| Non-heading Chinese cabbage(Brassica campestris ssp.chinensis Makino) belongs to Cruciferae. It is widely planted in south and north China. Along with the rapid development of some industry such as zinc mining, smelting and electroplating,zinc has become increasingly hazardous due to their involvement among pollutants of soils, resulted in the worse pollution vegetable and led to a series of physiological barriers. Furthermore the threat that it poses to human health is aggravated by food chains. Therefore it is very important to study the physiological ang biochemical mechanisms of zinc toxicity in non-heading Chinese cabbage. In this paper, five genotypes non-heading Chinese cabbage including suzhouqing, huangxinwu, piaoercai, kangre 605 and nannongaijiaohuang were selected. Pot experiment with sand .culture and solution culture experiment were conducted in sunlight greenhouse to investigate the effects of zinc stress on mineral nutrition uptake and physiology in non-heading Chinese cabbage. The main results were as follows:1. The shoot biomass of five varieties was slightly increased after irrigating nutition solution containing different concentration Zn2+(CK,100,200,400,800 mg/L). The root tolerance indexes of five genotypes ranged from 0.8 to 1.9. So they were tolerant to Zn stress at certain extent.2. The Zn content and accumulation in different organs were significantly increased with enhancing Zn concentration. The Zn content in roots was the highest, however Zn accumulation in it was the lowest, and the trend of the two indexes in leaves was contrast with that in roots. More than 60 percentage Zinc absorbed by roots was transferred to the ground. The redundant zinc absorbed by suzhouqing, huangxinwu, kangre 605 and nannongaijiaohuang mostly stored in petioles, and leaves was primary storing organ in piaoercai. Comparatively speaking, suzhouqing had the strongest ability of accumulating Zn, however nannongaijaohuang exhibited a characteristic with low accumulation and high translocation.3. During solution culture experiment, excessive zinc in nutrient solution did great damage to non-heading Chinese cabbage, such as, significantly decreased root activity, broke the mineral nutrition balance, disturbed the synthesis and degradation of soluble protein in leaves, petioles and roots, destroyed the ability of chlorophyll synthesis, induced metallic disturbance and chlorisis phenomenon, affected plant, s growth.4. Zinc stress dramatically decreased the activity of CAT in leaves and roots, the activity of SOD, APX in roots and the activity of POD in leaves. But the activity of some enzymes was markedly enhanced including SOD, POD, CAT, APX. So it could defense against oxidative stress by antioxidative enzymes system.5. Zinc forms in different organs had diversity. It was predominated with NaCl, ethanol and HAC—extractable forms. This indicated that zinc might be binded to many ligands. Under zinc stress the distribution of different zinc forms was changed, and the NaCl—extractable form content was highest among all the zinc forms. Hence non-heading Chinese cabbage had some organic ligands such as proteins and pectinates which formed compound body with zinc in order to alleviate zinc toxicity.6. Under zinc stress non-heading Chinese cabbage released lots of low-molecular-weight organic acids including Oxalic, Tartaric, Malic acid, Lactic Acid, acetic acid, Citric Acid and Succinic acid. They were beneficial for the mitigation of zinc toxicity by chelation and cell regionalization, enhanced the adaptation to zinc stress.
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