Content uploaded by Theodore W. Tibbitts
Author content
All content in this area was uploaded by Theodore W. Tibbitts
Content may be subject to copyright.
Humidity and Plants
Abstract
Humidity levels control directly the rate of transpirational water loss and stomatal aperture of plants. Thus, humidity regulates photosynthetic rates, tissue temperatures, plant water potentials, and concentrations of Ca in certain tissues. Humidity also controls water taken in by tissues through condensation and direct vapor uptake.
... Numerous more recent reports showed that several herbaceous and woody plant species tended to close their stomata in response to dry air whether within a plant community or in attached leaves or isolated epidermal strips (e.g. Hoffman and Rawlins 1971, Hoffman et al. 1971, Lange et al. 1971, Schulze et al. 1972, Aston 1976, Hall and Hoffman 1976, Rawson et al. 1977, Sheriff and Kaye 1977, Lösch 1977, 1979, Lösch and Schenk 1978, Tibbitts 1979, Ludlow and Ibaraki 1979, Lösch and Tenhunen 1981, Farquhar et al. 1980, Jarvis 1980, Tazaki et al. 1980, Hall and Schulze 1980, Bunce 1981, 1982, 1984, Leverenz 1981, Fanjul and Jones 1982, Meinzer 1982, Kaufmann 1982, Schulze and Hall 1982, Gollan et al. 1985, Körner 1985, Körner and Bannister 1985, Schulze 1986, Jarvis and McNaughton 1986, Ward and Bunce 1986, Bongi et al. 1987, Hirasawa et al. 1988, Pettigrew et al. 1990, Held 1991, Kappen and Haeger 1991, Tinoco-Ojanguren and Pearcy 1993). This apparently widespread phenomenon indicated the need for further detailed studies, and for its inclusion in plant community/environment ecosystem models (Jarvis and McNaughton 1986). ...
The review sums up research conducted at CIAT within a multidiscipline effort revolving around a strategy for developing improved technologies to increase and sustain cassava productivity, as well as conserving natural resources in the various eco-edaphic zones where the crop is grown, with emphasis on stressful environments. Field research has elucidated several physiological plant mechanisms underlying potentially high productivity under favourable hot-humid environments in the tropics. Most notable is cassava inherent high capacity to assimilate carbon in near optimum environments that correlates with both biological productivity and root yield across a wide range of germplasm grown in diverse environments. Cassava leaves possess elevated activities of the C4 phosphoenolpyruvate carboxylase (PEPC) that also correlate with leaf net photosynthetic rate (P
N) in field-grown plants, indicating the importance of selection for high P
N. Under certain conditions such leaves exhibit an interesting photosynthetic C3-C4 intermediate behaviour which may have important implications in future selection efforts. In addition to leaf P
N, yield is correlated with seasonal mean leaf area index (i.e. leaf area duration, LAD). Under prolonged water shortages in seasonally dry and semiarid zones, the crop, once established, tolerates stress and produces reasonably well compared to other food crops (e.g. in semiarid environments with less than 700 mm of annual rain, improved cultivars can yield over 3 t ha−1 oven-dried storage roots). The underlying mechanisms for such tolerance include stomatal sensitivity to atmospheric and edaphic water deficits, coupled with deep rooting capacities that prevent severe leaf dehydration, i.e. stress avoidance mechanisms, and reduced leaf canopy with reasonable photosynthesis over the leaf life span. Another stress-mitigating plant trait is the capacity to recover from stress, once water is available, by forming new leaves with even higher P
N, compared to those in nonstressed crops. Under extended stress, reductions are larger in shoot biomass than in storage root, resulting in higher harvest indices. Cassava conserves water by slowly depleting available water from deep soil layers, leading to higher seasonal crop water-use and nutrient-use efficiencies. In dry environments LAD and resistance to pests and diseases are critical for sustainable yields. In semiarid zones the crop survives but requires a second wet cycle to achieve high yields and high dry matter contents in storage roots. Selection and breeding for early bulking and for medium/short-stemmed cultivars is advantageous under semiarid conditions. When grown in cooler zones such as in tropical high altitudes and in low-land sub-tropics, leaf P
N is greatly reduced and growth is slower. Thus, the crop requires longer period for a reasonable productivity. There is a need to select and breed for more cold-tolerant genotypes. Selection of parental materials for tolerance to water stress and infertile soils has resulted in breeding improved germplasm adapted to both favourable and stressful environments.
