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Embryo sac is 7-celled structure. There is a large central cell with two polar nuclei, egg apparatus with egg cell and 2 synergids present at micropylar end and its chalazal end, 3 antipodal cells are present.
- In porogamy the tip of pollen tube enters the micropyle, pushes through the nucellar tissue & finally pierces the egg-apparatus end of the embryo sac. If pollen tube enters through chalazal side it is called chalazogamy & if it enters laterally it is called mesogamy.
- Each microspore divide by mitotic division making a smaller generative cell and a larger vegetative cell.
- Each pollen has two layered wall. The outer layer is thick, tough, cuticularised called exine which is composed of a material called 'sporopollenin'. It is highly resistant to biological and physical decomposition, due to which pollens are preserved for a long time in fossils.
- It is a Polygonum type ovule in which the body of ovule is straight i.e. funiculus, chalaza, embryo sac and micropyle lie in the same vertical axis.
Correct answer: In porogamy the tip of pollen tube enters the micropyle, pushes through the nucellar tissue & finally pierces the egg-apparatus end of the embryo sac. If pollen tube enters through chalazal side it is called chalazogamy & if it enters laterally it is called mesogamy.
Solution
The correct statement describes the three routes of pollen tube entry into the ovule/embryo sac: porogamy through the micropyle, chalazogamy through the chalaza, and mesogamy through the side. The other options discuss unrelated facts about pollen development, pollen wall structure, or ovule type.
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