玉/豆套作荫蔽对大豆光合特性与产量的影响

在“玉/豆”套作模式下研究了不同株型玉米遮荫对大豆光合特性与产量效益的影响。结果表明，不同株型玉米下大豆生长的温、湿度和透光率是导致大豆叶片形态和光合特性在四叶期后出现差异的直接原因。田间光照不足导致大豆叶面积指数增加，比叶重减小，光合速率和叶绿素a/b值降低，且荫蔽越严重，光合能力越弱，产量越低。玉米收获后，大豆前期遭受的光合抑制得到缓解，光合生产逐渐恢复，恢复能力最强的为紧凑型玉米下的大豆，其生育后期的光合能力已接近单作大豆。初花期组织切片观察发现，随着荫蔽程度的加重，大豆叶片变薄，表皮细胞体积变大，角质层变薄，栅栏组织和海绵组织分化不明显，细胞间隙增大。总之，与紧凑型玉米套作，可减缓大豆生长过程中的弱光胁迫，保证全年高产、高效。

Effects of Shading in Maize/Soybean Relay-Cropping System on the Photosynthetic Characteristics and Yield of Soybean

The maize/soybean relay-cropping experiment was conducted using three plant types of maize(with erect,semi-erect,and flat leaves),and the mono-cropping soybean as control.The results showed that different plant-types of maize led to a different micro-climate for soybean growth,which was a direct factor leading to the changes in morphological and photosynthetic characters of soybean leaves after four-leaf age stage.Poor light resulted in lower SLW,photosynthetic rate,chlorophyl a/b ratio,and higher LAI.And the more the shading,the lower photosynthetic ability and yield were.After harvesting maize,the photosynthesis inhibition by shading at early stage of soybean could be ameliorated,its photosynthetic capacity recovered gradually.The restoration capability of soybean that in relay-cropping with erect maize was better than in others,and similar to that in mono-cropping at late growing stage.From the section at early bloom,we found that under shading,the leaf thickness decreased,the epidermis cell became larger,the cuticle became thinner,the differentiation of palisade tissue,and spongy tissue was unconspicuous,intercellular space was larger.In conclusion,the relay-cropping with erect maize can reduce the shading stress and increase yield in soybean.