EN
Cracking is caused by physiological stress during the development of jujube fruit, and this causes considerable economic losses to fruit producers. The aim of this study was to clarify the mechanisms of water entry into the fruit and the events that lead to cracking. Differences in water absorption by fruit stalks and surfaces were observed in a cracking-sensitive variety (Ziziphus jujuba Mill. ‘Hupingzao’) and a cracking-resistant variety (Ziziphus jujuba Mill. ‘Yuanlingzao’). The response of the fruit surface to water absorption was studied, and the relationship between stomatal characteristics and cracking was analyzed. The cracking rate of ‘Hupingzao’ was higher during the coloring period. The relative amount of water absorbed through the fruit stalk of ‘Yuanlingzao’ after 10 h was 1.22 times higher than that of ‘Hupingzao’ during the coloring period. The rate of water absorption through the fruit surface of ‘Hupingzao’ was higher than that of ‘Yuanlingzao’ during the coloring period (3.73 and 3.04, respectively). Water was transported by the vascular bundle after entering the fruit through the fruit stalk, but was mainly distributed around the stomata of the epidermis and near-surface cells following entry through the fruit surface. After water was absorbed by the fruit surface, surface and stomatal cracks in ‘Hupingzao’ were apparent, and the degree of cracking of the stomata worsened with increasing water absorption time. The surface of ‘Yuanlingzao’ appeared cracked with increasing immersion time, but stomatal changes were not obvious. The stomatal size and aperture in the cracking-resistant variety of jujube fruit were lower than those in the cracking-sensitive variety. Stomatal size was positively correlated with the rate of fruit cracking. Water absorption through the surface was the main factor that induced fruit cracking. Stomatal characteristics, as well as the increased and deepened fruit surface microcracks caused by stomatal water absorption, were the primary factors related to cracking.