棉花早熟不早衰基因型的根系形态和生理机制研究

Root absorbs water and nutrients, as well as composes metabolites and proteins, which transport to shoot by xylem system, and affect shoot growth and development, so root morphology and physiology matters in shoot characteristics. Cotton often prematurely senesces, which results in reduction of yield and fiber quality. It was well documented about physiology and biochemistry of leaf senescence in cotton. However, the relationship of root morphology and physiology with shoot characteristics is rarely investigated, and the same for prevention and cure of pre-mature senescence by regulation of root morphology and physiology with coronatine. Our experimental results showed that root distribution in 20-40 cm soil was closely related to premature senescence, and that coronatine applied in soil retarded leaf senescence. Therefore, under field and soil column etc., with different cotton genotypes, respectively, with earliness and no premature senescence and with earliness and premature senescence, we will further investigated(1)root morphology(in-depth root distribution, root turnover and cell ultra-structure in root tip, etc.), (2)root physiology(root senescence, root-to-shoot signaling: targeted ionic profile, targeted metabolic profile and proteomics, etc.), and (3) shoot characteristics (leaf senescence, earliness, yield and quality), respectively, when non-grafted, reciprocally grafted between differently senesced genotypes and coronatine applied in soil. Based on the above results, it will be clarified about the morphological and physiological mechanisms of genotypes with earliness and no premature senescence and about root-to shoot signalling mechanisms of coronatine in delaying leaf senescence. This study will supply references for application of root morphology and physiology improvement in cotton breeding and cultivating, and for coronatine application against premature senescence.

根系形态和生理特性影响了地上部特性。棉花生产上经常出现叶片早衰，导致产量和纤维品质降低。棉花叶片衰老的生理生化特性等受到广泛研究，但根系形态和生理与棉花地上部特性的关系及通过调控根系形态和生理而防治棉花早衰的详细研究相对很少。我们证明土壤20-40cm层根系分布与早衰显著相关，根际施用冠菌素可以显著延缓易早衰棉花叶片衰老。本项目拟在大田、土柱等种植条件下，利用早熟不早衰与早熟但早衰基因型，分别在不嫁接、衰老特性不同基因型相互嫁接和冠菌素根际处理三种情况下，详细研究根系形态（根系分布、周转和根尖细胞超显微结构等）、根系生理（根系衰老与根冠通讯信号"目标无机离子谱、目标代谢物谱和蛋白质组等"）和地上部特性（叶片衰老、早熟性和产量品质）。根据上述研究结果，阐明①早熟不早衰基因型棉花的根系形态和生理机制，②冠菌素延缓叶片衰老的根冠通讯机制，为根系改良在棉花育种和栽培管理中应用提供参考。

早熟性棉花在生产上普遍存在早衰现象，这种早衰现象通常和钾缺乏之间密切相关。根系生长状况是棉花衰老特性的基础。本项目通过对比不同衰老特性棉花基因型根系动态，通过嫁接改变根系及通过使用冠菌素调节根系，研究根系形态和生理在棉花衰老方面的作用，研究根冠通讯物质中蛋白质和代谢物的种类与浓度变化，研究冠菌素调控根系活力的生理机制及乙烯在棉花根系伸长和侧根发生过程中的作用。结果表明，1易早衰性棉花根系长度在8月中旬前后明显高于不易早衰性棉花品种，而8月中旬前后正是棉铃生长高峰期，根系与铃之间对养分争夺激烈，导致了早衰；而冠菌素在7月中下旬使用，先抑制了根系生长后促进了根系生长，避免了根系和铃之间的激烈养分争夺，从而延缓了衰老。由此可见，在育种中培育的棉花品种应避免在棉花铃花生长高峰期根系也有大量生长。2棉花伤流液中发现存在大量抗逆相关和细胞壁发育相关蛋白，而这些蛋白均从根系细胞中分泌到伤流液（质外体）中，既反映了根系的抗逆状况和发育状况，又暗示了根系和地上部分的通讯状况；钾缺乏降低了棉花伤流液中大部分抗逆蛋白和细胞壁发育蛋白的表达，暗示了钾缺乏降低了棉花侧根发育，导致早衰及降低抗逆性的机理。3 冠菌素提高了根系活力，虽然同时显著提高了根系多酚含量及单位质量的呼吸速率, 但表明TTC还原能力可以用于表示冠菌素对根系代谢活性的促进, 而不受多酚的影响；同时显著增加根系活性氧的产生量，改变了抗过氧化物酶和非酶物质的表达状况，意味着活性氧作为信号物质传递了冠菌素的作用；冠菌素提高了低钾下棉花伤流液中蛋白质含量，改变了分泌蛋白的表达谱，暗示了冠菌素提高抗逆性的机理。4 乙烯信号抑制剂和产生抑制剂处理棉花根系和叶片，显示钾缺乏诱导乙烯释放增加或许是根系伸长受抑制的原因，改善叶片生长可积极调节根系生长和发育，进一步揭示了根冠之间协调性。因此，在低钾条件下，可通过改善叶片生长，改善根系生长，进而形成良性循环。