Characteristics Of Canopy Light Distribution And Its Effects On Growth And Development Of Cotton With Varieties Of Different Maturity

Cotton growth and development and yield formation are highly correlated with photosynthetically active radiation(PAR).Quantifying the distribution characteristics of PAR in the cotton canopy is helpful to clarify the law of light energy utilization during the growth period,and then reveal the interaction between light energy utilization and population growth and development.In this study,six cotton varieties with two types of different maturity were used as the research objects to conduct field experiments.(Including early maturity cotton: Zhong 425,Zhong 50 and Gan 5;middle-early maturity cotton: Gan0906,Gan 18 and Gan KS002).The spatial grid method was used to accurately measure the spatial distribution of canopy PAR in different growth stages.Kriging interpolation method was used to quantitatively analyze the spatial heterogeneity distribution of PAR in the canopy,and to quantify the temporal and spatial variation characteristics of PAR in the canopy of different maturity cotton varieties with the growth period.At the same time,combined with the investigation of leaf area index(LAI),dry matter accumulation,boll distribution and other agronomic traits and yield composition.To explore and analyze the spatial distribution of light in the canopy of cotton varieties with different maturity and its impact on cotton growth,development and yield.This provides theoretical support for breeding high lightefficiency cotton varieties suitable for double cropping wheat(oil)cotton in the Yangtze River Basin.The main findings are as follows:(1)The results of quantifying the spatial distribution of PAR in the cotton canopy using the light interception rate(i PAR)as an indicator show that: In the cotton canopy,the spatial distribution of the light energy of the two cottons with different maturity showed a "V"-shaped distribution.In the vertical direction,the light energy interception rate decreased gradually with the increase of plant height.In the horizontal direction,the PAR interception rate was low in the middle of the two rows of cotton,and the PAR interception rate on the cotton row was high.There is little difference in the performance of cotton with different maturity at the seedling stage,the plants are not fully developed,and the absorption and utilization rate of light energy is generally low.The leaves on the cotton row cross,the ability of the leaves to absorb light energy is stronger,and the "V" shape is more obvious.At the flowering and boll stage the cotton row has been sealed,compared with the early-maturing varieties,the middle-early-maturing varieties have taller plants,the light energy interception rate increases slowly,and the upper,middle and lower light energy distribution is more uniform;At the boll opening stage,the early-maturing cotton varieties had obvious leaf shedding,and the population light interception rate was greatly reduced.The leaves of the middle-early maturing varieties were less shed and still maintained a high light absorption and utilization capacity.It was observed in different spatial regions that the i PAR in the inner,outer,upper,middle and lower regions basically showed that the middle-early-maturing cotton varieties were higher than the early-maturing cotton varieties.(2)The canopy light interception of the two cotton varieties with different maturity during the growth period was positively linearly correlated with LAI and dry matter mass.The PAR interception rate was negatively correlated with the number of bolls in different boll-forming parts.Middle-early-maturing cotton varieties have a longer growth cycle than early-maturing cotton varieties.It absorbs more light energy and produces more dry matter throughout the growth period.However,its light energy utilization rate is lower than that of early-maturing cotton,and there is no significant correlation between seed cotton yield and dry matter accumulation of cotton varieties with different maturity.Among them,the total dry matter accumulation of Gan 18 is higher than that of early-maturing cotton Zhong50 and Gan5.But its seed cotton yield is lower than the former.This may be due to the excessive vegetative growth and the obstruction of dry matter transfer to the reproductive parts of midearly-maturing cotton varieties.