中文摘要：

为从茎秆强度的角度研究套作大豆苗期对荫蔽胁迫的响应及耐荫抗倒机制,采用耐荫性不同的3个大豆材料,在玉米大豆套作和单作两种种植模式下,对茎秆的纤维素、可溶性糖、蔗糖、淀粉含量及蔗糖代谢中关键酶活性以及茎秆抗折力、抗倒伏指数等进行测定,研究它们与套作大豆苗期倒伏的关系.套作大豆苗期倒伏严重,茎秆抗折力、抗倒伏指数、纤维素、可溶性糖、蔗糖、淀粉含量和相关酶活性均显著低于单作.不同大豆材料受套作荫蔽影响程度不同,强耐荫性大豆南豆12茎秆抗折力降低幅度最小,在套作环境下其茎秆抗折力、抗倒伏指数大,纤维素、可溶性糖、蔗糖、淀粉含量高,酶活性强.相关分析表明：套作大豆苗期茎秆糖含量均与抗折力呈极显著正相关,与倒伏率呈极显著负相关;蔗糖含量与蔗糖磷酸合酶（SPS）、蔗糖合酶（SS）、中性转化酶（NI）活性呈极显著正相关,与酸性转化酶（AI）活性相关性不显著;纤维素含量与SPS、SS呈极显著正相关,与NI呈显著正相关,与AI相关性不显著.套作环境下,强耐荫性大豆苗期茎秆中较高的SPS、SS活性是其维持高蔗糖和纤维素含量的酶学基础,而高纤维素含量有利于提高茎秆强度,进而增强其抗倒伏能力.本研究应用玉米大豆套作种植系统,从苗期抗倒角度,探明了光环境对不同基因型大豆茎秆纤维素代谢的影响机制,为下一步筛选耐荫抗倒大豆品种提供了理论依据.

英文摘要：

Physical characteristics of stem are closely relative to the crop lodging. Increase of stem strength is conducive to resolve the problem of lodging. Three soybean cultivars with different shade tolerance were planted under maize-soybean intercropping and soybean monocropping, respectively. Physiological and biochemical indices including cellulose, soluble sugar, sucrose, starch contents and enzyme activity were investigated to assess the snapping resistance and lodging resistance of the stems of soybean seedling, and snapping- and lodging-resistance indices were calculated for further verification. Furthermore, relationship analyses between these factors and the lodging of intercropped soybean showed that the intercropping soybean lodged seriously, the snapping resistance, lodging resistance index, contents of cellulose, soluble sugar, sucrose, starch and activities of the related enzymes were significantly lower than monocropping soybean at seedling stage. The three soybean cultivars showed different phenotypes in intercropping condition. The snapping-resistant Nandoul2 with strong shade-tolerant traits was the most lodging-resistant phenotype, and it also har- bored high contents of cellulose, soluble sugar, sucrose, starch and active enzymes. The lodging resistance index, cellulose content of the stems of intercropped soybean seedling were significantly positively correlated with the snapping resistance, and were significantly the actual lodging percentage. The activities of sucrose phosohate svnthase negatively correlated with （SPS）, sucrose svnthase （SS） and neutral invertase （NI） were positively correlated with sucrose is content, but not the acid invertase （AI）. The activities of SPS, NI and SS were positively correlated with cellulose content, but not AI. In a word, the high activities of SPS and SS in the soybean stem were the enzymatic basis to maintain relatively higher cellulose and sucrose content, which is conducive to improve the stem strength and enhance the lodging resistance abil