小盐芥营养器官的结构特点与其盐渍环境的关系研究

利用石蜡切片法研究了盐生植物小盐芥(Thellungiella halophila)营养器官的解剖结构。结果表明：小盐芥根的初生结构中表皮细胞为1层，且细胞大而高度液泡化，根毛数量较少；皮层仅由外皮层和内皮层2层细胞构成，细胞大，排列紧密；根次生维管组织发达。茎的初生结构中外剀维管束8～10束，大小不等，呈一轮排列；髓和髓射线发达；茎次生结构中维管组织也很发达。根和茎的这些结构特点提高了植物体吸收、运输水分的能力，而且根的特殊结构和输导系统将盐分限制在根内，适应于盐渍环境所造成的渗透胁迫和干旱胁迫。小盐芥叶片较小，上、下表皮细胞各1层，细胞大而高度液泡化，叶肉中栅栏组织与海绵组织分化不明显，但叶绿体体积大、数目多，细胞间隙较大，通气性能好，光合效率高。这些特点对其适应干旱盐渍环境有重要意义。小盐芥上述结构特征与典型真盐生植物、旱生植物相去其远，其营养器官内也无盐腺、囊泡等泌盐结构。由此推论，小盐芥更倾向于似盐生植物(拒盐植物)。

Relations between Anatomic Structures of Vegetative Organs of Thellungiella halophila and Its Brackish Environment

Paraffin sectioning was adopted to study anatomic structures of vegetative organs of Thellungiella halophila,a halophyte.The primary structure of its roots showed a layer of big and highly vacuolated cells and a small number of root hair.Its cortex consisted of only two layers of big and closely aligning cells,exodermis and endodermis.The secondary vascular tissues of its roots appeared well developed.The primary structure of its stem contained 8-10 vascular bundles of outer phloem that varied in size and aligned in a cycle as well as well-developed pith and pith rays.The secondary structure of its stem contained well-developed vascular tissues.These characteristics of its roots and stems made the plant have high capcities to take up and transport water,and that the specificities of its root in anatomic structue and conducting system could restrict saline substances inside the roots,thereby adapting to osmotic and drought stresses resulting from brackish environment.Thellungiella halophila had small leaves whose upper and lower epidermises consisted of one layer of big and highly vacuolated cells,and poorly differentiated palisade and spongy tissues,but it had a great number of large-size chloroplasis,a large intercellular space,a good air permeability,and a high photosynthetic rate.These characteristics played an important role in its adapting to the evvironments characterized by drought and salinity.Thellungiella halophila extremely differed in its above-mentioned characteristics from typical halophytes and xerophils.Its vegetative organs did not contain such salt-secreting structures as salt glands,bursas and vesicles.Accordingly,Thellungiella halophila tended to be a pseudo-halophyte in a large measure.