1. (5) Not all aquatic plants use water for pollination. Describe the nature of the mass of cells enclosed within the integuments. Distinctions are drawn between pollen transported above, on and beneath the water surface. POLLINATION "Pollination is defined as the process of transfer of pollen grains from anther to the stigma of the same flower or of different flower of the same species. :- 1. Pollination by Water: Pollination by water is quite rare in flowering plants and is limited to about 30 genera, mostly monocotyledons. It is noted in some orchids that the pollen has an injurious effect on the stigma of the same flower. iv. This kind of pollination is the transference of pollen grains from the anther of a flower to the stigma of the same flower or from a flower (male or bisexual) to a flower (female or bisexual), both found on the same individual plant. The flower is a highly specialized reproductive shoot. Ex: Zostera, Vallisneria Characters: Flowers are small and inconspicuous. Six agents of pollination are. Cross-pollination is the only method in such cases for the setting of seeds. This condition is known as dichogamy. (iii) In some drooping flowers the style is longer than the filaments, whereas in certain erect flowers the reverse may be the case. Light unwettable pollen grains are present in these plants. Here, the nucleus of the functional megaspore divides to form two nuclei; the primary micropylar and the primary chalazal nuclei. They are not coloured, and do not secrete any nectar. The small rounded head of the gynoecium is known as the stigma. The fusion of male and female gametes as well as double fertilization are equally responsible for the production of the viable seeds because absence of any one of these two may cause lethal effect, and the viable seeds are not produced. 1 See answer patelatish6635 is waiting for your help. Dimorphic heterostyly is seen in Oxalis, Linum, Polygonum fagopyrum, Woodfordia, etc. Most species are monoecious (individuals bear both male and female flowers) and feature underwater pollination. In Vallisneria, the female flower reaches the surface of water by the long stalk and the male flowers or pollen grains are … These agencies may be insects (e.g., bees, flies, moths, etc. The spathe bursts releasing the male flowers from the spadix, while still closed, and float on the surface of the water. Introduction to Modes of Reproduction 2. Pollen grain is the first cell of a male gametophyte. Besides the technique of direct injection of pollen suspension into the ovary, in vitro pollination of pistils has also been accomplished. This phenomenon was first discovered by Camerarius (1694) in the end of seventeenth century. This flap is pushed aside by the insect and thus cross-pollination is effected. Let us make an in-depth study of Modes of Reproduction in Angiosperms. The nuclei of generative and vegetative cells differ in size, structure and in staining qualities. (E.g. Female flowers lie at the base of the cavity and open earlier, whereas male flowers lie near the apical opening and open later so that pollen grains have to be brought over from another inflorescence. How can self-pollination be prevented? Various Modes of Reproduction in Angiosperms: The best answers are voted up and rise to the top. Wind and water pollinated flowers are not very colorful and do not produce nectar because. The opening through which the pollen grains are discharged from the pollen sac is called stomium. When there are two integuments then the inner integument is formed first and followed by the formation of the outer integument. They are found in temperate and subtropical climates around the world in intertidal and subtidal portions of coastal areas. The nucleus of the functional megaspore divides and develops into the female gametophyte or the embryo sac. The lower two whorls are called accessory whorls, and the upper two essential or reproductive whorls because only these two are directly concerned in reproduction. Now, one nucleus from each end or pole passes inwards, and the two polar nuclei fuse together somewhere in the middle of the embryo-sac, forming the secondary nucleus (2n). On the other hand, long-tongued insects can pollinate the flowers with long corolla tubes. Such cleistogamous flowers are very small and inconspicuous. They are carried by water currents reaching the female flowers and the stigma. •Vallisneria, Hydrilla, and Zosteraare the common example for hydrophily. It is a small generally oval structure and consists chiefly of a central body of tissue, the nucellus and one or two integuments. Nature favours cross-pollination and there are so many adaptations in flowers to achieve this type of pollination. In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. Autogamy: Transfer of pollen grains from the anther to the stigma … The innermost layer of these wall layers develops into a single layered tapetum. Entomophily (entomon = insect, phileo = to love): This type of pollination takes place through the agency of insects. ), wind and water. Pollination is the mechanism to achieve this objective. As mentioned, pollination is of two kinds: (1) Self pollination or autogamy (auto = self; gamos = marriage) and. Share Your Word File In normal case, one male gamete unites with the egg to form the zygote and the second travels a little farther and unites with the secondary nucleus. 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