Development of male and female reproductive organs in Trachyspermum ammi (L.) Sprague (Apiaceae)

Ajowan, belonging to Apiaceae, is one of the most medicinal plants in Iran and is naturally distributed in Ethiopia, Egypt, and India. Despite the homogeneity of flower characteristics in the family, nevertheless, a high diversity of flower morphology can be seen in this genus. Given the pharmacological importance of Ajowan, the developmental stages of its male and female organs were examined.

Flower buds in different developmental stages were harvested, fixed in FAA, and maintained in 70% Ethanol. After performing various steps, including clarification and embedding in paraffin, microtomy sections were made. The Hematoxylin-eosin was used to stain the slices.

Based on the results, the initiation pattern of floral organ development is acropetal, in which the sepals initiate first, followed by petals, and finally, stamens. Initiation of gynoecium occurs with delay to the stamen. Isostemonous stamens, secretory tapetum layer, tetrahedral microspore tetrad, spindle shape microspores, mature pollen with two-celled and three germinal furrows. Asynchrony of microspore development was observed in the anthers of the same plant flowers and the pollen sacs of the same anther. Also, the development of male and female gametophytes was not synchronized in the same flower. Inferior ovary, anatropous ovules, the linear type of megaspore tetrad, polygonum type of functional megaspore formation and embryo sac development are other characteristics of this plant.