The formation of the 'Abscission layer' in leaves is primarily triggered by:
- Ethylene
- Gibberellin
- Auxin
- Cytokinin
Explanation: Ethylene promotes the senescence and abscission of plant organs, particularly of leaves and flowers, by aiding layer formation.
The ripening of fruits like apples and tomatoes is significantly accelerated by:
- ABA
- Ethylene
- Cytokinin
- Auxin
Explanation: Ethylene is a gaseous hormone that enhances respiration (respiratory climacteric) and triggers the fruit ripening process.
Which hormone is essential for 'Xylem differentiation' during the healing of a plant wound?
- Ethylene
- Gibberellin
- ABA
- Auxin
Explanation: Auxin controls xylem differentiation and also plays a critical role in helping cells divide during tissue culture and wound healing.
Which of the following constitutes the 'Precursor' for Abscisic Acid (ABA)?
- Carotenoids
- Tryptophan
- Terpenes
- Methionine
Explanation: ABA is a derivative of carotenoids, whereas Gibberellins are terpenes and Auxin is an indole derivative.
The development of 'Heterophylly' in Larkspur is a classic example of:
- Dedifferentiation
- Redifferentiation
- Differentiation
- Plasticity
Explanation: Plasticity allows plants to produce different types of leaves in different life stages or environmental conditions (e.g., terrestrial vs aquatic leaves).
The phenomenon of 'Etiolation' (pale, long stems) occurs when plants are grown in:
- Pure nitrogen
- High oxygen
- Complete darkness
- Bright sunlight
Explanation: Plants grown in the dark become 'etiolated'—they have weak, elongated, pale stems due to a lack of chlorophyll development.
The 'Phytochrome' pigment is responsible for perceiving the stimulus of:
- Light duration
- Water concentration
- Gravity
- Temperature
Explanation: Phytochrome is a photoreceptor pigment in leaves that detects the ratio of red to far-red light, mediating photoperiodic responses like flowering.
The promotion of flowering by a period of low temperature is called:
- Senescence
- Vernalisation
- Dormancy
- Photoperiodism
Explanation: Vernalisation ensures that reproductive development and seed production occur only after the plant has experienced a cold winter.
Statement I: Growth in plants is generally 'open'.
Statement II: New cells are always being added to the plant body by meristems.
- Statement II correct
- Statement I correct
- Both are correct
- Both are incorrect
Explanation: Plant growth is unique because plants retain the capacity for unlimited growth throughout their life due to the presence of meristems.
Which hormone is used to induce 'Bolting' (sudden internode elongation) in rosette plants?
- Gibberellin
- Auxin
- Ethylene
- Abscisic Acid
Explanation: Gibberellins promote internode elongation just prior to flowering in plants like cabbage and beet, a process known as bolting.
Which hormone promotes the 'Respiratory Climacteric' during fruit ripening?
- ABA
- Ethylene
- Cytokinin
- Auxin
Explanation: Ethylene triggers a significant rise in the rate of respiration during fruit ripening, a phenomenon known as the respiratory climacteric.
Which specific hormone was isolated from the 'rotten oranges' that induced ripening in bananas?
Explanation: Cousins (1910) confirmed the release of a volatile substance (ethylene) from ripened oranges that hastened the ripening of stored unripened bananas.
Which effect of Ethylene is observed in seedlings as 'horizontal growth and swelling'?
- Apical dominance
- Triple response
- Climacteric rise
- Bolting effect
Explanation: The 'triple response' of Ethylene consists of inhibition of stem elongation, horizontal growth of the axis, and swelling of the seedling axis.
The hormone 'Zeatin' was first isolated from which of the following?
- Coconut milk
- Oat coleoptiles
- Corn kernels
- Rice seedlings
Explanation: Letham isolated Zeatin, a natural cytokinin, from corn (Zea mays) kernels. It is also found in coconut milk.
The growth of a 'Pollen tube' is a classic example of growth measured in terms of:
- Length
- Cell size
- Cell number
- Surface area
Explanation: In some cases, growth is best expressed as an increase in length, such as in the elongation of the pollen tube toward the ovary.
