Pollination related temporal sequences of reproductive development and tracing the path of pollen tubes in Cymbidium pendulum (Roxb.) Sw., an ornamental orchid

Abstract Orchids, known for their exquisite beauty, are highly priced as cut flowers and potted plants at at national and International market. More than I lac manmade hybrids are produced every year at intra to pleurigeneric levels. Therefore, it is of imperative interest to unravel the all aspects of orchids in details. In the present study, the flowers of Cymbidium pendulum, an ornamental important orchids, have been investigated. It is observed that the flowers of C. pendulum started wilting in 20 days without pollination and senesced within 8 days after the act of pollination, suggesting a rapid progression of senescence related events triggered by pollination. The placenta became meristematically active only after pollination. The ovule primordium consisted of an axial filament 5-7 cells high enclosed by epidermal cells. The uppermost cell of the nucellar filament differentiated into an archesporial cell at 20-26 days after pollination (DAP), which turned into megaspore mother cell at 26-30 DAP. The megaspore mother cell underwent meiosis resulting in the formation of a triad which converted in to an eight-nucleate polygonum type of embryo sac. Thus the total time taken to reach the organized embryo sac is between 55-60 days. The results were well confirmed by study with fluorescent microscope using fluorescent dye where the pollen tubes were observed to move through base of the column (6-10 DAP) and entered the ovarian locule (8-16 DAP) and grew on either side of the each placenta, stayed there till the embryo matures and then liberated male gametes for fertilization (54-58DAP). The fertilization occurred around 58-60 DAP. In the present studies, the detailed elucidation of post pollination reproductive development, along-with temporal sequences of path of pollen tubes, have generated valuable information, advantageously useful both for academicians and breeders.