[Show abstract][Hide abstract] ABSTRACT: Fresh-cut produce represents a good method to save about the 25% of kiwifruit not useful to meet the fresh fruit-marketing standard due to improper size and shape. For that reason, fresh-cut kiwifruit has been extensively studied. However, the comprehension of the influence of some aspect of cultivation might further increase the shelf life as well as the nutritional values of that fruit. Here, we explored the hypothesis that fully-exposed or partially-shaded grown kiwifruit differently perform upon storage as whole fruit and as minimally-processed produce. Flesh firmness (FF), total solids soluble (SSC), ascorbate (AAT), flavonoids (TFO) and phenols (TF) content were evaluated in sliced and whole fruit upon 3 d of storage at 4° C after 75 d of cold chamber storage at 0° C. The activity of two enzymes related to the softening process, polygalacturonase (PG) and pectinmethylesterase (PME), was evaluated as well. FF and SSC were constitutively higher in sun-exposed fruit and those characteristics remained higher during the storage as whole fruit. Greater constitutive content of AAT, TFO and TP was found in sun-exposed whole fruit although after cutting the reduction on their content was significantly lower in shade fruits. PME and PG activity were higher only in whole shade fruits while no relevant differences occurred after cutting. In few words, sun-exposed fruits resulted better suitable for fresh-fruit market, while the shade counterpart denoted a good predisposition to be used as fresh-cut produce, maintaining similar fruit maturity properties, but higher nutraceutical values when sliced than fruit grown under full sun.
Journal of Agricultural and Food Chemistry 04/2014; · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The putative photoprotective role of foliar anthocyanins continues to attract heated debate. Strikingly different experimental set-ups coupled with a poor knowledge of anthocyanin identity have likely contributed to such disparate opinions. Here, the photosynthetic responses to 30% or 100% solar irradiance were compared in two cultivars of basil, the green-leafed Tigullio (TG) and the purple-leafed Red Rubin (RR). Coumaroyl anthocyanins in RR leaf epidermis significantly mitigated the effects of high light stress. In full sunlight, RR leaves displayed several shade-plant traits; they transferred less energy than did TG to PSII, and non-photochemical quenching was lower. The higher xanthophyll cycle activity in TG was insufficient to prevent inactivation of PSII in full sunlight. However, TG was the more efficient in the shade; RR was far less able to accommodate a large change in irradiance. Investment of carbon to phenylpropanoid biosynthesis was more in RR than in TG in the shade, and was either greatly enhanced in TG or varied little in RR because of high sunlight. The metabolic cost of photoprotection was lower whereas light-induced increase in biomass production was higher in RR than in TG, thus making purple basil the more light tolerant. Purple basil appears indeed to display the conservative resource-use strategy usually observed in highly stress tolerant species. We conclude that the presence of epidermal coumaroyl anthocyanins confers protective benefits under high light, but it is associated with a reduced plasticity to accommodate changing light fluxes as compared with green leaves.
Physiologia Plantarum 03/2014; · 3.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study was undertaken to investigate how different cultivars of sweet basil (Ocimum basilicum) responded to boron (B) excess. Two purple-leafed and eight green-leafed cultivars were hydroponically grown for 20 days with 0.2 or 20 mg L-1 B in the nutrient solution. Leaf B content, gas exchanges, chlorophyll a fluorescence and oxidative stress were determined at the end of the treatment along with the severity of leaf necrosis. A range of tolerance to B toxicity was found: the green cultivars were more susceptible than the purple-leaved ones characterized by a higher constitutive anthocyanin content. In all the genotypes B excess resulted in oxidative stress as determined by accumulation of malondialdehyde by-products (MDA), reduced photosynthesis and the occurrence of leaf burn. A close correlation was found between leaf B accumulation and oxidative stress, as well as between oxidative stress and the severity of leaf burn. Net photosynthesis (Pn) was reduced due to both stomatal and non-stomatal limitations in the green cultivars whereas the reduction of Pn in the purple leaves was only attributable to stomatal factors. Chlorophyll a fluorescence revealed a decrease in the maximum quantum yield of PSII (Fv/Fm) and in the electron transport rate (ETR) in plants grown with B excess although less reduction was observed in the purple genotypes. The quantum yield of PSII decreased as a result of B toxicity only the green cultivars. It is concluded that anthocyanins were likely involved in attenuation of the negative effects of B toxicity.
