Morphological difference in 1y, 3y, and 5y tissue-cultured apple plants. A) The phenotypes of 1y, 3y, and 5y tissue-cultured apple plants. We collected stem tips of apple plants at 3 ages (1-yr-old, juvenile phase; 3-yr-old, transition phase; and 5-yr-old, adult phase, represent the transition from the juvenile to the adult phase) from the same 5-yr-old source tree and obtained apple plants at different ages via in vitro tissue culture (tissue-cultured apple plants at different ages, hereafter referred to as 1y, 3y, and 5y, respectively). B, C) Leaf area at different positions. Data are means ± Sd (n = 3). Images in B) were digitally extracted for comparison. D) Microscopic observation of adaxial and abaxial epidermal cells. Scale bar = 25 μm. E) Microscopic observations of leaf anatomy in different positions. Scale bar = 50 μm. F, G) The number and area of adaxial and abaxial epidermal cells. Data are means ± Sd (n = 14). H, I) The thickness of leaf and upper epidermis for 1y, 3y, and 5y apple leaves. Data are means ± Sd (n = 14). Values with different letters are significantly different according to 1-way ANOVA followed by Tukey's test (P < 0.05).