Reproduction in Plants, Biology tutorial

Introduction:

Reproduction is the capability of living organisms to generate offspring, that is, new individuals of their kinds. This is a significant feature of all living organisms. This is the only method in which each and every type of organism can continue to live on everlastingly, however the individual should ultimately die.

Organisms have developed numerous methods of reproducing. These can either be asexual or sexual. Asexual reproduction is a kind of reproduction in which just one parent is implicated. No gamete is made. Asexual reproduction takes place in both plants and animals. Sexual reproduction is the reproduction which comprises the sex cells - the sperm and the egg resultant to the formation of the zygote.

Reproduction in Flowering Plants:

Reproduction in the flowering plants can either be sexually or asexually.

Asexual Reproduction:

Asexual reproduction is the kind of reproduction in which just one parent is involved. No gamete is made. Vegetative propagation is an illustration of asexual reproduction in the flowering plants.

Vegetative Propagation:

Vegetative propagation comprises the use of parts of plants in multiplying the plant or if a new plant grows out of a parent plant, devoid of the use of seeds. Vegetative propagation comprises two techniques: Natural vegetative and artificial vegetative propagation.

Natural Vegetative Propagation:

Natural vegetative propagation is taken out by the plants themselves by use of leaves, stems and buds. Tiny plants growing from the leaf can later on break off to develop new plants, illustrations: Bryophyllum and Begonia.  A few of the stems are modified as rhizomes, runners, corms and tubers.

Artificial Vegetative Propagation:

Artificial propagation is the employ of parts of the parent plant to multiply the plant. Budding, cutting, grafting, layering and marcotting are few ways of the artificial vegetative propagation.

Sexual Reproduction in Flowering Plants:

In flowering plants, flowers include the reproductive organs of the plant that is androecium which is a male reproductive part and the gynoecium which is the female reproductive system of the plant. The whorls comprise calyx (sepals) and corolla (petals) at times the calyx and the corolla are fused and they are termed as the perianth. If one flower comprises of both the sexes, it is termed as a bisexual flower of hermaphrodite, odite and if one flower includes either of the sex organs it is termed as a unisexual flower.

Both the male and female gametes of the flower are unable to move. The problem of their coming altogether for fertilization is over come by the procedure of pollination. In this procedure pollen grains are moved by different agencies like wind, insects, water and other animals to the stigma. Once on stigma, the pollen grain generates a pollen tube to reach the ovum. The male gamete includes two cells, the vegetative nucleus and the generative nucleus. Both travel via this tube. The former nucleus fuses with the egg and the second nucleus fuses by the two haploid polar bodies to build the primary endosperm nucleus. This fusion is termed as triple fusion.

Subsequent to fertilization the zygote for the seed and the ovary becomes the fruit. The ovary guards the seeds, till they are mature and ready to grow into plants. At such a phase different agencies, as in pollination, assist the seed to spread away from the main plant. This procedure is termed as seed dispersal.

The Sexual reproduction in a flowering plant consists of two main phases: Pollination and Fertilization.  

Pollination:

Insect pollination:

For fertilization to occur, the male gamete within the pollen grain should reach the female gamete within the ovule. The transfer of pollen from anthers to the stigma is termed as pollination. Insects can take pollen. Insects like bees are fascinated to a flower by the scent and color of the petals. The bee grounds on the flower and nourishes on the nectar. Pollen from the anther is transported to the bee's back. The bee flies to the other flower of the same kind, again fascinated by the color and scent. While nourishing on the second flower the stigma gathers the pollen from the bee's back.

Wind pollination:

Pollen can as well be transferred from anther to the stigma by the wind. In a wind pollinated flower the stamen discharges light grains of pollen which are taken up by the wind. The feathery stigmas of the flowers trap the pollen grains as they float by. Simply pollen from the similar kind of flower can grow on the stigma. Grasses are an illustration of plants which based on the wind for pollination.

Fertilization:

Fertilization occurs after pollination. The male nucleus within the tube fuses with the female nucleus in the ovule to build up a zygote. A tube grows out of the pollen grain on the stigma and down via the style to the ovary. The male gamete is contained within the pollen tube. As it goes through the wall of the ovary the tube grows to the ovule. The tube enters the ovule via a tiny hole termed as the microphyle. The male nucleus within the tube fuses with the female nucleus in the ovule to form a zygote. This is fertilization and outcomes in the formation of the zygote.

After fertilization the fertilized ovule grows into the seed. As the petals and stamens shrivel and die the ovary wall develops the fruit. Plants generate two distinct types of fruit, fleshy and dry.

Germination:

Germination is stated as the procedure which comprises the gradual growth of the embryo of the seed into a seedling or a young plant. In another words germination is the sequence of changes through which an embryo in a seed grows into a seedling.

The embryo of grown seeds generally passes through a period of rest termed as dormancy.  Throughout this period, there is much little cell activity. The seeds can stay in this condition as long as they are dry and the condition for germination is not favorable. If conditions become favorable, the seeds experience various changes to build up into seedlings.

Type of Germination:

There are mainly two kinds of germination. These are epigeal and hypogeal germination.

Epigeal germination:

Epigeal germination is stated as the kind of germination in which the cotyledons or seed leaves are taken above the soil surface. Epigeal germination is related with dicotyledonous plants, example: germination of cowpea, ground-nut, melon, mango and so on.

Hypogeal germination:

Hypogeal germination is stated as the kind of germination in which the cotyledons, seed leaves or endosperm stay beneath the soil surface. Hypogeal germination is related with monocotyledonous plants, example: germination of maize, guinea corn, oil palm, millet, wheat and so on.

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