Question

In 82% of angiosperm families, ovule is
A. Anatropous
B. Orthotropous
C. Amphitropous
D. Circinotropous

Answer 1

Hint: An ovule is a part of the female reproductive system. A mature ovule consists of food for the growing seed. Double fertilisation takes place in an angiosperm.

Complete answer:
In angiosperms the integuments plays the role to protect the ovules during the maturation and fertilization, later it acts as seed coat. The outer integument acts as the testa and the inner coat forms tegmen. In major percent of angiosperm the anatropous ovule is observed. It is the ovule which is inverted. The micropyle bends down to the funiculus to which the ovule unites.
1. Orthotropous - It is the simplest and the primitive ovule. It is seen in Piper nigrum
2. Amphitropous - It is an ovule which is inverted in its stalk.
3. Circinotropous - In this the funicle is long and encircles the ovule.

Hence the correct answer is option A, i.e. anatropous.

Additional knowledge:
- Ovule holds a special role in reproduction in living organisms performing sexual reproduction. In Angiosperms, when pollen grain (the male gamete bearing part) falls and is stuck on a stigma of a flower belonging to the same species, the mating process begins. Many pollen grains land on the sticky surface of stigma, but selectively, only those which belongs to same species can participate in reproduction process, also out of all same species pollens, a few only able to develop the pollen tube, and out of those few, only one which reaches first to the ovule literally performs the reproduction.
- The pollen tubes grow in the style regions and reach to the ovary, via funicule, raphe and from the direction of micropyle the male gamete penetrate the ovule reaches to the eggs and perform double fertilization.

Note: The characteristic features of the anatropous ovule are the presence of the hilum at 90 degree of the micropyle, whereas the chalaza and micropyle are in 180 degree, and thus funicular is next to micropyle. Raphe is a ridge like structure, also present.