Dynamic Change Of Cinnamic Acid Content In Cucumber-Soil System Under Salt Stress

Cucumber is one of the vegetables liked by many people,and also is principal cultivars in vegetable production. The contradiction between growing market demand and the limited greenhouse acreage is becoming increasingly conspicuous, which resulted in the occurrence of continuous cropping barrie. Yield and quality of vegetable crops are affected severely. Soil salinization and autotoxicity are two main causes of continuous cropping barries. Cucumber is sensitive to autotoxicity, the cinnamic acid in its roots exudates have been identified to be a main allelochemical. Along with the growth of cucumber, the contents of cinnamic acid in plants and soil are also continually changing. If the dynamic transfer and distribution of cinnamic acid in cucumber-soil system can be understand, that is instrumental in revealling mechanism of allelochemicals action.This research took salt-tolerant species Jinlv 5 and salt-sensitive species Jinyou 1 as the test metirals. NaCl was used to as salt stress conditions at the concentration of 0, 585 mg·kg-1 soil. Cinnamic acid was applied at concentration of 0, 25, 50, 100, 200 mg·kg-1 soil. The content of cinnamic acid in each organ of cucumber and soil at different time after application was determined by HPLC. At the same time the growth and development indexes at different time was determined.The conclusions are as follows:1. Dynamic change of cinnamic acid content in time. At the concentration of 0~100 mg·kg-1soil, cinnamic acid content in cucumber plants showed a increasing tendency with its increasing dose. It was highest in each group at concentration of 100 mg·kg-1soil, then lowered little at concentration of 200 mg·kg-1soil. Cinnamic acid content in soil increased with its increasing dose at all concentration.2. Dynamic change of cinnamic acid content in space. Comparison between three growth periods showed that cinnamic acid content at 7th day and 14th day were similar, and increased significantly at 21st day. The cinnamic acid content in soil treated with cinnamic acid solution showed dynamic changes of"high-low-high"with time passing.3. Distribution of cinnamic acid content in cucumber-soil system. Cinnamic acids were absorbed by cucumber roots, then gradually transfered to the aboveground part and ultimately accumulated in leaves. In cucumber-soil system, cinnamic acid mainly remained in soil with a larger proportion compare with cucumber plants.4. Effects of salt stress on cinnamic acid retention. Two cultivars of cucumber had different turning points in the declining trend. The total cinnamic acid content in salt tolerant cultivar Jinlv No.5 cucumber plant decreased only at highest concentration of 200 mg·kg-1soil, while salt-sensitive cultivar Jinyou No.1 cucumber started to decrease at the concentration of 100 mg·kg-1soil.5. Effects of cinnamic acid on the growth indexes and yield under salt stress. Lower concentration of cinnamic acids improved the cucumber plant height, stem diameter, leaf area, dry weight, fresh weight, but the actions were not obvious. Higher concentration inhibited them these significantly. Effects of concentration of 50 mg·kg -1soil on growth indexes didn't show distinct regularity. Lower concentration of cinnamic acids increased the cucumber yield, while higher concentration of cinnamic acids reduced cucumber yield. By the both effection of salt stress and cinnamic acid resulted in further injured to cucumber plants.