棉花种子萌发响应盐胁迫及DPC调控其耐盐机制研究

Salinity is one of the major environmental factors that severely limits productivity and yield in many areas worldwide. Moreover, soil salinization is still expanding and becoming more serious in the world, mainly due to excessive irrigation and industrial pollution, posing a great threat to agricultural sustainability. Although cotton is classified as a salt tolerant crop, its growth is severely reduced at high salinity levels, especially at the germination stage. Salt stress can inhibit the metabolism of dividing and expanding cells, retarding germination and even leading to seed death. Germination is an important and vulnerable stage in the life cycle of plants in saline environments and determines seedling establishment and plant growth. Mepiquat chloride (DPC), a plant growth regulator, has been used worldwide to suppress excessive growth in cotton plants. In recent years, although previous studies have found that DPC can promote salinity tolerance of plants under salt stress, the mechanisms involved in underlying the specific components of protective mechanisms remain poorly understood. To better understand the role of DPC on germination stage, we conducted an experiment to investigate the effect of soaking seed with 200 mg L-1 DPC on germination stage by using four cotton cultivars (differing in salt sensitivities). Seed germination in, and recovery germination from, salt stress were recorded. The effects of salt stress on osmotic effect such as seed water uptake, osmotic adjustment substance and osmotic potential were measured. In addition, ionic effect such as absorption and distribution of Na+ and K+, expression level of ions transporter and H+-ATPase activity were also investigated. In the view of osmotic and ionic adjustment, we aim to investigate the mechanistic explanation for differential salinity tolerance among these cultivars and shed light on the effect of DPC soaking seed on the different coping strategies of salinity tolerance. This research will not only enrich knowledge of salinity tolerance of cotton germination stage in response to salt stress but also provide a framework to identify breeding targets for improving salt resistance in cultivated cotton.

盐害是影响农作物产量的主要因素之一，随着人类过度灌溉和工业污染等不合理的开发方式，使得土壤盐碱化程度越来越严重。棉花是一种耐盐作物，被认为是改良盐碱旱地的先锋作物。然而，棉花的耐盐性也是有限的，盐胁迫常抑制种子萌发、出苗，甚至导致死苗，盐碱地成苗难长期困扰棉花生产。近年来一些研究发现，通过生长调节剂缩节胺(DPC)浸种能提高植物的耐盐性，然而DPC调节其耐盐性的内在机理尚不清楚；为探究DPC浸种对盐胁迫下植物种子耐盐性的调节作用，拟选用四个耐盐性差异的棉花材料，从“种子萌发差异 — 渗透平衡态重建 — 离子平衡态重建”的思路进行剖析，阐述不同基因型种子萌发阶段的耐盐性差异，同时揭示DPC浸种调节“渗透和离子平衡态重建”耐盐策略的生理及分子机理。研究成果不仅明确棉花种子萌发阶段的耐盐机理，还可以为棉花耐盐性育种提供理论指导，具有较强的理论价值和实践指导意义。

棉花是一种耐盐作物，被认为是改良盐碱旱地的先锋作物。然而，棉花的耐盐性也是有限的，盐胁迫常抑制种子萌发、出苗，甚至导致死苗，盐碱地成苗难长期困扰棉花生产。前期研究发现，缩节胺(DPC/MC)浸种能提高萌发期棉花种子的耐盐性，然而MC调节其耐盐性的内在机理尚不清楚；为探究MC浸种对盐胁迫下棉花种子耐盐性的调节机制，以CZ91、CCRI44、CCRI49和Z571为材料，研究了MC浸种对盐胁迫下种子萌发差异、渗透平衡态重建及离子平衡态重建的影响，主要试验结果如下：.种子萌发及复水试验表明，CCRI44、CCRI49和Z571种子萌发期的耐盐性主要依赖于耐盐策略。而CZ91种子在盐胁迫下萌发受到明显抑制，但绝大多数未萌发的种子转移到蒸馏水中后完全恢复萌发，这表明CZ91采用了避盐策略。MC浸种可以缓解盐胁迫对耐盐策略品种(尤其是Z571)抑制效应，而对避盐策略品种CZ91无显著影响。MC浸种提高对耐盐策略品种的耐盐性主要归因于调节了三个重要相关的生理特性：(i)通过调控水孔蛋白PIPs促进水和溶质(即Na+和K+)的吸收增加渗透势；(ii)通过调控多种离子转运蛋白(如SOS、HKT1、NHX1、ATK1和HAK5)来调节Na+和K+的稳态，从而提高组织耐受能力；(iii)通过诱导H+-ATPase基因的表达进一步增强离子转运系统的功能。上述结果表明，MC浸种对盐胁迫的缓解机制十分复杂，并且与品种特性有关。