimilation rate/transpiration rate) was larger in the C(4) species than in the C(3) species at current atmospheric CO(2) concentrations, but the relative increase due to high CO(2) was larger in the C(3) than in the C(4) species.
Carbon exchange capacity of cucumber (Cucumis sativus L.) germinated and grown in controlled environment chambers at 1000 microliters per liter CO(2) decreased from the vegetative growth stage to the fruiting stage, during which time capacity of plants grown at 350 microliters per liter increased. Carbon exchange rates (CERs) measured under growth conditions during the fruiting period were, in fact, lower in plants grown at 1000 microliters per liter CO(2) than those grown at 350. Progressive decreases in CERs in 1000 microliters per liter plants were associated with decreasing stomatal conductances and activities of ribulose bisphosphate carboxylase and carbonic anhydrase. Leaf starch concentrations were higher in 1000 microliters per liter CO(2) grown-plants than in 350 microliters per liter grown plants but calcium and nitrogen concentrations were lower, the greatest difference occurring at flowering. Sucrose synthase and sucrose-P-synthase activities were similar in 1000 microliters per liter compared to 350 microliters per liter plants during vegetative growth and flowering but higher in 350 microliters per liter plants at fruiting. The decreased carbon exchange rates observed in this cultivar at 1000 microliters per liter CO(2) could explain the lack of any yield increase (MM Peet 1986 Plant Physiol 80: 59-62) when compared with plants grown at 350 microliters per liter.
In the spring of 1969 a small meeting was convened at the CSIRO Riverina Laboratory, Deniliquin, New South Wales, to discuss the biology of the genus Atriplex, a group of plants considered by those who attended to be of profound importance both in relation to range management in the region and as a tool in physiological research. The brief report of this meeting (Jones, 1970) now serves as a marker for the subsequent remarkable increase in research on this genus, and served then to interest the editors of the Ecological Studies Series in the present volume. This was an exciting time in plant physiology, particularly in the areas of ion absorption and photosynthesis, and unknowingly several laboratories were engaged in parallel studies of these processes using the genus Atriplex. It was also a time at which it seemed that numerical methods in plant ecology could be used to delineate significant processes in arid shrubland ecosystems. Nevertheless, to presume to illustrate and integrate plant physiology and ecology using examples from a single genus was to presume much. The deficiencies which became increasingly apparent during the preparation of the present book were responsible for much new research described in these pages.
The earth’s atmosphere and biosphere evolved together over time, the one affecting the other, such that the composition of the atmosphere was strongly influenced by the exchange of gases among them, lithosphere, and hydrosphere. Green plants, through photosynthesis and respiration, have had significant influence on the carbon dioxide, oxygen, and water budgets of the atmosphere.
Small greenhouses were used in the arctic to maintain Erioporum vaginatum-dominated tussock tundra for 10 wk at ambient CO"2 (340 @mL/L), elevated CO"2 (510 or 680 @mL/L), or elevated CO"2 and 4@?C above ambient temperature (680 @mL/L, ambient + 4@?). These treatments represent present levels of atmospheric CO"2 and temperature, and those predicted for the next century. Within 3 wk, plants maintained at elevated CO"2 exhibited a physiological adjustment of their photosynthetic rate so that plants grown at ambient and elevated CO"2 levels had similar photosynthetic rates at their respective growth CO"2 concentrations. The reduction in photosynthetic capacity for plants grown at elevated CO"2 levels did not appear to be due to stomatal closure or end-product inhibition. Other possible mechanisms were not explored. Transpiration rates and water use efficiency did not differ among treatments in the generally wet environment of tussock tundra. Relative leaf growth rate and the seasonal pattern of growth were also unaltered, suggesting that the growth of mature tillers is not, under normal ambient conditions, limited by temperature or carbohydrate. However, new tiller production was significantly increased at elevated CO"2, suggesting that the long-term effect of CO"2 enhancement in this sedge may be the production of a greater number of new tillers rather than an increase in the size or productivity of existing tillers. Our results are consistent with the notion that growth of Eriophorum vaginatum in the field is more limited by nutrient supply than by photosynthesis. We further suggest that photosynthetic rates reflect the sink activity. It is therefore very difficult to assign cause and effect between growth rates and photosynthetic rates.
