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Plant Focus

Quercus macdougallii
A rare oak endemic to the Sierra Juárez in Oaxaca

A Delayed Fertilization Process in Quercus acutissima and Its Ecological

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Min Deng, Cheng-Cheng Shi, Kai-Pin Yao,1 and Qian-Sheng Li

Published May 2022 in International Oaks No. 33: 63–72


In angiosperms, during the double fertilization process, a series of delicate interactions between male and female gametophytes have a great impact on plant adaptation and evolution. Though the genus Quercus is notorious for interspecific hybridization, little is known about the associated physiological mechanisms. In this study, we observed the pollination and fertilization processes in Q. acutissima, a biennial-fruiting oak, using microtome techniques. Our results showed that after pollination, in early to late April, many pollen tubes (PTs) penetrate the pistils through the transmitting tissue in the style and are then arrested at the style base for about 12 months. Only 2-4 PTs resume growth the following April, penetrating the upper region of the ovarian locule in one to two weeks. Once in the ovary, the PTs grow quickly through the micropyle to reach the embryo sac, and fertilization occurs in early to mid-June. The intermittent growth of PTs might reflect a unique male gametophyte recognition mechanism to avoid self-pollination. It might also play a role in increasing interspecific hybridization. The ecological and evolutionary significance of the delayed fertilization process in oaks needs further study, notably to compare PT behavior in self-, outcross-, and interspecific pollination.


pollen tube, embryo sac, male and female gametophyte interaction, Fagaceae


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