Research On Different Responses To Cinnamic Acid For Cucumber And Figleaf Gourd Roots

Cucumber (Cucumis sativus L.) is a favourable vegetable for Chinese and has become the main variety of greenhouse vegetables. However, the contradiction between limited land for vegetable production and year-round demand for the supply lead to monocropping as popular cropping systeam, resulting in a reduction both in productivity and the food quality. Autotoxicity is one of the most important factors responsible for continuous cropping obstacles. It has been documented that cucumber has autotoxic potencial, and more than 10 kinds of growth inhibitory substances including benzoic and cinnamic acids from its root exudates have been isolated and identified. These substances could significantly inhibit plant growth through influencing physiological metabolism process such as ion absorption, water utilization, photosynthesis and respiration etc. At present scientists have found that figleaf gourd (Cucurbita ficifolia Bouche), a plant in the same family with cucumber, do not suffer from these cucumber autotoxins. This study investigated the different responses to cinnamic acid for cucumber and figleaf gourd roots, discussed the mechanism of figleaf gourd resistance to cinnamic acid. The main results are as follows:1) Experiment was carried out to ascertain if there are difference responses in catabolic pathway of metabilism in the rhizosphere between cucumber and figleaf gourd. CA was significantly degraded in figleaf gourd, while in cucumber the degradation process was slower. Moreover, the comparison of CA content in bacteria free nutrient solutions with sterilized ones told us microorganism conduced to reducing the content of CA in both plants.2) To determine the effect of CA on antioxidant system, we investigated the activity of enzyme in cucumber and figleaf gourd roots. The results indicated that CA significant increased the activity of active oxygen scavenging enzymes such as catalase (CAT), ascorbate peroxidase (APX), guaiacol-dependent peroxidase (GPX) and superoxide dismutase (SOD). It is likely that the inhibition of plant growth is associated with oxidative stress triggered by cinnamic acid. Figleaf gourd roots showed higher activites of antioxidant enzymes than cucumber roots and no significant changes in the activites of...