Question

Orthotropous ovules occur in
A. Pisum sativum
B. Solanum nigrum
C. Polygonum
D. Helianthus

Answer 1

Hint:-Plants produce seeds after the fertilization of the male and the female parts. The seeds are important in the propagation of the plant species. In the seeds bearing plants, the ovule is an important structure and is related with the female reproductive organs as well as the cells.

Complete step-by-step solution:-
The ovule is a part of the female reproductive organ and it gives rise to the reproductive cells. In seed producing plants, the ovule consists of three distinct parts. The different parts of the ovules are the integument, nucellus and the female gametophyte.
The integument forms the outer layer of the ovule and the nucellus is actually the ruminant of the megasporangium. The female gametophyte forms is found in the central portion and it is formed from the haploid megaspore. In angiosperms, the female gametophyte is also called the embryo sac.
The ovules are classified on the basis of their orientation. On this basis, the ovule is divided into four types which are anatropous, amphitropous, campylotropous, or orthotropic.
In the orthotropous ovules condition, the ovule is present as a straight or erect structure. The chalaza lies in a straight line with funicles. The micropylar end lies at the opposite end of the stalk. The ovules appear as a megasporangium which is surrounded by the integuments. This type of arrangement of the ovule is found in the family Polygonaceae and in species such as Polygonum, P.nigrum, P.betel etc. This condition of the ovule is the most primitive and simplest in arrangement.
In Pisum sativum, the ovules are curved and the micropyle almost is in connection with the funicle. This type of arrangement of the ovules are similar to the anatropous condition but it shows a lesser curvature in relation to the anatropous condition. It is predominantly found in the Chenopodiaceae family.
In Solanum nigrum and Helianthus , the ovule is mostly of anatropous types.

Therefore, the correct option is option C.

Note:- Orthotropous ovules are also known as anatropous ovules. In this type of ovule, the ovule lies in a straight line as well as the micropyle is found at the opposite end of the stalk. The arrangement of the chalaza as well as the funicle lies in a straight line. This type of arrangement is found in species such as Polygonum belonging to the family Polygonaceae.