Lesson 2 of 12 · 7 min
Stamen, microsporangium and microsporogenesis
NCERT §1.2.1
Tap a ripe anther of Anu's paddy flower and yellow dust falls out. How many pollen mother cells had to divide to make that dust, and what fed them while they did?
The lesson in notes
In short
A stamen has a long thin stalk, the filament, and a terminal anther that is usually bilobed. The lower end of the filament is fixed to the thalamus or to a petal.
A typical angiosperm anther is bilobed and dithecous (each lobe has two thecae, separated by a lengthwise groove). In section it is four-sided with one microsporangium at each corner, two per lobe, so it is tetrasporangiate. The microsporangia mature into pollen sacs.
In transverse section a microsporangium looks nearly circular and has four wall layers, from outside in: epidermis, endothecium, middle layers and tapetum. The outer three protect it and help the anther dehisce to release pollen.
The tapetum, the innermost layer, nourishes the developing pollen. Its cells have dense cytoplasm and usually more than one nucleus.
In a young anther the centre of each microsporangium is filled by sporogenous tissue, a group of compact, uniform cells. Each of these cells can act as a pollen mother cell (PMC), also called a microspore mother cell.
Microsporogenesis is the making of microspores from a PMC by meiosis. The four haploid microspores of one PMC stay together at first as a microspore tetrad.
As the anther matures and dries, the tetrads separate and each microspore develops into a pollen grain. Each microsporangium forms thousands of pollen grains, which are set free when the anther dehisces.