Effect of the composite root population of wheat-cotton intercropping system on cotton root growth

Chinese. 探索麦棉套作两熟中棉花根系对逆境适应的生理机制，为采取合理调控措施、解决麦棉两熟双高产栽培中棉花弱苗晚发问题提供依据。在麦棉套作模式下，采用池栽和盆栽相结合的试验方法，设置麦棉自然根系套作(根系和肥水均可相互通过)、纱网隔根套作(肥水可相互通过，根系不能相互通过)和塑膜隔根套作(根系和肥水均不能相互通过)3种麦棉复合根系群体，研究套作小麦对棉花根系活力、内源保护酶活性及膜脂过氧化作用的影响。在麦棉共处期，麦棉自然套作复合根系中小麦根系对肥水的激烈竞争，导致棉花根系干物质累积量和根冠比均显著低于隔根处理。而小麦根系强烈的生理活动，使套作棉花根系处理相对隔根处理处于一种逆境胁迫状态，其根系活力增强，超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)等内源保护酶活性明显提高。同时，根系细胞膜脂过氧化程度也相应增大。到小麦收获后，种间竞争解除，麦棉自然根系处理棉花根系生长的环境条件得以改善，根系膜脂过氧化程度降低，但由于前期影响还未能完成消除，其根重仍明显低于隔根处理。套作棉花通过提高根系内源保护酶活性来适应小麦对其造成的营养逆境胁迫。

English. To study the physiological adaptation mechanism of the cotton root to the nutrition stress in the wheat-cotton intercropping environment, and to give clues on resolving the lag and weak growth of cotton in wheat-cotton intercropping system. Effect of the wheat-cotton composite root system on cotton root growth was studied by setting 3 treatments, i.e. WCRM rooting system in which the roots of wheat and cotton could grow and mix naturally as in the wheat-cotton intercropping field, WCRN rooting system in which the roots of wheat and cotton were separated by nylon net and WCRP rooting system in which the roots of wheat and cotton were separated by plastic film.The results showed that, in the symbiotic period, because of the strong nutrition and water consumption competition from the wheat roots, the cotton roots were in high nutrition stress condition, the root vigor and the cell membrane peroxidation increased and the content of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were significant higher in WCRM than that in WCRP, and the root-to-shoot ration (R/S-ratio) was the lest in WCRM. And these might be the key causes leading to the significant decrease of the accumulation of root dry mass per plant and R/S-ratio in WCRM than in WCRP. After wheat was harvested, with the competition of water and nutrition vanished, all the above indexes of the cotton root began to improve. And for the impact of the wheat still not complete erased, the dry mass of the cotton root in WCRM was still lower than that in WCRP or WCRN. The results suggest that the cotton getting to adapt to the nutrition stress through increase its endogenous cell-protect relating enzymes activity.