Adjustable crop load primarily involves bud manipulation, and usually switches from vegetative to reproductive buds. While this switch is not fully understood, it is still controlled by the ratio of hormones, which promote or inhibit bud formation. To determine the reasons for biennial bearing, the effect of apple rootstock, scion cultivar, crop load, as well as metabolic changes of endogenous phytohormones [zeatin, jasmonic acid, indole-3 acetic acid (IAA), abscisic acid (ABA), and gibberellins 1, 3, and 7 (GAs)], and soluble sugars (glucose, fructose, and sorbitol) were evaluated, and their connections with return bloom and yield of apple tree buds were analyzed. Cultivars “Ligol” and “Auksis” were tested on five rootstocks contrasting in induced vigor: semi-dwarfing M.26; dwarfing M.9, B.396, and P 67; and super-dwarfing P 22. Crop load levels were adjusted before flowering, leaving 75, 113, and 150 fruits per tree. Principal component analysis (PCA) scatter plot of the metabolic response of phytohormones and sugars indicated that the effect of the semi-dwarfing M.26 rootstock was significantly different from that of the dwarfing M.9 and P 67, as well as the super-dwarfing P 22 rootstocks in both varieties. The most intensive crop load (150 fruits per tree) produced a significantly different response compared to less intensive crop loads (113 and 75) in both varieties. In contrast to soluble sugar accumulation, increased crop load resulted in an increased accumulation of phytohormones, except for ABA. Dwarfing rootstocks M.9, B.396, and P 67, as well as super-dwarf P 22 produced an altered accumulation of promoter phytohormones, while the more vigorous semi-dwarfing M.26 rootstock induced a higher content of glucose and inhibitory phytohormones, by increasing content of IAA, ABA, and GAs. The most significant decrease in return bloom resulted from the highest crop load in “Auksis” grafted on M.9 and P 22 rootstocks. Average difference in flower number between crop loads of 75 and 150 fruits per tree in “Ligol” was 68%, while this difference reached ~ 90% for P 22, and ~ 75% for M.9 and M.26 rootstocks. Return bloom was dependent on the previous year’s crop load, cultivar, and rootstock.

可调节的农作物负荷主要涉及芽的操纵，并且通常从营养芽转变为生殖芽。虽然尚未完全了解这种转换，但仍受促进或抑制芽形成的激素比例控制。为了确定两年生轴承的原因，苹果砧木，接穗品种，作物载量以及内源植物激素[玉米蛋白，茉莉酸，吲哚-3乙酸（IAA），脱落酸（ABA）和评估了赤霉素1、3和7（GAs）和可溶性糖（葡萄糖，果糖和山梨糖醇），并分析了它们与苹果树芽的回花和产量的关系。对五个品种“ Ligol”和“ Auksis”在诱导活力上形成对比的五个砧木进行了测试：半矮M.26；使M.9，B.396和P 67相形见;；和超矮人P 22。开花前要调整农作物的负荷水平，每棵树有75、113和150个水果。植物激素和糖类代谢反应的主成分分析（PCA）散点图表明，半矮化M.26砧木的效应与矮化M.9和P 67以及超级矮化砧木的效果显着不同。使两个品种的P 22砧木都相形见war。与两个品种中强度较低的作物负荷（113和75）相比，最密集的作物负荷（每棵树150个水果）产生了明显不同的响应。与可溶性糖积累相反，增加的农作物负荷导致植物激素的积累增加，除了ABA。使矮脚砧木M.9，B.396和P 67以及超矮脚P 22产生改变的启动子植物激素积累，而使半矮脚M更具活力。26种砧木通过增加IAA，ABA和GA的含量来诱导更高含量的葡萄糖和抑制性植物激素。返华的最大幅度下降是由于嫁接在M.9和P 22砧木上的“ Auksis”中的农作物负荷最高。在“ Ligol”中，每棵树上75到150个水果的作物负荷之间的平均花数差异为68％，而对于P 22而言，这一差异达到〜90％，对于M.9和M.26砧木，这一差异达到〜75％。退花期取决于上年的农作物负载，品种和砧木。在“ Ligol”中，每棵树上75到150个水果的作物负荷之间的平均花数差异为68％，而对于P 22而言，这一差异达到〜90％，对于M.9和M.26砧木，这一差异达到〜75％。退花期取决于前一年的作物负荷，品种和砧木。在“ Ligol”中，每棵树上75到150个水果的作物负荷之间的平均花数差异为68％，而对于P 22而言，这一差异达到〜90％，对于M.9和M.26砧木，这一差异达到〜75％。退花期取决于前一年的作物负荷，品种和砧木。