College of Landscape Architecture, Sichuan Agricultural University, Chengdu, 611130, China.
Chongqing Industry Polytechnic College, Chongqing, 401120, China.
Planta. 2023 Feb 9;257(3):52. doi: 10.1007/s00425-023-04082-7.
Enhanced secretion of Na and Cl in leaf glands and leaf vacuolar sequestration of Na or root retention of Cl, combined with K retention, contribute to the improved salt tolerance of tetraploid recretohalophyte P. auriculata. Salt stress is one of the major abiotic factors threatening plant growth and development, and polyploids generally exhibit higher salt stress resistance than diploids. In recretohalophytes, which secrete ions from the salt gland in leaf epidermal cells, the effects of polyploidization on ion homeostasis and secretion remain unknown. In this study, we compared the morphology, physiology, and ion homeostasis regulation of diploid and autotetraploid accessions of the recretohalophyte Plumbago auriculata Lam. after treatment with 300 mM NaCl for 0, 2, 4, 6, and 8 days. The results showed that salt stress altered the morphology, photosynthetic efficiency, and chloroplast structure of diploid P. auriculata to a greater extent than those of its tetraploid counterpart. Moreover, the contents of organic osmoregulatory substances (proline and soluble sugars) were significantly higher in the tetraploid than in the diploid, while those of HO and malondialdehyde (MDA) were significantly lower. Analysis of ion homeostasis revealed that the tetraploid cytotype accumulated more Na in stems and leaves and more Cl in roots but less K loss in roots compared with diploid P. auriculata. Additionally, the rate of Na and Cl secretion from the leaf surface was higher, while that of K, Mg, and Ca secretion was lower in tetraploid plants. X-ray microanalysis of mesophyll cells revealed that Na mainly accumulated in different cellular compartments in the tetraploid (vacuole) and diploid (cytoplasm) plants. Our results suggest that polyploid recretohalophytes require the ability to sequester Na and Cl(via accumulation in leaf cell vacuoles or unloading by roots) and selectively secrete these ions (through salt glands) together with the ability to prevent K loss (by roots). This mechanism required to maintain K/Na homeostasis in polyploid recretohalophytes under high salinity provides new insights in the improved maintenance of ion homeostasis in polyploids under salt stress.
增强的叶腺中 Na 和 Cl 的分泌以及叶液泡中 Na 的隔离或根中 Cl 的保留，加上 K 的保留，有助于四倍体返盐生植物 P. auriculata 提高耐盐性。盐胁迫是威胁植物生长和发育的主要非生物因素之一，通常多倍体比二倍体具有更高的耐盐性。在泌盐叶表皮细胞盐腺中分泌离子的返盐生植物中，多倍体化对离子稳态和分泌的影响尚不清楚。在这项研究中，我们比较了盐胁迫处理 300mM NaCl 0、2、4、6 和 8 天后，二倍体和同源四倍体 P. auriculata Lam. 的形态、生理和离子稳态调节。结果表明，盐胁迫对二倍体 P. auriculata 的形态、光合作用效率和叶绿体结构的影响大于四倍体。此外，多倍体中有机渗透调节剂（脯氨酸和可溶性糖）的含量显著高于二倍体，而 HO 和丙二醛（MDA）的含量显著低于二倍体。离子稳态分析表明，与二倍体 P. auriculata 相比，四倍体细胞型在茎和叶中积累更多的 Na 和根中更多的 Cl，但根中 K 损失更少。此外，四倍体植物叶片表面 Na 和 Cl 的分泌率更高，而 K、Mg 和 Ca 的分泌率更低。叶肉细胞的 X 射线微分析表明，Na 主要在四倍体（液泡）和二倍体（细胞质）植物的不同细胞隔室中积累。我们的结果表明，多倍体返盐生植物需要将 Na 和 Cl 隔离（通过积累在叶细胞液泡中或通过根部卸载）并选择性地分泌这些离子（通过盐腺）的能力，以及防止 K 损失（通过根部）的能力。这种在高盐度下维持多倍体返盐生植物 K/Na 稳态的机制，为盐胁迫下多倍体更好地维持离子稳态提供了新的见解。