Examining the cues and drivers influencing seed production is crucial to better understand forest resilience to climate change. We explored the effects of five climatic variables on seed production over 22 years in an everwet Amazonian forest, by separating direct effects of these variables from indirect effects mediated through flower production. We observed a decline in seed production over the study period, which was primarily explained by direct effects of rising nighttime temperatures and declining average vapour pressure deficits. Higher daytime temperatures were positively related to seed output, mainly through a flower‐mediated effect, while rainfall effects on seed production were more nuanced, showing either positive or negative relationships depending on the seasonal timing of rains. If these trends continue, they are likely to lead to significant changes in forest dynamics, potentially impacting both forest structure and species composition.
The increase of the global population, climate change and the scarcity of resources are some of the reasons why the improvement of the agricultural sector has become a crucial issue for the future of our society. Recently, the growth of Internet of Things (IoT) has meant a revolution in many industries, including the agricultural sector, where the employment of this technology is considered the ideal formula to boost crop efficiency. In this work, a complete high performance IoT solution consisting of an innovative printed smart radio frequency identification (RFID) tag and an autonomous measuring system based on a robot is demonstrated for soil monitoring purposes. The smart RFID tags are employed to obtain soil parameters, crucial for the correct development of the crops: humidity, oxygen concentration and temperature. The tag is novelly developed on a humidity dependent and flexible transparent foil as substrate. The former feature is to directly extract the value of the relative humidity (RH) by a capacitive structure defined on the substrate while the latter characteristic is to allow the sensing of the oxygen content via a membrane whose luminescence intensity changes with the influence of this parameter. Effects on the antenna response are measured when the tag is placed in soil environment at root depth to validate the excellent sensing behaviour of the tag. Finally, to take the work a step further and in order to show the promising performance of the tags as part of a monitoring system in the field of smart agriculture, we design a robot equipped with an UHF reader and IoT features, capable of automating the finding and reading of the designed RFID tags. This robot sends the information via internet for its further processing, thus constituting a low-cost, large-scale and environmentally friendly solution, ideal for enhancing crops performance.
Understanding phenological responses of tropical forest plant communities is crucial for identifying climate-induced changes in ecosystem dynamics. Monitoring phenology across diverse species in natural habitats provides cost-effective insights for conserving both species and forests. We studied tree phenology in a lowland evergreen dipterocarp forest in the Western Ghats, India. About 719 tree individuals representing 95 species were monitored for their vegetative and reproductive phenology from April 2021 to September 2023. Circular statistics detected seasonality in phenological events and Generalized Linear Mixed Modelling (GLMM) identified influence of climate variables on the phenological responses of the tree community. We also assessed how the activity and intensity of phenophases vary over the study period. Our results showed that leaf flushing and flowering peaked during the dry season, with mass flowering observed in two dominant dipterocarps. Fruit production peaked before the monsoon. We also observed diversity in vegetative and reproductive phenodynamics across species groups (forest strata, sexual system, and seed size). Leaf flushing was positively correlated with maximum relative humidity and negatively correlated with maximum temperature and the number of rainy days. Flowering had negative correlations with maximum relative humidity, rainfall days, and maximum temperature but showed a positive correlation with minimum temperature. Fruiting was positively correlated with maximum temperature and negatively correlated with rainy days. This detailed phenological information provides critical knowledge on resource availability and insights into how climate and seasonal changes affect plant growth cycles thereby aiding reforestation and biodiversity conservation strategies in vulnerable forest areas.