Journal of Plant Nutrition and Soil Science 12/2013; · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A non-destructive fluorescence-based technique for evaluating Vitis vinifera L. grape maturity using a portable sensor (Multiplex ®) is presented. It provides indices of anthocyanins and chlorophyll in Cabernet Sauvignon, Merlot and Sangiovese red grapes and of flavonols and chlorophyll in Vermentino white grapes. The good exponential relationship between the anthocyanin index and the actual anthocyanin content determined by wet chemistry was used to estimate grape anthocyanins from in field sensor data during ripening. Marked differences were found in the kinetics and the amount of anthocyanins between cultivars and between seasons. A sensor-driven mapping of the anthocyanin content in the grapes, expressed as g/kg fresh weight, was performed on a 7-ha vineyard planted with Sangiovese. In the Vermentino, the flavonol index was favorably correlated to the actual content of berry skin flavonols determined by means of HPLC analysis of skin extracts. It was used to make a non-destructive estimate of the evolution in the flavonol concentration in grape berry samplings. The chlorophyll index was inversely correlated in linear manner to the total soluble solids (°Brix): it could, therefore, be used as a new index of technological maturity. The fluorescence sensor (Multiplex) possesses a high potential for representing an important innovative tool for controlling grape maturity in precision viticulture.
Journal of Agricultural and Food Chemistry 11/2013; · 2.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study aimed to evaluate the behavior of zucchini (Cucurbita pepo L.) and cucumber (Cucumis sativus L.) under boron (B) excess. Plants were grown under greenhouse conditions in a sandy soil-peat mixture using a nutrient solution containing 0.2 (control), 10 and 20 mg L(-1) B. Visible symptoms were quantified and leaf B accumulation, gas exchanges, chlorophyll (Chl) a fluorescence, malondialdehyde by-products and antioxidants were investigated 20 days after the beginning of the treatments. Boron toxicity induced oxidative load and leaf necrotic burns coupled with the reduction of leaf growth and biomass accumulation in both species. Boron excess resulted in a decrease of Chl a/b ratio, potential (Fv/Fm) and actual (ΦPSII) PSII quantum efficiency, photosynthetic rate (Pn), stomatal conductance (gs), and transpiration (E) as well. A general stimulation of the antioxidant enzymes ascorbate peroxidase, catalase and superoxide dismutase was observed, and a significant increase in the oxidized form of ascorbate and glutathione was evidenced for treated plants of both species. A difference between the two species was observed: C. pepo appeared to be more sensitive to B stress being damaged at all B concentration. C. sativus grown at 10 mg L(-1) B in nutrient solution showed some down-regulated mechanisms, i.e. increase in Chl b content and a good photochemical PSII efficiency as well as a higher amount of constitutive antioxidant molecules, that, however, are not sufficient to contrast the negative effects of B.
Journal of Plant Research 06/2013; · 2.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The concentrations of different metabolites in olive (Olea europaea (L.)) fruit at harvest can be affected by water availability, with significant consequences on the composition and the quality of the resulting oil. The aim of the present study was to profile the metabolic composition of ripe olives (cv. Cipressino) grown under water-stress and irrigated conditions applied during the last part of the fruit developmental cycle (from pit hardening to commercial harvest). The imposed conditions resulted in a moderate water stress (−3.5 MPa) at the end of the experimental period. Samples (pulp + skin) of fruit collected at the stage of complete epicarp pigmentation were analyzed by means of GC–MS. In total, 176 metabolites were detected, of which 57 were identified. Principal component analysis (PCA) of stress and non-stress treatments resulted in clearly separated profiles with the first principal component (PC1) mostly corre-lated with the organic acid content. Of the 57 compounds identified, 19 metabolites (organic acids, fatty acids, soluble sugars, and terpens) accumulated differently in the two sets of samples. A reduction in soluble sugars and unsaturated fatty acids was detected in water stressed samples, suggesting an accel-eration of the ripening process. These results highlighted the validity of metabolic profiling to study the effects of water stress in terms of both fruit composition and physiology.
