Tag: reproductive health of humans

In angiosperms, pollen grains are typically shed at either the 2-celled stage (vegetative and generative cell) or the 3-celled stage (vegetative cell and two male gametes).

Endosperm is triploid (3n). Pisum sativum (2n=14, 3n=21), Oryza sativa (2n=24, 3n=36), Nicotiana tabacum (2n=48, 3n=72), Allium cepa (2n=16, 3n=24). Matching: a-v, b-iv, c-i, d-ii.

The exine of a pollen grain is composed of sporopollenin, which is one of the most resistant organic materials known, protecting the pollen from degradation.

The nucellus is a diploid tissue (2n). The microspore mother cell (MMC) is also a diploid cell derived from the sporophytic tissue, so it has the same chromosome number.

In angiosperms, the female gamete is the egg cell, which is located within the embryo sac inside the ovule.

Palynology is the scientific study of pollen grains and spores, both living and fossilized.

An orthotropous ovule is one where the micropyle, chalaza, and funiculus lie in a straight vertical line.

Microspore mother cells undergo meiosis to produce microspores, which then develop into pollen grains.

Option B is incorrect because multiple pollen tubes can grow into the style, although only one typically enters the ovule to effect fertilization.

The most common type of ovule in angiosperms is the anatropous ovule, not the orthotropous one.