Study on Developmental Stage of Gynoecium and Megagametophyte in Rannunculus arvenisis L.

Study of gynoecium and female gametophye is important in botany and plant taxonomy. This research was done for studying the developmental stages of ovule in Ranunculus arvensis and comparing with other reported taxa in this family. Flowers and young buds were collected in different developmental stages, fixed in FAA70 and stored in 70% ethanol. Specimens were sliced using microtome after dehydration and embedding in the paraffin wax and stained. Developmental stages of ovule and embryo sac were studied and photographed using a light monitoring microscope. Results showed that the ovule is anatropous, unitegumic with 4 or 5 layers and full-nucellus. Embryo sac development is followed monospori and polygonum type. Increasing of antipodal cells and in some cases increasing of synergids were observed. Also their nuclei were polyploid. Archeosporial cells were surrounded by callosic wall after their formation. Megaspore's tetrads had linear and T-shaped ornamentations. Embryo sac was large with irregular shape and considerably grows longitudinal in its maturation step. Results showed that although the overall pattern of ovule development in the studied species is similar to previous reports, but the tetrad arrangement, increasing of antipodal and synergid cells, and the presence of Hypostase, Postament and Nucellar Cap is the specific characteristic for this species.