向日葵芽苗期离子对复合盐胁迫的响应

研究向日葵耐盐的离子响应机制,可为快速筛选耐盐向日葵品种提供科学依据。本试验以油用向日葵盐敏感品种‘YK18’、中度耐盐品种‘YK06’和耐盐品种‘GF01’为试验材料,研究0 mmol·L~(–1)、50 mmol·L~(–1)、100 mmol·L~(–1)、150 mmol·L~(–1)、200 mmol·L~(–1)和250 mmol·L~(–1)复合盐(NaCl和Na_2SO_4按9∶1摩尔比混合)浓度下的种子萌发和离子在萌发幼苗中积累分布情况,并利用离子流检测技术,动态监测了复合盐胁迫24 h后植株根系的K~+、Na~+、Ca~(2+)等离子的流速流向。结果表明,复合盐胁迫抑制向日葵种子萌发,导致发芽率下降,平均发芽时间延长。盐胁迫后向日葵根系K~+大量外排,流速为‘YK18’‘YK06’‘GF01’;随着盐胁迫浓度升高,根系Na~+流速由内吸转为外排,内吸时‘YK18’速度最大,‘YK06’次之,‘GF01’最小,外排时‘GF01’流速最大,其"排盐"现象明显。复合盐胁迫后,整株的Na~+积累量增加,K~+减少,K~+/Na~+随着盐浓度升高而下降;低盐浓度(150 mmol·L~(–1))下‘GF01’和‘YK06’茎秆中K~+/Na~+低于‘YK18’;高盐胁迫(≥150 mmol·L~(–1))下,‘GF01’整株Na~+积累最少,叶片K~+/Na~+最高。另外,盐胁迫下向日葵幼苗根系Ca~(2+)的吸收速率加快,‘GF01’是‘YK18’的2倍。由此可见,不同耐盐性的油用向日葵植株在盐胁迫下可通过调节Na~+、K~+和Ca~(2+)的吸收与外排来适应盐胁迫环境,耐盐性强的品种具有更强的保K~+能力,并通过区域化Na~+(低盐胁迫)和拒盐机制(高盐胁迫)来提高其对盐胁迫的耐受性,维持植株叶片中合理的K~+/Na~+值。本研究结果可为盐碱地耐盐品种筛选和栽培提供理论依据。

Ion response of sunflower at sprouting stage to mixed salt stress

Research on the mechanism of response of sunflower to salt stress can provide scientific basis for rapid screening of salt re-sistant varieties, a critical element in the exploitation of saline-alkali lands. In this study, salt-sensitive variety 'YK18', moderately salt-tolerant variety 'YK06' and highly salt-tolerant variety 'GF01' of sunflower were used to analyze seed germination, ion accumula-tion and distribution in seedlings of different varieties of sunflower under mixed salt (NaCl/Na2SO4of 9/1 mol) concentrations of 0 mmol·L–1, 50 mmol·L–1, 100 mmol·L–1, 150 mmol·L–1, 200 mmol·L–1 and 250 mmol·L–1. Scanning ion-selective electrode technique (SIET) was used to determine K+, Na+ and Ca2+fluxes in roots after 24 h mixed salt stress. The results showed that seed germination, germination rate and germination index decreased under salt stress and the average germination time of oil sunflower extended. Under salt-stress condition, there was an obvious K+efflux in roots. Compared with high salt-tolerant variety 'GF01', the roots of salt-sensitive variety 'YK18' and moderate salt-tolerant variety 'YK06' had higher K+ extrude capacity. Salt stress led to a net Na+ influx in the range of 0–100 mmol·L–1 in mixed salt concentrations, and was highest for salt-sensitive variety 'YK18'. The pattern of Na+ flux in roots changed significantly under higher mixed salt concentrations (150–200 mmol·L–1) and there was a clear efflux of Na+ in seedlings, which was highest for salt-tolerant variety 'GF01'. After mixed salt stress, Na+ content increased while K+ content decreased, resulting in a decrease in K+/Na+ ratio in the whole plant.Salt-tolerant variety 'GF01' had the lowest K+/Na+ ratio, had the potential to intercept Na+ in stems under low salt concentration (<150 mmol·L–1). The sunflower variety 'GF01' had higher capacity to extrude Na+. As a result, 'GF01' had the least Na+ content (for the whole plant) and had higher K+/Na+ ratio in leaves under high salt stress (≥150 mmol·L–1). SIET data also showed that after 24 h exposure to mixed salt stress, a clear Ca2+ influx in salt stressed seedlings that was proportional to the mixed salt concentration developed. The Ca2+absorption rate of 'GF01' was higher than that of 'YK18'. In conclusion, different de-grees of salt tolerance in different sunflower varieties were regulated by Na+ and K+ absorption and efflux as a mode of adaption to the salt stress environment. Strong salt tolerant variety had stronger ability to protect K+, but K+ can also be protected by regional Na+ appli-cation (under low salt concentration), salt rejection mechanisms to enhance salt tolerance and then by maintaining reasonable K+/Na+ ratio in leaves. In addition, accelerated absorption of Ca2+ by plants alleviated salt damage in plants after salt stress. The results of the study provided theoretical basis for the selection and cultivation of salt tolerant varieties. And the established ion flux detection technique was a reliable screening method for salt tolerant varieties selection in plant breeding.