The present study attempted to quantify and value of supporting services of India's forest ecosystem. The supporting services comprises by habitat and biodiversity services across India's sixteen forest types was estimated using data for various factors through Remote Sensing and secondary sources as per the proposed model. Indicators were combined using an Analytical Hierarchical Process, and various class of each service was also estimated using the equal interval method in QGIS. Hotspot analysis was used to identify key areas for forest conservation. The results suggest that littoral and swamp forest had maximum habitat services and tropical semi-evergreen forest had maximum biodiversity service and tropical wet evergreen forest had maximum supporting services. Out of total forest of country, 11.52%, 17.48% and 10.34% forest area was having high value for habitat, biodiversity and supporting service, respectively. Hotspot analysis revealed that 22.93%, 23.61% and 26.44% Indian forest had high habitat, biodiversity and supporting service, respectively.
Gene editing tools for banana crop improvement necessitates efficient embryogenic cell suspensions, which are derived through embryogenic calli (EC). Although many factors are known to influence EC formation, the roles of seasonal effects and environmental factors in EC induction of banana remain unclear. We therefore examined the formation of EC from immature male flower buds (IMFB) collected in each month of the years 2020 and 2022. Among 12 batches examined, IMFB initiated between January and April produced the highest percentage of EC in both years. In 2020, the percent of EC ranges from 8.22 to 12.14, whereas in 2022 the EC percentage ranges from 2.50 to 4.47. IMFB initiated from May to August produced moderate response and those initiated between September and December gave the lowest percentage of EC in both the years. Plants that generated highest percentage of EC underwent transition from vegetative to reproductive phase in autumn and flowered in winter. During this period, environmental factors such as global radiation, relative humidity and temperature were relatively low compared to summer. In contrast, plants that underwent vegetative–reproductive transition under extreme summer conditions and flowered at the end of summer and autumn yielded lowest percentage of EC. Exposure to high temperature and radiation during this period might have altered inflorescence development. Our results indicate that seasonal alterations in environmental factors influence the rate of EC induction.
Climate models predict that everwet western Amazonian forests will face warmer and wetter atmospheric conditions, and increased cloud cover. It remains unclear how these changes will impact plant reproductive performance, such as flowering, which plays a central role in sustaining food webs and forest regeneration. Warmer and wetter nights may cause reduced flower production, via increased dark respiration rates or alteration in the reliability of flowering cue‐based processes. Additionally, more persistent cloud cover should reduce the amounts of solar irradiance, which could limit flower production.
We tested whether interannual variation in flower production has changed in response to fluctuations in irradiance, rainfall, temperature, and relative humidity over 18 yrs in an everwet forest in Ecuador.
Analyses of 184 plant species showed that flower production declined as nighttime temperature and relative humidity increased, suggesting that warmer nights and greater atmospheric water saturation negatively impacted reproduction. Species varied in their flowering responses to climatic variables but this variation was not explained by life form or phylogeny.
Our results shed light on how plant communities will respond to climatic changes in this everwet region, in which the impacts of these changes have been poorly studied compared with more seasonal Neotropical areas.
Background: Djulis (Chenopodium formosanum Koidz.) is a nutrient-rich plant with potential health benefits, but its intensive fertilization hinders its yield, raising environmental concerns. Biofertilizers like purple non-sulfur bacteria (PNSB) offer an eco-friendly alternative to enhance growth and yield, yet limited research has investigated their efficacy on different crop lines or varieties. Therefore, the current study aimed to investigate PNSB's effectiveness on two djulis lines in two fields, one control and the other inoculated with PNSB.
Methods: Data on the growth and yield of djulis lines were collected, and the results were statistically analyzed using independent sample t-tests and Duncan's multiple-range test.
Results: The results showed that PNSB inoculation in the red line led to a significant increase in plant height (24%), leaf chlorophyll content (15%), spike length (35%), spike fresh weight (94%), shoot dry weight (207%), grain yield (86%), root length (119%), root volume (100%), and root dry weight (23%). As in the yellow line, PNSB inoculation significantly increased plant height (14%), spike length (26%), spike fresh weight (43%), shoot dry weight (53%), root length (36%), root volume (72%), and root dry weight (24%). Inoculation of PNSB had opposite effects on the maturity period of red and yellow djulis lines. It significantly improved the yield of the low-performing red line but had only minor effects on the high-performing yellow line, indicating the importance of selecting suitable lines.
