Development and Structure of Pollen and Embryo Sac in Peanut (Arachis hypogaea L.)

Of the eight stamens in the flower of peanut (Arachis hypogaea L.), four have oblong anthers and four globose ones. Each oblong anther contains four loculi and each globose anther two. The anther wall development follows the basic pattern. Cytomictic channels between microsporocytes were found from pachytene to telophase II. The mature pollen is two-celled. The mature generative cell, which has a PAS positive wall, associates with the vegetative nucleus and may form a male germ unit. There are two ovules, both hemianatropous and bitegmic. Cells of both integuments and nucellus contain starch grains. The nucellar epidermal cells have a larger nucleus, larger starch grains, and thicker walls than other cells of the ovule. A few cells at the micropylar end persist as a nucellar cap. Embryo sac development is of the Polygonum type. The central cell contains many large starch grains, and the antipodal cells are ephemeral. The synergids possess a filiform apparatus. Wall ingrowths occur in the central cell; those at the micropylar end are more massive than those at the chalazal end. Meiosis in microsporocytes occurs earlier and proceeds faster than that in the megasporocyte. The time required for formation, differentiation, and maturation of the generative cell and the egg cell is the same.