砂培条件下两种磷效率棉花根系形态及根际特征差异

为对比两种磷效率棉花在两种磷水平(0.1和5 mmol/L)的根系形态和根际特征的差异。以磷高效型棉花ZM42和磷低效型棉花XLZ13为研究对象设计砂培花盆分层试验，测定生物量、吸磷量、根系形态数据、分层Olsen－P、 pH值和酸性磷酸酶。结果表明：在砂培条件下两种磷效率棉花生物量和磷素积累量随施磷量的增加均有不同程度增加； ZM42在两种磷处理的根部生物量、吸磷量以及根冠比都优于XLZ13。在两种磷处理下， ZM42根系中根径(0~0.4 mm)的细根长度较XLZ13长，细根在总根长中的比例较高。总根长中细根越多有利于促进植株对磷的吸收。生长介质中磷含量降低时，棉花根际pH值也随之降低，高效品种ZM42的根际pH值降低幅度显著高于XLZ13；两种磷效率棉花在两个时期的根际土壤磷酸酶活性均随着施磷量的减少而增加，磷高效棉花ZM42分泌的土壤磷酸酶活性均高于磷低效棉花XLZ13。由此可见，两种磷效率棉花在相同生长介质中根际机理存在差异，且在低磷胁迫下磷高效棉花根系形态特征改变是根际磷活化主要机理之一。

Effect of phosphorus levels on root morphology and rhizospheric characteristic between the different phosphorus ef-ficiency cotton under sand culture condition

The experiment was conducted to investigate effects of different P levels ( P1 0. 1 mmol/L, P2 5 mmol/L) on root morphology and characteristics of rhizosphere in different P-efficiency cotton under the gravel culture conditions. Two differ-ent P-efficient cotton genotypes (the P efficient ZM42 and the P inefficient XLZ13) were selected for the study. Crop bio-mass, P uptake amount, root morphology, available P, pH and phosphatase activity in the rhizosphere were measured. Result showed that under the sand culture cotton biomass and accumulation of phosphorus increased with phosphorus applica-tion for both the P-efficient genotypes cotton. Root biomass, P uptake and root to shoot ratio of ZM42 was better than XLZ13. length of fine root (0~0. 4 mm) in ZM42 was looger than XLZ13, and the proportion of fine roots in the total root length was higher, which was helpful to promote phosphorus absorption of plant. When the phosphorus content in growth medium was lower, to reduce the pH in the cotton rhizosphere also decreased. The pH of the rhizosphere of ZM42 was sig-nificantly higher than XLZ13. Rhizosphere phosphatase activity of two kinds of phosphorus efficiency cotton was increased as the phosphorus content decreased in the two periods. Phosphatase activity of ZM42 was higher than that of XLZ13. Thus, there was a difference with rhizosphere mechanism between the two phosphorus efficiency of cotton in the same growth medi-um, the change of root morphology characteristic of the P efficient cotton was one of the main mechanisms of rhizosphere phosphorus activation.