| The Syzygium hancei community is the main types of native vegetation and excellent germplasm resources in Guangxi. Because of human disturbance and natural regeneration difficulty, the community degradates severely. Therefore, it is necessary to research the relationship between the factor of water and salt which affect the natural regeneration and the growth, to provide a scientific basis for the Syzygium hancei community’protection and restoration as well as the construction of coastal protection forest and green land.This paper took the Syzygium hancei seedlings of the forests regeneration as test materials. It experimented with pot-cultivated for water-salt stress. It was determine the growth index, physiological and biochemical index and photosynthetic physiological indexes to understand and explore the growth characteristics and the mechanism of adaptation of seedlings under water-salt stress. The results showed that:(1) It has an effects on seedling height growth and diameter growth due to salinity and drought extent varies under water-salt stress. It can promote the growth of seedlings when the soil contains certain salt. It has small inhibition of height and diameter at salt concentration of0.2%. It has a little effect on seedling growth when relative water content is60%. It has a significant effect on seedlings under the interaction of water and salt stress. With the increase of salt content and the decrease of relative water content, the growth speed of seedling height and ground diameter was slow.(2) The content of chlorophyll a and b change d obviously under water-salt stress. When the salt content increased to0.4%, the synthesis of chlorophyll was promoted. When the salt content increased to0.8%, there were certain hinder to the synthesis of chlorophyll a and b. The chlorophyll a content can still maintain a high level in drought conditions. The ratio of a and b has erratic changes, the response of chlorophyll b was fast under low salt; and chlorophyll a has response quickly under high salt. Under the influence of different water and salt level, stress aggravated, the greater the relative conductivity values, MDA content increased. When the salt concentration was1.0%, this phenomenon was obvious; When the salt concentration was less than0.6%and mild drought, cell membranes were damaged by small degrees. Meanwhile osmotic adjustment and active oxygen metabolism also had some response. Soluble sugar content and free proline content increased significantly to maintain osmotic balance in salt concentration of0.4%, soluble protein content was particularly sensitive of0.6%. Of0.4%salt and40%relative water content, the activity of CAT and POD were enhanced, when the salt concentration reached1.0%, activity of CAT and POD decreased. Under water-salt stress interaction, these physiological changed behave obviously.In light response curve parameters, when stressed severely, Pmax and AQY were decreased, Rd was increased, this phenomenon was obvious on salt concentration of0.6%and the relative moisture content of40%. In this case, LCP was higher and LSP was lower, The plant was on a narrow range of available light, light utilization capacity was diminished, the changes in six photosynthetic parameters was consistent. When the salt concentration of0.6%and relative water content of40%, Pn, Tr, Gs values had declined, leaf photosynthesis reduced. When the salt concentration of0.6%and relative water content of60%, WUE was high; of1.0%salt concentration and20%relative water content, WUE was decreased severely. Water use would reach the maximum concentration on a certain salt condition. Under water-salt stress interaction, these photosynthetic physiological changed behave obviously.(4) From the results obtained, the Syzygium hancei seedlings can grow well when salt concentration was less than0.4%, and can grow normally in the soil water content of60%. |
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