Sexual Reproduction in Flowering Plants Test - 23

Plants which have one or few ovules are generally pollinated by wind and this pollination by wind is called anemophily. Such plants have very less ovaries so wind pollination can effectively bring the pollen in contact with the stigma.

Other agents like birds, insects etc. might damage the flowers and since there are only one or few ovules, such plants prefer to get pollinated by wind.

It is a type of seed formation in which the nucellar cells that are present in the embryo divide and form many more embryos. These are the exact clones of the parents because these are formed from nucellar cells.

Nuclear polyembryony is seen in the members of the citrus family.

Apomixis is a kind of asexual reproduction in which viable embryo is formed within the confines of the seed coat, without meiosis and syngamy.

Adventives embryony is a type of Apomixis found in Citrus in which there is the formation of extra embryos due to sporophytic budding. One or more diploid sporophytic cells, either nuclellus or integuments undergo stages of embryogeny and eventually develop into mature embryos.

Hence, in Citrus Apomictic embryos arise from maternal sporophytic tissue in the ovule.

Total number of meiotic divisions required for forming 100 zygote/100 grains of wheat arc 125. Zygote is the fusion product of pollen grains and egg. 100 zygotes require 100 pollen grains and 100 embryo sacs.

100 pollen grains are produced from 25 microspore mother cells while 100 embryo  sacs are formed from 100 functional megaspores which as a result being produced by 100 megaspore mother cells, since these, out of four megaspores degenerate in each case.

Perisperm is persisting nuclellus in the seeds. Generally till maturity, whole of the nuclellus is consumed in seeds but in some cases.

A thin layer of nuclellus is present in mature seeds, which is called perisperm.

16 Because from one pollen mother cell 4 pollen grains are formed so from 4 pollen mother cell.

4 × 4 = 16

Body of the anatropous ovule gets inverted and Micropyle is on lower side (downward). Further Micropyle and funiculus lie side by side and Micropyle is close to Hilum.

Vegetative propagation in Pistia occurs by offset. Offsets are branches originated from the main stem and upper portion of each branches is curved bearing a group of leaves while lower portion bearing roots.

Each branch when separate can grow independently forming a new plant.

The sporogenous tissue is surrounded by the tapetum layer which provided nourishment to the pollen or microspore mother cell present in the sporogenous tissue. Callose is deposited on the wall of the pollen mother cell.

In some species of Asteraceae and Poaceae, seeds are formed without fertilisation. This is due to the direct development of a seed into an embryo without any meiosis. Production of seeds without meiosis and fertilisation is called Apomixis.

Whereas the development of fruit without fertilization is called parthenocarpic.