Conclusion: This study highlights PNSB's potential as a sustainable and cost-effective biofertilizer for djulis production, bolstering both food security and agricultural productivity.
The humidity of the atmosphere profoundly affects every aspect of morphogenesis and the practical importance of this has provided the impetus for extensive research, particularly in agriculture. Maximov’s (13) excellent monograph delineates the effects of various moisture regimes on growth, structure and composition of crop plants, and Wangerman’s (23) review focuses on effects of water supply and humidity on plants which can regulate their water content and those which cannot. These and other reviewers have been quick to point out that effects of relative humidity are frequently confounded by interrelationships with other factors, including particularly temperature, light and soil moisture. Thus the analysis of morphological and histochemical effects of atmospheric humidity per se is frequently difficult.
Calcium is the fifth most abundant element in the earth’s crust, accounting for more than 3% of its composition. The exchangeable Ca content of a “normal” soil ranges from 65 to 85% of its total exchange capacity (12). Leaves of dicotyledonous plants generally contain from 0.5 to 5.5% Ca on a dry weight basis (44). The aboveground woody portions of trees in a 36-year-old apple orchard (35 trees per acre) contain about 200 lb. of Ca/acre as compared to about 175 lb. of all other nutrient elements combined (98). Recognizable foliar symptoms of Ca deficiency are seldom observed on field-grown fruit or vegetable crops. Despite these facts, serious economic losses occur annually from physiological disorders resulting from an inadequate level of Ca in the fruits, storage roots, or tubers of many plants or to the heart leaves of cabbage, lettuce, and other compact leafy vegetables.
Foliar sprays of Ca(NO 3 ) 2 or CaCl 2 completely controlled lettuce tipburn in the variety ‘Meikoningen’ when directed to susceptible immature leaves. Analysis of treated and untreated plants showed that treatment markedly increased the Ca content of tipburn susceptible leaves and revealed a 5-fold increase in Ca content as one progressed from immature heart leaves to mature basal leaves in untreated plants. Foliar sprays of organic acid salts, particularly oxalate, accelerated the development of tipburn and increased its severity. When Ca and oxalate treatments were alternated, application of Ca at the beginning of the dark period and oxalate in the morning resulted in markedly less tipburn than application of these sprays in the reverse order.
‘Thaxter’ and ‘Fordhook 242’ lima bean ( Phaseolus lunatus L.) cultivars were subjected to climatic variables in controlled-environment cabinets to determine conditions which were adverse to their reproduction. High night temperature promoted flower opening but was deleterious to pod set and retention. High humidity increased pod set and retention, apparently by promoting good pollen germination. High humidity, however, was unfavorable when it was combined with high temperature. Low night temperature was unfavorable when it was combined with low humidity. The most favorable environment for pod set and retention consisted of high humidity, low night temperature, and high soil moisture. ‘Fordhook 242’ set and retained fewer pods under environmental stress than ‘Thaxter’.
The influence of atmospheric moisture levels of 85% and 50% relative humidity (RH) (3.5 and 11.6 mb saturation vapor deficit respectively) at 20°C for 16:8 long day (LD) cycle on butterhead lettuce, ( Lactuca sativa L. cv. Meikoningen), during a growth period of 4 weeks from seeding, was studied in organic soil and liquid cultures. Significantly faster growth rates were evident on plants developing under 85% RH than under 50% in both soil and liquid culture with the largest increases occurring with plants grown in soil culture. The higher humidity level increased leaf number 15%, leaf size 30%, dry weights 62%, and leaf water contents from 93% to 94%. The differences in leaf number and dry weight equalled about 2 days growth difference at 4 weeks after seeding. The density of stomata was greater on plants grown under 50% RH but the total number of stomata per leaf under the 2 humidity levels was the same. The leaf resistance was significantly higher on plants grown under 50% than under 85% RH. The principle significance of high humidity level during growth of lettuce is the production of larger marketable heads with a higher water content in a slighly reduced period of time.
