盐胁迫下不同基因型冬小麦渗透及离子的毒害效应

以4种不同基因型冬小麦为试验材料,利用分根法研究了盐胁迫对小麦的渗透胁迫和离子毒害的效应。结果表明,在盐胁迫下,小麦既受渗透胁迫,也受盐离子胁迫。渗透胁迫效应比较快,大约在处理后1-2d内发生;离子毒害效应比较缓慢,大约需3-4d时间。在一半盐胁迫(200mmol/L NaCl)和一半非盐胁迫的分根条件下,小麦没有明显的渗透胁迫效应,小麦植株地上部Na⁺ 累积到毒性水平之前盐处理对小麦生长无抑制效应。小麦具有将Na⁺ 从盐胁迫一侧转移非盐一侧的能力,说明小麦吸收的Na⁺ 有一部分可以从地上部回流到根系中,回流率可达76%-89%。无水分胁迫(不加入PEG)的回流率大于水分胁迫(加入PEG)的回流率。不同基因型小麦在盐分吸收累积和回流,及渗透和离子胁迫的速度和程度等方面具有明显差异。NR 9405和小偃6号的Na⁺ 累积速度要少于陕229和RB 6;NR 9405根系排Na⁺ 能力强于陕229和RB 6。因此,NR 9405和小偃6号的耐盐性高于陕229和RB 6。

Osmotic and ionic stress effects of high NaCl concentration on seedlings of four wheat (Tritium aestivum L.) genotypes

The osmotic and ionic effects of salt stress on seedlings of four winter wheat genotypes were investigated using a split-root system with hydroponic solutions. The four genotypes differed in canopy temperature and included a warm canopy temperature genotype (NR 9405), a medium to cold canopy temperature genotype (Xiaoyan 6), and two cold canopy temperature genotypes (Shaan 229 and RB 6). Seeds of similar size and vigor were chosen, sterilized with 10% Javel water, and then placed on a floating mesh in distilled water to germinate in the dark. At the two-leaf stage, uniformly sized seedlings were transplanted to the split-root system, with roots from each seedling uniformly divided between the two sides of the baffle. There were 15 plants per pot. The basic culture solution was 1/2 Hoagland's nutrient solution.There were five treatments: T1: 0/0 (T1-1/T1-2); T2: PEG-6000/PEG-6000 (T2-1/T2-2); T3: NaCl/NaCl (T3-1/T3-2); T4: 0/NaCl (T4-1/T4-2); T5: PEG-6000/NaCl (T5-1/T5-2). The concentration of the NaCl solution was 200 mmol/L. The concentration of the PEG-6000 solution was 274.09 g/L. The water potential of the PEG-6000 solution was 0.88 MPa and was similar to the 200 mmol/L NaCl solution. Each treatment was replicated three times. Overall, the results showed that salt stress had both osmotic and ionic effects on the seedlings. The osmotic effect was rapid and occurred in 1 or 2 days, but the ionic effect developed more slowly, occurring after about 3 to 4 days when Na⁺ accumulation reached a threshold level. In T4, half of the root system was treated with Hoagland solution containing 200 mmol/L NaCl while the other half of the root system was in Hoagland's solution without salt stress. The results showed that salt stress had no significant osmotic effect on the wheat seedlings. There was no significant inhibition of leaf growth when Na⁺ levels within the shoots were below toxic levels. In the NaCl treatment (T3), the Na⁺ accumulation rate and accumlation amount were less for NR 9405 (warm) compared to the other three genotypes. The rate of Na⁺ accumulation decreased when the Na concentration in one cell was significantly reduced (T5). The reduction in accumulation rate was greater for NR 9405, Shaan 229, and Xiaoyan 6 than for RB 6. An increase in water potential on one side of the baffle (T4) significantly reduced the Na⁺ accumulation rate in NR 9405 and Xiaoyan 6. Furthermore, the Na⁺ content of NR 9405 and Xiaoyan 6 was significantly lower than Shaan 229 and RB 6. This suggested significant variation in water regulation and salt absorption capacity among wheat genotypes with different canopy temperatures. Specifically, warm canopy temperature genotypes had greater water regulation ability and salt absorption capacity than cold temperature genotypes. The Na⁺ concentration of the solution in the cell with no NaCl increased significantly during the experiment, which indicated that part of the Na⁺ absorbed by the plants could be recycled through the roots. The recycling rate ranged from 76% to 89%. Reducing the salt concentration (or increasing the water potential) of one cell in the system removed the osmotic effect and delayed the ionic effect, but could not prevent salt accumulation in plants. The recycling rate was slower when plants were under water stress. Comparisons among the winter wheat genotypes showed significant differences in Na⁺ accumulation, Na⁺ recycling rate, the time to the onset of osmotic and ionic stress, and the degree of osmotic and ionic stress. The Na⁺ accumulation in NR 9405 and Xiaoyan 6 was less than in Shaan 229 and RB 6, but Na⁺ recycling was greater in NR 9405 compared to Shaan 229 and RB 6. In summary, these results indicated that NR 9405 and Xiaoyan 6 had greater salt tolerance than Shaan 229 and RB 6.