Question

Type of ovule present in Opuntia is
a. Amphitropous
b. Campylotropous
c. Circinotropous
d. Orthotropous

Answer 1

Hint: The ovule is the one in which the female reproductive parts are contained in the plants with seeds. The options given are the types of ovule based on the orientation of the parts in ovule.

Complete answer:
Opuntia is an edible cactus found in extremely hot conditions. They produce bisexual flowers, which eventually gives rise to berry with arillate seeds. As I mentioned earlier, the orientation of the parts (Chalaza, funiculus, raphae and nucleus) in the ovule can be categorised into various types, as follows:

> Amphitropous – They are in the shape of a horseshoe with the ovule and its embryo sac very much curved. Example: Poppy, Alisma,Lemna.

> Campylotropous – The word ‘kampylos’ means curved in Greek. So, these are also curved, almost in a right angle, such that the chalaza and micropyle are not aligned in a straight line. However, the embryo sac is only slightly bent. Example: Capsella, Mustard.

> Circinotropous – This type has a coiled structure where the funicle is longer and wraps around the ovule. The micropyle and nucleus are found to point upwards. Example: Opuntia.

> Orthotropous – They are also known as Atropous. This is the most primitive type with the nucleus, chalaza and micropyle in the same plane. Example: All gymnosperms.

Hence, the correct answer is option (C).

Note: There are two more types of ovules.
Anatropous – The ovule turns completely downwards during development with the micropyle being close to the hilum (as shown in the figure). This is the most commonly found type occurring in almost all the angiosperms.
Hemitropous – The body of the ovule is at right angles to the funiculus with the micropyle and chalaza in the same plane. Example: Ranunculus.