Tag: reproductive health

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.

Pollen grains are haploid (n) structures containing half the somatic chromosome number. If the pollen grain has 6 chromosomes (n = 6), the leaf tip cells, which are diploid (2n), will have 2 * 6 = 12 chromosomes.

Root cells are diploid (2n = 14). Synergids are part of the embryo sac and are haploid (n). Thus, n = 7.

During double fertilization, the pollen tube typically grows into the embryo sac and discharges its male gametes and contents into one of the two synergid cells.

After arriving at the wall of the ovary, the pollen tube enters the ovule either through the micropyle or by some other route. The entrance of the pollen tube through the micropyle is the normal condition and is known as porogamy. In some cases the pollen tube enters the ovule through the chalaza(chalazogamy e.g., Casuarina), or through integuments (mesogamy e.g. Cucurbita).

In the given figure A-central cell, B-egg nucleus, C-plasma membrane, D-synergid, E-filiform apparatus, F-male gametes, G-vegetative nucleus.

The body of the ovule consists of a mass of parenchymatous cells named nucellus. It is equivalent to megasporangium $(2n)$. Megaspore mother cell or megasporocyte is a diploid$(2n)$ cell which undergoes meiosis to form a linear tetrad of four haploid megaspores (n). Normally, the chalazal megaspore is the functional megaspore while the other three degenerate.

In many aquatic plants with emergent flowers, pollination occurs by wind or insects, e.g., lotus, water lily, water hyacinth.