Impacts Of Solar Radiation Changes On Growth And Development In Rice Under Global Dimming

In recent years,global dimming has become more apparent due to the increasing aerosol pollution associated with the acceleration of urbanization and economization in China.As one of the main trends of climate change,global dimming decreases global radiation but increases diffuse radiation fraction,and therefore,affects the growth and development of crops.Rice is the major food crop in China,and its yield stability is of utmost importance for ensuring the food security.In this study,field experiments were conducted in 2019,Kangbo Village,Baimao Town,Changshu City,Jiangsu Province(31°30'N,120°33 'E),with rice(Oryza sativa L.)cultivar Changyou 5 grown under different changes of solar radiation that were created by open global dimming simulation platform.This study aimed to assess the effects of growth stages and dry matter production under different changes of solar radiation on rice,through measuring the canopy temperature,photosynthetic rate,leaf area index and light interception.It will provide theoretical basis and experimental data support for establishing the simulation model,which could be used for precisely assessing the impacts of global dimming on crop growth and development.The main results are as follows:1.The decreased global radiation reduced the canopy temperature of rice,and thereby prolonged growth duration,while the increased diffuse radiation fraction had no effect on growth duration.When the diffuse radiation fraction similarly,the global radiation decreased by 10%,the canopy temperature decreased by 0.2?,0.5? and 0.4?at stem-elongating,heading and grain-filling stage,respectively;the growth duration can be prolonged by 1.6d,and the pre-heading and post-heading phases prolonged 0.6d and 1.0d during,respectively.However,when global radiation reduced similarly,the increase in the diffuse radiation fraction had no significant changes on growth duration and canopy temperature.2.When the diffuse radiation fraction similarly,the decreased global radiation reduced the canopy intercepted global radiation and leaf photosynthetic rate at early growth duration,and ultimately led to a significant reduction in dry matter production and grain-yield.When the diffuse radiation fraction similarly,the global radiation decreased by 10%,the above-ground dry matter accumulation can be decreased by 6.71%in maturity,grain yield can be decreased by 6.45%,harvest index can be decreased 1.10%;the canopy intercepted global radiation can be decreased by 10.0%;the initial light energy use rate can be decreased by 8.9%-17.4%at stem-elongating but increased by 3.2%-51.2%at grain-filling;the light-saturated gross photosynthetic rate can be decreased by 4.5%-11.2%at stem-elongating but increased by 0.8%-8.9%at grain-filling-the leaf area index can be increased by 2.5%-13.0%.Although the decreased global radiation increased the light-saturated gross photosynthetic rate and photosynthetic areas,the photosynthetic productivity still decreased due to the significant decrease in the canopy intercepted global radiation,and thus,the above-ground dry matter and grain-yield reduced.3.When the global radiation reduced similarly,the increase in the diffuse radiation fraction enhanced the canopy intercepted global radiation and photosynthetic rate at the middle and lower leaves,and therefore,has "fertilization effect" on dry matter production and grain-yield.When the global radiation reduced similarly,the diffuse radiation fraction increased by 10%,the above-ground dry matter accumulation can be increased by 3.30%in maturity,grain yield can be increased by 2.37%;the canopy intercepted global radiation increased by 6.0%;the initial light energy use rate increased by 6.4%-8.7%at the second top leave,increased byl.4%-71.0%at the third top leave,the light-saturated gross photosynthetic rate increased by2.8%-12.0%at the second top leave,increased by11.7%-18.7%at the third top leave;the leaf area index decreased by 2.5%-13.0%,light extinction coefficient increased by 4.8%-8.5%.When solar global radiation reduced similarly,the diffuse radiation fraction increased,can be make the canopy light distribution more evenly,increased the canopy intercepted global radiation,photosynthetic rate,and maintained a higher photosynthetic area.All these characters were of benefit to impact on biomass production and grain yield of rice.The study defined the effect on the growing and grain-yield of the“fertilization effect”of the increase in the diffuse radiation fraction under global dimming.The results provide theoretical basis and experimental data support for rice production to cope with climate change.