山核桃（Carya cathayensis）种仁营养价值高，但产量低，难以满足市场需求。授美国山核桃（C. illionensis）花粉的山核桃果实明显增大，前人已从分子标记和胚胎学层面证实授粉子代增大不是由于遗传物质的变化引起的，果实变异为花粉直感效应。申请者前期研究发现授美国山核桃花粉的山核桃叶片光合速率未发生变化，但其外果皮的光合能力明显提高，初步证明果实增大可能是由于父本花粉影响了与果实发育直接相关的另一个重要光合源，即外果皮的光合作用引起的。本项目拟从生理和分子生物学层面，研究授不同花粉（山核桃和美国山核桃花粉）的山核桃果实发育期内外果皮光合性能的变化，揭示花粉直感对山核桃外果皮光合特性的影响作用，明晰授不同花粉的外果皮对光合调节剂的光合响应差异，探讨花粉直感下山核桃外果皮光合作用对其果实发育的影响。研究成果对利用花粉直感效应实现山核桃增产、提高经济效益具有重要的实践价值。

Hickory (Carya cathayensis) seeds, has a high nutritional value, however, the market demand for its low yield has not been satisfied. It has been found that hickory has larger-size fruits/seeds with greener pericarp after pollinated with pollen from pecan (C. illionensis) than control (trees pollinated with hickory pollen). Previous studies have revealed that this phenomenon is not caused by genetic changes in terms of molecular markers and embryology, indicating this is the effect of metaxenia. We have found in the previous study that there is no change in the photosynthetic rate of hickory leaves, but a higher photosynthetic rate in the pericarp of hickory fruits after pollinated with pollen from pecan, which preliminarily indicates that pollen has some effects on an important photosynthetic source (the photosynthesis of pericarp) directly associated with fruit development. In order to elucidate the effect of metaxenia on the photosynthesis of pericarp and to explore the effect of photosynthesis of pericarp on fruit development, we intend to study in terms of molecular biology and physiology the dynamic changes in photosynthetic property of pericarp and clarify differences in the photosynthetic responses to photosynthetic regulators of pericarp during the fruit development of hickory when pollinated with pollen from both hickory itself and pecan. The results will be of important practical value for achieving a high yield with the use of metaxenia and improving economic benefits.