Ultrastructural changes arising from the pericarp cell of young apricot fruit under frost conditions
Spring frost always seriously reduces the apricot yield. Previous studies demonstrated that the young fruit is the most susceptible to low temperature compared with petal, stamen and pistil in apricot. In order to explore the injury mechanism induced by spring frost in young apricot fruits, the young fruits (10th day after full bloom) of (Prunus armeniaca L. 'Luotuohuang') were selected as experimental materials. The ultrastructural characteristics of pericarp cell in cold-treated fruits were observed using the transmission electron microscopy (TEM). The results showed that the apricot pericarp cells were markedly damaged under -2°C for 3 h. In the normal apricot pericarp cell, there are big vacuoles and the tonoplast is integrated. The chloroplast is ellipsoidal in shape, with many regular stroma lamellae. The mitochondria are round or oval, with rich clear cristae and outer envelope. The nucleoplasm is homogeneous with distinct double nucleus membrane. In contrast to the normal fruit cell, in the cold-treated pericarp cells, the main injury occurred in the chloroplast and tonoplast. The chloroplast swelled and irregular hollow spaces appeared among stroma lamellae. The tonoplast was partly dissolved. When the cold-treatment time was prolonged to 6 h, severe injury occurred in pericarp cells. The plasmolysis phenomenon was occurring, the cristae of mitochondria were disrupted and even became empty, the nucleus membrane was partly dissolved and the nucleoplasm nearly collapsed. These results indicated that the chloroplasts and the tonoplast were more susceptible to frost conditions. To our knowledge, this is the first cytological evidence that describes the chilling injury process occurring in apricot young fruit.
Zhang, J.H., Wang, Y.Z., Sun, H.Y., Yang, L. and Jiang, F.C. (2016). Ultrastructural changes arising from the pericarp cell of young apricot fruit under frost conditions. Acta Hortic. 1130, 117-122
apricot, ultrastructure, injury, pericarp, frost