The discovery of 'Auxin' was initiated by observations of phototropism in canary grass by:
- Skoog and Miller
- F.W. Went
- Charles Darwin
- E. Kurosawa
Explanation: Charles Darwin and his son Francis Darwin observed that the coleoptiles of canary grass responded to unilateral illumination by bending toward light.
Cytokinins were first crystallized from herring sperm DNA and were named:
- Kinetin
- Gibberellic acid
- Indole butyric acid
- Zeatin
Explanation: F. Skoog and his co-workers identified and crystallized a cytokinesis-promoting active substance, which they termed Kinetin.
Which of the following is the 'Relative Growth Rate' also known as?
- Plasticity index
- Efficiency index
- Absolute rate
- Arithmetic index
Explanation: The relative growth rate (r) measures the ability of the plant to produce new plant material and is referred to as the efficiency index.
The production of 'Parthenocarpic' (seedless) tomatoes is induced by:
- Gibberellins
- Cytokinins
- Auxins
- Ethylene
Explanation: Auxins are widely used in agriculture to induce parthenocarpy (fruit development without fertilization) in various plants like tomatoes.
Which plant hormone is responsible for the phenomenon of 'Apical Dominance'?
- Auxins
- Ethylene
- Gibberellins
- Cytokinins
Explanation: Auxins produced at the shoot tip inhibit the growth of lateral (axillary) buds. Removing the tip (decapitation) allows lateral buds to grow.
Which of the following hormones is derived from the nucleic acid base Adenine?
- Terpenes
- Auxins
- Cytokinins
- Gibberellins
Explanation: Cytokinins (like Kinetin and Zeatin) are N6-furfurylamino purine derivatives, which are modified forms of the base Adenine.
Plants like 'Wheat and Barley' are classified as:
- Long Day
- Heat Sensitive
- Short Day
- Day Neutral
Explanation: Long Day Plants (LDP) flower only when they are exposed to a light period exceeding a critical duration (e.g., in early summer).
Which naturally occurring plant growth regulator was famously isolated from 'liquid endosperm' (coconut milk)?
- Gibberellic acid
- Zeatin cytokinin
- Abscisic acid
- Indole acetic acid
Explanation: Zeatin is a naturally occurring cytokinin. Following the discovery of kinetin, researchers seeking natural substances with similar cell-division-promoting activities successfully isolated zeatin from corn kernels and coconut milk.
The 'Apical hook' formation in dicot seedlings is a characteristic response to:
- ABA
- Auxin
- Ethylene
- Cytokinin
Explanation: Ethylene influences the 'triple response' in seedlings, which includes the formation of an apical hook to protect the tender tip.
The ability of plants to follow different pathways in response to environment is called:
- Senescence
- Dedifferentiation
- Differentiation
- Plasticity
Explanation: Plasticity is seen in plants like Cotton and Coriander, where leaf shapes differ between juvenile and adult stages or in different habitats (heterophylly).
Which hormone is functionally used to prevent 'Fruit and leaf drop' at early stages?
- ABA
- Auxins
- Gibberellins
- Ethylene
Explanation: Auxins prevent the early abscission (dropping) of young fruits and leaves, though they promote the abscission of older, mature parts.
Which of the following is a 'Day Neutral Plant' that flowers irrespective of photoperiod?
- Wheat
- Radish
- Tobacco
- Cucumber
Explanation: Day Neutral Plants like Cucumber, Tomato, and Pepper do not show a correlation between exposure to light duration and flowering.
Which hormone promotes the 'Malting' process in the brewing industry?
- ABA
- Auxin
- Ethylene
- Gibberellin
Explanation: GA3 is used to speed up the malting process in barley by inducing the synthesis of hydrolytic enzymes like alpha-amylase.
Which of the following hormones is functionally antagonistic to Auxin regarding lateral bud growth?
- Abscisic Acid
- Ethylene
- Gibberellin
- Cytokinin
Explanation: While Auxin promotes apical dominance (inhibits lateral buds), Cytokinin helps overcome it by promoting lateral bud development.
