Hydrophily ( Water Pollination )

STD-12      UNIT-6     CHA-2

REPRODUCTION IN FLOWERING PLANT

Hydrophily ( Gk . hydor- water , philein- to love ; Water Pollination ) . 

• It is the mode of pollination or transfer of pollen grains from the mature anther of a flower to the stigma of another flower which is accomplished through the agency of water . 
• ( i ) Flowers are small and inconspicuous . 
• ( ii ) Perianth and other floral parts are unwettable . 
• ( iii ) Nectar and odour are absent . 
• ( iv ) Pollen grains are naked ( without exine ) , thread like for under water pollination and spherical for surface water pollination . They are light and unwettable due to presence of mucliage cover . 
• ( v ) Stigma is long , sticky but unwettable . 
• Hydrophily occurs only in some 30 genera of mostly monocots e.g. , Vallisneria . Zostera , Ceratophyllum , etc. 
• In many aquatic plants with emergent flowers , pollination occurs by wind or insects , e.g .. Lotus , Water Lily , Water Hyacinth .

• Hydrophylly is of two types - hypohydrophily and epihydrophily . 

• Hypohydrophily occurs below the surface of water , e.g .. Zostera , Ceratophyllum . 

• Epihydrophily takes place over the surface of water , e.g. , Vallisneria . 

• In Zostera , the marine angiosperm ( Sea Grass ) , the pollen grains are long ribon - like ( upto 2500 pm ) and without exine . 
• They have the same specific gravity as that of water . 
• The pollen grains can , therefore , float below the surface of water . 
• The stigmas are also long . 
• The filamentous pollen grains have great chances to touch the long stigmas and coil around the latter to perform pollination .

• Ceratophyllum is a submerged fresh water plant which bears both male and female Nowers on the same plant . 
• A male lower has 30-45 stamens . 
• The mature anthers break , rise upwardly and dehisce on the surface . 
• The liberated pollen grains are rounded and without exine . 
• They germinate and sink . While sinking , they come in contact with long and sticky swaying stigmas to effect pollination .

• Vallisneria is a submerged dioecious fresh water aquatic plant . 
• The male plants produce a large number of male flowers . 
• The male flowers abscise and rise to the surface where they float .
• The male flowers have two fertile stamens . 
• Two of their tepals form a boat shaped structure while the third one functions as a sail . The female plants bear long stalked solitary pistillate flowers . 
• The mature female flowers are brought to the surface of water by the elongation of their stalks . 
• They have large sticky trifid stigmas . While floating , the male flowers are drawn in the depression surround ing each female flower . 
• One anther of a male or staminate flower comes in contact with the stigma of the female flower . 
• The anther bursts and pollination is performed . 
• Pollen grains are cov ered by mucilage which helps them in sticking to stigma as well as protection from wetting by water . 
• After pollination , the female flower is pulled inside water by the coiling of its stalk .

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