Category: Biology Second Paper

After fertilization the ovum is stimulated. Ovarian changes occur. The ovule changes into a seed. The watery part of the ovule is reduced and the soft part dries up to form a hard seed. Ovule develops into ovule, ovule into ovule, ovule into ovule and ovule into sporule.

After fertilization, the ovary of the flower is stimulated. The uterus grows and changes in its various parts. As a result, the uterus grows. The wall of the uterus forms the placenta. If the ovary of each flower of an inflorescence develops into a fruit, it is called simple fruit or single fruit. Mango, jam, litchi, plum etc. are single fruits. When a single fruit is produced from a complete inflorescence, it is called a compound fruit. Composite fruits like jackfruit, pineapple etc.

As the embryo develops in the embryo sac, the seed nucleus divides repeatedly in the process of mitosis to form many nuclei. Nuclei become cells containing cytoplasm. The cells fuse to form the seed or endosperm. The seeds are stored as food for the embryo. When the developing embryo absorbs the entire seed of the seed, the seed becomes asexual. A seed without a seed is called a seed. Mangoes, beans, chickpeas etc.

If the developing embryo does not absorb the whole seed, some part of the seed is still present in the seed. Such seeds are called sasyal seeds. Vegetable seeds like paddy, wheat, bhutra, redi, cotton etc.

A seed which does not remain after the completion of the embryo is called a sterile seed.

A seed in which a seed exists after the completion of the embryo is called a viable seed.

The fusion of the diploid secondary nucleus with the haploid sperm of the embryo is called triploidy. That is, the union of three nuclei with two polar nuclei and one pungamete occurs in triploidy. Hence it is called Trimilan.

One of the two sperm unites with the egg, a phenomenon called syngamy. Strasburger first observed syngamy in 1884.

 

1. The growth of the female gametophyte stops at the octanuclear stage. Growth resumes after double-fertilization.
2. Beans provide nutrients to the growing embryo. Double fertilization is essential for viable seed formation.
3. The secondary nucleus stops cell division before fertilization. Triple fusion helps the dormant nucleus acquire the ability to divide.
4. Dichotomous stamens help determine plant and host characteristics.

The process of simultaneous fertilization of two spermatozoa, one with the ovum and the other with the secondary nucleus, is called double fertilization. Dicotyledons occur in herbaceous plants. In 1990, scientist Williams Friendman discovered bi-toxicity in the gymnosperm Ephedra. In 1898 scientist Navasin observed double fertilization in Lilium martagon and Fritellaria tenella plants. Double fertilization occurs in paddy, wheat, bhutra, redi etc.

Uterus → fruit

Intein → tegmen

Uterine wall → ovary

Ovary→Sperm

Ovule→seed

Nucellus → destroyed, perisperm

Ovum → Embryo

Secondary nucleus→seed or endosperm

Ovule or micropyle → Spore

Helper cells or synergids are destroyed

Umbilical cord or Hyalum → Umbilical cord

Antipodal→destroy

Ovule or Funiculus → Spore

Ovule or calaja→sperm or perishes

Exine→testa/seed coat