增密对少分枝大豆品种光合特性和产量形成的影响

Effects of Close Planting on Photosynthetic Characteristics and Yield of Less Branched Soybean Varieties

为深入分析在农业机械水平提高、精量播种技术提升背景下应运而生的少分枝大豆品种对密度增加的响应情况,探讨其最适播种密度,优化大豆栽培模式,以2个不同分枝类型的品种(少分枝中作XA12938和多分枝中黄13)为供试材料,于2018—2019年,设置6个种植密度(13.5万,18.0万,22.5万,27.0万,31.5万和36.0万株·hm^(-2)),研究增密种植条件下不同分枝类型品种光合特性变化和产量差异。结果表明:(1)冠层光截获率随种植密度的增加而增加,增至27万株·hm^(-2)时趋于稳定,与中黄13相比,中作XA12938关键时期冠层光截获率提高4.90%。(2)SPAD随密度的增加而增大,且高密度处理(31.5万和36.0万株·hm^(-2))下SPAD最大值可提前至R3期出现,此外,与中黄13相比,中作XA12938 SPAD高值持续期较长。(3)Fv/Fm随种植密度的增加而降低,中黄13高密度处理降低幅度(5.10%)大于中作XA12938(3.51%)。被动耗散占比Y(NO)中作XA12938与中黄13相比,处理间随密度增大而增加幅度较小,极值出现晚。(4)中作XA12938和中黄13最大净光合速率分别为30.46和24.34μmol·m^(-2)·s^(-1),且随种植密度增加,中作XA12938净光合速率降幅(17.73%)小于中黄13(22.51%),各密度条件下中作XA12938净光合速率表现均存在优势。(5)随种植密度增加大豆产量总体先增加后趋平,当种植密度大于18.0万株·hm^(-2)时即可达到增产效果。中作XA12938产量潜力更高,且耐密植能力更强。综合分析说明,增加种植密度有利于提高大豆光能利用效率,尽管大豆单株光合能力下降,但少分枝品种单株净光合速率和Fv/Fm在增密条件下降幅更小且稳定性较强。少分枝品种中作XA12938产量潜力较高,且密植条件下叶片持绿性强,冠层光能截获率和叶片净光合能力增强,被动耗散占比增幅较小,有利于光能资源利用,可在高密度种植条件下稳定增产。因此,生产中可选用密植时光合特性较稳定的少分枝品种,通过适当增加种植密度提高产量、增加效益。

In order to investigate the response of less branched soybean varieties to increased density in the context of improved agricultural machinery and precision sowing technology,to explore their optimum sowing density and to optimize soybean cultivation patterns,this study used two varieties with different branching types(less branched variety Zhongzuo XA12938 and more branched variety Zhonghuang 13)as test materials and planted at six densities(1.35×10^(5),1.80×10^(5),2.25×10^(5),2.70×10^(5),3.15×10^(5) and 3.60×10^(5) plants·ha^(-1))from 2018 to 2019.The planting densities(1.80×10^(5),2.25×10^(5),2.70×10^(5),3.15×10^(5) and 3.60×10^(5) plants·ha^(-1))were used to study the photosynthetic characteristics and yield differences between varieties with different branching types under close planting conditions.(1)Canopy light interception rate increased with increasing planting density and stabilized at 2.70×10^(5) plants·ha^(-1),with 4.90%higher light interception in the canopy during the critical period in Zhongzuo XA12938 compared to Zhonghuang 13.(2)The SPAD increased with increasing density and the highest SPAD values could occur earlier up to the R3 stage at high density treatments(3.15×10^(5) and 3.60×10^(5) plants·ha^(-1)).In addition,the high SPAD values lasted longer in Zhongzuo XA12938 compared to Zhonghuang 13.(3)Fv/Fm decreased with increasing planting density,and the decrease was greater for Zhonghuang 13(5.10%)high density treatments than for Zhongzuo XA12938(3.51%).The photodamage percentage Y(NO)of Zhongzuo XA12938 increases less with increasing density between treatments and the maximum value occured later compared to the photodamage percentage Y(NO)of Zhonghuang 13.(4)The maximum net photosynthetic rates of Zhongzuo XA12938 and Zhonghuang 13 were 30.46 and 24.34μmol·m^(-2)·s^(-1),respectively,and the decrease in net photosynthetic rate with increasing planting density was smaller in Zhongzuo XA12938(17.73%)than in Zhonghuang 13(22.51%),with Zhongzuo XA12938 showing an advantage in net photosynthetic rate at all densities.(5)With increasing planting density,soybean yield generally tends to increase before leveling off.Yield increases were achieved when planting density was greater than 1.80×10^(5) plants·ha^(-1).In addition,comparing the two varieties,we found that Zhongzuo XA12938 had a higher yield potential and was more tolerant to dense planting.It was found that increasing planting density was beneficial to the improvement of soybean light energy use efficiency,and although the photosynthetic capacity of soybean individual plants decreased,the net photosynthetic rate and Fv/Fm increased density of less branched varieties decreased in a smaller and more stable way.In summary,the less branched variety Zhongzuo XA12938 has a high yield potential,and under dense planting conditions the leaves have a strong green holding capacity,the canopy light energy interception rate and the net photosynthetic capacity of the leaves are strong,smaller increase in percentage of light damage,which is conducive to the use of light energy resources and can increase yields steadily under high density planting conditions.Therefore,in production,we can use less branched and dense planting varieties with more stable photosynthetic characteristics,and increase the planting density appropriately,so as to improve the yield and benefit.