In a sigmoid growth curve, the initial slow phase of growth is referred to as the:
- Lag phase
- Stationary phase
- Log phase
- Exponential phase
Explanation: The sigmoid curve consists of an initial Lag phase (slow growth), followed by a Log/Exponential phase (rapid growth), and finally a Stationary phase.
Photoperiodism refers to the response of plants to the relative length of:
- Temperature change
- Gravity levels
- Soil moisture
- Light and dark
Explanation: Photoperiodism is the physiological reaction of organisms to the length of night or a dark period.
Gibberellins are used to extend the market period of fruits like citrus because they:
- Promote ripening
- Delay senescence
- Increase acidity
- Kill pests
Explanation: Gibberellins delay the aging (senescence) of fruits, allowing them to be left on the tree longer and extending their availability in the market.
Which of the following is a 'Short Day Plant'?
- Tomato
- Radish
- Sugar beet
- Tobacco
Explanation: Short Day Plants require a light period less than a critical duration. Tobacco and Soybeans are classic examples.
The 'Richmond-Lang effect' refers to the delay of leaf senescence by:
- Ethylene
- Auxins
- Cytokinins
- Gibberellins
Explanation: Cytokinins delay senescence by promoting the mobilization of nutrients to the leaves, maintaining their greenness and vitality.
The application of which hormone can increase the yield of sugarcane by as much as 20 tonnes per acre?
- Cytokinin
- Auxin
- Ethylene
- Gibberellin
Explanation: Sugarcane stores sugar in its stems. Spraying the crop with gibberellins increases the length of the stem, thereby increasing the total yield.
Which of the following plants requires 'Vernalisation' to flower in its second year?
- Rice
- Sugar beet
- Maize
- Wheat
Explanation: Biennial plants like Sugar beet, Cabbage, and Carrots are monocarpic plants that require cold treatment (vernalisation) to flower.
Which phase of growth is characterized by cells having dense protoplasm and large conspicuous nuclei?
- Meristematic phase
- Maturation phase
- Senescent phase
- Elongation phase
Explanation: Cells in the meristematic region are rich in protoplasm, possess large nuclei, and have thin primary cell walls with abundant plasmodesmatal connections.
In tissue culture, a 'High Auxin to Cytokinin' ratio typically promotes:
- Shoot formation
- Root formation
- Seed dormancy
- Leaf abscission
Explanation: The balance of these two hormones determines morphogenesis; higher auxin favors rooting, while higher cytokinin favors shooting.
Which specific hormone is used to increase the length of grape stalks?
Explanation: Gibberellins (like GA3) cause an increase in the length of the axis; they are used to increase the length of grape stalks and improve fruit spacing.
The 'Bakanae' (foolish seedling) disease of rice led to the discovery of:
- Zeatin
- ABA
- Gibberellins
- IAA
Explanation: The disease was caused by a fungus, Gibberella fujikuroi. E. Kurosawa identified that the symptoms were due to a chemical secreted by the fungus.
Which hormone is used to 'break' the dormancy of potato tubers for early planting?
- Ethylene
- ABA
- Cytokinin
- Auxin
Explanation: Ethylene (often as ethephon) is used to break seed and bud dormancy and to initiate sprouting in potato tubers.
Which hormone promotes 'Female' flower production in cucumbers to increase yield?
- Auxin
- Ethylene
- Gibberellin
- Cytokinin
Explanation: Ethylene is used to promote femaleness in some plants like cucumbers, which increases the total number of fruits produced.
The 'Avena curvature test' is a bioassay used to identify the presence of:
- Gibberellin
- Cytokinin
- ABA
- Auxin
Explanation: This bioassay, developed by F.W. Went, measures the concentration of auxin based on the degree of bending in oat (Avena) coleoptiles.
Which hormone stimulates the production of 'new leaves' and 'chloroplasts' in plants?
- Ethylene
- Gibberellin
- Auxin
- Cytokinin
Explanation: Cytokinins help produce new leaves, chloroplasts in leaves, lateral shoot growth, and adventitious shoot formation.
The 'Ethephon' solution, widely used in agriculture, is a source of:
- Gibberellin
- Cytokinin
- Ethylene
- Auxin
Explanation: Ethephon is an aqueous solution that is readily absorbed and transported within the plant, where it slowly releases ethylene gas.
