滨海盐碱地施钾影响棉花纤维长度形成的生理机制研究

Fiber length, which together with fiber strength and micronaire is known as the "quality indexes" of cotton, is the most important factor for single yarn strength. Compared with low sodium soil, the application of potassium fertilizer can make the cotton leaves overcome K+ malabsorption due to high Na+, and significantly improve the cotton fiber length. Improving fiber length is very important for enhancing the international competitiveness of the cotton. In order to investigate the effect of K application on fiber elongation development and fiber length formation of cotton grown in saline-alkali soil, field and pot experiments will be designed with two cotton cultivars (CCRI 79, salt-tolerant；Simian 3, salt-sensitive) under three salinity levels(EC=1.15, 6.00, 11.46 dS m-1), meanwhile three potassium levels (0,150 and 300kg K2O ha-1) will be applied to each salinity level. The objectives of our research are(1) to study the effect of different potassium levels, sodium levels and K+/Na+ ratios in soil on potassium and sodium accumulation and distribution in cotton plants; (2) to explore the effect of K+/Na+ ratio in cotton plants on photosynthesis and biomass partitioning; (3) to understand the dynamic changes of matters (soluble sugar, K+, malic acid) and enzymes (plasmalemma H+-ATPase, PPase, SuSy, SPS, PEPC) involving fiber elongation, and enzymes (β-1,4-glucanase, Expansin, XET) involving cell wall loosing under different K+/Na+ ratios in cotton plants; (4) to identify the sensitive matters and enzymes to K+/Na+ ratios and compare the differences in gene expression of sensitive enzymes. These studies will be beneficial to reveal the physiological mechanism of the effect of potassium application on the growth and formation of fiber length in saline-alkali soil and it also provide theoretical basis for exploring the physiological regulation of cotton fiber elongation in saline-alkali soil.

纤维长度、比强度和马克隆值是棉花三大纤维品质指标，其中纤维长度是对纺织成纱单纱强力影响最大的因素。滨海盐碱地棉田增施钾肥可使棉株克服由Na+过高导致的K+吸收障碍，极显著提高棉纤维长度。因此，本研究拟通过设置低、中、高3个盐分水平（EC=1.15、6.00、11.46 dS m-1）、3个施钾量（0、150、300kg K2O hm-2）、2个棉花品种（中棉所79，耐盐型；泗棉3号，盐敏感型）综合性试验，研究土壤不同钾钠水平对棉株K+、Na+的吸收与分配、棉叶光合产物的形成与转化的影响，研究棉株K+/Na+对调控纤维伸长的膨压物质及相关酶活性、纤维细胞壁松驰酶活性的影响，明确对棉株K+/Na+变化敏感的关键膨压物质、膨压物质代谢与纤维细胞壁松驰的关键酶及基因表达差异，揭示滨海盐碱地施钾影响棉纤维长度形成的生理机制，研究结果为生产上探索滨海盐碱地改善棉纤维长度的生理调控途径提供理论依据。

盐碱地钠钾丰富，但K+/Na+比过低，Na+因性K+吸收障碍严重影响了棉花纤维产量和品质，品质指标中以纤维长度影响最大。本项目探究了盐碱地施钾调控棉纤维长度形成的生理机制，揭示了：.（1）盐胁迫下施钾，可一定程度上缓解因铃数、铃重的下降而导致的籽棉产量和纤维品质的下降。150kg hm-2及以上施钾量可缓解中盐胁迫；300kg hm-2施钾量对高盐胁迫下中棉所79（耐盐型）的产量缓解系数为59.1%-65.3%，对纤维长度和比强度缓解系数分别为51.1%-60.0%和29.8%-40.6%。高盐胁迫仍是限制籽棉产量纤维品质提升的主要因素。.（2）盐胁迫下施钾，促进了棉株对K+的吸收与分配，提高了棉株尤其纤维中K+/Na+比；籽棉产量、纤维长度分别与棉株及棉铃对位叶中K+含量、K+/Na+比呈显著正相关，与Na+含量呈显著负相关。.（3）棉株K+含量、K+/Na+比的提高，减缓了因盐胁迫引起的棉铃对位叶叶绿素分解速率以及净光合速率和气孔导度的下降速率，降低了SPS和SuSy酶活性，促进棉铃对位叶中蔗糖向棉铃转运，减少了棉铃对位叶中蔗糖和淀粉的累积，促进了棉叶光合作用。.（4）纤维K+含量、K+/Na+比的增加，提高了纤维伸长期最大伸长速率；提高了花后14 d纤维SuSy、PEPC、PPase和PM-H+-ATPase的活性以及细胞膨压物质的含量，且K+含量的增幅约是可溶性糖、苹果酸的2倍多，说明盐胁迫下纤维伸长期细胞膨压的维持主要是通过增加纤维细胞中K+含量来实现的。.（5）纤维中K+含量、K+/Na+比的增加，还增加了花后28d的磷酸蔗糖酶、β-1,3-葡聚糖酶的活性以及蔗糖及β-1,3-葡聚糖含量，提高了纤维素最大累积速率，促进纤维蔗糖转向纤维素的累积，提高了纤维比强度。.上述研究结果，对我国盐碱地植棉提升棉花纤维产量和品质意义非常重大。