A hydroponics experiment was conducted to investigate the effects of decapitation which is a conventional technique in cotton production in Xinjiang on the root activity and malonaldehyde (MDA) content of cotton under low and high nitrogen supply,respectively.The results showed that comparing with non-decapitated plants,the root activities of the decapitation,the decapitation plus smearing lanolin,the decapitation plus smearing lanolin and NAA treatments were remarkablely increased by 94.4％ ～ 110.0％,55.9％ ～85.7％ and 51.5％ ～ 147.4％,respectively; and the MDA content were also increased by 12.0％ ～17.3％,5.2％～6.5％ and 9.7％～ 10.9％,respectively.It is concluded that the decapitation and decapitation plus NAA smearing enhanced the growth of plant,and the activity and the total absorbing area of cotton roots.%为了揭示新疆棉花栽培技术中“打顶”措施与棉花早衰问题之间的关系,在水培条件下研究了低氮(1.0×10-3 mol·L-1)和高氮(4.0×10-3 mol· L-1)两种供氮水平下,不打顶、打顶、打顶后涂抹羊毛脂和打顶后涂抹羊毛脂+萘乙酸处理对棉花功能叶丙二醛含量和根系活力的影响.结果表明:在两种供氮水平下,棉花打顶、打顶后涂抹羊毛脂和涂抹羊毛脂+萘乙酸处理比不打顶处理根系活力增幅分别为94.4％～110.0％、55.9％～85.7％和51.5％～147.4％,差异显著；丙二醛(MDA)含量增幅分别为12.0％～17.3％、5.2％～6.5％和9.7％～10.9％,差异不显著.打顶和打顶后涂抹萘乙酸可促进棉花根系生长,提高根系活力和总吸收面积.
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