Factors influencing fruit abscission in Siberian apricot (Prunus sibirica L.)

• The physiological fruit drop of P. sibirica consists of a rapid and a slow abscission period. • Carb competition key in rapid drop, worsened by cold, rainy conditions. • Insufficient mineral nutrition, high temps, low rainfall key in slow drop stage. • An imbalance hormones were related to P. sibirica fruit abscission. Pronounced fruit drop in Prunus sibirica significantly reduces seed kernel yield. However, few studies have reported on P. sibirica fruit abscission, and the underlying factors remain unclear. In this study, we examined the fruit abscission pattern in the 'Shanxing No 1′ variety, comparing carbohydrate and mineral nutrients in fruit, new shoots, and leaves, along with hormone levels and hydrolase activity between non-abscised and abscised fruit, and weather factors were monitored. The study revealed that fruit abscission occurred in two stages: a rapid drop stage and a slow drop stage. The growth of new shoots was a significant factor contributing to the rapid drop stage, which was further exacerbated by low temperatures and rainy weather. Insufficient nutrition of the tree body, high temperatures, and low rainfall contributed to the slow drop stage. A correlation has been demonstrated between an imbalance of IAA, GA, CTK, and ABA in fruits and the occurrence of fruit drop. In addition, the application of N, P, K, Zn, Mg, and Mn fertilizers was crucial during the rapid drop stage, whereas N, K, and Mg fertilizers were required during the slow drop stage. In summary, an inadequate supply of carbohydrates and minerals and unfavorable weather factors may trigger endogenous hormonal disorders, which induce abnormal increases in cell wall-degrading enzyme activity in the pulp, causing fruit drop.