What is the relation between megasporogenesis and cellular senescence
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This chapter reviews gamete development and the interval between pollination andfertilization (progamic phase) in flowering plants and discusses the various hypotheses that have been put forward as to the functions of the callose walls. Flowering plant (angiosperm) gametes develop by mitosis from haploid gametophyte cells that are formed bymeiosis from diploid sporocytes. Male gametes are contained within multicellular pollen grains and female gametes within a multicellular embryo sac. Transient callose walls are a conspicuous feature of the processes that lead to the production of both types of gametes. Mature pollen grains germinate and produce a tube that conveys the male gametes to the embryo sac where fertilization takes place. Flowering plant pollen tubes are characterized by a thick, inner wall of callose and regular callosic cross walls.