Embryology of sunflower Helianthus annuus (Asteraceae)

Abstract

The abortion of sunflower fruits during different moments of its development could be due to abnormalities in the reproductive process. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures on three commercial hybrids, DK 4050, CF 17 and P30, and a line, HA 89 is reported. The anther wall consists of epidermis, endothecium, one middle layer and a plasmodial tapetum with binucleate cells efore integrating. A peritapetal membrane with orbicules encloses the pollen grains, which are triporate, angulaperturate and shed at tricellular stage. HA89 also presents tetraporate pollen grains. The ovule is tenuinucelate, unitegmic and anatropous. The young embryo-sac is formed by six cells and eight nuclei. Antipodes, which vary in number and in the amount of nuclei on their cytoplasm, usually show thick walls between themselves and the middle cell. Differences between the genotypes studied may justify the contradictions found on previous accounts.The abortion of sunflower fruits during different moments of its development could be due to abnormalities in the reproductive process. A comparative study of the sporogenesis, gametogenesis and the development of the related sporophytic structures on three commercial hybrids, DK 4050, CF 17 and P30, and a line, HA 89 is reported. The anther wall consists of epidermis, endothecium, one middle layer and a plasmodial tapetum with binucleate cells efore integrating. A peritapetal membrane with orbicules encloses the pollen grains, which are triporate, angulaperturate and shed at tricellular stage. HA89 also presents tetraporate pollen grains. The ovule is tenuinucelate, unitegmic and anatropous. The young embryo-sac is formed by six cells and eight nuclei. Antipodes, which vary in number and in the amount of nuclei on their cytoplasm, usually show thick walls between themselves and the middle cell. Differences between the genotypes studied may justify the contradictions found on previous accounts.