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
Available water stored in deep soil layers could increase the photosynthetic capacity of cotton. It was hypothesized that the photosynthesis of cotton would be enhanced by changing the fertilizer application depth under different deep-layer water conditions. We examined two deep-layer water levels, i.e.,
well-watered (W80) and not watered (W0), combined with surface application (F10) and deep application (F30) of basal fertilizer. Compared to W0, W80 resulted in increased leaf area (LA), photosynthetic pigment contents, maximal PSII efficiency (Fv/Fm), effective quantum yield of PSII (YII) and PSI (YI), electron transport rate of PSII (ETRII) and PSI (ETRI). W80 also increased the aboveground and root dry mass by 39 and 0.6%, respectively, and decreased the root/shoot ratio by 40-73%. Under the W0 condition, higher values of Fv/Fm, YII, YI, ETRII, and ETRI were measured for F10 compared to F30 after 69 d from emergence. Under the W80 condition, cotton plants with F10 showed higher LA, Fv/Fm, YII, YI, ETRII, and ETRI, but there were no significant differences in the photosynthetic pigments compared to F30. Our results suggest that sufficient water in deeper soil layers and the surface application of basal fertilizer could increase photosynthetic activity and efficiency, which promoted aboveground dry mass accumulation and partitioning towards reproductive organs., Z. K. Chen, Y. P. Niu, H. Ma, A. Hafeez, H. H. Luo, W. F. Zhang., and Obsahuje seznam literatury