Question

When the ovule is curved and embryo sac becomes horse-shoe shaped, such an ovule is called as:
A. Amphitropous
B. Circinotropous
C. Campylotropous
D. Orthotropous

Answer 1

Ovule in the seed plants is the structure which gives rise to and contains female reproductive cells. Ovule consists of three parts: the integument which forms its outer layer, the nucellus or the remnant of megasporangium, and the female gametophyte that is formed from a haploid megaspore which is in its center. In angiosperms, the megagametophyte, also known as the female gametophyte, is also known as the embryo sac. It produces an egg cell for fertilization.

Complete answer:
Option A Amphitropous: The ovule in which the nucellus is bent strongly along both the upper and lower sides, with a lower basal body termed as amphitropous ovule. In this stage, the ovule becomes curved and the embryo sac becomes horse-shoe shaped. The body of the ovule is placed transversely at right angles to the funicle and its micropyle and chalaza lie in a straight line.
Hence option A is correct.
Option B Circinotropous: A type of ovule where the funicle is long which creates nearly a full circle around the ovule with micropyle pointing to an upward direction, termed as circinotropous ovule. The female reproductive cells are created here and kept which then eventually after fertilization develops into a seed. The embryo sac here is not horse shoe shaped.
Hence option B is not correct.
Option C Campylotropous: The ovule which is curved more or less at right angle to funicle is termed as a campylotropous ovule. Here, the micropylar end is slightly bent down.
Hence option C is not correct.
Option D Orthotropous: The simplest and most primitive type of ovule is the Orthotropous ovule. The micropyle, chalaza, and funiculus all lay in the same vertical plane in an Orthotropous ovule. The embryo sac is not horse shoe shaped.
Hence option D is also not correct.

Hence, Option A Amphitropous is the correct answer.

Note:
Initially, the ovules are composed of diploid maternal tissue which includes a megasporocyte. Megasporocyte is a cell which will undergo meiosis in order to produce megaspores. The megaspores remain inside the ovule and divide by mitosis which further produces haploid female gametophyte or megagametophyte, which remains inside the ovule. The remnants of megasporangium tissue surrounds the megagametophyte.