Which hormone delays the senescence of leaves by promoting nutrient mobilization?
- ABA
- Auxin
- Cytokinin
- Ethylene
Explanation: Cytokinins delay leaf senescence (Richmond-Lang effect) by mobilizing nutrients toward the treated parts.
Which process describes a living differentiated cell regaining the capacity to divide under certain conditions?
- Vascularization
- Differentiation
- Redifferentiation
- Dedifferentiation
Explanation: Dedifferentiation occurs when mature cells, like parenchyma, become meristematic to form interfascicular cambium or cork cambium.
Seed dormancy can be broken by treating seeds with which hormone?
- Coumarin
- Phenolic acid
- ABA
- Gibberellin
Explanation: Gibberellins and Nitrates are often used to overcome seed dormancy. ABA and phenolic acids are inhibitors that induce dormancy.
Gibberellins are chemically defined as being derivatives of:
- Terpenes
- Adenine
- Indole compounds
- Carotenoids
Explanation: Gibberellins are acidic terpenes. Auxins are indole derivatives, and ABA is a carotenoid derivative.
The precursor for the biosynthesis of the hormone Ethylene is:
- Tryptophan
- Methionine
- Mevalonic acid
- Acetyl CoA
Explanation: Ethylene is synthesized in tissues from the amino acid Methionine. Tryptophan is the precursor for IAA (Auxin).
The 'Stress Hormone' that triggers stomatal closure during water scarcity is:
- Cytokinin
- Gibberellic acid
- Ethylene
- Abscisic Acid
Explanation: ABA stimulates the closure of stomata and increases the tolerance of plants to various kinds of stresses, hence its name.
Which hormone is widely used as a herbicide to kill broad-leaved dicotyledonous weeds?
Explanation: 2, 4-dichlorophenoxyacetic acid (2, 4-D) is a synthetic auxin used to control dicot weeds in monocot cereal crops.
Growth can be measured in terms of increase in fresh weight, dry weight, or:
- Chlorophyll count
- Sugar content
- Protein density
- Surface area
Explanation: Growth is measured by several parameters including length (pollen tube), volume (fruits), cell number (watermelon), or surface area (leaves).
The geometric growth of a plant population can be expressed mathematically as:
- Lt = L0 + rt
- W1 = W0 + rt
- W1 = W0ert
- Lt = L0ert
Explanation: In geometric growth, both daughter cells continue to divide. Here, 'e' is the base of natural logarithms, and 'r' is the relative growth rate.
The removal of the shoot tip to promote the growth of tea bushes is a practice based on:
- Increasing ABA
- Reducing GA
- Removing bolting
- Removing dominance
Explanation: In tea plantations and hedge making, decapitation removes the source of auxin, thereby breaking apical dominance and promoting bushiness.
In plants, the site of perception of the light/dark duration for flowering is the:
- Root tips
- Lateral bud
- Shoot apex
- Leaves
Explanation: While the shoot apex modifies into a flowering apex, the stimulus of photoperiod is perceived by the leaves via pigments like phytochrome.
Which PGR is often referred to as 'anti-GA' because it inhibits seed germination?
- Abscisic Acid
- Cytokinin
- Auxin
- Ethylene
Explanation: Abscisic Acid (ABA) acts as a general plant growth inhibitor and is functionally antagonistic to Gibberellins regarding germination.
Which of the following is a classic example of a 'Redifferentiated' tissue?
- Secondary xylem
- Parenchyma
- Cork cambium
- Intrafascicular cambium
Explanation: Secondary xylem and phloem are produced by the activity of the cambium (a dedifferentiated tissue) and eventually lose their ability to divide.
The arithmetic growth of a plant organ can be expressed mathematically as:
- W1 = W0ert
- Lt = L0 + rt
- Lt = L0ert
- W1 = W0 + rt
Explanation: In arithmetic growth, only one daughter cell continues to divide. The formula represents a linear increase where 'r' is the growth rate.
Which of the following hormones is a gaseous plant growth regulator?
Explanation: Ethylene ($C_2H_4$) is the only gaseous plant hormone, primarily involved in fruit ripening and senescence.