新疆棉花叶限制下棉铃蔗糖代谢机制及与比强度形成关系的研究

Xinjiang, with a typical continental dry climate and fertile soils, has fairly rich light and heat resources and is an important production base of commodity cotton. Recently, fiber strength decrease year by year, increase proportion of middle and low-grade and decrease on proportion of top-grade in Xinjiang. These are the main reason for the low national level. With the rapid development of the textile industry, cotton fiber, especially fiber strength, needs continual improvement. Hence, it is a significant scientific research topic how to increase fiber strength on Xinjiang cotton production. But during the later growth stage of cotton the sharp drop in temperature, especially the very low night temperature has become the limiting factor for fiber development. And cotton picker and its comprehensive techniques, especially defoliation, are applied in early September. Therefore, leaf photosynthetic product is hindered transportation-distribution orientation by low temperature and defoliation. These are likely factors that fiber strength is lower. The project takes the onset time of rapid cellulose deposition as the breakthrough point, takes cotton shell storaged transporting leaf photosynthetic product as the center, and uses the means of night warming temperature and defoliation. The objective is to investigate effect of the insufficient leaves source on carbohydrate transformation in boll-leaf system during the cotton later growth stage, and to reveal the regulation mechanism of key enzymes activity on the cellulose synthesis and carbohydrate transformation. Confirm the physiological mechanism that photosynthetic product of cotton shell could be used for fiber development on the insufficient leaves source, and to explore a much more effective solution to improve cotton quality.

新疆棉区光热资源丰富，是我国重要的商品棉生产基地。近年来，新疆纤维比强度逐年下降，差档和中档所占比例增加、强档所占比例减少，因此，解决纤维比强度偏低的问题成为新疆棉产业重要的研究课题。比较新疆棉区气温的变化和机采棉配套技术的实施，在棉花生长后期气温急剧下降以及脱叶剂广泛使用造成的棉花叶片光合产物输出受阻，可能是造成机采棉纤维强力偏低的影响因素。本项目以纤维素快速累积期起始时间为切入点，以贮存和转运光合产物的铃壳为中心，采用控制夜间温度和使用化学脱叶催熟剂的方法，研究棉花生长后期叶限制对铃-叶系统中糖类物质转运和比强度形成的影响，探明铃-叶系统中蔗糖代谢关键酶活性对糖类物质转运和纤维素累积的协同调控作用，揭示叶限制条件下铃壳将贮存的光合产物用于纤维发育的生理机制。研究结果为充分利用新疆棉区的优势资源，改善棉花纤维品质提供理论依据，同时为新疆选育高强力优质棉花品种提供理论参考。

针对新疆棉区棉花生长后期气温急剧降低、机采棉品质变劣等问题，本项目以纤维素累积特性为切入点，以调节棉铃发育和提升纤维品质为突破口，重点开展了以下的研究：（1）新疆棉区温度变化对纤维强力形成的影响及调控。纤维比强度受纤维素快速累积期持续时间（T）、开花至纤维素快速累积期起始时间的平均累积速率（V1）和纤维素最大理论含量（Wm）的显著影响，纤维发育期≥15℃有效积温是影响纤维比强度的主要温度因子。自棉花开花至纤维素快速累积期起始时间内，较多的有效积温使V1直线降低，不利于纤维比强度的提高；纤维素快速累积期≥15℃有效积温的增加显著提高了V1，纤维素快速累积期持续时间（T）随有效积温的增加而显著延长，纤维比强度亦呈增加趋势。若获取≥30 cN/tex的纤维比强度，就需要V1维持在1.32%/d—1.76%/d，纤维素累积时间经历39.0—46.9 d，则需要187.2℃—358.6℃。因此，棉纤维不同发育阶段≥15℃有效积温对V1影响的差异性是造成纤维比强度差异的主要原因，适宜V1有利于形成高强纤维。（2）脱叶催熟剂对机采棉铃发育和纤维品质的影响。喷施脱叶催熟剂后7 d内是实现良好脱叶效果的关键时间段，期间的最高温度和每日≥12℃有效积温则是影响的关键因素，应满足该时间段最高温度大于27.2℃、每日≥12℃有效积温大于7.0度·日。喷施脱叶催熟剂使棉铃铃期缩短，单铃纤维重和单铃棉籽重显著降低，以铃龄44 d时喷施时的单铃重减少最小、铃龄30 d时喷施则减少了26%—40%。脱叶催熟剂对纤维长度的影响较小，且有半数品种呈增加趋势。纤维比强度对脱叶催熟剂的反应更为敏感，其损伤量变幅更大、集中分布在-4 cN/tex—0 cN/tex，并随喷施时间提前损伤变幅显著扩大。可根据“脱叶催熟剂喷施时的棉铃铃龄(d)与铃期(b)的比值（Rd/b）”这一指标综合考虑棉铃铃期和单铃重损伤量及比强度损伤量，以确定脱叶催熟剂的喷施时间。当生产＞31 cN/tex的纤维就需要棉铃铃期＞60.0 d，确保Rd/b＞0.68，在铃龄40.9 d后喷施脱叶催熟剂可控制纤维比强度损伤小于0.5 cN/tex。通过项目研究，明确了适宜纤维素累积和形成高强纤维所需的温度条件，提出了适宜脱叶催熟的棉铃形态参数。研究成果对新疆机采棉优质高效栽培技术的制定，为新疆高品质棉花生产提供了科技支撑。