Optimal planting pattern of cotton is regulated by irrigation amount under mulch drip irrigation.

Objective: It is of great importance to explore agronomic management measures for water conservation and cotton yield in arid areas. Methods: A four-year field experiment was conducted to evaluate cotton yield and soil water consumption under four row spacing configurations (high/low density with 66+10 cm wide, narrow row spacing, RS66+10H and RS66+10L; high/low density with 76 cm equal row spacing, RS76H and RS76L) and two irrigation amounts (CI:conventional drip irrigation; LI:limited drip irrigation) during the growing seasons in Shihezi, Xinjiang. Results: A quadratic relationship was observed between the maximum LAI (LAImax) and seed yield. Canopy apparent transpiration rate(CAT), daily water consumption intensity (DWCI) and crop evapotranspiration (ETC) were positively and linearly correlated with LAI. The seed yields, lint yields, and ETC under CI were 6.6-18.3%,7.1-20.8% and 22.9-32.6%higher than those observed under LI, respectively. The RS66+10H under CI had the highest seed and lint yields. RS76L had an optimum LAImax range, which ensured a higher canopy apparent photosynthesis and daily dry matter accumulation and reached the same yield level as RS66+10H; however, soil water consumption in RS76L was reduced ETC by 51-60 mm at a depth of 20-60 cm at a radius of 19-38 cm from the cotton row,and water use efficiency increased by 5.6-8.3%compared to RS66+10H under CI. Conclusion: A 5.0

Boll-leaf system gas exchange and its application in the analysis of cotton photosynthetic function.

Estimating the boll development and boll yield from single-leaf photosynthesis is difficult as the source-sink relationship of cotton (Gossypium hirsutum L.) is complicated. As the boll-leaf system (BLS), which includes the main-stem leaf, sympodial leaf, and non-leaf organs, is the basic unit of the cotton source-sink relationship and yield formation, the concept of "BLS photosynthesis" is introduced in this study. We speculate that the characteristics of BLS gas exchange can more accurately reflect the photosynthetic function of the system, thus revealing the law of photosynthesis in the process of boll development. The results showed that the photosynthetic rate of single leaves measured by a BLS chamber was consistent with that measured by a standard single-leaf chamber. BLSs exhibited typical light response curves, and the shape of the curves was similar to those of single leaves. The light compensation point and respiration rate of BLSs were higher than those of single leaves, while the apparent quantum efficiency of BLSs was lower. Compared with single leaves, the duration of the photosynthetic function of BLSs was longer. Increasing plant density decreased the gas exchange rate per unit BLS more significantly under field conditions. There was a better linear correlation between the net CO2 assimilation rate, respiration rate of BLSs and boll biomass. Therefore, we think that the gas exchange of BLSs can better reveal the changes in photosynthetic function of BLSs and boll development. This provides a new basis for analyzing the mechanism and regulation of cotton yield formation.

Single boll weight depends on photosynthetic function of boll-leaf system in field-grown cotton plants under water stress.

Cotton has many leaves and even more bolls, which results in a complicated source-sink relationship. Under water stress, the single boll weight (SBW) of cotton remains relatively stable, while both the leaf area and leaf photosynthetic rate decrease greatly. It is therefore difficult to understand how the formation of SBW is regulated under water stress solely by considering single-leaf photosynthesis. Considering the cotton boll-leaf system (BLS: including the main-stem leaf, sympodial leaves, and non-leaf organs) as the basic unit of the cotton canopy, we speculated that the formation of SBW may depend on photosynthesis in the corresponding BLS under water stress. To verify this hypothesis, five water treatments were set up in the field. The results showed that with increasing water stress, the relative water content (RWC) of the main-stem and sympodial leaves decreased gradually, and the decrease in the sympodial leaves was more obvious. The SBW and the number of BLSs decreased slightly with increasing water stress, while the number of bolls per plant decreased significantly. The area of the BLS decreased gradually with increasing water stress, and the area of sympodial leaves decreased more than that of the main-stem leaves. Gas exchange showed that the photosynthetic rate of the BLS (Pn(BLS)) decreased gradually with increasing water stress. In addition, the single-leaf photosynthesis and carboxylation efficiency (CE) decreased progressively and rapidly with the increase of water stress. Compared with the main-stem leaf, the photosynthetic function of the sympodial leaf decreased more. Further analysis showed that compared with leaf photosynthetic rate, there was a better correlation between Pn(BLS) and SBW. Thus, the formation of SBW mainly depends on Pn(BLS) under water stress, and the increase of BLS to boll is also helpful to maintain SBW to some extent. In BLS, the photosynthesis of the main-stem leaf plays a very important role in maintaining the stability of SBW, while the photosynthetic performance in sympodial leaves may be regulated plastically to influence SBW.