黄花草木樨耐NaHCO_3盐碱胁迫的解剖学解释

Anatomical mechanism of Melilotus officinalis tolerance to NaHCO_3 aline-alkaline stress

土壤的盐化、碱化是人类面临的生态环境危机之一,严重制约了农牧业生产的发展。研究耐盐植物的适应机制,充分利用丰富的耐盐植物资源对改良和利用广袤的盐碱土地具有重要意义。以150和200mmol/L NaHCO3处理旱生耐盐植物黄花草木樨幼苗,以无盐生长的植株作为对照。制作石蜡切片和超薄切片,分别对其根、茎、叶3个器官和内部细胞器叶绿体和线粒体解剖结构进行观察。结果表明,NaHCO3使贯通于根、茎、叶3个器官的维管组织变小,尤其是木质部导管直径显著变小,极大地限制了水分向地上部分的运输和横向扩散;使茎的横切面由近四边形变为不规则形,增加了茎的表面积从而增强了茎的光合能力;叶片表皮细胞加厚,同时维管束木质部导管直径锐减,降低了水分的气孔和非气孔损失。至于细胞器,叶、茎细胞内的叶绿体和根细胞中的线粒体均受害较轻。叶绿体内的类囊体和线粒体内的嵴仍具有完整的膜系统和边缘清晰的片层结构。这些变化表明在盐碱胁迫下,草木樨能够积极地通过改变组织和细胞的形态和结构来保护细胞内细胞器结构的完整性。

Salinization and alkalization of soil is one of the ecological factors seriously limiting agricultural pro- duction. This study investigated the adaptive mechanisms of salt-tolerant plants to help make full use of the a- bundant halophyte resources to improve the utilization of vast areas of saline and alkaline soil. Seedlings of Me- lilotus officinalis were treated with NaHCOa solution at three concentrations, 0 （control）, 150 and 200 mmol/L. The anatomical structure of three organs （roots, stems and leaflets） and ultrastructure of two organ- elles （chloroplast and mitochondria） were observed using paraffin sections and ultrathin sections. The results showed that NaHCO3 treatments significantly affected the vascular system of M. officinalis. With NaHCO3 treatments, vascular tissue throughout the roots, stems and leaflets of seedlings were smaller. In particular, the diameter of xylem vessels was drastically reduced which greatly limited the transportation and transverse diffusion of water. The cross section of stems was changed from near quadrangle to irregular shape, which in- creased the surface area of the stems and furthered opportunity for photosynthesis. Epidermis cell wall cutiniza-tion occurred and the diameter of xylem vessels in vascular bundles greatly decreased which reduced water loss through stomata and non-stomata pathways. Chloroplast in stems and leaflets and mitochondria in root tissue were only slightly damaged. Thylakoid in chloroplasts and ridges in mitochondria still had an intact membrane system and a sharp-edged laminated structure. All changes protected by active structural morphological changes in M. indicated that structural integrity of organelles was officinalis tissue under saline and alkaline stress.