BIOGENESIS AND FUNCTION OF THE LIPIDIC STRUCTURES OF POLLEN GRAINS

Pollen grains contain several lipidic structures, which play a key rol e in their development as male gametophytes. The elaborate extracellul ar pollen wall, the exine, is largely formed from acyl lipid and pheny lpropanoid precursors, which together form the exceptionally stable bi opolymer sporopollenin. An additional extracellular lipidic matrix, th e pollen coat, which is particularly prominent in entomophilous plants , covers the interstices of the exine and has many important functions in pollen dispersal and pollen-stigma recognition. The sporopollenin and pollen coat precursors are both synthesised in the tapetum under t he control of the sporophytic genome, but at different stages of devel opment. Pollen grains also contain two major intracellular lipidic str uctures, namely storage oil bodies and an extensive membrane network. These intracellular lipids are synthesised in the vegetative cell of t he pollen grain under the control of the gametophytic genome. Over the past few years there has been significant progress in elucidating the composition, biogenesis and function of these important pollen struct ures. The purpose of this review is to describe these recent advances within the historical context of research into pollen development.