Experiments with Prunus armeniaca were carried out under conditions of constant temperature but varying air humidity. Experiments were also contucted with a constant water vapor difference between the evaporating sites in a leaf and the air, but with varying leaf temperature. These served as a basis for predicting the daily course of total diffusion resistance under the natural climatic conditions of a desert. For the simulation, the rsults of the experiments at constant conditions with only one variable factor are fitted with empirical equations which serve as "calibration curves" to predict the change in diffusion resistance caused by a change in humidity and temperature calculated from the meteorological data of a desert day. The simulation shows that for P. armeniaca humidity and temperature are the dominating factors in controlling the daily course of diffusion resistance. For meteorologically very different days the simulation allows the increase in diffusion resistance in the morning to be predicted with an accuracy of 90%-105% as compared to directly observed measurements. In the afternoon, especially after extreme climatic conditions during the morning, the deviation between predicted and observed values of diffusion resistance may be greater, but not more than -20% to -30%. This possibly indicates the existence of an additional factor of significance which was not included in the simulation. The two peaked curves of net photosynthesis and transpiration characteristic of plants living under arid conditions can be explained in this species by the humidity-and temperature-controlled stomatal response. This stomatal regulation leads to a decreasing total daily transpirational water loss on a dry day as compared to a moist one. The significance of this controlling mechanism for the primary production and the water relations of P. armeniaca is discussed.
Many investigations have been made on transpiration and photosynthesis of plants. However, the relationship between transpiration and photosynthesis has not been completely estabilished. The study reported here was planned to elucidate the effect of transpiration on the apparent photosynthesis and the relation of temperature and photosynthesis in several crops: sweet potato, rice, soybean and peanut. 1) Experiments were conducted outdoors under full sunlight using an apparatus which has a humidity-controlling system (Fig. 1). In early growth stage, photosynthesis was not affected by restraint of the transpiration caused by increasing humidity in the chamber, but in late growth stage a marked increase of photosynthetic rates occurred by restraining the transpiration (Figs. 2-5). These results suggest that water supply from root to the photosynthetic organ turns insufficient in the late growth stage. 2) Fig. 6 and Fig. 7 indicate the relation of leaf temperature and photosynthesis in sweet potato and soybean plant at various growth stages. In early growth stage, apparent photosynthesis was insensible of high temperature from 30 to 40°C. In late growth stage, however, apparent photosynthetic rates showed a rapid decrease at high-temperature range. These phenomena were also recognized in other crops, e.g., rice and peanut. From results of the investigation for the stomatal opening and fluctuation of water level in sweet potato leaves under various temperature condition, it may be concluded that depression of photosynthetic rate at high-temperature range was due to a deficit of water content and high stomatal resistance in leaf. 3) In the series of experiments as shown in Figs. 2-5, water vapour transfer coefficient (D) was calculated for several crops from the equation presented in the note of Fig. 9. There was a close relationship between the transpiration and the ‘D’ value. The ‘D’ values, selected under approximately constant conditions with leaf temperature of 35°C and air volume passing through a chamber of 8-11 m³/hr, showed high correlations to photosynthetic rates in three crops except soybean plant (Fig. 10). The ‘D’ value is a reciprocal of diffusion resistance(r) which can be divided into two components: (i) resistance in external air during diffusion away from leaf(ra), and (ii) resistance through the stomata(rs). It is considered that the ‘D’ mainly depends on 1/rs in the case of Fig. 10. Accordingly, when photosynthetic rate is high at high leaf temperature, stomata are widely open. 4) Two factors, total sugar content in root and the ratio of root dry weight (R) to leaf area (F), must be concerned with the water supply from root to photosynthetic organ. Therefore, both factors, whose changes with time are shown in Fig. 14, would be correlated to the ‘D’ values of each growth stage.