Question

When the pollen tube enters the ovule through the integuments, the phenomenon is known as
A. Isogamy
B. Porogamy
C. Mesogamy
D. Chalazogamy

Answer 1

Hint: There are several ways for the pollen tube to reach the embryo sac for pollination. In botany, the integuments are the ovule's outer layer (s) and develop into a seed coat as the ovule matures after fertilization.

Step by step solution:
The male gamete (pollen grain) fuses with the female gamete (egg) to form a diploid zygote during fertilization. This process starts with the stigma and ends in the ovary sac. When the anther reaches the stigma, it begins to germinate, and a pollen tube grows inside the pistil, carrying the anther to the ovary. The pollen tube can now enter and drop the anther through two openings in the ovary sac. These are the micropylar and integumentary ends, respectively. Later, the anther transforms into a haploid nucleus, which then integrates with the haploid egg nucleus within the ovule (the inner sac of an ovary) to form a diploid zygote.
Fertilization in seed plants is siphonogamous as it occurs via a pollen tube. The pollen tube penetrates the style tissue via the stigmatic papillae. When the pollen tube enters the ovary region, it can enter the ovule in three ways. Mesogamy refers to the process of pollen tube entry through integuments or funiculus. It can be found in Cucurbita and Pistacia. The pollen tube entry into the ovary via micropyle is known as porogamy, and when the pollen tube enters via chalaza, it is known as chalazogamy, as in Betula.

So, option C is correct.

Note: Isogamy is a type of sexual reproduction that occurs in most unicellular eukaryotes and involves gametes with the same morphology (indistinguishable in shape and size). Since both gametes resemble each other, they cannot be classified as male or female—for example, Ulothrix and Spirogyra.