The effect of long-term exposure to elevated levels of CO2 on biomass partitioning, net photosynthesis and starch metabolism was examined in cotton. Plants were grown under controlled conditions at 350, 675 and 1000 μl l(-1) CO2. Plants grown at 675 and 1000 μl l(-1) had 72% and 115% more dry weight respectively than plants grown at 350 μl l(-1). Increases in weight were partially due to corresponding increases in leaf starch. CO2 enrichment also caused a decrease in chlorophyll concentration and a change in the chlorophyll a/b ratio. High CO2 grown plants had lower photosynthetic capacity than 350 μl l(-1) grown plants when measured at each CO2 concentration. Reduced photosynthetic rates were correlated with high internal (non-stomatal) resistances and higher starch levels. It is suggested that carbohydrate accumulation causes a decline in photosynthesis by feedback inhibition and/or physical damage at the chloroplast level.
A series of experiments is presented investigating short term and long term changes of the nature of the response of rate of CO2 assimilation to intercellular p(CO2). The relationships between CO2 assimilation rate and biochemical components of leaf photosynthesis, such as ribulose-bisphosphate (RuP2) carboxylase-oxygenase activity and electron transport capacity are examined and related to current theory of CO2 assimilation in leaves of C3 species. It was found that the response of the rate of CO2 assimilation to irradiance, partial pressure of O2, p(O2), and temperature was different at low and high intercellular p(CO2), suggesting that CO2 assimilation rate is governed by different processes at low and high intercellular p(CO2). In longer term changes in CO2 assimilation rate, induced by different growth conditions, the initial slope of the response of CO2 assimilation rate to intercellular p(CO2) could be correlated to in vitro measurements of RuP2 carboxylase activity. Also, CO2 assimilation rate at high p(CO2) could be correlated to in vitro measurements of electron transport rate. These results are consistent with the hypothesis that CO2 assimilation rate is limited by the RuP2 saturated rate of the RuP2 carboxylase-oxygenase at low intercellular p(CO2) and by the rate allowed by RuP2 regeneration capacity at high intercellular p(CO2).
Phaseolus vulgaris (cv. Hawkesbury Wonder) was grown over a range of NaCl concentrations (0–150 mM), and the effects on growth, ion relations and photosynthetic performance were examined. Dry and fresh weight decreased with increasing external NaCl concentration while the root/shoot ratio increased. The Cl- concentration of leaf tissue increased linearly with increasing external NaCl concentration, as did K+ concentration, although to a lesser degree. Increases in leaf Na+ concentration occurred only at the higher external NaCl concentrations (≧100 mM). Increases in leaf Cl- were primarily balanced by increases in K+ and Na+. X-ray microanalysis of leaf cells from salinized plants showed that Cl- concentration was high in both the cell vacuole and chloroplast-cytoplasm (250–300 mM in both compartments for the most stressed plants), indicating a lack of effective intracellular ion compartmentation in this species. Salinity had little effect on the total nitrogen and ribulose-1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) content per unit leaf area. Chlorophyll per unit leaf area was reduced considerably by salt stress, however. Stomatal conductance declined substantially with salt stress such that the intercellular CO2 concentration (C
i) was reduced by up to 30%. Salinization of plants was found to alter the δ13C value of leaves of Phaseolus by up to 5‰ and this change agreed quantitatively with that predicted by the theory relating carbon-isotope fractionation to the corresponding measured intercellular CO2 concentration. Salt stress also brought about a reduction in photosynthetic CO2 fixation independent of altered diffusional limitations. The initial slope of the photosynthesis versus C
i response declined with salinity stress, indicating that the apparent in-vivo activity of RuBP carboxylase was decreased by up to 40% at high leaf Cl- concentrations. The quantum yield for net CO2 uptake was also reduced by salt stress.
Water status and growth responses of wheat (Triticum aestivuum L. (GWO-1809)) to increased COâ concentration and water stress were studied in controlled-environment chambers. Plants were grown in 350 ..mu..l/liter or 1000 ..mu..1/liter COâ at similar temperature, irradiance, and photoperiod conditions. Groups of plants were subjected to water stress by withholding irrigation for one or two cycles of treatment. In most treatments, decreasing leaf water potential was correlated with decreasing osmotic potential. In leaves grown in both low and high COâ concentrations, the osmotic potentials were lower during the second stress cycle than during the first cycle. The stomata of plants in the low COâ concentration closed at a higher leaf water potential than those in the high COâ concentration. Stem and head production was greater in plants grown in high COâ concentrations than those grown in low COâ, perhaps the result of turgor-pressure maintenance as leaf water potential decreased. In controlled-environment chambers, wheat plants adapted to water stress, apparently because of high COâ concentration and repeated stress cycles.
