Q. 28

Explain the proce

Answer :

Process of double fertilization in plants-

i. After compatible pollination, the intine of the pollen grain forms the pollen tube.


ii. The contents of the pollen grain move into the formed pollen tube.


iii. Pollen tube carrying the two male gametes enters the ovule through micropyle.


iv. The pollen tube then enters one of the synergids with the help of filiform apparatus.


v. After entering the synergid, the pollen tube releases the two male gametes into the cytoplasm of synergid.


vi. One of the male gametes fuses with the nucleus of egg cell resulting in the formation of diploid zygote. This process is called as syngamy.


vii. The other male gamete fuses with the two polar nuclei present in the central cell forming a triploid Primary Endosperm Nucleus (PEN). This process is called triple fusion.


vii. Since two types of fusion- syngamy and triple fusion takes place, this phenomenon is called as the double fertilization.



OR


(a) Difference between spermatogenesis and oogenesis are-



(b) Function of middle piece-


It contains mitochondria, thereby providing energy for the movement of sperm.


Function of tail-


It provides motility to the sperm thereby helping in its propulsion which is essential for fertilization.


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