盐碱胁迫对海岛棉种子萌发及幼苗根系生长的影响

为明确海岛棉种子萌发及幼苗根系对盐胁迫的响应,并筛选出耐盐能力较高的海岛棉品种。以新疆阿克苏地区主推海岛棉品种新海31号、新海35号、新海43号和新海48号为试材,采用NaCl、Na2SO4以及NaCl、NaHCO3以物质的量1∶1混合分别模拟中性盐混合盐(中性盐)和碱性盐混合盐(碱性盐)两种盐类型,胁迫处理总盐浓度(Na+)为0、120、180、240、300、360 mmol L~(–1),研究了盐胁迫下海岛棉种子萌发和幼苗根系生长参数。结果表明,在两种盐类型下,随着盐浓度的增加,海岛棉种子的萌发参数、生物量、根冠比、盐敏感指数、盐耐受指数、根系长度、根系表面积及根系体积均呈下降趋势;高盐浓度下,海岛棉株高、根系生物量及茎叶生物量与盐浓度呈显著负相关,说明高盐环境抑制了棉种发芽及幼苗的正常生长。120 mmol L~(–1)浓度下,中性盐处理的新海48号的根系总长度比对照无显著增加,其余品种均有显著增加,各品种根系总体积与总表面积均无显著差异,低盐促进了各品种细根(d≤0.5 mm)的伸长及生长,新海43号的中根(0.5d≤2.0 mm)长度比CK增加显著,导致此品种根系的总体积与总表面积有显著增加;碱性盐处理的根系总长度、表面积及体积除新海31号与对照差异不显著外,其余品种均有显著降低。180～240mmolL~(–1)浓度下,中性盐处理的根系总长度、表面积及体积与对照相比除新海43号有显著下降外,各品种均差异不显著;碱性盐处理的各品种均是下降显著,其中新海35号的根系总长度下降幅度比其余品种缓慢。300～360mmolL~(–1)浓度下,两种盐处理的各品种的根系总长度、体积与表面积均急剧下降。碱性盐胁迫比中性盐胁迫下降的趋势更为显著。本试验条件下,海岛棉幼苗正常生长所能承受的盐浓度为240 mmol L~(–1),但碱性盐对于海岛棉幼苗的伤害远大于中性盐,供试品种耐盐碱程度为新海35号新海43号新海31号新海48号。

Effects of salinity stress on seed germination and root growth of seedlings in island cotton

In order to determine the response of seed germination and seedling root system of island cotton to salt stress, and to screen out island cotton varieties with high salt tolerance, an experiment was conducted using main sea island cotton varieties Xinhai 31, Xinhai 35, Xinhai 43, and Xinhai 48 grown in Xinxiang Aksu area, with treatment of neutral salt (neutral salt) mixed with NaCl, Na₂SO₄ at 1:1 of mole ratio and treatment of alkali salt (alkaline salt) mixed with NaCl and NaHCO₃ at 1:1 of mole ratio, Total salt concentration (Na ⁺) was 0, 120, 180, 240, 300, and 360 mmol L ^-1. Seed germination and seedling root growth parameters of island cotton under the stress were measured. The germination parameters, biomass, root and crown ratio, salt sensitivity index, salt tolerance index, root length, root surface area and root volume of the island cotton seeds decreased with the increase of salt concentration. Moreover, under high salt concentration, there was a significant negative correlation of plant height, root biomass, stem and leaf biomass with salt concentration, indicating that high salt environment inhibited cotton seed germination and normal growth of seedlings. Under the concentration of 120 mmol L ^-1, the total length of the root system of Xinhai 48 treated with neutral salt did not increase significantly compared with that of the control group, while that of the other varieties increased significantly. There was no significant difference in the total volume and total surface area of the roots. The low salt concentration promoted the elongation and growth of the fine roots (d ≤ 0.5 mm). The middle root (0.5 < d ≤ 2.0 mm) of Xinhai 43 increased significantly than that of CK, resulting in a significant increase in total root volume and total surface area. The total length, surface area, and volume in alkaline salt treatment were not significantly different from those of Xinhai 31 and the control, while decreased significantly in other varieties. At the concentration of 180-240 mmol L ^-1, the total length, surface area and volume of roots in neutral salt treatment had a significant decrease compared with these of the control except for Xinhai 43; there was no significant difference among all varieties; lot a decrease in alkaline salt treatment. Among them, the total length of the roots of Xinhai 35 decreased more slowly than that of other varieties. At the concentration of 300-360 mmol L ^-1, the total root length, volume and surface area of the two salt varieties dropped sharply. The alkaline salt stress had a more significant decrease effect than the neutral salt stress. Under the conditions of this experiment, the normal growth of island cotton seedlings could withstand the salt concentration of 240 mmol L ^-1, but the damage of alkaline salt to island cotton seedlings was much greater than that of neutral salt. The order of salt tolerance of the tested varieties was Xinhai 35, Xinhai 43, Xinhai 31, and Xinhai 48.