关键词: 红豆蔻, 主动自交, 繁殖保障, 花柱卷曲, 适应性

Abstract:

Autonomous selfpollination is considered to be a reproductive assurance mechanism for plants when facing extreme environments that scarce in pollinators, and it also has disadvantages like inbreeding depression and pollen/ovule discounting. In several genera of Zingiberaceae like Alpinia and Amomum, a specialized mechanism named flexistyly exists, precedent studies consider its significance as preventing unnecessary selfpollination and sexual interference. However according to our field observation, if pollen grains on cataflexistylous (CATA) flowers remain on the anther when the style curves downwardly, potential exists that the stigma contacts the pollen, thus autonomous selfpollination occurs. Here, we studied the breeding system of Alpinia galanga, the results show that (1) Alpinia galanga is selfcompatible in which inbreeding depression occurs to some degree; (2) The anaflexistylous (ANA) morph of Alpinia galanga allocates more resource into outcrossing than the CATA morph; (3) The P/O ratio of the ANA morph is significantly lower than that of the CATA morph, as Alpinia galanga has constant six ovules in each ovary, the significant difference in P/O value reflects the contrast in pollen production. This phenomenon may be interpreted as the ANA morph provides pollen exclusively for the CATA morph. But the CATA morph, despite delivers pollen to the ANA morph, also need its own pollen for potential autonomous selfpollination. In summary, autonomous selfpollination exists in Alpinia galanga, and while flexistyly functions to avoid unnecessary selfpollination and sexual interference, it also provides advantages for delayed autonomous selfpollination as a necessary reproductive assurance and preventing conflict among these three major features by controlling the time of autonomous selfpollination. This peculiar mechanism in Alpinia galanga thoroughly demonstrates its adaptation to unfavorable surrounding during the evolutionary process.

Key words:  Alpinia galanga, Autonomous self-pollination, Reproductive assurance, Flexistyly, Adaptive significance