Table 1: Phenology of microspore and megaspore
development in F.
(2009) found that exposure to 50 mg [L.sup.-1] cadmium led to a significant reduction in megaspore
germination, which was as low as 58%.
The spores produced in the ovules are larger than the spores produced in the anthers and are therefore termed megaspores
. Likewise the egg (in the ovule) is larger, a megagamete.
megasporangium The structure in which megaspores
Elapsed time from megaspore
stage to somatically mature female gametophyte (Table 1) is approximately 150 days in Ginkgo (Favre-Duchartre 1958) and ranges from 120 days (Zamia; D.
The nucellus beneath the megaspore
mother cells continuously elongated and developed into mature finger- like shape (Fig.
Experimental studies on megaspore
viability, parthenogenesis and sporophyte formation in Marsilea, Pilularia and Regnellidium.
The primary sporogenous cell enlarges to form the megasporocyte (megaspore
mother cell-MMC) (Fig.
After three days of megaspore
culture, the first sporophytes could be observed.
: Haploid cell produced by meiosis in the ovules of angiosperms; a single megasporocyte produces four megaspores
, only one of which remains functional.
Abbreviations: MMC, megaspore
mother cell; PMC, pollen mother cell.
In this primordium, an archeosporial cell produces a megaspore
mother cell, which undergoes meiosis, forming a linear tetrad.