FLOWERING AND POLLINATION CHARACTERISTICS OF CHINESE-GROWN PECAN (CARYA ILLINOINENSIS)

The morphological flowering characteristics, pollen viability and stigma receptivity of Chinese-grown pecan [Carya illinoinensis (Wangenh.) C. Koch] under defined developmental stages were investigated by digital photography, in vitro germination, and benzidine-H₂O₂ testing, respectively. The results show that the optimal time for pollen collection is at stage V when the angle between bracts and catkin rachis is about 90° and anthers turn yellow. The pollen viability of ‘Pawnee’ is the highest among the tested cultivars. The stigma receptivity of pecan cultivars such as ‘Mahan’ begins to rise since stage II with increasing dehisced angle, and peaks when the angle is about 90° which lasts 2 to 3 days. The dehisced angle is relatively small in other pecan cultivars, such as ‘Pawnee’ whose stigma receptivity rises as the stigma begins to dehisce, and the optimal stigma receptivity at stage II lasts for 2 days. The stigma loses receptivity when it begins to wither and turn brown. Pollen of ‘Pawnee’ shed overlaps nearly the whole time when ‘Mahan’ is receptive, proving that ‘Pawnee’ is a good pollinated cultivar of ‘Mahan’. The pollination chart suggests a fair amount of variation compared with the cultivar blooming patterns in the US.