镉对花椰菜光合作用的影响及其在亚细胞中的分布

Abstract

研究Cd在花椰菜的残留分布及其对光合作用的影响,设置0、5、15、30mg·L-14个Cd浓度的水培试验,测定生长期间叶片的叶绿素含量,光合作用参数,Cd的亚细胞分布,化学形态分布和器官(根、茎、叶、花球)分布。结果表明,Cd处理两周后,叶片叶绿素a和b含量明显比对照降低,气孔导度、净光合速率和蒸腾速率亦显著降低,胞间CO2浓度变化不大。不同浓度Cd处理的叶片中Cd在亚细胞中的分布主要以细胞质组分为主(70.19%~74.40%),其次为细胞壁组分(22.56%~27.12%),叶绿体和线粒体组分仅占0.90%~2.49%。叶片中Cd的化学形态分布比率大小顺序为氯化钠提取态>去离子水提取态>醋酸提取态>乙醇提取态>盐酸提取态>残渣态。在不同器官分布上,Cd5mg·L-1处理下,花球Cd累积最少(14.50mg·kg-1),其次是茎叶(78.30~87.30mg·kg-1),而根的累积达857.90mg.kg-1。

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 > FH2O> FHAC> FAlcohol> FHCl> 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.