Role Of IAA In Root Iron-deficiency Stress Responses Of The Genus Malus

Mains xiaojinensis and Mains baccata were employed as the materials in the solution culture to measure roots endogenesis IAA, the medium pH and Ferric reductase activity in order to investigate the relationship between IAA and iron-deficient responses. The results were as follows: Compared to the normal iron level (40 p M Fe), M. xiaojinensis had higher IAA concentration, rhizosphere acidifying and higher Ferric reductase activity in roots under iron deficiency stress (4 u M Fe or 0 u M Fe). The increase of IAA concentration, root medium pH and Ferric reductase activity was restrained with decapitation and TIBA-smearing. However, There was no significant difference in IAA concentration, medium pH and Ferric reductase activity of Iron-inefficient species M. baccata roots under iron-deficiency stress and normal iron. The grafting experiments showed that whatever genotype of roots, grafting seedling had higher IAA concentration and lower solution pH if the shoots were iron-efficient species. There was no significant difference in three indexes under iron-deficiency stress when Iron-inefficient species M. baccata was shoot. The results obtained in the experiments lead to the conclusion that IAA was probable a signal regulation the iron-deficiency physiological availability of the genus Malus. The difference of varity genotypic Malus in response to iron-deficiency availability would provide foreground for screening Iron-efficient species and inheritance breeding.The results showed that the higher of IAA concentration of Mxiaojinensis would be blocked if the activity of indolepyruvate decarboxylase (IPDC) of the key enzyme of IAA biosynthesis by B -phenylpyruvic acid was restricted. However, the IAA oxidase activity was not variable. It can be concluded that the higher of IAA concentration of Mxiaojinensis under iron-deficiency stress were probably connected with the IAA biosynthesis without IAA oxygenous decomposability. The results showed that the increase of root IAA concentration was due to IAA biosynthesis of shoots and tropism transportation to roots.