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.

Formation of new protoplasm is known as real growth.

Increase in mass and increase in number of individuals are twin characteristics of growth. A multicellular organism grows by cell division. Unicellular organisms grow by cell division. One can easily observe this in in vitro cultures by simply counting the number of cells under the microscope.

Cytokinin.

Charles Darwin and his son, Francis Darwin.

3. Ethylene hormone induces female characters.

Ethylene.

1. Apical meristem.
2. Lateral meristem.

Ethylene.

By increasing the length of internodes.

Gibberellin is the plant hormone related with internodal elongation. This phenomenon is called bolting.

Two processes common to both plants and animals are:

1. Cell division.
2. Cell differentiation.

Cousins; it is ethylene.

Abscisic Acid.

Apical shoot buds, root tips and developing seeds.

Dedifferentiation: The living differentiated cells also show another interesting phenomenon during which they regain the capacity to divide mitotically under certain conditions.The dedifferentiated cell can act as meristem, e.g., formation of interfasicular cambium and cork cambium from fully differentiated parenchyma cells.

Beetroot is known as long-day plant because flowering takes place when the plants are exposed to day length longer than a critical photoperiod.

Because of their cytokinesis-promoting activities.

The correct chronological sequence of developmental stages in plants is: Germination → Vegetative growth → Flowering → Fruiting.

F.W. Went; from oat coleoptiles.

Vegetative phase of growth helps the plant gain maturity. A mature plant would be in a better position to withstand the demands of bearing flowers and fruits. Thus, vegetative phase of growth helps in survival of the plant species.

The rice seedlings infected with fungus Gibberella fujikuroi are called foolish seedlings because infected plants grow excessively taller than rest of the non infected rice plants in the field, fall over and be unharvestable.

Shoot apices, leaf primordia and developing seeds.

The plants which show no response to light for flowering are called day neutral plants or DNPs.

Meristems are the actively dividing cells present in the higher plants gymnosperms and angiosperms.

1. Abscisic acid.

It represents that growth slows down due to limited nutrient supply.

The phenomenon is called apical dominance. Auxin is the phytohormone involved in promoting this phenomenon.

The process of parthenocarpy produce the seedless fruits. This is a process in which fruits are developed without fertilization, so, seeds are not formed in the fruit. Artificially parthenocarpy can be induced by spraying auxin and gibberellin to produce seedless watermelons.

• Autoclaved herring sperm.
• It is a modified form of adenine, a purine base.

Because cytokinins retard ageing of plant organs by promoting protein synthesis and mobilisation of nutrient resources.

Climacteric refers to the increased rate of respiration during ripening of fruits.

The symptoms of growth are:

1. Permanent increase in size (length and volume).
2. Increase in fresh weight.

Gibberellin.

5. Gibberellin hormone induces flowering in long photo period requiring plants.

Plants grow throughout their life due to the activity of certain regions, called meristems, where cells retain the capacity to divide.

The growth in plants is indeterminate while that in animals is determinate. A branch of plant can grow up to varied lengths, while a particular organ of an animal grows up to a definite size only.

Higher concentration of auxins inhibit growth of the plants. In normal course in nature, self produced auxin in plants inhibits the growth and development of lateral buds and as a result lateral bud remains dormant.

Leaves are mainly responsible for perception of light intensity in plants. The pigment that receives this stimulus is called phytochrome.

If meristematic cells cease to divide, the growth of the plant will be hindered and will undergo a period of dormancy depending upon the seasonal changes in the climate.

Ethylene.

Meristematic region of shoot.

4. Synthetic auxin (2,4-D) is used as weedicide.

Abscisic acid.

It is the continuous duration of light, which must not exceeded in short day plants/ should be exceeded in long day plants for flowering.

​​​​​​​Auxin hormone is responsible for phototropism.

Cytokinin.

2, 4-D is selective herbicide (weed killer), spray of 2, 4-D is used to kill plants with broad leaved weeds.

Increase in surface area.

Abscisic acid.

Growth at cellular level refers to an increase in the quantity of protoplasm.

Roots, endosperm region of seeds, growing embryos, developing shoot buds, etc.

The situation is known as dormancy of seeds.

1. Ethylene hormone is gaseous in nature.