Free Forms and Functions of Plants MCQs with Answers

41. Which of the following process causes substances to move across membranes without the expenditure of cellular energy?

• A. Endocytosis
• B. Diffusion
• C. Active transport
• D. None of the above

Explanation: The correct answer is Diffusion. Diffusion is characterized by the passive movement of molecules from an area of higher concentration to an area of lower concentration, which occurs naturally and does not require energy input from the cell. In contrast, Endocytosis and Active Transport both require energy because they involve active movement of substances against their concentration gradients. Therefore, the only process listed that matches the criteria of not using cellular energy is diffusion.

42. The movement of water molecules from a region of higher water potential to a region of lower water potential through a semi-permeable membrane is referred to:

• A. Active transport
• B. Osmosis
• C. Diffusion
• D. Photosynthesis

Explanation: Osmosis, the correct answer, refers to the movement of water molecules from an area of higher water potential to an area of lower water potential through a semipermeable membrane. This process occurs naturally and does not require energy. Option A, Active transport, is incorrect because it involves energy use to move substances against their gradient. Option C, Diffusion, does not specifically pertain to water and does not require a semipermeable membrane. Option D, Photosynthesis, is unrelated to the transport of water molecules.

43. Four plants are present in different environmental conditions. Plant A is present in a warm climate with continuous rainfall, plant B is present in a cool forest, plant C is present in a warm climate with little breeze, while plant D is present in a warm climate with high wind speed. Which one of the above plants will have the highest rate of transpiration?

• A. Plant B
• B. Plant D
• C. Plant A
• D. Plant C

Explanation: When it comes to questions like these, do not confuse the option letter with the letter of the plant itself. The factors which affect the rate of transpiration are: temperature, as at a higher temperature, more water vapour is given up by the leaves of the plant; humidity, as more humid conditions decrease the concentration gradient of water vapour between the air spaces of the leaves and the atmosphere so, the rate of transpiration decreases; wind speed, as a greater wind speed moves away more of the water vapour collected around the leaves and stomata, thereby increasing the concentration gradient between the air spaces of the leaves and the atmosphere.Plant A has a warm atmosphere but has continuous rainfall. Rainfall would imply a humid atmosphere so, the rate of transpiration is not very high.Plant B has a cool atmosphere so, the rate is low.Plant C is present in a warm climate but the breeze is slow so, when wind speed is low, more water vapour accumulates around the leaves of the plant thereby reducing the concentration gradient between the air spaces and the atmosphere. Hence, the rate of transpiration is not very high.Plant D is present in a warm climate in addition to having a high wind speed so, both factors contribute to a high rate of transpiration. Hence, the option which mentions plant D is the correct answer, which is option B.

44. Widely accepted theory that explains transport of organic solutes in plants is supported by:

• A. Pressure flow theory
• B. Diffusion
• C. Imbition
• D. Ascent of sap

Explanation: The widely accepted theory that explains the transport of organic solutes in plants is the Pressure Flow Theory, also known as the Mass Flow Hypothesis. This theory describes how sugars (mainly sucrose) are transported from source tissues (where they are produced, usually leaves) to sink tissues (where they are utilized or stored, such as roots, fruits, or storage organs) through the phloem.

45. Which organ of a plant has functions of anchoring, storage of food, absorbing water, and minerals:

• A. Shoot
• B. Leaves
• C. Flowers
• D. Root

Explanation: The root anchors the plant in the soil, absorbs water and minerals, and also stores food in some plants like carrots and radishes.

46. The hormone(s) synthesised in the meristematic tissue of the plant shoot and root is/ areI. Abscisic acidII. AuxinIII. Cytokinin

• A. I only
• B. II only
• C. I and II
• D. II and III

Explanation: The correct answer is D. II and III. Both auxin and cytokinin are hormones synthesized in meristematic tissues of plants. Auxin is primarily responsible for cell elongation and is synthesized at the tips of shoots and roots. Cytokinin promotes cell division and differentiation and is also synthesized in these meristematic areas. Abscisic acid, on the other hand, is mainly involved in stress responses and is not typically synthesized in meristematic tissues, making options A, B, and C incorrect.

47. The given diagram shows a stem tendril helping a plant to climb up a support.The type of growth movement exhibited by the plant is

• A. Epinasty
• B. Nutation
• C. Hyponasty
• D. Nyctinasty

Explanation: Nutation is a type of growth movement where a plant part, such as a stem or tendril, exhibits revolving or spiraling motion. The tip of a climbing plant's stem or tendril may sway back and forth (nutation) as it searches for a support. So option B is correct. All other processes are not related to the climbing movement shown.

48. Auxins and gibberellins are plant hormones. The common role of these hormones is to

• A. Delay both bud initiation and leaf senescence
• B. Promote both bud initiation and leaf senescence
• C. Promote bud initiation and delay leaf senescence
• D. Promote leaf senescence and delay bud initiation

Explanation: The correct answer is that auxins and gibberellins promote bud initiation and delay leaf senescence. These plant hormones are involved in various growth processes, including the stimulation of bud growth. They help maintain the plant's vitality by delaying the aging of leaves, which is a process known as leaf senescence. The incorrect options either misstate the effects of these hormones on buds and leaves or reverse their roles entirely.

49. The given diagrams, I and II, show the growth of a plant without and with hormone treatment. Based on the shown effect in diagram II, the hormones used in the mixture must be

• A. Ethene and Auxin
• B. Auxin and Gibberellin
• C. Abscisic acid and Ethene
• D. Gibberellin and Abscisic acid

Explanation: The correct answer is Option B: auxin and gibberellin. These two hormones are known to promote plant growth by stimulating cell elongation and division. In the context of the diagrams, this combination would result in enhanced growth as shown in diagram II. Other options are incorrect because they include hormones like abscisic acid, which inhibits growth, or ethene, which primarily affects fruit ripening and leaf abscission rather than growth promotion.

50. Consider the given diagram. The phenomenon which induces the growth of plant I is

• A. Vernalization
• B. Seed dormancy
• C. Photoperiodism
• D. Seed germination

Explanation: The correct answer is Vernalization . Vernalization is a process in which the prolonged exposure to cold temperatures triggers the flowering of plants. This is essential for certain plants to transition from vegetative growth to flowering. The other options are related to plant growth but do not specifically describe the cold-induced flowering process:Seed dormancy refers to a period when seeds are inactive and not germinating, which is unrelated to the specific growth induction described.Photoperiodism involves the plant's response to the duration of light and dark periods, primarily affecting flowering time rather than the initial growth process.Seed germination is the process of a seed starting to grow, which is a different stage of development and not induced by cold exposure as vernalization is.