OBTURATOR OF PLANT: Meaning, occurance, features, anatomy & function.

In several families of angiosperms a characteristic placental outgrowth is present near the ovule and is referred to as obturator. This obturator grows into the space between the nucellus and the integuments and also between the ovary and ovary wall.

An obturator is said to be helping in directing the growth of pollen tube towards micropyle. Obturator exhibits a great amount of diversity in its origin, morphology, anatomy and mode of development.

Obturator originated from placenta of funiculus or from both. In Combretum, Sterculia the obturator arises at a swelling of the funiculus. In Rivina humilis the obturator arises from the wall of the ovary. In Ceratocephalus, the cells of the funicular epidermis a little above the micropyle radially elongate and develop into the obturator. In some species obturator arises from placenta. Obturator may arise from stylar canal.

OBTURATOR FROM FUNICLE

In Chrozophora the obturator is composed of small thin walled compactly arranged cells, while in Euphorbia the cells of the obturator are loose elongated and hair like. In some species obturator constitutes of short hair developed from the inner surface of the funicle.

Structurally the cells of the obturator may be generally said to be thin walled loosely or compactly arranged may be isodiametric or long and hair like. Sometimes the cells may be secretory in function.

Ultra structurally, the cells of the obturator are rich in ER, dictyosomes, vesicles and many other organelles. The cells of the obturator may secrete an exudates which may chemotropically guide the pollen tube.