Relationship Between Peach Pit-Splitting and Specific Vascular Bundle Development and Nitrogen Application

Abstract

Vascular bundles play an important role in fruit development and quality. Each set of bundles has its own specific functions. In order to learn the relationship between endocarp cracking and vascular bundles, specific vascular bundle development was investigated during fruit growth after a range of N treatments. The results show that embryo bundle and ventral bundle development are closely related to pit-splitting. The pit-splitting was caused by interaction of the over-expanded seed (or double seeds) and the weakened endocarp. The rapid development of the seed was controlled by an abnormally thickened embryo vascular bundle. The weakened endocarp was caused by an abnormal thickening of the ventral vascular bundles that formed two grooves on the endocarp of the abdominal suture, thus rendering the endocarp weak and fragile. Once the expansion force of the seed is too large, the endocarp will rupture due to a weak position of the grooves, a phenomenon known as pit-splitting. The results demonstrate that the over-development of the embryo bundle and ventral bundles is the key cause of pit-splitting, and nitrogen application promoted over-development of these bundles.