Scientia Horticulturae 04/2013; 159:52-58. · 1.40 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Boron (B) toxicity induces oxidative stress and alterations in the photosynthetic process. The occurrence of visible symptoms depends on plant species and even on cultivar. However, limited information is available concerning antioxidant responses to B toxicity; therefore a study was carried out to assess the role of antioxidants in hydroponically grown sweet basil submitted to B excess. Two cultivars were compared: the purple-leaved ‘Red Rubin’ that shown scarce symptoms of B-induced toxicity and the green-leaved ‘Tigullio’ in which they were evident.Sweet basil plants were grown in “floating raft system” for 20 days with 0.2 (control), 2 and 20 mg L−1 of B in the nutrient solution. At the end of treatments visible symptoms of damage were evaluated and some parameters were measured: growth, leaf B accumulation, gas exchange and chlorophyll fluorescence, pigment, phenols and malondialdehyde (MDA) concentrations, total non-enzymatic antioxidant ability, antioxidant molecules and enzymes.B excess negatively affected growth and photosynthesis in both cultivars but differential mechanisms were recorded. ‘Tigullio’ exhibited a larger B accumulation in leaves as compared to ‘Red Rubin’. Moreover, in ‘Red Rubin’ plants a greater constitutive content of ascorbic acid, glutathione, anthocyanins and, consequently, a stronger antioxidant ability than ‘Tigullio’ were recorded. MDA test confirmed that the extent of oxidative stress was larger in ‘Tigullio’ than in ‘Red Rubin’. A general stimulation of antioxidant enzymes occurred by increasing B concentration in the growth medium. Notable, anthocyanins were likely involved in the B tolerance shown by ‘Red Rubin’ in consideration of their antioxidant properties and because of the role of these compounds in photoprotection. This paper represents a contribution to understanding the role of antioxidant compounds in plant tolerance to B toxicity.
Environmental and Experimental Botany 01/2013; 85:64-75. · 2.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The detection of pigments and colourless flavonoids in apples can provide a useful indication of fruit quality. Optical methods are preferable because they are fast and non-destructive. In this study, a fluorescence-based portable sensor was used in order to non-invasively determine the content of chlorophylls, anthocyanins and flavonols in Fuji, Granny Smith and Golden Delicious apple cultivars. The aim was to define new non-destructive optical indices of apple quality.
The anthocyanin index (ANTH) in Fuji was higher in the sunny (i.e. sun-exposed) side of the fruit compared to the shady side. For all cultivars, the flavonol index (FLAV) was higher in the sunny side compared with the shady side. The chlorophyll index (CHL) for the shady sides of Granny Smith and Golden Delicious was significantly higher than for the sunny sides. Fine linear regressions were found between the ANTH, FLAV and CHL indices and the actual anthocyanin, flavonol and chlorophyll concentrations, respectively, which were determined destructively on the apple peel extracts. A negative correlation was found between the apple sugar content and the chlorophyll fluorescence in the far-red spectral band.
Our results indicate that a single multiparametric fluorescence-based sensor can provide valuable non-destructive markers of ripening and quality in apples.
Journal of the Science of Food and Agriculture 01/2012; 92(9):1855-64. · 1.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigated the effects of the foliar and fruit application of sodium selenate on selenium (Se) accumulation, fruit growth and ripening in peach and pear. Trials were conducted in two growing seasons. In 2008 selenate was applied at a rate of 0.1 and 1.0 mg Se L⁻¹ to the leaves of peach. In 2009 selenate was applied at a rate of 1 mg Se L⁻¹ via foliar (LT) or fruit (FT) application to peach and pear.
The foliar addition of selenate to peach resulted in an increase in Se concentration both in leaves and fruit. The higher Se content in fruit resulted in an increase in flesh firmness and a decrease in soluble solid content. LT significantly increased the Se content in the leaves and fruit of peach and pear, and leaves showed the highest Se concentrations. FT increased the fruit Se concentration in both crops, and it was more effective than LT in increasing Se content. After storage, flesh firmness decreased in all treatments, but it was significantly higher in FT compared to LT and control samples.
Foliar and fruit selenium spraying appeared effective in increasing the Se content of fruit in peach and pear. The enhanced Se concentration affected the shelf life of fruit, delaying the reduction in flesh firmness and fruit ripening, thus positively affecting fruit storage.
