Drought stress causes changes in vein and stomatal density. The objectives of this study were to determine (1) if the changes in vein and stomatal density are coordinated in cotton (Gossypium hirsutum L.) and (2) how these changes affect water-use efficiency (WUE). The results showed significant positive correlations between vein density and stomatal density when cotton was grown under different degrees of drought stress. WUE was significantly positively correlated with the densities of both veins and stomata. Stomatal pore area and stomatal density on the abaxial leaf side, but not the adaxial side, were significantly correlated with WUE, stomatal conductance, leaf net photosynthetic rate, and transpiration rate. In conclusion, coordinated changes in vein and stomatal density improve the WUE of cotton under drought stress. The abaxial leaf side plays a more important role than the adaxial side in WUE and gas exchange., Z. Y. Lei, J. M. Han, X. P. Yi, W. F. Zhang, Y. L. Zhang., and Obsahuje bibliografii
Roots of six Cucurbitaceae species were exposed to low (14 °C), middle (24 °C), and high (34 °C) temperatures while aerial parts of plants were maintained at ambient temperatures between 23 and 33 °C. The highest dry mass (DM), photon-saturated rate of net photosynthesis (PNsat), and stomatal conductance (gs) were found at 14 °C in figleaf gourd and turban squash plants, at 24 °C in cucumber and melon plants, while bitter melon and wax gourd plants had lower DM, PNsat, and gs at 14 °C than at 24 or 34 °C. Sub-or supra-optimum root temperatures did not induce photoinhibition but induced slight changes in the quantum efficiency of photosystem 2, PS2 (ΦPS2) and photochemical quenching (qp). Meanwhile, xylem sap abscisic acid (ABA) concentration followed a contrasting change pattern to that of gs. Thus the change in PNsat was mainly due to the change in gs and roots played an important role in the regulation of stomatal behaviour by delivering increased amount of ABA to shoots at sub-or supra-optimum root temperatures. and Y. P. Zhang ... [et al.].
a1_Soil water deficit is a major limitation to agricultural productivity in arid regions. Leaf photosynthesis can quickly recover after rewatering and remains at a higher level for a longer period, thus increasing crop yield and water-use efficiency (WUE). We tested our hypothesis that leaf photosynthesis and root activity of water-stressed cotton (Gossypium hirsutum L.) plants could quickly recover after rewatering at a certain growth stage and it should not influence a cotton yield but increase WUE. Treatments in this study included two degrees of water stress: mild water stress (V1) and moderate water stress (V2) imposed at one of four cotton growth stages [i.e., S1 (from the full budding to early flowering stage), S2 (from early flowering to full flowering), S3 (from full flowering to full bolling), and S4 (from full bolling to boll-opening)]. The soil water content before and after the water stress was the same as that in the control treatment (CK, 70-75% of field capacity). Water deficit significantly reduced the leaf water potential, net photosynthetic rate, and stomatal conductance in cotton. The extent of the decline was greater in S2V2 treatment compared to others. Water deficit also reduced root activity, but the extent of inhibition varied in dependence on soil depth and duration. When plants were subjected to S1V1, the root activity in the 20-100 cm depth recovered rapidly and even exceeded CK one day after rewatering. An overcompensation response was observed for both photosynthesis and aboveground dry mass within one to three days after rewatering. Compared with the CK, S1V1 showed no significant effect on the yield but it increased total WUE and irrigation WUE., a2_These results suggest that even a short-term water stress during the S1, S2 and S4 stages mitigated, with respect to the root activity, the negative effect of drought and enhanced leaf photosynthesis compensatory effects of rewatering in order to increase cotton WUE with drip irrigation under mulch in arid areas., H. H. Luo, Y. L. Zhang, W. F. Zhang., and Obsahuje seznam literatury
Changes in photosynthetic attributes related to genetic improvement of cotton yield were studied in seven Chinese cotton cultivars widely grown in Xinjiang during the past 30 years. Our results showed that a chlorophyll (Chl) content and net photosynthetic rate (PN) of the 1980s cultivar was the highest among all after 60 days from planting (DAP). However, after 75 DAP, the Chl content, PN, and actual photochemical efficiency of PSII of the old cultivars declined gradually, whereas those of the new cultivars remained relatively high. Compared to the old cultivars, leaves of the new cultivars endured a longer period and their senescence was slower, shoot and boll dry mass was higher, but the root to shoot ratio was lower. The lint yield of the 2000s cultivars was 14.7 and 21.4% higher than that of 1990s and 1980s cultivars, respectively. The high yield of the new cultivars was attributed to a greater number of bolls per unit of area with high lint percentage. We suggested that the improved photosynthetic capacity and the increased ability to deliver photosynthates to reproductive sites during the peak boll-setting stage to boll-opening stage were the key physiological basis in the evolution process of cotton cultivars from 1980s to 2000s for the cotton yield improvement within a short growing period., H. H. Luo, H. L. Zhang, Y. L. Zhang, W. F. Zhang., and Obsahuje bibliografii
Characterization of different component processes of photosynthesis is useful to understand the growth status of plants and to discover possible unintended effects of genetic modification on photosynthesis in transgenic plants. We focused on the changes in photosynthetic gas-exchange properties, reflectance spectra, and plant growth traits among groups of different transgenic barley T1 (TolT1) and its isogenic controls (TolNT1), TolT1, and group of its own transgenic progenies T2 (TolT2), TolNT1 and its wild type (WT), respectively. Gas-exchange measurements showed that only the net photosynthetic rate (P N) and the light-use efficiency (LUE) differed significantly between TolT1 and TolT2 with no obvious changes of other characteristics. Reflectance measurements indicated that the reflectance ratio was sensitive to identify the differences between two barley groups. Differences in reflectance expressed on an index basis depended on barley groups. The relationship between LUE and the photochemical reflectance index (PRI) at a leaf level among different barley groups of WT, TolNT1, TolT1 and TolT2 did not changed obviously. The differences in the total leaf area per plant (LA) between WT and TolNT1 as well as between TolT1 and TolT2 were significant. This study finally provided a plausible complex explanation for the unintended effects of genetic transformation on photosynthesis-related properties in barley at different levels. Furthermore, it was concluded that the photosynthesis-related properties of transgenic plants based on gas exchange, leaf reflectance, and plant growth measurements responded to the same environment in a more different way between two subsequent generations than to the processes of the gene insertion by Agrobacterium and associated tissue culture., C. X. Sun ... [et al. ]., and Obsahuje bibliografii