盐氮处理下盐地碱蓬种子成熟过程中的离子积累和种子萌发特性

研究了盐氮处理条件下盐地碱蓬种子成熟过程中的离子积累以及种子萌发特性,以理解盐地碱蓬在种子发育及萌发过程中对高盐低氮生境的适应性。结果表明,种子成熟过程中,不同浓度盐氮处理下(0.5和5 mmol/L NO₃^--N;1和500 mmol/L NaCl),与果皮和果枝相比, 胚中Na⁺、K⁺、Cl^- 和NO₃^-离子含量几乎没有变化。所有盐氮处理下Na⁺ 和Cl^-都是果皮和果枝中高于胚中,尤其是在高盐处理下。高盐处理下,K⁺ 和NO₃^-含量呈现相反的趋势。高氮时无论高盐还是低盐,果皮中NO₃^-离子含量高于胚中,而果枝中NO₃^-离子含量低于胚中。而低氮时果皮及果枝中NO₃^-离子含量均显著低于胚中。与高氮环境下收获的种子相比,低氮环境下收获的种子萌发率,萌发指数,活力指数都要明显高。上述结果说明,盐地碱蓬种子成熟过程中存在完善的离子调控机制,保护胚免受Na⁺ 和Cl^-等有害离子的伤害并且促进K⁺ 和NO₃^-等营养离子的积累。低NO₃^--N下收获的种子对外界的NO₃^-含量比较敏感,施以较高浓度的NO₃^-能够促进种子萌发,提高萌发指数和活力指数,可能与盐地碱蓬长期适应高盐低氮生境有关。

Characteristics of ion accumulation and seed germination for seeds from plants cultured at different concentrations of nitrate nitrogen and salinity

Suaeda salsa is an annual euhalophyte. Fresh branches of S. salsa are valued as a vegetable, and the seeds contain edible oil. Seeds of S. salsa have a high germination rate under high salinity, but the soil NO₃^--N is very low in the habitat where the species occurs naturally. However, it is unknown how combined salinity and nitrate nitrogen during seed maturation affects the salt tolerance of seeds for this species. In the present study, we investigated the characteristics of ion accumulation and germination of seeds from plants cultured in different concentrations of nitrate nitrogen and salinity, in an attempt to understand the adaptation of S. salsa to high salinity and low nitrogen during seed maturation and germination. The results showed that S. salsa had a higher ability to maintain ion homeostasis (e.g., Na⁺, K⁺, Cl^- and NO₃^-) in embryos compared to pericarp or fruiting branches when plants were cultured at different concentrations of nitrogen and salinity (i.e., 0.5 and 5 mmol/L NO₃^--N combined with 1 and 500 mmol/L NaCl). Na⁺ and Cl^- concentration in the pericarp and fruiting branches were higher than those in embryos, especially at high NaCl (500 mmol/L) regardless of NO₃^--N concentration. At 500 mmol/L NaCl, the opposite trend was shown for K⁺ and NO₃^-. At 5 mmol/L NO₃^--N, the NO₃^-was higher in the pericarp, but lower in the fruiting branches than that in the embryos when plants was cultured in either 1 or 500 mmol/L NaCl, while the NO₃^-was lower in the pericarp and fruiting branches than that in the embryos at 0.5 mmol/L NO₃^--N supply. At 0.5 mmol/L NO₃^--N, the concentrations of Na⁺, K⁺ and Cl^- in embryos and pericarp were higher than those at 5 mmol/L NO₃^--N. The seed germination, germination index and vigor index were higher for seeds from plants cultured at lower nitrogen supply than seeds from plants cultured at higher nitrogen supply. In conclusion, the species may have a perfect ion regulation mechanism to maintain ion homeostasis during seed maturation. Compared to seeds from plants cultured in higher nitrogen supply, seeds from plants cultured in lower nitrogen supply had higher seed germination, germination index and vigor index, which may be related with higher concentrations of Na⁺, K⁺ and Cl^- in embryos and pericarp of seeds from plants cultured in lower nitrogen supply. The trait may be related to the adaptation of S. salsa to low soil NO₃^--N content in the habitat where the species occurs.