Journal of the Science of Food and Agriculture 09/2011; 92(4):781-6. · 1.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and Aims: Monitoring of anthocyanins (Anth) in winegrape (Vitis vinifera L.) is fundamental for the production of top-quality red wines. This work was aimed at testing a new fluorescence-based sensor for Anth detection in the vineyard.Significance of the Study: The present study showed a new important innovative technology for viticulture. The sensor evaluation of the large spatial and temporal heterogeneity in Anth accumulation can be useful as support parameter in the harvest date decision or for vineyard zoning of phenolic maturity.Methods and Results: Anth in grape (cv. Aleatico) bunches attached to the vine were monitored non-destructively in the field using a fluorescence-based sensor during the 2008 and 2009 seasons and under different water regimes. The ANTHRG index = log(far-red-fluorescenceR/far-red-fluorescenceG), with fluorescence signals excited with red (R) and green (G) light, was inversely correlated through an exponential function (r2 = 0.875) to the Anth concentration derived from the HPLC analysis of berry skin extracts. ANTHRG was effective in detecting the earlier ripening process in 2009 with respect to 2008 and differences in the Anth accumulation between seasons and in relation to different water regimes. Water deficit imposed in 2009 enhanced Anth concentration in berries because of a reduction in berry size but also an increase of Anth biosynthesis. This effect was observed by both destructive and ANTHRG non-destructive measurements.Conclusions: Our results show that the employed fluorescence sensor represents a reliable, rapid and non-invasive tool for monitoring and determining Anth accumulation in situ.
Australian Journal of Grape and Wine Research 05/2011; 17(2):181 - 189. · 2.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have conducted a UV-exclusion experiment in which plants grew at 35 or 100% sunlight irradiance, in the presence or in the absence of UV-irradiance, with the aim of exploring the effects of visible-light and UV-irradiance on the physiology and biochemistry of Ligustrum vulgare, a world-wide distributed shrub, which inhabits partially shaded areas of the Mediterranean Basin. We measured relevant physiological and biochemical traits, namely: (i) leaf expansion and leaf area expansion rates; (ii) the net CO2 assimilation rate and the PSII photochemistry; (iii) the concentrations of soluble carbohydrates and photosynthetic pigments; (iv) the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX); (v) the share of assimilated carbon recovered in individual polyphenols; (vi) the leaf oxidative damage. UV-irradiance had a relatively minor impact on most examined traits, as compared with the effect of visible-light irradiance. UV-induced variations in plant growth and net CO2 assimilation rate were minor. Maximal (Fv/Fm) and actual (ΦPSII) efficiencies of PSII photochemistry varied to a greater extent because of visible-light than UV-irradiance, and full-sun leaves had smaller Fv/Fm and ΦPSII than the partially shaded ones. The conversion state of violaxanthin-cycle pigments was either largely increased by visible-light or unaffected by UV-radiation, as also observed for the activities of antioxidant enzymes (with the exception of SOD). In contrast, UV-radiation greatly enhanced the allocation of carbon to polyphenols, particularly flavonoids, irrespective of visible-light irradiance. Lipid peroxidation and protein oxidation were superior in UV-treated leaves growing under partial shading, whereas leaf oxidative damage was unaffected by UV-radiation in full-sun leaves. We explain the differential UV-induced oxidative damage in partially shaded or full-sun leaves, on the basis of visible-light-induced biochemical adjustments, aimed at avoiding the generation and reducing reactive oxygen forms (ROS). These adjustments included an increase in (1) violaxanthin-cycle pigments, particularly antheraxanthin and zeaxanthin, relative to chlorophyll; (2) antioxidant enzyme activities and flavonoid concentration, which may effectively inhibit the generation and quench ROS once formed.
Environmental and Experimental Botany 01/2011; 70:88-95. · 2.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of the present work was to evaluate the effects of water stress and
different rootstocks on the quality indices and nutritional characteristics of
peach fruit, cv. Suncrest. The results show how pre-harvest factors, such as
the type of rootstock and water stress, can influence the quality indices and
nutritional properties of peach fruits. Rootstocks type influenced both quality
indices such as flesh firmness (FF) and soluble solid content (SSC), but it is
unclear how rootstock exerted its influence. Also water stress induced changes
in quality indices of peach fruit grafted on GF 677 andMontclar whereas minor
effects were recorded when water stress was applied on Penta. The content of
hydroxycinnamic acids was similar in control fruits of GF677, Montclar and
Penta and it increased significantly only in fruit of trees grafted on GF 677 following
water stress. Anthocyanins content in fruit of control plants was higher
in Montclar in comparison with the fruit grafted on the other two rootstocks
while procyanidin content was higher in fruit of control plants grafted on Penta.
Following the water stress an increase in total anthocyanins was observed in
GF 677 and Penta whereas no significant differences were found for Montclar.
Water stress induced a significant decrease in procyanidin content in Penta.
In conclusion in fruits of trees grafted on Penta following water stress quality
indices did not show changes but significant variations in some phytochemicals,
i.e. anthocyanins and procyanindins were observed. The results suggest that
the regulation of water management is an important factor to maintain a good
quality of the fruits. In fact, if irrigation stress can induce a higher biosynthesis
of phytochemical compounds and an increase of SSC, at the same time, it can
change fruit quality traits, such as a lower FW in Montclar, a higher titratable
acidity (TA) in GF 677 and Penta and a lower FF in Gf 677 and Montclar.
