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The periods of flower bud differentiation and fruit growth for Camellia oleifera overlap greatly affect the allocation of photoassimilates to flower buds and fruit, resulting in obvious alternate bearing. To export the cause and mitigate alternate bearing of Camellia oleifera, the allocation of photoassimilates to buds and fruit supplied by leaves at different node positions was studied by the addition of labeled 13CO2 during the slow fruit growth stage. The fate of 13C photoassimilated carbon was followed during four periods: slow fruit growth (4 hours and 10 days after 13C labeling); rapid growth (63 days after 13C labeling); oil conversion (129 days after 13C labeling); and maturation (159 days after 13C labeling). Photosynthetic parameters and leaf areas of the leaves shared a common pattern (fifth > third > first), and the order of photosynthetic parameters of different fruit growth stages was as follows: oil conversion > maturation > rapid growth > slow growth. The most intense competition between flower bud differentiation and fruit growth occurred during the oil conversion stage. Dry matter accumulation in different sinks occurred as follow: fruit > flower bud > leaf bud. Photoassimilates from the labeled first leaf were mainly translocated to the first flower bud, and the upper buds were always differentiated into flower buds. The photoassimilates from the labeled third leaf were distributed disproportionately to the third flower bud and fruit. They distributed more to the third flower bud, and the middle buds formed either flower or leaf buds. However, the photoassimilates from the labeled fifth leaf were primarily allocated to the fruit that bore on the first node of last year’s bearing shoot, and basal buds did not form flower buds. Based on our results, the basal leaves should be retained for a high yield in the current year, and the top leaves should be retained for a high yield in the following year. Our results have important implications for understanding the management of flower and fruit in C. oleifera. The thinning of fruit during the on-crop year can promote flower bud formation and increase the yield of C. oleifera crops in the following year. During the off-year, more fruit should be retained to maintain the fruit yield. The thinning of middle-upper buds could promote more photoassimilates allocate to the fruit.
Large-fruit bud mutations are important factors in fruit tree breeding. However, little is known about the differences between varieties and bud mutations. The ploidy identification of Korla fragrant pear (Pyrus sinkiangensis Yu) and its large bud mutation Zaomeixiang pear showed that the large-fruit characteristic was not caused by chromosome doubling. By counting mesocarp cells at different stages, we found that the number of cells increased continuously after pollination, and the difference was the greatest at 28 days after full bloom (DAFB), and was about 9.4 × 106. After 28 days, the difference in cell volume became bigger and bigger, so both the cell volume and cell number caused the difference in fruit size between Korla fragrant pear and Zaomeixiang pear. To obtain more insights into the differences in fruit size driven by cell division, we analyzed the endogenous hormones [indole ascetic acid (IAA), zeatin riboside (ZR), gibberellic acid (GA), and abscisic acid (ABA)], and the main sugars (glucose, fructose, sucrose, and sorbitol). The ZR content of Zaomeixiang pear was always greater than that of Korla fragrant pear at all stages. The ABA content was the opposite except for at 7 DAFB during cell division; the greatest difference was 30.87 ng/g, which appeared at 28 DAFB. ABA and ZR correlated negatively with cell number. After 7 DAFB, the ratio of IAA/ABA, ZR/ABA, and GA/ABA in Zaomeixiang pear was always greater than that for Korla fragrant pear at 28 DAFB. The difference in glucose content at 21 DAFB was the greatest, at 4.80 ng/g. Large amounts of sorbitol accumulated during whole-cell division. Glucose and sorbitol correlated positively with cell numbers. In summary, the data suggest that the different contents of glucose, sorbitol, ZR, and ABA, and the ratio of endogenous hormones might be related to cell division in Korla fragrant pear and Zaomeixiang pear. The result provides a theoretical basis for the large-size fruit’s high-quality production and genetic breeding of Korla fragrant pear and its bud mutation.