Each of these microspores, after further mitoses, becomes a pollen grain ( microgametophyte ) containing two haploid generative ( sperm ) cells and a tube nucleus.
42.
Tissue culture techniques with respect to wheat and triticale have seen continuous improvements, but the isolation and culturing of individual microspores seems to hold the most promise.
43.
Spore mother cells in the microsporangia divide by meiosis to form haploid microspores that develop further by two mitotic divisions into immature male gametophytes ( pollen grains ).
44.
After meiosis, each microspore undergoes mitotic cell division, giving rise to multicellular pollen grains ( six nuclei in gymnosperms, three nuclei in flowering plants ).
45.
Microspores ( the smaller of the two spore types produced by the fungus ) were not accounted for in their original description, although they are present in the type.
46.
The microgametophyte a pollen grain which has germinated from a microspore is employed for dispersal, only releasing its desiccation-prone sperm when it reaches a receptive megagametophyte.
47.
They bear sporocarps of two types, either megasporangia that are few in number ( approximately 10 ), each with single megaspore, or many microsporangia, each with 64 microspores.
48.
The cones usually bear two kinds of sporangia : lobed megasporangia in the lower part of the cone which produce megaspores and simple microsporangia in the upper part which produce many tiny microspores.
49.
In a process called "'microsporogenesis "', four haploid microspores are produced from each diploid sporogenous cell ( microsporocyte, pollen mother cell or meiocyte ), after meiotic division.
50.
The sacs at the bottom of leaves create two types of spores, female ( megaspores, about 0.5 mm diameter ) and male ( microspores, a few micrometres in diameter ).
