Plant Growth and Development Test - 2

Growth is measured by a variety of parameters some of which are: increase in fresh weight, dry weight,length, area, volume and cell number.

one single maize root apical mersitem can give rise to more than17,500 new cells per hour, whereas cells in a watermelon may increase in size by upto 3,50,000 times.

In the former, growth is expressed as increase in cell number; the latter expresses growth as increase in size of the cell.

The process of de-specialisation of differentiated cells so that they become undifferen­tiated and able to divide is known as dedifferentiation. It involves activation of certain genes which not only reverse differentiation but also stimulate cell division.

Cork cambium, wound cambium and inter-fascicular vascular cambium are always produced through dedifferentia­tion.

Plant callus is a growing mass of unorganized plant parenchyma cells. In living plants, callus cells are those cells that cover a plant wound.

The initial growth is slow (lag phase), and it increases rapidly thereafter – at an exponential rate (log or exponential phase). Here, both the progeny cells following mitotic cell division retain the ability to divide and continue to do so. However, with limited nutrient supply, the growth slows down leading to a stationary phase.

Auxins promote stem elongation, inhibit growth of lateral buds (maintains apical dominance). They are produced in the stem, buds, and root tips.

Example: Indole Acetic Acid (IA).

Auxin is a plant hormone produced in the stem tip that promotes cell elongation

The living differentiated cells that have lost the capacity to divide can regain the capacity of division under certain conditions. This phenomenon is termed as dedifferentiation.

Absolute growth rate refers to the measurement and comparison of total growth per unit time.

Thus, Absolute growth = Growth in given time period.

Relative growth rate refers to the growth of a particular system per unit time, expressed on a common basis

Growth, differentiation and development are very closely related events in the life of a plant. Broadly, development is considered as the sum of growth and differentiation.

Development is a term that includes all changes that an organism goes through during its life cycle from germination of the seed to senescence.

Plants follow different pathways in response to environment or phases of life to form different kinds of structures. This ability is called plasticity. This phenomenon of heterophylly is an example of plasticity.