Annals of Applied Biology 01/2011; 158:226-233. · 2.15 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Application of exogenous plant growth regulators was examined as a viable technique to increase the efficiency of plant metal extraction from contaminated soils. The aim of this study was to investigate the alteration of Ni phytoextraction by Alyssum murale, a Ni hyperaccumulator, following the application of cytokinins. The following parameters were investigated: Ni accumulation, plant growth, gas exchange, stomata behavior and the concentration of nonprotein thiols (glutathione, y-Glu-Cys, and phytochelatins). In a pot experiment, A. murale plants grown in a serpentine soil were treated with a mix of naturally occurring cytokinins. Results showed that Ni accumulation in plants ranged from 4000 to 7000 mg kg(-1) confirming the hyper-accumulation ability from the soil used. Cytokinin treatments produced a significant increase in plant biomass and transpiration rate whereas no significant variation in Ni accumulation or the concentration of non-protein thiols was observed. The results suggest that A. murale is a plant species sensitive to cytokinin treatment and that cytokinin treatment is potentially useful in increasing the phytoextraction capability by increasing biomass. Moreover, for first time, evidence was obtained that the Ni hyperaccumulation mechanism is independent of water flux and transpiration rate.
International Journal of Phytoremediation 01/2011; 13 Suppl 1:90-101. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cuttings of Sesuvium portulacastrum L. (Aizoaceae) were taken from plants cultivated under severe saline conditions. The obtained seedlings were grown on sand and irrigated with nutrient solution over 5 weeks under no (0 mM NaCl), moderate (200 mM NaCl), or high (400 mM NaCl) salinity conditions. A follow-up of gas exchange was performed weekly and pigment levels and patterns of fully expanded leaves were determined after 3 and 5 weeks of treatment. At the end of the 5-week period, immunoblot analysis of the main polypeptides of photosystem I and II was performed with the aim to investigate salt-induced variations in photosystem composition. Net CO2 assimilation rate (Pn) increased under salinity up to 3 weeks of treatment then decreased to reach the value of 0mM-treated plants at the end of the experiment. For stomatal conductance (gs) and intercellular CO2 concentration (Ci), the opposite occurred. These results were concomitant with an increase in practically all pigment levels, mainly under high salinity, with the exception of zeaxanthin. The de-epoxidation index (DEPS index) was much lower under saline than non-saline conditions in the 3rd week, indicating light stress in 0mM-treated plants. At the end of the experiment, this index showed much lower values with no significant differences between treatments, which coincided with no significant differences in gas exchange as well. Protein amounts of D1, CP47, and CP43 did not show noticeable variations with salt treatment, whereas LHCII underwent a slight but significant decrease (-15%) at the highest NaCl concentration. LHCI polypeptides were unaffected by the salt treatments, where conversely, the highest concentration induced a significant decrease in PsaA/B amount (-18%).
Journal of plant physiology 11/2010; 167(16):1336-41. · 2.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The interactive effects of root-zone salinity
and sunlight on leaf biochemistry, with special emphasis
on antioxidant defences, were analysed in Olea europaea
L. cv. Allora, during the summer period. Plants were
grown outside under 15% (shade plants) or 100% sunlight
(sun plants) and supplied with 0 or 125 mM NaCl. The
following measurements were performed: (1) the contribution
of ions and soluble carbohydrates to osmotic
potentials; (2) the photosystem II (PSII) photochemistry
and the photosynthetic pigment concentration; (3) the
concentration and the tissue-specific distribution of leaf
flavonoids; (4) the activity of antioxidant enzymes; and
(5) the leaf oxidative damage. The concentrations of Na+
and Cl� were significantly greater in sun than in shade
leaves, as also observed for the concentration of the
‘antioxidant’ sugar–alcohol mannitol. The de-epoxidation
state of violaxanthin-cycle pigments increased in response
to salinity stress in sun leaves. This finding agrees with a
greater maximal PSII photochemistry (Fv/Fm) at midday,
detected in salt-treated than in control plants, growing in
full sunshine. By contrast, salt-treated plants in the shade
suffered from midday depression in Fv/Fm to a greater
degree than that observed in control plants. The high
concentration of violaxanthin-cycle pigments in sun leaves
suggests that zeaxanthin may protect the chloroplast from
photo-oxidative damage, rather than dissipating excess
excitation energy via non-photochemical quenching mechanisms.
