土壤镉胁迫对龙葵(Solanum nigrum L.)幼苗生长及生理特性的影响

Effects of Soil Cadmium on Growth and Physiological Characteristics of Solanum nigrum L. Plants

采用盆栽试验研究了不同浓度Cd(0、10、20、40、80、160 mg·kg-1)处理下,龙葵(Solanum nigrum L.)幼苗对氮(N)、磷(P)和钾(K)吸收及质膜ATPase活性的影响。结果表明,土壤添加Cd浓度≤40 mg·kg-1时显著促进龙葵幼苗生长及生物量的积累与分配,添加Cd浓度>40 mg·kg-1时抑制作用加强;叶绿素含量随Cd添加浓度的增大而下降,在较低浓度Cd(10 mg·kg-1)处理时,显著提高叶绿素含量。随Cd添加浓度的增加,根、茎、叶和果实中的全N、全P和全K含量先升后降(除茎全P降低外);叶片中的Cd积累量最高,茎次之,果实中最低;丙二醛含量与过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性增大,但超氧化物歧化酶(POD)活性先升后降;幼苗地上(茎与叶)和地下(根)部H+-ATP以及地下部Ca2+-ATP酶活性随Cd添加浓度的增加不断降低,而地上部Ca2+-ATP酶活性则先升后降。这些结果表明,龙葵在高Cd胁迫(≥40 mg·kg-1)下,能通过加快根系对Cd离子积累来提高抗氧化酶(CAT和SOD)活性、降低POD与质膜ATP酶活性、改变对N、P和K的吸收,从而起到对Cd胁迫的解毒作用。

Solanum nigrum L. has been discovered to be a Cd hyperaccumulating species, and is therefore used for phytomining and phytoextracting Cd contaminated soils. In this work, the effects of cadmium on nutrients [nitrogen(N), Phosphorus(P)and potassium(K)] absorption and plasma membrane ATP activity in S. nigrum were investigated in a soil culture experiment. Results showed that lower Cd treatments(≤40 mg·kg- 1) enhanced plant growth and biomass accumulation, whereas higher Cd(>40 mg·kg- 1) inhibited plant growth. Leaf chlorophyll a(Chla), chlorophyll b(Chlb)and total chlorophyll(Chl)contents were increased by 10 mg Cd·kg-1, but decreased at higher Cd doses. With increasing Cd rates, the contents of N, P and K in roots, stems, leaves and fruits firstly increased and then decreased, except P in the stem, while the Cd accumulation in root, stem, leaf and fruit kept increasing, with leaf>stem>root>fruit. In addition, the content of malondialdehyde(MDA)and the activities of catalase(CAT)and superoxide dismutase(SOD)increased with increasing Cd doses, while peroxidase(POD)activity showed a upside down'V'trend. However, shoot(leaf plus stem)and root H+-ATPase activities and root Ca2+-ATPase activity decreased, but the activity of shoot Ca2+-ATPase firstly increased and then decreased as Cd rates increased. Results obtained in this study suggest that S. nigrum plants may tolerate high Cd(≥40 mg·kg-1)through accelerating the accumulation of Cd ions in root, improving antioxidant enzymes(CAT and SOD) activity, decreasing POD and plasma membrane ATP activity, and enhancing N, P, and K absorption.