Effects of Exogenous Manganese (Mn) on Mineral Elements, Polyamines and Antioxidants in Apple Rootstock Malus robusta Rehd.

Manganese(Mn)is one of the essential microelements in all organisms.However,high level of Mn is deleterious to plants.In this study,the effects of exogenous manganese application on mineral element,polyamine(PA)and antioxidant accumulation,as well as polyamine metabolic and antioxidant enzyme activities,were investigated in Malus robusta Rehd.,a widely grown apple rootstock.High level of Mn treatments decreased endogenous Mg,Na,K and Ca contents,but increased Zn content,in a Mn-concentration-dependent manner.Polyamine metabolic assays revealed that,except the content of perchloric acid insoluble bound(PIS-bound)spermine,which increased significantly,the contents of putrescine(Put),spermidine(Spd)and spermine(Spm)all decreased progressively,accompanied with the decreased activities of arginine decarboxylase(ADC,EC 4.1.1.19)and ornithine decarboxylase(ODC,EC 4.1.1.17),and the increased activities of diamine oxidase(DAO,EC 1.4.3.6)and polyamine oxidase(PAO,EC 1.5.3.3).Further antioxidant capacity analyses demonstrated that contents of anthocyanin,non-protein thiols(NPT)and soluble sugar,and the activities of guaiacol peroxidase(POD,EC 1.11.1.7),catalase(CAT,EC 1.11.1.6)and superoxide dismutase(SOD,EC 1.15.1.1),also increased upon different concentrations of Mn treatments.Our results suggest that endogenous ion homeostasis is affected by high level of Mn application,and polyamine and antioxidant metabolism is involved in the responses of M.robusta Rehd.plants to high level of Mn stress.

Responses of Apple Rootstock Leaf Structure on Water Stress

[Objective] The aim was to explore, leaf structure characters of Malus rockii and Malus robusta at drought and rewatedng. [Method] The research used Malus rockii and Malus robusta as test materials to conduct water stress treatment by water control and rewatering. [Result] Malus rockii consists of two layers of pal- isade tissue and Malus robusta consist of three layers of columnar cells. Leaf of Malus robusta is thicker, and the thickness of leaf palisade tissue-to-the thickness of spongy tissue ratio is higher. In contrast, leaf stoma of Malus rockii performs more sensitively to water change, and the stoma area after rewatering is 10 times as high as Malus robusta. Besides, after rewatering, SR grows higher, the thickness of leaf palisade tissue-to-the thickness of spongy tissue ratio declines of the two test materials, but the changes of Malus robusta prove more significant. [Conclusion] The two test materials are different in responses to drought and rewatering, and the leaf structure characters of Malus robusta changes obviously than that of Malus rockii during water variation in terms of resisting drought.