15

Q1. Gibberellin was discovered from 

• Algae
• Fungi
• Bacteria
• Roots of higher plants

Solution

GA was first isolated by Kurasawa in 1926 from the fungus Gibberella fujikuroi, the causal organism of foolish seedling disease of rice plants in Japan.

Q2. The phytohormone which induces triple response is

• IAA
• ABA
• GA
• C₂H₄

Solution

Ethylene is a gaseous hormone which stimulates shoot growth, root growth and differentiation which is otherwise called triple response.

Q3. The phenomenon exhibited by green plants when grown in darkness is called

• Photomorphogenesis
• Etiolation
• Photoperiodicity
• Thermoperiodicity

Solution

If a plant is allowed to grow in complete darkness, then it shows etiolation.

Q4. Phytochrome is involved in  

• Phototropism  
• Photorespiration  
• Photoperiodism  
• Geotropism  

Solution

Phytochrome is a photosensitive pigment which exists in two states. It is involved in photomorphogenetic responses, seed germination, bud dormancy, synthesis of gibberellin and ethylene and photoperiodism.  

Q5. Which one increases in the absence of light?

• Uptake of minerals
• Uptake of water
• Elongation of internodes
• Ascent of sap

Solution

The absence of light reduces overall growth, photosynthesis, uptake of minerals and ascent of sap. However, the elongation of internodes is seen to occur in the absence of light.

Q6. An auxanometer is used to measure

• The growth in length of a plant organ
• The growth in breadth of a plant organ
• Population of the pests attacking a plant
• The growth of leaves

Solution

Growth is measured by measuring an increase in length, volume, area, diameter etc. So, an auxanometer is used to measure the growth in length of a plant organ.

Q7. Growth can be measured in various ways. Which of these can be used as parameters to measure growth?

• Increase in cell number
• Increase in cell size
• Increase in length and weight
• All of the above

Solution

Growth can be measured when there is an increase in cell number, cell size, length and fresh or dry weight.

Q8. What is the best example of commitment?  

• Final structure at maturity of cells  
• Interfascicular vascular cambium  
• Wound meristem  
• Vascular elements  

Solution

The final structure at maturity of cells appearing due to the same meristem is determined by location of cells. The root cap cells when pushed to the periphery produce the epidermis.  

Q9. A hormone delaying senescence is 

• Auxin
• Cytokinin
• Ethylene
• Gibberellin

Solution

Richmond and Lang proved that cytokinin delayed senescence. They observed that application of cytokinins increased the chlorophyll content which delays senescence for several days.

Q10. Cell elongation in the internodal regions of green plants occurs due to   

• Indole acetic acid  
• Cytokinins  
• Gibberellins  
• Ethylene  

Solution

Cells elongate due to the presence of the synthetic auxin indole acetic acid. Cell elongation occurs because the cell walls become plastic and due to endosmosis.  

Q11. Intercalary meristem results in 

• Secondary growth
• Primary growth
• Apical growth
• Lateral growth

Solution

Cells of the meristematic region have the capacity to divide. Root apical meristem and shoot apical meristem contribute to cell elongation of plants which is called primary growth.

Q12. Geocarpic fruits are produced by  

• Onion  
• Watermelon  
• Groundnut  
• Carrot  

Solution

Geocarpy refers to the ripening of fruits underground. For groundnut, the young fruits are pushed into the soil as a result of the post-fertilisation curvature of the stalk.  

Q13. Plasticity in plant growth means that  

• Plant roots are extensible.  
• Plant growth is dependent on the environment.  
• Stems can extend.  
• None of the above.  

Solution

Plant organs change their structures to cope with the change in the environment; this is called the property of plasticity.  

Q14. A plant hormone used for inducing morphogenesis in plant tissue culture is

• Gibberellin
• Cytokinin
• Ethylene
• Abscisic acid

Solution

The ratio of cytokinin to auxin controls cell differentiation. If there is more cytokinin than auxin, then shoot buds develop. Relatively more auxin than cytokinin leads to the development of roots. Abscisic acid is known as a natural plant growth inhibitor. Gibberellin stimulates stem elongation, leaf expansion, bolting, flowering etc. Ethylene is a fruit-ripening hormone.

