BIOLOGY 1 Marks Question

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

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.

Differentiation 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.

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

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

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

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

Growth 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. Developmental heterophylly.
2. Environmental heterophylly.

Skoog and Miller.

Cytokinin delays senescence, while ABA promotes senescence.

Gibberella fujikuroi.

Ranuculus flabellaris.

Internal factors that control development in plants are:

1. Genetic factors (intracellular).
2. Plant growth regulators (intercellular).

Open form of growth refers to the form of growth where new cells are added by the activity of meristems.

Vascular cambium, cork cambium.

By promoting root growth and root hair formation and thereby increasing the area of absorption.

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

Ethephon.

Florigen is the hormone involved in photoperiodism. Its chemical nature is not yet established. It induces flowering in plants.

Apical meristem.

Genetic factors and plant growth regulators.

1. Seed dormancy.
2. Zeatin.

1. Male flowers.

Callus (i.e., undifferentiated mass of cells) proliferates only when nutrient medium containing auxin was supplemented with coconut milk because it contains kinetin (a cytokinin) which stimulates growth of plant tissues.

Cytokinin has the ability to initiate morphogenesis in plant tissues and organs.

The farmer should apply ethylene.The plant hormone ethylene increases the number of female flowers in cucumber.

When seed dormancy is because of internal causes, it is called inherent seed dormancy.

Plant growth is unique, as plants retain the capacity to grow throughout their life. This ability is due to the presence of meristems. The cells of meristematic tissue have the capacity to divide and self-perpetuate. This form of growth, where new cells are continuously added to the plant body by the activity of meristems, is called open form of growth.

After germination of seed, shoots with leaves are produced at first. This marks the vegetative growth of plant. This is important for synthesizing enough resources which could be utilized in sexual reproduction. And hence, flowering follows after this phase.

Spraying of sugar plants with gibberellin can increase the yield of sugar. Spraying increases the length of internodes and increased or lengthy internodes will produce more sugar.

• Vernalisation.
• Gibberellins.

Cytokinin.

Ethylene.

1. Shoot apices, leaf primordia and developing seeds.
2. Apical shoot buds, root tips and developing seeds.
3. Roots, endosperm region of seeds, growing embryos, developing shoot buds, etc.

Some plants require specific long day periods or specific cold treatments for flowering. Bolting can be induced artificially the treatment of gibberellins.

Presence of ethylene hormone can affect other apples in the basket.

The sudden elongation of internodes prior to flowering in rosette plants, is called bolting.

IBA and 2, 4-D are used to induce formation of roots on cuttings of many ornamental, horticultural and forest trees, 2, 4-D can also be used as a weedicide.

In geometric growth, all daughter cells produced after mitotic cell division undergo cell division.

Zeatin is the growth regulator isolated from endosperm. It controls cell division (cytokinesis) even in non-meristematic tissues.

Seed germination.

Gibberellic acid is the phytohormone that induces production of hydrolytic enzymes (protease, amylase, lipase) in the endosperm of germinating seeds.

1. Naphthalene acetic acid (NAA).
2. 2, 4-dichlorophenoxy acetic acid (2, 4-D).

Callus is an undifferentiated mass of parenchyma cells produced during tissue culture.

Shoot apex and root apex.

Callus will develop into shoot buds first.

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

Closure of stomata.