耐密性春大豆品种光合特性研究

选用耐密性不同的两个大豆品种，设置了22.5万株·hm^-2、30.0万株·hm^-2和37.5万株·hm^-2等3个密度，研究耐密性大豆的光合特性。试验结果表明，耐密品种垦丰16号，叶形指数高，上部冠层叶柄短，随着密度增加，耐密植品种垦丰16冠层上部叶柄长度显著低于普通品种，叶形指数高于普通品种，尤其是高密度条件下从第9节位开始垦丰16的叶形指数显著或极显著高于普通品种合丰39，从第11节开始叶柄长度短于合丰39，有利于通风透光；随着密度增大，耐密植品种垦丰16的叶色值峰值出现时期没有明显变化，密植条件下生育后期叶片持绿性更强；随着密度增加耐密植品种垦丰16净光合速率和水分利用率下降速度慢，当密度为30.0万株·hm^-2时垦丰16与合丰39的净光合速率和水分利用率差异达到显著水平（分别为P=0.0423，P=0.0384），密度为37.5万株·hm^-2时差异达到极显著水平（分别为P=0.0026，P=0.0042）；随着密度增加耐密品种垦丰16产量逐渐增加，不耐密品种合丰39产量呈现先上升后降低的趋势，密度为37.5万株·hm^-2时，两个品种间差异达到极显著水平（P=0.0024）。不同密度条件下垦丰16与合丰39在形态和光合生理指标的变化可以看出，耐密性春大豆品种冠层结构更有利于在高密度条件下通风透光，密植条件下后期持绿性强，光合速率和水分利用率受密度影响小，因此在高密度条件下能够获得较高的产量。

Photosynthetic characteristics of spring soybean cultivars with high density tolerance

We used two soybean cultivars and conducted three treatments of planting density, 225 000, 300 000, and 375 000 plant·hm^-2. The results showed that the high density tolerance cultivars like KenFeng16 had high leaf shape index and short petioles at upper canopy. With the density increased, Kenfeng16 had shorter leaf petiole length and higher leaf index than conventional cultivars like Hefeng39. The leaf color did not change significantly and the duration of leaf stay-green was longer. The net photosynthetic rate and water use efficiency differed significantly between Kenfeng16 and Hefeng39 under the density of 300 000 plant·hm^-2 and 375 000 plant·hm^-2. The reason that Kenfeng16 outyielded Hefeng39 under high density is that it had a rational canopy structure, resulting in favorable conditions of air and light for soybean.