Mdm-miR156a and MdSPL14 are involved in the CK-dependent regulation of leaf size in apple. A) The phenotypes of mdm-miR156a-OE/MdSPL14-OE apple plants in the background of 1y plants. OE, overexpressing. B) Relative expression levels of MdCKX5 in roots. C) Leaf area. D) Endogenous tZ content in leaves. FW, fresh weight. Data are means ± Sd (n = 3). E, F) The area and number of adaxial epidermal cells. Data are means ± Sd (n = 10). Values with different letters are significantly different according to 1-way ANOVA followed by Tukey's test (P < 0.05).