Gynodioecism in East Mediterranean Hirschfeldia incana. Cruciferae

Populations of Hirschfeldia incana, which occupy various disturbed habitats in Israel, were found to be gynodioecious and to contain between 2% and 10% male sterile plants. Flowers of male sterile plants have generally smaller corollas and always shorter stamens than those of hermaphrodite plants The sterile anthers maintain their original introrse orientation during anthesis, their endothecium lacks a dehiscence strip, and their tapetum persists longer than that in fertile anthers Meiosis is similar in male sterile and hermaphrodite plants, but in the former, microspores disintegrate within the tetrads or are released after a delay, and their exine remains underdeveloped. At low temperatures-10 C or less-the expression of male sterility diminishes. Occasionally, gynomonoecious plants with a mixture of male fertile, partially fertile, and sterile flowers are encountered.