Plant Growth And Development-Quick Revision

1

Differentiation

1. In this process, cells derived from root apical and shoot apical meristems and cambium differentiate and mature to perform specific functions.

2

Dedifferentiation

1. Process in which living differentiated cells regain their capacity to divide.

3

Methods for growth measurement

Growth can be measured in terms of
1. Increase in the length or girth
2. Increase in fresh or dry weight
3. Increase in area or volume
4. Increase in the number of cells produced

4

Plant hormones

There are four types of plant hormone. They are as follows:
1. Auxins- Involved in differentiation of vascular tissue, control cellular elongation, prevention of abscission, involved in apical dominance and various tropisms, stimulate the release of ethylene, enhance fruit development
2. Cytokinins- Affect cell division, delay senescence, activate dormant buds.
3. Gibberellins- Initiate mobilization of storage materials in seeds during germination, cause elongation of stems, stimulate bolting in biennials, stimulate pollen tube growth.
4. Abscisic acid- Maintains dormancy in seeds and buds, stimulates the closing of stomata.

5

Fucntions of ethylene

1. Promotes senescence and abscission.
2. Highly effective in fruit ripening.
3. Enhances the respiration rate.
4. Breaks seed and bud dormancy.
5. Initiates germination in peanut seeds.
6. Sprouting potato tubers promotes root growth root hair formation.

6

Importance of photoperiodism

1. Photoperiodism determines the season in which a particular plant shall come to flower. For example, short-day plants develop flowers in autumn-spring period (e.g., Dahlia, Xanthium) while long-day plants produce flowers in summer (e.g., Amaranthus).
2. Knowledge of photoperiodic effect is useful in keeping some plants in vegetative phase (e.g., many vegetables) to obtain higher yield of tubers, rhizomes etc., or keep the plant in reproductive phase to yield more flowers and fruits.
3. A plant can be made to flower throughout the year by providing favourable photoperiod.
4. Helps the plant breeders in effective cross-breeding in plants.
5. Enable a plant to flower in different seasons thus fruits can be produced during their offseason by controlling photoperiod.

7

Vernalization

Vernalization is the induction of a plant’s flowering process by exposure to the prolonged low temperature.

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Phases of ideal sigmoidal growth curve

The whole growth process occurs in three phases:

1. Initial lag phase
2. Exponential phase
3. Stationary phase

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Plasticity

1. Plasticity is the ability of an organism to change its phenotype in response to changes in the environment.