BIOLOGY OF TETRADS, POLYADS AND POLLINIA

摘要

During the process of microsporogenesis, the tetrads are produced with 4 pollen grains, which separate into monads and shed, as a normal feature in the angiosperms. Apart from tetrads, polyads are also produced by the increase in number of pollen grains, in multiples of 4, and in yet other instances the pollen mass is not shed, being retained within sac-like structures, namely pollinia. In the pollination activity, the transport of the haploid pollen takes place in the form of tetrads, polyads or pollinia, associated also by suitable carrying mechanisms, and germination process with appropriate floral modifications. The above situations are exemplified in pollen morphosystems of the families Mimosaceae (tetrads and polyads: anemophilous), Asclepiadaceae and Orchidaceae (Pollinia: entomophilous) which are reviewed in the present treatise.