Growth‐Related Changes in Subcellular Ion Patterns in Maize Leaves (Zea mays L.) under Salt Stress

Na⁺ accumulation in the leaf apoplast has been suggested to lead to dehydration, later wilting and finally, the death of the affected leaves. Our aim has been to evaluate whether the reduction in the plant growth of sensitive maize in response to salinity is correlated with higher amounts of Na⁺ and Cl^? concentrations in the leaf apoplast. Subcellular ion patterns in intact leaves were investigated by using deionised water infiltration. We found an increase in soluble Na⁺ and Cl^? concentrations of about 16‐ and 4‐fold, respectively, compared with the control. These concentrations characterized the apoplasts of expanding leaves that had entirely developed under salinity. Interestingly, the K⁺ concentration was significantly reduced by 64 % compared with its control in the symplast under salinity. Our finding of a significantly decreased Ca²⁺ concentration in shoots suggested a possible association of Ca²⁺ concentration with the reduction in leaf expansion under salinity. As the absolute increase in the apoplastic Na⁺ concentration during salt treatment was much lower compared with the increase in the symplastic Na⁺ concentration, salt treatment in maize appears not to result in osmotic stress imposed by a high apoplastic Na⁺ concentration as has been suggested for other plant species (Oertli hypothesis).     

Post‐Anthesis Salt and Combination of Salt and Waterlogging Affect Distributions of Sugars,Amino Acids,Na+ and K+ in Wheat

Salinity and waterlogging are worldwide environmental constraints to crop production. In this study, plants of winter wheat were grown in pots in the semi‐field with transparent waterproof top and subjected to salt (ST), waterlogging (WL) and their combination (SW) stresses since 7 days after anthesis (DAA). The effects of ST, WL and SW on the contents of sugars, free amino acid (FAA), starch, protein, Na⁺ and K⁺ in flag leaves, stems and grains were investigated during grain filling stage. ST and SW significantly reduced total soluble sugars (TSS) and sucrose contents in both vegetative organs and grains, and fructan content in stems. ST and SW also reduced FAA contents in stems and grains, whereas they increased FAA content in flag leaves. This resulted in a significant decrease in the ratio of TSS to FAA under ST and SW stresses in flag leaves. Moreover, ST and SW increased Na⁺ content, whereas they reduced K⁺ content, which resulted in a reduction in K⁺/Na⁺ ratio, especially during the late filling stage. In addition, ST and SW caused a reduction in starch and protein accumulations in grains. Finally, the temporal (time‐course) and spatial (different organs) responses of sugars, FAA, Na⁺ and K⁺ to ST, SW and WL and their relationships to grain starch and protein formation were further investigated.     

盐胁迫下棉花K~+和Na~+离子转运的耐盐性生理机制

为了探究棉花的耐盐机制,以中棉所49、中棉所35和中51504为材料,研究了盐胁迫对棉花幼苗的生长及K+/Na+平衡生理的影响。结果表明,150 mmol·L-1 Na Cl处理对幼苗的生长具有明显抑制作用,降低了叶片的光合速率(Pn)、PSⅡ实际光量子产额(ΦPSII)和电子传递速率(ETR),增加了非光化学荧光猝灭系数(q N)。与中棉所49和中棉所35相比,中51504的干物质累积受盐胁迫影响最小,且保持较高的Pn、ΦPSII、ETR和q N值及较低的ETR/Pn值。盐胁迫提高了棉花组织中Na+的浓度,降低了K+的浓度;但中51504组织中保持了相对较低的Na+浓度和较高的K+浓度,维持了较高的K+/Na+比;通过非损伤微测技术(NMT)测定的离子流结果也表明,中51504的根系对Na+有较强的外排能力,而对K+有较强的保留和向地上部转运能力。能够有效地调节Na+和K+的跨膜转运进而维持K+/Na+平衡是棉花耐盐的重要生理机制之一。