The limitations on carbon dioxide assimilation by plants caused by stomata, particularly when the plant is under stress, are discussed. Mechanisms by which stomatal movement is integrated with photosynthesic requirements are described.
Three parameters influencing the capacity for carbon accumulation, i.e. photosynthesis, respiration, and leaf extension growth, were studied in Beta vulgaris L. (sugar beet) cultured in nutrient solution containing 0.5 to 500 mol m−3 NaCl. Leaf extension growth was the parameter most sensitive to salinity: the initial rate of leaf extension and final leaf length each declined linearly with increase in external NaCl concentration. Photosynthetic O2 evolution of thin leaf slices did not decline until salinity levels reached 350 to 500 mol m−3 NaCl, while respiratory O2 consumption was not affected by salinity throughout the range. The results suggest that the influence of salinity on the capacity for carbon accumulation in B. vulgaris occurs primarily through reduction in the area of photosynthetic surface.
Plants of the salt marsh grass Spartina alterniflora Loisel were collected from North Carolina and grown under controlled nutrient, temperature, and photoperiod conditions. Plants were grown at two different illumination levels; substrate salinity was varied, and leaf photosynthesis, transpiration, total chlorophyll, leaf xylem pressure, and specific leaf weight were measured. Conditions were controlled so that gaseous and liquid phase resistances to CO2 diffusion could be calculated. Growth at low illumination and high salinity (30 ppt) resulted in a 50% reduction in photosynthesis. The reduction in photosynthesis of plants grown at low illumination was correlated with an increase in gaseous resistance. Photosynthetic rates of plants grown at high salinity and high illumination were reduced only slightly compared to rates of plants grown, in 10 ppt and Hoagland's solution. Both high salinity and high illumination were correlated with increases in specific leaf weight. Chlorophyll data indicate that specific leaf weight differences were the result of increases in leaf thickness. It is therefore hypothesized that photosynthetic response can be strongly influenced by salinity-induced changes in leaf structure. Similarities in photosynthetic rate on an area basis at high, illumination were apparently the result, of increases in leaf thickness at high salinity. Photosynthetic rates were generally quite high, even at salinities close to open ocean water, and it is concluded that salinity rarely limits photosynthesis in S. alterniflora.
In the first part of this review the main features of salt tolerance in higher plants are discussed. The hypothesis of intracellular compartmentation of solutes is used as a basis for models of tolerance mechanisms operating in roots and in leaves. Consideration is given to the implications of the various mechanisms for the yield potential of salt-tolerant crop plants.
Some work on the more salt-tolerant members of the Triticeae is then described. The perennial species Elytrigia juncea and Leymus sabulosus survive prolonged exposure to 250 mol m−3 NaCl, whereas the annual Triticum species are severely affected at only 100mol m−3 NaCl. In the perennial species the tissue ion levels are controlled within narrow limits. In contrast, the more susceptible wheats accumulate far more sodium and chloride than is needed for osmotic adjustment, and the effects of salt stress increase with time of exposure.
Two different types of salt tolerance are exhibited in plants capable of growing at high salinities. In succulent Chenopodiaceae, for example, osmotic adjustment is achieved mainly by accumulation of high levels of sodium and chloride in the shoots, accompanied by synthesis of substantial amounts of the compatible solute glycinebetaine. This combination of mechanisms allows high growth rates, in terms of both fresh and dry weight. At the opposite end of the spectrum of salt tolerance responses are the halophytic grasses, which strictly limit the influx of salts into the shoots, but suffer from very much reduced growth rates under saline conditions. Another variation is shown in those species that possess salt glands. The development and exploitation of crop plants for use on saline soils is discussed in relation to the implications of these various mechanisms.
