盐胁迫下3种滨海盐生植物的根系生长和分布

我国广大滨海地区的盐土上发育着大量的盐生植物,这些植物的根系对维持土壤稳定性,减小风蚀和水蚀具有重要作用。在水培条件下,针对碱蓬、盐角草和盐地碱蓬3种滨海盐生植物,研究它们在不同盐浓度条件下根系分布的差异。结果表明:一定浓度的盐分可以促进3种盐生植物生长,但较高浓度的盐抑制其生长,特别是对根系生长的抑制作用更大。在同样盐浓度下,盐地碱蓬的生长最快,生物量也最大。在盐分浓度较低时,3种盐生植物的主根长和总根长都有所增加,与对照相比,盐角草增加的幅度较大,但高浓度的盐会抑制根系总长度的增加,其中盐角草较碱蓬和盐地碱蓬抑制的程度轻。盐分对3种植物的根系平均直径没有显著的影响,但有减小的趋势。在水培条件下,碱蓬和盐角草的根系上、中、下部分布的较均匀,而盐地碱蓬的根系中部比上部和下部有显著的增加,盐分对每种植物的根系的分布没有显著的影响。从根系的分布特征可以推断:盐角草比碱蓬和盐地碱蓬具有较强的抗盐性和耐瘠薄能力;碱蓬的耐盐能力较其它两种植物差,盐角草的耐盐性最强。根据3种滨海盐生植物的根系生长和分布特征,证明这3种植物的根系分属于2种功能型,碱蓬是浅根系功能型,盐角草和盐地碱蓬是深根系功能型。根系分布的参数表明3种滨海盐生植物中盐地碱蓬是用来加强土壤稳定性最好的植物。

Root system characters in growth and distribution among three littoral halophytes

Soil erosion and sloughing is a major environmental problem in the coastal areas. This sediment movement decreases available farmland, changes stream habitat, and increases the need of river and harbor dredging. It has been shown that soil stability can be increased through growing plants, but the extent to which this occurs is not known. The coastal regions of China are mostly sa1ine soil, on which halophytes grow widely. These roots of halophytes can maintain the stability of soil, and can reduce water erosion and wind erosion. However, root growth and distribution of these halophytes in the coastal region was very much unknown. We hypothesized that plants with higher root length densities and larger root diameters should stabilize the soils more than plants with lower root length densities and smaller root diameters. Three littoral halophytes: Suaeda glauca, Suaeda salsa and Salicornia europaea, were chosen in this study to investigate the differences in growth and distribution of their roots under varying salt concentration conditions in a solution culture. The results showed that: certain salt concentration could promote development of these three halophytes; but higher salt concentration could inhibit their growth, especially that of roots. Under the same salt concentration, Suaeda salsa grew the fastest, and accumulated the largest amount of biomass. Under relatively lower salt concentration, the length of axial root and the total length of the roots of all three halophytes were increased; and comparing to the control, the roots of Salicornia europaea grew the fastest, but high salt concentration could restrain the increase of total root length. For all the three halophytes, salinity did not induce significant difference on the average diameter of roots, but with slight trend to reduce. Under the solution culture conditions, the middle and lower parts of the roots of Suaeda glauca and Salicornia europaea were rather equally distributed, but the central zone of Suaeda salsa roots was significantly increased than the upper and lower zones. Salt concentration did not result in significant difference on roots spatial distribution of the three halophytes. The experimental results show that the saline tolerance capacity of Suaeda glauca was the lowest than the other two halophytes, and the capacity of Salicornia europaea was ranked at the top place. Suaeda salsa and Salicornia europaea belonged to a deep root type and its survival depended on water in deeper soil and groundwater. Suaeda glauca belonged to shallow-rooted types and thus depended on water in shallow upper soil. Different functional types of the root systems of littoral halophytes had profound influence on the growth and distribution of root system, and this implied that the functional types had formed different mechanisms to effectively adjust their own to water conditions in the soil during their adaptations. The parameters of root distribution indicated that Suaeda salsa should have the best capability to increase soil stability.