Effects Of Night-time Warming And Increased CO₂ On Seed Yield And Quality Of Vicia Sativa

High-quality forage seed production is the material basis for ecological restoration and high-quality grassland construction.In the context of global climate change,the increase in atmospheric CO₂and temperature increase can affect plant growth and reproduction to different degrees.Therefore,studying the effects of increasing atmospheric CO₂and temperature on forage seed yield and quality is of positive significance for the grass seed industry to adapt to climate change.In this study,the legume forage grass Vicia sativa was subjected to six treatments:ambient control（CK）,night-time warming after flowering（FW）,night-time warming at full growth period（GW）,CO₂enrichment（CO₂）,night-time warming after flowering with CO₂enrichment（FW+CO₂）,and night-time warming at full growth period with CO₂enrichment（GW+CO₂）.The effects of night-time warming and enrichment of CO₂on the growth characteristics,reproduction,and quality of Vicia sativa were investigated.The main results were as follows:1.Night-time warming and enrichment of CO₂treatments for two consecutive years from 2020 to 2021 did not significantly affect soil water content,p H,and total soil nitrogen,total phosphorus,and available nitrogen content,but significantly affected soil total potassium and soil available phosphorus and available potassium content.FW+CO₂treatment significantly increased soil total potassium content in2020.FW treatment significantly increased soil available potassium content in 2021,while CO₂,FW and FW+CO₂treatments significantly decreased available phosphorus content.2.Night-time warming and enrichment of CO₂treatments promoted the growth of V.sativa and prolonged the phenological period,with GW+CO₂treatment extending the growth period by 4 and 5 days in 2020 and 2021,respectively.The growth period was significantly longer in 2021 compared to 2020,with 89 and 102days for the CK,respectively.Compared to the CK,GW+CO₂treatment significantly increased V.sativa plant height,stem biomass,leaf biomass,aboveground biomass,pod biomass,net photosynthetic rate,intercellular CO₂concentration,and leaf chlorophyll contents for two consecutive years.3.Night-time warming and enrichment of CO₂treatments significantly increased pod biomass and seed biomass of V.sativa,while showed no significant effect on harvest index.Compared to the CK,the pod biomass was increased by 13.8%、21.0%and 32.3%with CO₂,FW+CO₂and GW+CO₂treatments,respectively,in 2020;and by 20.0%with GW+CO₂treatment in 2021.Consistent with this,single plant seed biomass increased by 17.2%,-5.9%,27.5%,19.3%and 48.9%in 2020,and 4.3%,12.3%,10.8%,15.7%and 29.1%in 2021 for CO₂,FW,FW+CO₂,GW and GW+CO₂treatments,respectively,compared to the CK.4.Night-time warming and enrichment of CO₂treatments significantly increased the thousand seed weight with value of 65.8 g in 2020 for GW+CO₂treatment,a significant increase of 16.6%compared with CK,and 70.9 g in 2021 in GW+CO₂treatment,a significant increase of 9.5%compared with CK.Correlation analysis showed that the number of reproductive branches per plant,number of seeds per pod and thousand seed weight were the main factors affecting seed yield in 2020,and the number of reproductive branches per plant and thousand seed weight were the main factors affecting seed yield in 2021.5.Night-time warming and enrichment of CO₂treatments affected V.sativa seed quality,and GW+CO₂treatment significantly reduced V.sativa seed conductivity by21.3%compared to the CK.The effects of Night-time warming and enrichment of CO₂treatments favored longer seed longevity,with an average seed longevity of 140.3h and 134.5 h for GW+CO₂treatment in 2020 and 2021,respectively,compared with106.4 h and 115.2 h for the CK.