Abstract:

Exploring the effects of continuous drought stress on photosynthetic characteristics and yield of cotton (Gossypium hirsutum L.) at bud stage can provide scientific irrigation basis for high-yield cultivation in arid cotton area. Four treatments of soil water were set up including normal water (CK, 80%-85% FC), moderate drought (MD, 50%-55% FC), mild drought and severe drought (SD, 30%-35% FC). After drought treatment, the photosynthetic physiology and yield structure were measured at a frequency of 7-10 days/time. The results showed that the continuous drought stress accelerated the process of cotton growth period, and the development period was 4-18 days earlier than that of the control. With the aggravation of drought stress, the plant height of cotton decreased. Compared with the control, the growth rate of plant height decreased by 17%-24%, under drought stress. Continuous drought stress changed the time when the leaf area index of cotton reached the maximum, and the leaf area index increased first and then decreased. The net photosynthetic rate, maximum photochemical efficiency, dry matter weight and plant moisture content of cotton were always lower than those of the control under moderate and severe treatments. Under mild treatment, they were higher than those of the control from squaring stage to flowering and boll-setting stage, but lower than those of the control from boll-opening stage till the growth stopped. Under different drought stress treatments, the single boll weight and boll abscission rate increased with the aggravation of drought. Compared with the control, the boll abscission rate increased by 6.9% under severe stress, but there was no significant difference in single boll weight under different treatments. The boll number per plant and yield decreased, and the yield decreased by 31%-55% under drought stress. Taken together, the moderate drought stress at the beginning of bud stage is beneficial to maintain high net photosynthetic rate and improve dry matter quality of cotton within a certain range. The extent to which yield components were affected by continuous drought at bud stage showed the following order: boll number per plant on final yield>boll abscission rate>boll weight.

Key words: bud period, drip irrigation under mulch, drought stress, photosynthetic characteristics, yield, cotton

摘要：

探究蕾期开始的持续干旱胁迫对棉花（Gossypium hirsutum L.）光合特性及产量的影响，为干旱棉区高产栽培提供科学灌溉依据。现蕾期设置重度胁迫、中度胁迫、轻度胁迫和正常灌溉4个水分梯度。梯度灌溉后以每次7—10 d的频率进行光合生理及产量结构的观测。结果显示，蕾期开始的持续干旱胁迫加快了棉花生育期的进程，与对照相比，发育期提前了4—18 d。随着干旱胁迫的加剧，棉花株高呈下降趋势，与对照相比，干旱胁迫下株高增长率降低了17%—24%。干旱胁迫使得棉花叶面积指数达到最大值的时间发生了改变，叶面积指数呈先升高后下降的趋势。棉花净光合速率、最大光化学效率、干物质量和植株含水率，中度和重度处理下始终小于对照，轻度处理下蕾期至花铃期高于对照，裂铃期至停止生长期低于对照。不同发育时期叶片净光合速率对干旱胁迫的响应存在差异，现蕾期和开花期高于裂铃期和吐絮期。棉花叶片最大光化学效率（F_v/F_m）随发育时期变化总体呈先增加后减少的趋势。蕾期开始的适度干旱胁迫在一定时间范围内可以增加棉花干物质，当干旱胁迫超过一定时间，干物质量迅速下降。不同干旱胁迫处理下单铃质量差异不显著，单铃质量和蕾铃脱落率随干旱的加剧升高，与对照相比，重度胁迫下蕾铃脱落率增加6.9%；单株铃数和产量降低，干旱胁迫较对照减产31%—55%。研究表明，蕾期开始的适度干旱胁迫在一定范围内有利于棉花保持较高的净光合速率，提高干物质量。蕾期持续干旱对产量构成因素的影响程度为：对最终产量的影响单株结铃数>蕾铃脱落率>铃质量。

关键词: 蕾期, 膜下滴灌, 干旱胁迫, 光合特性, 产量, 棉花