| The intensive cultivation of dwarfing rootstock is the mainstream direction of apple development in the world,and selecting and combining scion and rootstocks is one of the key practices.Flower formation and plant shaping of apple sapling are the important indexes to evaluate their performances.With several main scion-rootstock combinations as its subjects,this study investigated the differences of tree growth,flowering,root distributions and various types of hormones on the ground and underground for apple sapling.The relationship among precocious flower?early fruit ?easy formability and endogenous hormones were analyzed by morphological and physiological indicators,which provided the theoretical basis for the evaluation of scion-rootstock combinations,and theoretical guidance and technical support for apolegamy of excellent scion-rootstock combinations in Weibei Loess Plateau.This paper has made the following progress:1.Investigation on the indexes of tree growth,flower,fruit in different scion-rootstock combinations for apple sapling,which the differences between early fruit and easy formability were analyzed.(1)The growth potentials of different scion-rootstock combinations were as follows:vigorous rootstock > dwarfing rootstock > dwarfing interstock.The combination of T337 rootstock had a strong growth potential,and T337 interstock and M26 rootstock had a weak growth potential.(2)T337 from interstock and rootstock had more inflorescence and a high yield per plant.M26 dwarfing rootstock combination showed higher spur flower formation rate,and total inflorescence number,but the fruit-setting rate was the lowest.Furthermore,the number of inflorescence,fruit set percentage of inflorescence and yield were the lowest in vigorous tree,which was not conducive to the early high yield of young trees.2.This study investigated root distributions in the different scion-rootstock combinations of apple sapling by sectoral digging and trenching,and analyzed the relationship among root characteristics ?early fruit and easy formability.(1)It showed that the root architecture of young trees from 8 kinds of typicalscion-rootstock combinations were classified into five types,M dwarfing rootstock combinations,SH dwarfing rootstock combinations,vigorous rootstock combinations,M dwarfing interstock combinations and SH dwarfing interstock combinations.(2)The roots of the apple saplings with three years distributed horizontally and vertically within the limits of 0~60 cm,and the further away from their trunks and the deeper into soil,the less dense they distributed.With the different scion-rootstock combinations,the longest roots were roots with diameters of<2mm followed by roots with diameters of 2~5mm,and the shortest roots were those with diameters of more than 10 mm.(3)There were more thick roots and less fibrous roots with the arborescent seedling root stocks than with the dwarfing clone rootstocks;among the dwarfing rootstocks,fibrous roots dominated with the M rootstocks and less with the SH and Qingzhen rootstocks.(4)Of the trees,there was a significant positive correlation between root length,root length density and root surface area density of fine roots(diameter <2mm)and the indexes of the branch numbers,short-shoot proportions and flower bud numbers.There was a negative correlation between thick roots(diameter>10mm)number and related indexes of tree composition,blossom and bearing.3.We compared the differences of all kinds of hormones,analyzed the correlation of endogenous hormones between aerial part and underground part,and research the relationship among endogenous hormones,precocious flower and easy architecture.(1)It showed that the content of IAA and ZR in young leaves reached the peak when the spring and autumn shoots began to grow.Furthermore,the content of IAA,ZR,and GA3 in the fine root reached the peak when the root was in the second high growth period.(2)In the critical period of bud physiological differentiation,IAA and IAA/ZR in fine root of M26 rootstock were higher than T337 combinations.Compared with T337 combinations,there were high level of ZR and low level of IAA in young leaves of M26.The difference was that the content of IAA in young leaves of M26 was lower than that of T337.The IAA and IAA /ZR in the root of T337 rootstock were slightly lower than those of M26,but higher than that of SH16 rootstock.In addition,the change rate of ZR and ZR/GA3 in the young leaves of T337 was faster,especially in the long type of T337,and GA3 content was decreased.(3)There was a negative correlation between IAA in the fine root and ZR in young leaves,and there was a positive correlation between the above-ground and the underground of IAA and GA3.(4)In the critical period of bud physiological differentiation,IAA and ZR in leaves were positively correlated with the amount of shoots,ZR and ZR/GA3 were positivelycorrelated with the proportion of spurs,and GA3 was negatively correlated with the number of inflorescence.The meta-analysis results showed that whether long branch or spur combinations of T337 sapling were easy to shape and early to fruit in Weibei;because it was better to absorb nutrition by well developed fibrous root system.The IAA content was lower in fine root while the ZR content was higher in young leaves,so that T337 combination was easy flower.In addition,M26 combination was precocious flower and difficult architecture,because it had high levels of ZR in young leaves,and the fibrous root system was weaker than T337 combination.The vigorous tree was tall,and it was late to flower.Besides,this combination had well developed rough root system but less fibrous root.Perhaps,this result was caused by the high content of IAA in fine root and the low content of ZR in young leaves. |
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