Biology: Stamen, Microsporangium, and Pollen Grain

Structure of a Stamen

• A typical stamen consists of two parts: the filament (a long, slender stalk) and the anther (a terminal, generally bilobed structure)
• The filament is attached to the thalamus or petal of the flower at its proximal end
• The number and length of stamens vary in flowers of different species

Structure of an Anther

• A typical angiosperm anther is bilobed, with each lobe having two theca (dithecous)
• A longitudinal groove often runs lengthwise, separating the theca
• The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe

Microsporangium

• The microsporangia are located at the corners of the anther and extend longitudinally throughout its length
• They are packed with pollen grains and develop further to become pollen sacs
• A typical microsporangium appears near circular in outline in a transverse section
• It is surrounded by four wall layers: epidermis, endothecium, middle layers, and tapetum
• The outer three wall layers provide protection and aid in anther dehiscence, while the innermost wall layer (tapetum) nourishes the developing pollen grains

Tapetum

• Tapetal cells have dense cytoplasm and often have more than one nucleus (bi-nucleate)
• The tapetum provides nutrients to the developing pollen grains

Microsporogenesis

• The cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads as the anther develops
• The ploidy of the cells of the tetrad is haploid

This quiz covers the structure and function of stamens, microsporangium, and pollen grains in flowers. Learn about the filament, anther, and other components of stamens.