DOES ACID INVERTASE REGULATE THE SEED DEVELOPMENT OF LITCHI CHINENSIS?
The seed development of litchi fruit is closely linked with fruit set and fruit quality. The aborted (shrivelled or chicken tongue) seeds are believed to be a consequence of both the environment and genotype. However, the mechanism of abortion based on the physiological point of view is poorly documented. The aril sugar composition directly influences flavour of litchi. In our previous study, we investigated the aril sugar compositions of 42 litchi cultivars and grouped them into 3 families according to the difference of hexose/sucrose. Interestingly we noticed that most of the cultivars with lower hexose/sucrose concentrations have abortive seeds. The weight of seeds varied from 0.26±0.09 to 3.47±0.98 g among the selected 20 cultivars. The weight of seeds was significantly positively correlated with the ratio of hexose/sucrose. Extremely low activities of soluble and cell wall acid invertase were detected in the seed pedicel and seed coat of fruits with abortive seeds. In the cotyledon of litchi, no vascular tissue was present and no plasmodesma was observed under TEM (transmission electron microscope) in the cotyledon of litchi, indicating that the cotyledon is symplastically isolated. In contrast, plasmodesmatal continuity remains intact providing a transfer path for sucrose throughout most maternal sinks such as seed pedicel and seed coat. Cell wall invertase can markedly increase localized hexose levels in these instances and promote unloading through the apoplastic pathway. In other crops, invertases mediate the initiation and expansion of many new sink structures, but in litchi, much lower activities of acid invertase might lead to seed abortion due to the weak unloading capacity.
Yang, Z.Y., Zhang, J.Q., Wang, T.D., Huang, X.M., Hu , G.B. and Wang, H.C. (2014). DOES ACID INVERTASE REGULATE THE SEED DEVELOPMENT OF LITCHI CHINENSIS?. Acta Hortic. 1029, 301-308
Litchi chinensis Sonn., seed development, acid invertase, phloem unloading