镉胁迫对龙葵生长、质膜ATP酶活性及氮磷钾吸收的影响

Effects of cadmium on growth, plasma membrane ATPase activity, and absorption of N, P and K in Solanum nigrum L. seedlings

采用模拟镉(Cd)污染土壤培养法研究不同浓度Cd(0、10、20、40、80、160 mg kg–1)处理对Cd超积累植物龙葵(Solanum nigrum)幼苗营养元素氮(N)、磷(P)、钾(K)吸收及质膜ATP酶活性的影响.结果表明,Cd处理浓度≤40 mg kg–1时显著促进龙葵幼苗的生长(叶性状、主根长、株高度和基径粗度)以及生物量的积累与分配;而当Cd处理浓度>40 mg kg–1时则出现明显的抑制作用.而当Cd处理浓度为10 mg kg–1时,则提高显著幼苗叶片叶绿素(Chl.a、Chl.b、Chl.[a+b])含量,达到最高值;且叶绿素含量随胁迫程度的增强而先升后降.随胁迫程度的增强,幼苗根、茎、叶和果实中的N、P和K含量先升后降(除茎P降低外);而植株组织中的Cd积累量逐渐增大且分布为叶>茎>根>果实.同时,丙二醛(MDA)含量与过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性随Cd浓度增大而增大,但超氧化物歧化酶(POD)活性先升后降.随胁迫程度的增强,幼苗地上(茎与叶)和地下(根)部H+-ATP以及地下部Ca2+-ATP酶活性不断降低,而地上部Ca2+-ATP酶活性先升高后降低.因此,龙葵在高浓度Cd胁迫(≥40 mg kg–1)下,可能通过加快根对Cd离子的吸收和转运,提高抗氧化酶(CAT和SOD)活性,降低POD与质膜ATP酶活性,调节对N、P和K的需求,从而起到对Cd胁迫的解毒作用.

This study aimed to investigate by a soil pot experiment the effects of cadmium（Cd） stress on the plasma membrane ATP activity and absorption of nutrients including nitrogen（N）,phosphorus（P） and potassium（K） in the hyperaccumulator plant Solarium nigrum.The results showed that low-dose Cd treatment（≤40mg kg^–1） enhanced the accumulation and distribution of biomass,thus promoting overall plant growth.On the other hand,high-dose Cd（ 40 mg kg^–1） significantly inhibited the growth of S.nigrum seedlings.Moreover,10 mg kg^–1 Cd treatment increased leaf chlorophyll a（Chl.a）,chlorophyll b（Chl.b） and total chlorophyll（Chl.[a＋b]） content.With the increase of Cd dose,these chlorophyll contents showed a trend of increase followed by decrease,same with that of N,P and K content in seedling tissues（roots,stems,leaves and fruits） except for the stem P content）.With the increase of Cd doses,the Cd accumulation of root,stem,leaf and fruit all gradually increased（leaf〉 stem 〉root〉 fruit）.In addition,the content of malondialdehyde（MDA）,and the activities of catalase（CAT） and superoxide dismutase（SOD） also increased with increasing Cd doses,while the activity of peroxidase（POD）showed a trend of increase followed by decrease.Simultaneous with increasing Cd doses,shoot（leaf plus stem） and root H^＋-ATPase activities and root Ca^2＋-ATPase activity decreased,but the activity of shoot Ca^2＋-ATPase first increased and then decreased.These results suggested that S.nigrum plants may alleviate Cd detoxification under higher dose of Cd treatment（≥ 40 mg kg^–1） through accelerating the absorption and transportation of root Cd ions,improving antioxidant enzymes（CAT and SOD） activity,decreasing POD and plasma membrane ATP activity and regulation N,P,K demand.