Q15. Which of the following is an intrinsic factor which controls the development of an organism?

• Genetic
• Temperature
• Hormonal
• Both A and C

Solution

The process of development is controlled by intrinsic factors such as genetic and hormonal factors. Extrinsic factors include light, temperature, water and oxygen.

Q16. Phytochrome is involved in

• Phototropism
• Photorespiration
• Photoperiodism
• Geotropism

Solution

Phytochrome is involved in photomorphogenetic responses, seed germination, bud dormancy, synthesis of gibberellins and photoperiodism.

Q17. Light grown seedlings are

• Sturdy
• Green with shorter internodes
• Expanded leaves
• All of the above

Solution

Light grown seedlings are sturdy, green with shorter internodes, expanded leaves and upright apex.

Q18. Mowing the grass lawn facilitates better maintenance because

• Wounding stimulates regeneration
• Removal of apical dominance and stimulation of intercalary meristem
• Removal of apical dominance
• Removal of apical dominance and promotion of the lateral meristem

Solution

According to Thimann and Skoog, the removal of the apical bud causes the sprouting of lateral buds with stimulation of the intercalary meristem and this is the reason that mowing a grass lawn facilitates better maintenance.

Q19. Culturing of plant tissues is an example of

• Differentiation
• Redifferentiation
• Dedifferentiation
• Both B and C

Solution

Culturing of plant tissues is an example of dedifferentiation and redifferentiation. During this technique, a lump of permanent tissue from the portion of pith is dissected out and cultured on solid culture media. 

Q20. When the rate of growth is proportional to the size of the tuber, it is called  

• Formative growth  
• Absolute growth  
• Law of mass growth  
• Geometric growth  

Solution

The law of mass growth is the rate of growth which is proportional to the size of the tuber.  

Q21. The xylem which differentiates has a thick secondary wall made of

• Lignin
• Pectin
• Suberin
• Cellulose

Solution

The development of a thick secondary wall is made of lignin, and it becomes living permanent cells of the parenchyma.

Q22. The hormone responsible for apical dominance is

• IAA
• GA
• ABA
• Florigen

Solution

Apical dominance is the phenomenon in which the presence of an apical bud does not allow the nearby lateral buds to grow. This is characteristically caused by auxins.

Q23. Which method out of the following renders the seed coat permeable to water so that embryo expansion is not physically retarded?  

• Stratification  
• Denudation  
• Vernalisation  
• Scarification  

Solution

In many plants, the seed coat is quite tough and provides mechanical resistance to the growth of the embryos. Scarification by abrasion through machine, threshing, filling etc., ruptures or weakens the seed coat and promotes germination.   

Q24. What is the last stage of a plant called?

• Senescence
• Vernalisation
• Dormancy
• Scarification

Solution

The last phase of development is senescence. Senescence or old age leads to death.

Q25. Gibberellins promote

• Seed germination
• Seed dormancy
• Leaf fall
• Root elongation

Solution

Gibberellin increases the length of hypocotyls and cotyledonary leaf area during germination. GA induces synthesis of α-amylase and other hydrolytic enzymes in seeds of monocots and dicots.

Q26. Which one of the following plant is LDP?  

• Xanthium  
• Soybean  
• Wheat  
• Tobacco  

Solution

LDPs (i.e. long-day plants) require long days of summer which provide the plants perfect photoperiods to permit flowering.  

Q27. 'Foolish seedling' disease of rice led to the discovery of   

• ABA  
• 2-4 D  
• IAA  
• GA  

Solution

Gibberellins (GA) were first isolated from the fungus Gibberella fujikuroi, the causal organism of foolish seedling disease of rice plants, by Kurasawa in Japan in 1926.

