Fertilization
 

Hi. I wondered if anyone could answer a simple question. Once an ova
has been fertilized by the pollen nucleus, I understand that the ovary
of the plant becomes the fruit and the ovule becomes a seed. What
happens to the other ovum? Also if the ovule becomes the seed, are
fruit with multiple seeds (e.g apple) a result of mitosis?

Kind regards from a physisist who should probably know better.

JB

Fertilization
 

In message om, JB
writes
Hi. I wondered if anyone could answer a simple question. Once an ova
has been fertilized by the pollen nucleus, I understand that the ovary
of the plant becomes the fruit and the ovule becomes a seed. What
happens to the other ovum? Also if the ovule becomes the seed, are
fruit with multiple seeds (e.g apple) a result of mitosis?

Kind regards from a physisist who should probably know better.

JB


In plants an ovary is a structure divided into one or more locules, each
of which contains one or more ovules. The ovary develops into the fruit,
and the ovule into the seed. (To complicate the matter, an apple is what
is known as a pome, which is a type of false fruit, i.e. a fruit (in the
vernacular sense) that is not wholly derived from the ovary. In the case
of the apple, the core is the true fruit; IIRC, the flesh of the apple
is derived from the base of the flower, which is known as a hypanthium.

A pollen grain is composed of two or three cells. The large, the
vegetative cell, forms the pollen tube. Within the vegetative cell is to
be found either two sperm cells, or a single generative cell, which
later divides into two sperm cells.

Within an ovule there develops a megasporocyte, which divides into 4
haploid cells. Typically 3 of these degenerate, and the fourth
differentiates into the embryo sac, which technically is the female
gametophyte, and is composed (mostly) of haploid cells. Only one of
these cells is an ovum, which on fertilisation by a sperm cell develops
into the embryo. In flowering plants a process called double
fertilisation occurs, in which another of the embryo sac cells,
typically diploid, is fertilised by the second sperm cell, and develops
into the endosperm of the seed. IIRC, the remainder of the ovule
develops into the seed coat.
--
Stewart Robert Hinsley, ex physicist