Combined Functions Of Protogyny And Delayed Autonomous Self-Pollination In A Desert Herb Zygophyllum Macropterum

Protogyny and delayed autonomous self-pollination are very common in angiosperms. They rarely occur within a species, especially in Zygophyllaceae. Zygophyllum macropterum is a perennial herb in Zygophyllaceae. Protogyny and delayed autonomous self-pollination were determined in Z. macropterum, and combined functions of protogyny and delayed autonomous self-pollination were studied in this species. The main results were as follows:(1)The anthesis of Z. macropterum was3d, including the female stage and the bisexual stage. The stigma was exposed prior to ten anthers exposure due to style growth in early anthesis. The distance was reduced between10anthers and the stigma due to the filament growth in middle-late anthesis. Normally, the first four anthers overtopped the stigma. The stigma was already receptive when the stigma was exposed. The duration of the best stigma receptivity was45h. In addition, the duration of the highest pollen viability per anther was36h.(2) The data from different pollination experiments indicated fruit set and seed set after cross-pollination was the highest, so cross-pollination increased fruit set and seed set in the female stage. The data from bagged flowers after emasculation indicated Z. macropterum did not exhibit apomixes. In addition, fruit set and seed set after natural pollination were higher due to pollinator pollination and delayed autonomous self-pollination, and delayed autonomous self-pollination provided reproductive assurance when pollinators were absent.(3)The only attracted pollinator of Z. macropterum was Anthophora plumipes. Pollinator frequency was significantly different in different stages of anthesis of the same time of a day. The pollinator frequency e was0.28±0.04times-flower-1·h-1in female stage. As corolla mouth diameter became larger, the pollinator frequency became higher. The pollinator frequency was the highest in late anthesis.(4)Pollinators that visited the flowers in the female stage promoted cross-pollination. Delayed autonomous self-pollination deposited some pollen grains on the stigma to assure fertilization of the ovule in middle-late anthesis. In addition, pollen tube growth was clearly viewed under a fluorescence microscopy. The pollen grains germinated after cross-pollination and delayed autonomous self-pollination.