关键词: 花椰菜, 叶绿素, 光合作用, 镉残留分布

Abstract:

The effects of cadmium (Cd)（5、15、30 mg·L^-1）on chlorophyll levels and photosynthesis of cauliflower (Brassica oleracea L. var. botrytis) were studied under different concentrations of Cd using hydroponics system. Meanwhile, the differential centrifugation techniques and sequential extraction methods were used to determine the subcellular distribution and chemical form of Cd in leaves. Cd contents in different parts of plant were also measured after harvest. The results showed that, after different contents of Cd were supplied for two weeks, except intercellular CO₂ concentration(Ci), the levels of chlorophyll a and b, net photosynthesis rate(Pn), stomatal conductance(Gs) and transpiration rate(Tr) all decreased significantly compared with the control. For the leaves, Cd was mainly distributed in the fractions of cytoplasm(70.19%－74.40%) and cell wall (22.56%－27.12%), and less distributed in the fractions of mitochondrion and chloroplast(0.90%－2.49%). The sequential extraction results of Cd in leaves indicated that NaCl extractable Cd was predominated (33%—39%), and the distribution of six Cd forms in leaves was as following: F _NaCl > F_H2O> F_HAC> F_Alcohol> F_HCL> FResidue. Most of Cd absorbed by plant was accumulated in roots, little of them was transported to the aboveground portions. The order of Cd accumulation in different plant parts was: roots>stems, leaves>flowers.

Key words: cauliflower, Cd residues, chlorophyll a and b, photosynthetic parameters