Question

Growth in plants speech in english ​

Answer 1

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Explanation:

In this essay we will learn about Growth of Plants. After reading this essay you will learn about: 1. Introduction to Growth of Plants 2. Stages in Growth of Plant 3. Measurement 4. Effects of Light 5. Growth Regulators 6. Other Growth-Regulating Substances 7. Synthetic Growth Regulators.

Contents:

Essay on the Introduction to Growth of Plants

Essay on the Stages in Growth of Plants

Essay on the Measurement in Growth of Plants

Essay on the Effects of Light in Growth of Plants

Essay on Growth Regulators in Plants

Essay on Other Growth-Regulating Substances from Plants

Essay on the Synthetic Growth Regulators in Plants

Essay # 1. Introduction to Growth of Plants:

One of the most self-evident of all natural phenomena is the continuous increase in size of plants and production of new organs at least during some stage of their life histories. The term growth is popularly employed to designate this complex of pro­cesses, which depends on many other physiological processes.

It is impossible to under­stand plant growth without a sound knowledge of the basic facts of absorption, transport of materials such as minerals to the place of synthesis and metabolism itself. Besides these processes other factors specific to growth and development such as hormones must be mentioned. The advances made in this field during the previous 30 or 40 years have really been tremendous.

Growth may be defined as a permanent and irreversible change in any dimension of an organism.

The dry matter which is incorporated into the structure of both protoplasm and cell walls during growth comes almost entirely from the foods synthesised by plants themselves.

In the synthesis of new protoplasm, i.e., in the production of new cells, the foods which are assimilated are largely proteins, for protoplasm, as we know, is largely proteinaceous. Foods which are assimilated in the formation of cell walls are mostly carbohydrates, e.g., cellulose and pectins.

As a result of assimilation, a growing region, such as stem tip or root tip increases in dry weight during growth, i.e., new cells are continuously being formed from pre-­existing cells.

The mere increase in size of a plant or plant part is not necessarily, the result of growth. We know that dry seeds when soaked in water, imbibe water and certainly increase in volume and in weight. But that cannot be considered as growth for removal of water will also reduce the volume of the seeds to original volume and size and there is also no increase in dry weight.

We know that growth of plant occurs in regions of growing points known as meristems.

Three main changes occur in meristems:

Cell division, cell enlargement and cell differentiation.

The growth of a plant may be due either to cell division or to cell enlargement.

This is possible only because the two daughter cells produced, enlarge to the approximately same size of the mother cell, before they divide again. Thus the growth of a plant or plant organ is essentially an increase in size due to an enlargement of cells and this cell enlargement must be irreversible and not simply a reversible increase due to normal increase in hydrostatic pressure, caused by turgour.

In classical concept of cell growth, the causative force is turgour pressure. Yet it is a fact that mature cells have higher turgour pressure than younger meristematic cells. The mature cells, however, have more rigid cell walls but the growing cells stretch more readily.

Consequently a small turgour pressure is sufficient to stretch the walls of a young growing cell which may not be sufficient to stretch the wall of a more mature cell. As water enters the cell during cell enlargement, solutes also are absorbed.

In this way, the cell maintains a high osmotic pressure of the cell sap, and conditions for the development of sufficiently high turgour pressure to stretch the cell walls, are well maintained.

Besides water and solute absorption other changes also occur during cell growth. New cell wall materials are laid down by intussusception, i.e., insertion of new molecules of cellulose on the old wall particles that become softened to permit the stretching the wall undergoes during enlargement.

Thickening may also take place by opposition, i.e., deposition of new cell wall matter on the inner surface of the wall during the matura­tion phase of the cell.

The meristematic cell is filled with cytoplasm and has only a few very small vacuoles. As the cell enlarges, the vacuoles increase in number and by coalescing with each other, occupy a much larger proportion of the cell and the cytoplasm as a result becomes a thin layer, lining the large central vacuole.