15: Plant Growth And Development : Neet-xi-biology

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#1-a
growth,
Ans : Growth

It is an irreversible and permanent process, accomplished by an increase in the size of an organ or organ parts or even of an individual cell.

#1-b
differentiation,
Ans : Differentiation

It is a process in which the cells derived from the apical meristem (root and shoot apex) and the cambium undergo structural changes in the cell wall and the protoplasm, becoming mature to perform specific functions.

#1-c
development,
Ans : Development

It refers to the various changes occurring in an organism during its life cycle - from the germination of seeds to senescence.

#1-d
dedifferentiation,
Ans : De-differentiation

It is the process in which permanent plant cells regain the power to divide under certain conditions.

#1-e
redifferentiation,
Ans : Re-differentiation

It is the process in which de-differentiated cells become mature again and lose their capacity to divide.

#1-f
determinate growth,
Ans : Determinate growth

It refers to limited growth. For example, animals and plant leaves stop growing after having reached maturity.

#1-g
meristem and
Ans : Meristem

In plants, growth is restricted to specialised regions where active cell divisions take place. Such a region is called meristem. There are three types of meristems - apical meristem, lateral meristem, and intercalary meristem.

#1-h
growth rate.
Ans : Growth rate

It can be defined as the increased growth in plants per unit time.

Qstn #2
Why is not any one parameter good enough to demonstrate growth throughout the life of a flowering plant?

Ans : In plants, growth is said to have taken place when the amount of protoplasm increases. Measuring the growth of protoplasm involves many parameters such as the weight of the fresh tissue sample, the weight of the dry tissue sample, the differences in length, area, volume, and cell number measured during the growth period. Measuring the growth of plants using only one parameter does not provide enough information and hence, is insufficient for demonstrating growth.

#3-a
Arithmetic growth
Ans : Arithmetic growth

In arithmetic growth, one of the daughter cells continues to divide, while the other differentiates into maturity. The elongation of roots at a constant rate is an example of arithmetic growth.

#3-b
Geometric growth
Ans : Geometric growth

Geometric growth is characterised by a slow growth in the initial stages and a rapid growth during the later stages. The daughter cells derived from mitosis retain the ability to divide, but slow down because of a limited nutrient supply.