Floral Biology and Reproductive Morphology of Nymphaea Lotus
|Keywords||Nymphaeaceae Nymphaea lotus flora biology embryology reproditive morphology|
Nymphaea lotus belongs to the genera Nymphaea of the family Nymphaeaceae in the order Nymphaeale.The Nymphaeales were consistently identified as one of the three earliest lineages of angiosperms. The Nymphaeacea belongs to Nymphaeales and have long been assigned a key, basal, pivotal evolutionary position in classificaton systems of angiosperms. Flora biology of Nymphaea lotus was studied little and about the embrology has not been studied in present. The flora biology and reproductive morphology was carefully investigated in this paper.In this paper flowers of Nymphaea lotus were oberserved to be night-flowering, opened from 8:00 p.m. to 11:00 a.m. The stigma can secrete fluid in the first day and the fluid disappeared the second day. In the first day, bees call on the flowers. There are appendages over the stigma. From the studies on flora biology, it is infered that the fluid was advanced to germinition of the pollen.The morphology of pollen, ovule and stigma were observed by using scanning electron microscopy (SEM). The pollen is global with smooth surface, and with an encircling latitudinal band-like aperture on their surface. It is suggested that Anasulcate pollen of lotus represents the most primitive pollen type in the angiosperm. The outer one of the two integuments is cup-shaped. The micropyle formed only by the inner integument. It is suggested that hood-shaped outer integument is primitive and the cup-shaped one is derived in Nymphaeaceae. The stigma is wet bearing such a fluid secretion at the receptive stage, and the receptive surface is covered with a uniseriate multicellular papillate that is often consisted of three to ten cells. On the basis of correlation investigation confered that dry stigema is primitive and the wet is derived.The megasporogenesis, microsporogenesis, female and male gametophyte development, development of embryo and endosperm were observed by using paraffin wax. The anther wall consists of an outer epidermis, an endothecial layer, twomiddle layers, and a tapetum. The tapetum is secretory and its cells are binucleated. The microspore mother cells undergo simultaneous cytokinesis following the meiotic divisions, which results in the formation of tetrahedral microspore tetrads. The pollen contains three cells when shed. The ovule is anatropous, bitegmic, and crassinucellate. Meiosis of the megaspore mother cell results in the production of a linear triad of megaspores. The two micropylar megaspore cells degenerate while the chalazal one acts as the functional megaspore. The mature female gametophyte comprise four cells (an egg cell, two synergids and a uninucleate central cell). The first division of zygote is transverse and forms a basal cell and an apical cell. The basal cell does not divide, but increases in size, acting as a unicellular funiculus, while the apical cell divides many times. The endosperm development is of helobial type.