Embryology of Balsaminaceae — I

Abstract

AbstractThe development of anther, ovule, male and female gametophytes has been studied in ten species of Impatiens. The floral parts develop acropetally. The anther wall development follows the ‘basic’ type. Sterile bands of sporogenous origin, divide the sporo‐genous tissue in small groups. The present study confirms the tetrasporangiate nature of the anthers in I. clavicornu refuting the statement of SHIMIZU et al. (1990), that they are trisporangiate. Cytokinesis takes place by furrowing. Ripe pollen is 2‐celled and the generative cell is elongated. The pollen grains are 3‐ to 5‐colpate and show onci.The ovule in Impatiens is tenuinucellate, bitegmic, and anatropous with dorsal raphe. The integuments are free in I. grandis (I. hookeriana) and fused nearly to the top in the remaining species. The micropyle is formed by the inner integument alone. An endothe‐lium is differentiated. Both linear and T‐shaped megaspore tetrads have been observed. The embryosac development conforms to the Allium type in I. oliveri and Polygonum type in the remaining species. The antipodals are ephemeral. Polar nuclei fuse before fertilization. The embryosac elongates crushing the nuclear cells below and reaches the chalazal end. The mature embryosac borders upon the endothelium.