The effect on plant growth of doubling the normal aerial CO2 content was studied in lucerne, faba bean, perennial ryegrass, wheat, maize, poplar and potato. Because nutrients often limit growth, the effect of CO2 under N or P shortage was also studied. Doubling CO2 had the largest effect on DM yield with a good nutrient supply, but with N shortage part of the CO2 effect was retained even in non-leguminous spp. Except for faba bean, no CO2 effect existed with P shortage. Maize showed a small positive CO2 reaction under good nutrient supply but a negative one with nutrient shortage. Potato showed a small negative reaction to CO2 enrichment. (Abstract retrieved from CAB Abstracts by CABI’s permission)
Typescript. Thesis (M.S.)--Duke University, 1985. Includes bibliographical references (leaves 49-52).
Plants of the C3 species Phaseolus vulgaris and Xanthium strumarium and of the C4 salt-sensitive Zea mays and the C4 halophyte Atriplex halimus were grown with and without NaCl salt-stress at normal (∼340 μl I−1) and at high (∼2500 μl I−1) ambient CO2. In all four species growth (dry weight increment) was enhanced by CO2 supplementation. The relative response was greater in the salinized than in the control plants. Plant tops responded more
to CO, than the roots. CO2 supplementation appears to increase plant tolerance of low levels of salinity.
Physiological effects. In CO and Plants, the Respotise of Platits to Rising Leyels of Atmospheric Carbon Dioxide
- R W Pearcy
- O Bjorkman
Pearcy, R.W. & Bjorkman, O. (1983) Physiological effects. In CO and Plants, the Respotise of Platits to Rising Leyels of Atmospheric Carbon Dioxide (ed. E. R. Lemon), pp. 65-105 AAAS selected symposium 84, Westview Press, Boulder Colorado.
The effects of carbon dioxide enrichment on two C4grassland species
- G H Riechers
Riechers, G.H. (1983) The eflects of carbon dioxide enrichment on two C4 grassland species. Ph.D. thesis. Duke University.
C (1987) Physiological and growth response of Eriophorum vagittatwn to elevated COj and temperature in the Alaskan tundra
- D T Tissue
- W Oeehel
Tissue, D.T. & Oeehel, W.C (1987) Physiological and growth response of Eriophorum vagittatwn to elevated COj and temperature in the Alaskan tundra. Ecology (in press).
Plant growth and development. Iti CO, and Plants. The Respon.se of Plants to STRAIN Rising Leyels of Atmospheric Carbon Dioxide Photosynthetic and stomatal response of two mangrove species, Aegiceras corniculatum and Avicennia tnaritia, to long term salinity and humidity eonditions
- D N Baker
- H Z W D Enoch
- B R Bowman
Baker, D.N. & Enoch, H.Z. (1983) Plant growth and development. Iti CO, and Plants. The Respon.se of Plants to W. D. BOWMAN & B. R. STRAIN Rising Leyels of Atmospheric Carbon Dioxide (ed. E. R. Lemon). pp. 107-130. AAAS select symposium 84, Westview Press, Boulder, Colorado. Ball, M.C. & Farquhar, G.D. (1984) Photosynthetic and stomatal response of two mangrove species, Aegiceras corniculatum and Avicennia tnaritia, to long term salinity and humidity eonditions. Plant Physiology, 74, 1-6.
Atmospheric carbon dioxide in the 19th eentury Chemical analyses of plant tissues from the Hubbard Brook ecosystem in New Hampshire Effects of sahnity and illumination on photosynthesis and water balanee of Spctrtina atterniftora Loisel
- Cd Keeling
- G E Likens
- F H Bormann
Keeling, CD. (1978) Atmospheric carbon dioxide in the 19th eentury. Science, 202, 1109. Likens, G.E. & Bormann, F.H. (1970) Chemical analyses of plant tissues from the Hubbard Brook ecosystem in New Hampshire. Buttetin 74, Yale School of Forestry, New Haven, Connecticut. Longstreth. D.J. & Strain, B.R. (1977) Effects of sahnity and illumination on photosynthesis and water balanee of Spctrtina atterniftora Loisel. Oecotogia, 31, 191-199.
Plant growth and development In CO2 anil Plants. The Response of Plants to Rising Levels of Atmospheric Carbon Dioxide
- D M Baker
- U Z Enoch
Chemical analyses of plant tissues from the Hubbard Brook ecosystem in New Hampshire
- G E Likens