The occurrence of shade and drought stress either individually or simultaneously causes altered morphophysiological and molecular responses in crops. Nevertheless, responses of crop plants to combined shade and drought stress are unique as compared to those of individually occurring stress which urges need to study and identify distinctions, commonalities, and the interaction between responses of plants to these concurrent stress factors. In the present review, we outlined currently available knowledge on responses of plants to shade and drought stress on a shared as well as the unique basis and tried to find a common thread potentially underlying these responses. Then, we briefly described some plausible mitigation strategies to cope with these stresses along with future perspectives. A deeper insight into plant responses to co-occurring shade and drought stress will help us to generate crops with broad-spectrum stress tolerance and increased resilience to such stresses in high planting densities or intercropping systems, thus, ensuring food security.
Anticipating warming related to climate change, commercial mango plantations in China have been shifting from lower to higher elevations. Such a practice may expose mangoes to climatic conditions that could affect photosynthesis. Photosynthesis research on mango has previously examined mature plantations but exploring adequate functions before the time of fruit production is necessary for later crop success. Therefore, we established two main commercial mango cultivars, Tainong No. 1 and Jinhuang, at 450 m and 1,050 m and examined their photosynthetic performance. Our results showed that photosynthetic capacity parameters, including maximum photosynthetic rate, apparent quantum yield, maximum carboxylation rate, and photosynthetic electron transport rate, were significantly different between cultivars due to elevation and positively correlated with leaf nitrogen per area. Moreover, the seasonal gas exchange of the two cultivars showed variations due to elevation, particularly during the warmer seasons. Therefore, elevation affects the photosynthetic performance of these mango cultivars.
Nondestructive methods to estimate individual leaf area (LA) accurately, by leaf length (L) and/or width (W), is helpful for the in situ and successive LA measurements. However, leaf shape and size may covary with environment and thus alter the coefficients of LA estimation models. To test such hypothesis, we carried out an experiment by measuring Saussurea stoliczkai C. B. Clarke leaves along an altitudinal transect in Damxung county, central Tibet. In July 2011, we selected seven sites at about every 150 m in altitude from 4,350 m to 5,250 m a.s.l. A total of 1,389 leaves (182 to 203 leaves for each site) were measured. For each site, models developed by two leaf dimensions [LA = a (L×W) + b] could estimate LA more accurately than those by single dimension. L, W, LA and leaf shape index (L:W ratio) all decreased with increasing altitude, leading to significant differences in coefficients of two-dimension model between almost every two sites. Accordingly, a common
two-dimension model is unlikely to occur for S. stoliczkai across the whole altitudinal transect, indicating that the varying leaf shape may alter the coefficient of LA estimation models., Z. Wang, L. Zhang., and Obsahuje bibliografii
In a field experiment, two winter wheat (Triticum aestivum L.) cultivars, Tainong 18 (a large-spike cultivar) and Jinan 17 (a multiple-spike cultivar), were treated with 78% (S1), 50% (S2), and 10% (S3) of full sunshine (S0, control) from anthesis to maturity to determine the responses of photosynthetic characteristics and antioxidative enzyme activities in a flag leaf. Compared with S0 treatment, the chlorophyll (Chl) content and maximal efficiency of photosystem II (PSII) photochemistry (Fv/Fm) of flag leaves were enhanced in treatments S1 and S2. From 0 to 7 d post flowering, the Chl content and Fv/Fm in S3 were also higher than those in S0, but significantly lower than those in controls, respectively. With the increase of shading intensity, the effective quantum yield of PSII (ΦPSII) was promoted; whereas, the ratio of Chl a/b declined. Compared with S0, treatments S2 and S3 significantly suppressed the activities of superoxide dismutase (SOD) and peroxidase (POD), net photosynthetic rate (PN), and contents of total soluble sugar, nevertheless, S1 treatment showed positive effects on the above parameters. Under the same shading condition, Jinan 17 had larger Chl content and higher activities of PSII and antioxidative enzymes, but lower malondialdehyde (MDA) content than Tainong 18. The results indicated that multiple-spike cultivar was more advantageous for the Huang-Huai-Hai Plain, where shading problem occurs later during the growth period, than the large-spike cultivar, because of the lesser damage in a flag leaf and better photosynthetic function of the former one. Wheat plants under S1 shading condition had relatively high activities of antioxidative enzymes and a low degree of membrane lipid peroxidation, which was in favor of stress resistance, maintaining high PN duration, and accumulation of photosynthates in wheat plants., C. Xu ... [et al.]., and Obsahuje bibliografii
Wheat (Triticum aestivum L.) cv. Jimai22 was used to evaluate the effect of ethylene evolution rate (EER) and 1-aminocyclopropane-1-carboxylic acid (ACC) and their relations with photosynthesis and photochemical efficiency in plants well-watered (WW) and under a severe water deficit (SWD). SWD caused a noticeable reduction in the grain mass. The marked increases in both EER and the ACC concentration were observed under SWD; it was reversed effectively by exogenous spermidine (Spd) or amino-ethoxyvinylglycine (AVG). Thermal images indicated that SWD increased obviously the temperature of flag leaves, mainly due to the decrease in transpiration rate under SWD. Exogenous Spd or AVG decreased to some extent the temperature of the flag leaves. The strong decline in photosynthetic rate (PN) and stomatal conductance as well as the photodamage of PSII were also observed under SWD after 14 and 21 days after anthesis (DAA). Intercellular CO2 concentration was reduced at 7 DAA, but slightly increased at 14 and 21 DAA under SWD, indicating that the decreased PN at 7 DAA might result from stomatal limitations, while the decline after 14 and 21 DAA might be attributed to nonstomatal limitations. Correlation analysis suggested that EER and ACC showed negative relations to photosynthesis and photochemical efficiency. Data obtained suggested that the effects of SWD were mediated predominantly by the increase in EER and ACC concentration, which greatly decreased the leaf photosynthesis and photochemical efficiency, and, therefore, reduced the grain mass. Application of Spd or AVG reduced the EER and ACC, and thus positively influenced photosynthesis and photochemical efficiency under SWD., W. Yang, Y. Yin, W. Jiang, D. Peng, D. Yang, Y. Cui, Z. Wang., and Obsahuje bibliografii