Genetic mobility in Typha

Abstract

The female part of the inflorescence of Typha latifolia L. remains receptive to pollen for 4 weeks, but the highest proportion of receptive female flowers is found during the first 2 weeks following anthesis. Typha latifolia pollen has been demonstrated to be effectively dispersed only by strong winds. Under normal conditions the pollen remains viable for at least 4 weeks, but it is sensitive to high humidity and high and low temperatures. In spite of this, a very high degree of self-pollination is found. Most of the pollen falls from the male inflorescence directly of to the female. More seeds are set at the top of the female part of the inflorescence than at the bottom. Typha angustifolia L. shows a higher cross- or neighbourpollination rate than T. latifolia. This has been demonstrated to be due to the lighter pollen and higher positioned male inflorescence in T. angustifolia. The success quota between pollination (adhering pollen grains) and fertilization (seed set) is about 63% in T. angustifolia and 54% in T. latifolia. The pistillodia (club-shaped, modified flowers) are evenly distributed throughout the female inflorescence; in humid conditions the club-shaped tip swells and thus protects the ripe seeds from water. The inflorescence bursts and liberates the fruits in dry conditions probably due to a combination of the shrinking of the pistillodia heads and a hygroscopically controlled spreading of the perianth hairs. The fruit is effectively wind distributed. When the fruit lands on water the perianth hairs with the water. The pericarp wall is also hygroscopically controlled and opens quickly when this contact takes place. The seed is liberated into the water and sinks.