套作荫蔽对苗期大豆叶片结构和光合荧光特性的影响

Effects of Shading on Leaf Structure and Photosynthetic Fluorescence Characteristics of Soybean Seedlings in Maize-Soybean Relay Intercropping System

间套作系统中荫蔽是影响低位作物生长发育的主要因素。本研究采用玉米-大豆套作种植模式,以南豆12大豆品种为研究对象,设置2个行比配置,即1∶1(A1处理;1行玉米间隔1行大豆,间距50 cm)和2∶2(A2处理;2行玉米间隔2行大豆,玉米和大豆各自的行距均为40 cm,玉米和大豆间距为60 cm),净作大豆为对照(CK),研究玉米和大豆不同行比套作配置下荫蔽对大豆叶片光合荧光特性、解剖结构及超微结构的影响。结果表明,套作处理A1、A2的光合有效辐射(PAR)分别比CK显著降低91.2%、66.8%。叶绿素a含量分别降低50.2%和27.9%,净光合速率分别降低63.2%和37.8%。套作大豆功能叶片荧光参数F_v'/F_m'和F_q'/F_m显著高于净作大豆,而F_v/F_m、qP和NPQ低于净作。对于叶片结构,套作大豆叶片厚度、栅栏组织厚度、海绵组织厚度均低于CK,且净作大豆叶片厚度分别是A1和A2处理下的2.15倍和1.69倍;套作大豆叶片的叶绿体结构比较完整,无破碎现象,含淀粉粒稀少,随着荫蔽程度的加重,嗜锇颗粒、基粒片层和基质片层增多,叶绿体减小但其数目增多,而净作大豆叶片叶绿体中淀粉粒较多且色泽亮白,基粒片层和基质片层稀少。因此,玉米-大豆套作种植中不同行比配置导致低位作物大豆冠层光环境差异,直接影响大豆叶片结构特征和光合荧光特性。

Shading in relay intercropping system is a major factor affecting the low growing of crop growth and development. This study attempted to compare leaf structure and photosynthetic characteristics of cultivar Nandou 12 under maize-soybean relay intercropping systems. Three treatments were designed including one row maize to one row soybean with 50 cm of row space between maize and soybean（A1）; two rows maize to two rows soybean with 40 cm of row space for maize or soybean and 60 cm of row space between maize and soybean（A2）, sole cropping of soybean. The result indicated that shading caused the changes of both anatomical structure of leaf and photosynthetic characteristics in maize/soybean relay strip intercropping systems. During the V5 stage of soybean, the PAR density in treatments（A1 and A2） were lower than that in CK by 91.2% and 66.8%, respectively. The content of Chl a of treatments（A1 and A2） was lower than that in CK by 50.2% and 27.9%. The Pn of treatments（A1 and A2） was lower than that in CK by 63.2% and 37.8%. The Fv/Fm, qP, NPQ in leaf of treatments（A1 and A2） were lower than there in CK significantly, Fv＇/Fm＇ and Fq＇/Fm＇ of treatments（A1 and A2） were higher than that in CK. Under light microscope, compared with CK, A1 and A2 treatments decreased palisade tissue thickness and spongy tissue thickness of leaf. The leaf of treatment CK was 2.15 and 1.69 times as thick as that of treatments A1 and A2. In A1 and A2 treatments leaf chloroplast morphology was normal, the number of chloroplasts, granule lamella and osmophilic globule in chloroplast increased; the structure of chloroplast was not damaged; There were few starch grains in chloroplasts; and the structure of cell organelles was normal. Therefore, the different spatial patterns of maize-soybean intercropping system result in different light environments above the soybean canopy, and directly affect soybean leaf structure and photosynthetic fluorescence characteristics.