Dihydroxy B-ring-substituted flavonoid glycosides
accumulate greatly in the mesophyll, not only in the
epidermal cells, in response to high sunlight. The activity
of antioxidant enzymes varied little because of sunlight
irradiance, but declined sharply in response to high
salinity in shade leaves. Interestingly, control and particularly
salt-treated plants in the shade underwent greater
oxidative damage than their sunny counterparts. These
findings, which conform to the evolution of O. europaea in
sunny environments, suggest that under partial shading,
the antioxidant defence system may be ineffective to
counter salt-induced oxidative damage.
Tree Physiology 09/2009; 29(9):1187-1198. · 2.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A pot experiment was conducted with two Prunus genotypes (GF 677 and Mr.S.2/5, commercial rootstocks for peach), which are widely used in Italy and other European countries. Selenium (Se) was added as sodium selenate to 3-month-old micropropagated plants at a rate of 0 (control), 1.0, 2.5, and 5.0 mg Se (kg soil)–1. Plant growth, gas exchange, and Se accumulation were studied. Selenium added at a rate of 2.5 and 5.0 mg Se kg–1 appeared to be highly toxic for the two young peach rootstocks. Thirty-three days after the treatment, the plants showed a high mortality rate. The fast growing rootstock, GF 677, appeared to be more sensitive to Se toxicity, the mortality rate reaching 52%. The higher the Se concentration in the soil, the higher it also was in the plant. In general, both genotypes were able to take up Se and to translocate high amounts from root to leaf. After selenate addition to the soil, both GF 677 and Mr.S.2/5 plants showed reduced plant growth with the highest Se treatments. Furthermore, Se induced a partial stomatal closure, as evidenced by the values of stomatal conductance, resulting in a reduction in net assimilation, and thus a decrease in dry-matter production. Selenate applied at a low rate (1 mg Se kg–1) stimulated plant growth in GF 677. One year after the Se treatment, a remobilization of Se from the storage organs to the young shoots was detected. This study demonstrates genotypic variation in Se uptake and accumulation in peach rootstocks.
Journal of Plant Nutrition and Soil Science 03/2009; 172(2):261 - 269. · 1.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Root-zone salinity stress and high solar irradiance concomitantly occurs in the Mediterranean basin, where Olea europaea is the dominating fruit-tree crop-species. Although the effect of each individual stressor on plant performance has been widely investigated, much less is known on the interaction effects of salinity stress and solar irradiance on the physiology and biochemistry of olive plants. Here we analyzed how changes in root-zone NaCl concentration and sunlight radiation affect relevant physiological and biochemical features in olive cv. Cipressino. Two-year-old plants were supplied with 0 or 125 mM NaCl and exposed to 15% (shade) or 100% sunlight (sun) over a 5-week period, starting from July 10th, 2005. Measurements were conducted of (i) gas exchange and plant growth, (ii) the concentrations of cations and chloride, (iii) the concentrations of soluble carbohydrates, violaxanthin-cycle pigments and polyphenols, and (iv) the protein oxidation and the lipid peroxidation in the leaves. Salt-induced reductions in gas exchange performance and plant growth were greater at the sun than at the shade site, mostly due to light-induced changes in leaf water relations and vapour pressure deficit (vpd), rather than in the concentration of potentially toxic ions. Light-induced increases in leaf Na+ and Cl− concentrations were countered by parallel enhancements in the concentrations of K+ and Ca2+. Sun leaves had sharply greater concentrations of mannitol and xanthophylls, irrespective of root-zone salinity. The amount of “newly assimilate carbon” allocated to polyphenols, especially to flavonoids, increased in response to salinity stress and high sunlight. Remarkably, the protein oxidation was greater in shade than in sun leaves of well-watered plants, and increased more at the shade than at the sun site because of high salinity. We suggest that heat-stress (on average maximum T exceeded 33 °C for 50% of the experimental period), which acted in concert with salinity stress and sunlight irradiance in determining plant responses in our experiment, was responsible for leaf oxidative damage in plants growing under contrasting solar radiation. Indeed, sun leaves of salt-stressed plants were equipped with an extraordinary-rich arsenal of antioxidant compounds, distributed in different cell compartments, i.e., mannitol, zeaxanthin and flavonoids, which likely countered effectively the oxidative damage driven by heat-stress, a clear example of cross-tolerance.