POSTPOLLINATION EFFECTS ON SEED PATERNITY: MECHANISMS IN ADDITION TO MICROGAMETOPHYTE COMPETITION OPERATE IN WILD...

Area of Science:

• Plant reproductive biology
• Evolutionary ecology
• Population genetics

Background:

• Seed paternity is determined by multiple factors after pollen lands on the stigma.
• Microgametophyte competition is a known factor, but maternal choice and embryo competition are less understood and often confounded.
• Wild radish (Raphanus raphanistrum) is a model system for studying these complex reproductive processes.

Purpose of the Study:

• To investigate the roles of maternal choice, genetic complementation, and embryo competition in determining seed paternity in wild radish.
• To assess how environmental stress affects these reproductive mechanisms.
• To differentiate the impacts of various paternity mechanisms on reproductive success.

Main Methods:

• Wild radish plants were subjected to single and mixed pollen loads.
• Reproductive components (fruit abortion, seed number, seed weight, total seed weight) were measured under control and stressed conditions.
• Maternal-plant × pollen-donor interactions and the effects of pollen donor number and stress were analyzed.

Main Results:

• Significant maternal-plant × pollen-donor interactions were observed for all reproductive variables, suggesting genetic complementation or maternal choice.
• Multiply sired fruits generally showed higher reproductive component values than singly sired fruits.
• Reproductive components were more sensitive to paternity under stress, indicating altered embryo competition or increased maternal selectivity.

Conclusions:

• Mechanisms beyond microgametophyte competition, particularly maternal choice, play a crucial role in pollen sorting on wild radish stigmas.
• These maternal effects are likely significant in natural field conditions, especially under environmental stress.
• The study provides evidence for complex post-pollination selection processes influencing plant reproductive outcomes.