Abstract

Zhimin Liu* and Huanpu Ma

 Vascular bundles play a very important role in fruit development and quality. Each set of bundles has its own specific function. In order to know the relationship between endocarp cracking and vascular bundles, we observed specific vascular bundle development during fruit growth. The results showed that embryo bundles and ventral bundles are closely related to pit-splitting. We found that pit-splitting was caused by the occurrence of both an over-expanded seed and a weakened endocarp. The rapid development of the seed was controlled by abnormally thickened embryo vascular bundles. 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. Our results demonstrate that the over-development of the embryo bundle and ventral bundles is the key cause of pitsplitting. We anticipate our assay to be a starting point for more studies examining the relationship between vascular bundles and fruit quality. For example, excessive nitrogen, water and thinning can cause pit-splitting; however, the manner in which these factors influence the development of the embryo vascular bundle and abdominal vascular bundle of the endocarp is unknown. The individual and combined effect of these factors on pit-splitting could be tested and related to other fruit quality problems.