Botany and Plant Science

Primary wall is elastic due to the absence of lignin. Lignin is water-resistant. It reinforces cell walls, keeping them from collapsing.

Collenchyma occurs in the climbing stems. They provide structural support, protecting the plant by serving as an inner framework. Plants are exposed to numerous structural challenges and without these cells, most plants would be too fragile to withstand the damage caused by heavy rains, high winds and other stresses.

In sclerenchyma, wall is lignified. Due to lignification, the cells lose their living characters at maturity.

 In aquatic plants, parenchyma cells have star like air cavities in between the cells. They are called aerenchyma. The air trapped in the cavities make the plants lighter in weight and help them to float in water.

 Collenchyma is a mechanical tissue with unlignified walls.These cells are often found under the epidermis, or the outer layer of cells in young stems and in leaf veins.

 Phloem tissue conducts prepared food from the leaf to storage organs and growing regions.Phloem tissue consists of: conducting cells, generally called sieve elements; parenchyma cells, including both specialized companion cells or albuminous cells and unspecialized cells; and supportive cells, such as fibres and sclereids.

 A ‘thallus’ refers to plant body having no distinction of stem, leaves and roots.

Naked seed condition of gymnosperms stands in contrast to the seeds and ovules of flowering plants (angiosperms), which are enclosed within an ovary.  

In angiosperms (dicots), the Polygonum type of embryo sac is the most common. In this embryo sac, the arrangement of the nuclei is 3 + 2 + 3, i.e. 3 in antipodal cells, 2 in polar nuclei (which later fuse and form a diploid secondary nucleus) and 3 in egg apparatus (2 in synergids and 1 in egg cell).

In angiosperms, male gametophyte consists of a tube cell and a generative cell. The generative cell divides to form two male gametes.

Central cell is the largest cell of embryo sac and is the mother cell of endosperm. The enlargement of the embryo sac after the last nuclear division is largely due to inflation of the large central vacuole of central cell.

Micropyle is the narrow passage left by the integuments at one end of the ovule. It allows the entry of pollen tube into the ovule. This phenomenon is known as porogamy. For example, lily.

Pollen grain is the mother cell of male gametophyte. Development of male gametophyte begins inside themicro sporangium. The microspore nucleus divide mitotically to form a smaller generative cell and a much larger, vegetative cell (tube cell). The generative cell produces two male gametes, whereas, the vegetative cell form pollen tube after pollination. Pollen grain contains two cells, i.e., tube cell and generative cell at the time of pollination.

This is an incorrect option as pollen wall does not have cavities containing proteins.

According to Farmer and Moore, four daughter cells are formed from single cell in meiosis. As a result ofmicrosporogenesis (meiotic division) in four microspore mother cells, 16 pollen grains will be produced.