Effects Of The Sodium Chloride Induced Root Lignification On Cadmium Accumulation By Tobacco

Cadmium(Cd)is a toxic heavy metal that is widespread in farmland soil and easily accumulates in crops,where it ultimately causes severe health problems in humans.The root cortex lignification,in vascular plants,could act as a natural barrier on the way of macromolecule absorption.The rational use of this mechanism by inducing plant root lignification becomes a hot topic of agronomic research.As a worldwide cash crop,tobacco can accumulate a considerable amount of Cd.In this study,tobacco cultivar K326(Nicotiana tabacum L.)was used as experimental material to screen the proper induction technique for the purpose of reducing Cd uptake by tobacco plant.Additionally,the physiological mechanism of plant induction inhibiting Cd absorption was clarified by comparing the different absorption characteristics of Cd and zinc(Zn).The current study has provided new strategies and ideas for reducing Cd absorption by crops and improving the safety of agricultural products through cultivation measures.The main results are listed as follow:-The tobacco seedlings,60 days old,treated by 100 mM NaCl for 7 days could significantly reduce the Cd uptake within its lifecycle,with no significant side effects on plant growth,NPK absorptions,SPAD value,and the net photosynthetic rate.-Tobacco(N.tabacum)has no specific capacity on Cd absorption,but mostly achieved by robbing the gateways architected for other elements,like the transporters or channels of Ca2+,Mg2+and Zn2+,and there were obvious cation competitions between Cd2+and other divalent metal ions during elements absorption.-The stele coarsening and cortex lignification in primary lateral roots induced by NaCl could be a reasonable explanation for the Cd uptake reduction.-Different from Cd,NaCl priming has negligible influence on the Zn absorption in tobacco.When the apoplastic absorption was limited based on root structural variation,proteins NtNramp5 and NtHMA4 might participate in the compensatory absorption of Zn via the symplastic absorption.-A biological explanation of NaCl priming reducing tobacco Cd absorption was that it induced the expression of the genes and proteins related to root lignification and peroxidases which reinforced the lignification degree of tobacco root afterwards.