Fertilization & Mode of Entry of Pollen Tube in Ovule MCQ

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Fertilization & Mode of Entry of Pollen Tube in Ovule

The fusion of male and female gametes is called fertilization.
The pollination results in the landing of pollen grains on the stigma.
The sequence of events that take place from landing to the fusion of gametes constitutes the fertilization.
In angiosperms, the male gametes present in the pollen grain are brought to the female gamete present in the female gametophyte by a pollen tube. This is called the siphonogamy.
The vegetative cell of the pollen grain germinates through one of the germ pores and the pollen tube grows within the style carrying the male gametes.
The pollen tube grows through the tissues of the stigma and style and reaches the ovary.
In some plants, pollen grains are shed at two-celled condition (a vegetative cell and a generative cell).
In such plants, the generative cell divides and forms the two male gametes during the growth of the pollen tube in the stigma.
In plants which shed pollen in the three-celled condition, pollen tubes carry the two male gametes from the beginning.
The pollen tube enters the ovule through the following:
- Through the micropyle, called the porogamy, as seen in lily
- Through the chalaza, called the chalazogamy, as seen in Juglans
- Through the integuments or funicle, called the misogamy, as seen in cucurbits

Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the synergids through the filiform apparatus.
All these events–from pollen deposition on the stigma until pollen tubes enter the ovule–are together referred to as pollen-pistil interaction.
Pollen-pistil interaction is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.