Q28. Which amino acid is responsible for indole acetic acid formation?  

• Tryptophan  
• Tyrosine  
• Phenylalanine  
• None of the above  

Solution

IAA is synthesised in shoot apices, leaf primordia and developing seeds from the amino acid tryptophan.  

Q29. Seeds of some plants are unable to germinate even when conditions are favourable. This is called

• Dormancy
• Quiescence
• Vivipary
• Non-viability

Solution

Seed dormancy is the innate inhibition of germination of a viable seed placed in the most favourable environment for germination.

Q30. If a plant contains more nitrogenous compounds, then it produces

• More cytoplasm
• Less cytoplasm
• Vigorous vegetative growth
• Both A and C

Solution

If a plant contains more nitrogenous compounds, then it produces more cytoplasm, less mechanical tissues and vigorous vegetative growth.

Q31. A mass of undifferentiated cells is called

• Meristem
• Callus
• Culture
• Both C and D

Solution

The dividing cells form a mass of undifferentiated cells called callus.

Q32. Differentiation of the shoot is controlled by  

• High gibberellin-cytokinin ratio  
• High auxin-cytokinin ratio  
• High cytokinin-auxin ratio  
• High gibberellin-auxin ratio  

Solution

The ratio of cytokinins to auxins controls differentiation. If both of these are present in equal quantities, the cells divide but fail to differentiate. If there is more cytokinin than auxin, shoot buds develop. If there is more auxin than cytokinin, roots develop.  

Q33. Ripening of fruit is controlled by

• Ethylene
• Gibberellin
• Auxin
• Cytokinin

Solution

The ripening of fruits is controlled by ethylene. Ethylene is produced in plants from the amino acid methionine.

Q34. Vernalisation is done at  

• Lower temperature  
• Low light intensity  
• Higher temperature  
• High light intensity  

Solution

Vernalisation is the promotion of flowering in plants at a low temperature. Plants grow vegetatively during the warm season, receive low temperature treatment during the winter and grow further to bear flowers and fruits in the warm season.  

Q35. The maximum growth rate occurs in

• Stationary phase
• Senescent stage
• Lag phase
• Exponential phase

Solution

The maximum growth rate occurs in the exponential phase because each cell divides to form two cells. This phase has the greatest rate of increase in population size. The rate is influenced by environmental conditions such as temperature, aeration and composition of medium. 

Q36. Coconut milk (coconut water) is widely used in tissue culture because it contains  

• Auxins  
• Ethylene  
• Cytokinin  
• Gibberellins  

Solution

Skoog observed that coconut milk contained a substance which stimulated cell division. The substance was later on called cytokinin.   

Q37. What are the important aspects of growth?

• Maturation and cell division
• Cell division and differentiation
• Cell division and plasmatic growth
• Maturation and differentiation

Solution

Cell division and differentiation are important aspects of growth, because cell division is an important phase which determines the birth of a cell and differentiation is required to become a permanent cell as morphological change occurs in a meristematic daughter cell.

Q38. Phytohormones are

• Chemicals regulating flowering
• Chemicals regulating secondary growth
• Hormones regulating growth from seed to adulthood
• Regulators synthesised by plants and influencing physiological processes

Solution

Phytohormones are plant hormones, i.e. organic substances which are naturally produced in plants and control the growth or other physiological functions at a site away from their place of synthesis and are active in extremely minute quantities.

Q39. What will be the effect on phytochrome in a plant subjected to continuous red light?

• Level of phytochrome decreases
• Phytochrome is destroyed
• Phytochrome synthesis increases
• Destruction and synthesis of phytochrome remain in equilibrium

Solution

Continuous exposure to red light causes conversion of Pr to Pfr which is rapidly destroyed and the inhibition of synthesis of Pr. Thus, the total amount of phytochrome is decreased.

Q40. The increase of growth per unit time is defined as

• Growth rate
• Geometric growth
• Absolute growth rate
• Exponential growth

Take Another Test