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棉花(陆地棉)生长势、开花量和成铃率的降低是衰老的特征。缺氮促进衰老,据报道缺氮还会引起生长抑制激素脱落酸(ABA)浓度的增大。“岱字棉61”的田间试验表明缺氮影响果枝中ABA和IAA的浓度,这两种激素与棉花的生长势、开花量和成铃率有关。据1987年铃期获得的3组数据可见:随着生长势的减弱,果枝中ABA和IAA的浓度的变化。从1988年获得的3组数据亦确定了蕾和花中ABA和IAA的浓度的变化。低N株的果枝总是比高N株的短,且后期生长的果枝比早期生长的短的多。7月9日以后,果枝中ABA的浓度下降,并且低N株果枝中ABA浓度总是比高N株的低。因此,这一结果并不符合ABA在缺N棉花果枝中积累并抑制生长的假设。而IAA含量降低会减弱果枝的生长势。在铃期果枝中IAA浓度在下降,且低N株中比高N株中要低得多(除最后一组数据外),随着成铃率降低,3天的幼铃中ABA增加、IAA减少;蕾、花中ABA的浓度相对稳定,且不受缺N的影响;同样,蕾、花中IAA的浓度也不受N的影响,但铃期蕾中IAA的浓度逐渐降低。总的结论是:缺N影响着果枝中IAA的浓度,结铃期IAA浓度降低,并可能是致使生长势、开花量和成铃率降低(通常称作衰老)的一个因素。
Cotton (Upland cotton) growth potential, flowering and boll rate reduction is characterized by aging. Nitrogen deficiency promotes aging, and nitrogen deficiency is reported to cause an increase in the concentration of growth-inhibitory hormone abscisic acid (ABA). Field trials of “Dai Zi 61” showed that nitrogen deficiency affected ABA and IAA concentrations in fruiting branches. The two hormones were related to the growth potential, flowering rate and boll rate of cotton. According to the three sets of data obtained in 1987, we can see the change of ABA and IAA concentration in fruiting branches with the decrease of growth potential. Three sets of data obtained from 1988 also identified changes in the concentrations of ABA and IAA in buds and flowers. The fruit shoots of low N plants were always shorter than those of high N plants and fruiting branches growing later were much shorter than those of the early stage. After July 9, the concentration of ABA in fruit branches decreased, and the ABA concentration in fruit branches of low N plants was always lower than that of high N lines. Therefore, this result is not consistent with the hypothesis that ABA accumulates and inhibits growth in N deficient cotton bolls. The decrease of IAA will weaken the growth potential of fruiting branches. The concentration of IAA in the fruiting branches decreased at the boll stage and was much lower in the lower N plants than in the high N plants (except for the last set of data). The IAA The concentration of IAA in buds and flowers was relatively stable and not affected by N deficiency. Similarly, the IAA concentration in buds and flowers was not affected by N, but IAA concentration in buds decreased gradually. The general conclusion is that N deficiency affects the concentration of IAA in fruiting branches, decreases the IAA concentration during the boll stage, and may be a contributing factor to reduced growth vigor, flowering and boll rate (commonly referred to as senescence).