Flower Anatomy: Stamen Structure

Structure of a Stamen

• A 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

Anther Structure

• 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 Structure

• In a transverse section, a microsporangium appears near circular in outline
• 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 to release pollen
• The tapetum, the innermost wall layer, nourishes developing pollen grains
• Tapetal cells have dense cytoplasm and often have more than one nucleus

Sporogenous Tissue and Microsporogenesis

• The sporogenous tissue occupies the centre of each microsporangium in young anthers
• The cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads as the anther develops
• The ploidy of cells in the tetrad is haploid

Structure of a Stamen

• A 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

Anther Structure

• 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 Structure

• In a transverse section, a microsporangium appears near circular in outline
• 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 to release pollen
• The tapetum, the innermost wall layer, nourishes developing pollen grains
• Tapetal cells have dense cytoplasm and often have more than one nucleus

Sporogenous Tissue and Microsporogenesis

• The sporogenous tissue occupies the centre of each microsporangium in young anthers
• The cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads as the anther develops
• The ploidy of cells in the tetrad is haploid