Annual dynamic analysis of leaf endogenous hormones and mineral nutrition on young ‘Fuji’ apple trees

Abstract: 【Objective】High density planting with dwarfing rootstocks has been a new growing model for ap⁃ple production in China. Successful high density planting depends on suitable dwarfing rootstooks for apple scion variety. Field trial for screening suitable dwarfing rootstooks is time-consuming. Therefor, earlydetecting the potential darfing rootstocks for specific scion variety is of prime importance. Researchershad confirmed that the lower ratios of IAA/ABA and (IAA+GA+ZR)/ABA in the leaves of apple trees wereassociated with drawfing effects of the rootstocks. Fertilization also has an important influence on the vigorof apple trees. Leaf diagnose is a common way for detecting the nutritional status of apple trees. This studyaimed at selecting the appropriate stage of sampling of leaves for ensuring the accuracy of the leaf nutrientanalysis and the hormone analysis through annual dynamic analysis of leaf endogenous hormones and min⁃eral nutrition on young apple trees o‘f Fuji’.【Methods】The test was conducted from april to November in2015. The young‘Fuji’apple trees with three kinds of rootstocks were used as test materials. The root⁃stocks were M9T337, M9T337/M. baccada, and M. baccada respectively. There were six young trees for aplot of each treatment with three repeats. The trees had been cultivated in pearlite in greenhouse sinceApril 1 in 2015. Fertigation was made with nutrient solution based on the modified Hoagland formula, tomix and the solution was replaced every 20 days. The samples of the seventh to ninth leaves in the middleof new shoot were collected every 30 days from June 1. 3 to 4 leaves for one tree were taken for each sam⁃pling. The contents of plant hormones and mineral elements were measured after preparation of the samples.【Results】The trees on the rootstock of M. baccada were most vigrous and the trees on M9T337/M. baccada were least vigrous. The contents of plant hormones in the leaves were different in different samplingstages, the ratios of IAA/ABA and (IAA+GA+ZR)/ABA in the leaves of the trees varied with the rootstocksfrom 60 to 90 days after planting, and the order was M. baccada>T337 /M. baccada>T337, while the leafABA content was T337>T337/ M. baccada>M. baccada. The stronger the growth vigor of the young treewas, the bigger the ratio of leaf IAA/ABA and (IAA+GA+ZR)/ABA ratio was, and the lower the leaf ABAcontent was. Leaf mineral elements contents were also different in different sampling periods. The leaf Nand P content of the‘Fuji’apple trees on three rootstcoks changed smoothly from 90 to 150 days afterplanting. The leaf K, Ca and Mg content changed a liittle from 60 to 90 days after planting. This indicatedthat the leaf mineral element contents of young‘Fuji’apple tree changed more smoothly during the periodof 90 to 120 days after planting. The mineral element contents of all kinds of young‘Fuji’apple trees’were not accorded with the apple leaf standard nutritional values made by Li Gangli except for the contentof Ca. The correlation of endogenous hormones and some mineral elements content of young‘Fuji’appletree was significant. The content of IAA and the content of Ca，GA and P，ABA and P in the leaves was sig⁃nificantly and negatively correlated. The content of IAA andthe content of K or Mg，ZR and Ca，IAA/ABAand P was significantly and positively related. The correlation coefficients were between 0.5 and 0.8. Thecontent of leaf ABA and the content of Ca had a very significantly positive correlation, (IAA+GA+ZR)/ABA and IAA/ABA had a very significantly negative correlation with the content of Ca, and both correlation coefficients were over 0.8.【Conclusion】The leaf ratios of IAA/ABA, (IAA+GA+ZR)/ABA and the contents of ABA, Ca were correlated with the dwarfing potential of young‘Fuji’apple trees. The Suitablesampling of the apple leaves of young trees for analysis of endogenous hormones was 60 to 90 days afterplanting. And the suitable period of leaf nutrition diagnosis was 90 to 120 days after planting.