Free Plant Nutrition and Transport MCQs with Answers

31. The following leaves have salt glands on the upper surface.

• A. Lakes
• B. Ponds
• C. Oceans
• D. Deserts

Explanation: As an adaptation to the environment, plants in oceans have salt glands to excrete excess salt from their body. So option C is correct. Plants in lake, ponds and desert do not have salt glands. So A,B and D are incorrect.

32. In the cross section of trunks of large trees, a central dark region called heartwood is observed.It is significant to plants because it

• A. Forms the bark
• B. Helps in translocation
• C. Involves in ascent of sap
• D. Is resistant to insect and fungal attacks

Explanation: Heartwood is the central, dark region in the cross section of a tree trunk. It is primarily dead tissue that no longer conducts water but provides structural support. Its resistance to insect and fungal attacks is due to the accumulation of chemical compounds such as tannins. In contrast, the other options describe functions of the sapwood or outer layers of the tree: bark formation is related to the outer cambium layers, translocation occurs in the phloem, and the ascent of sap involves active xylem.

33. The products formed during light dependent reactions are:

• A. ATP, NADH2, O2
• B. ATP, NADPH, O2
• C. ATP, NADPH, CO2
• D. PGA, NADH, O2

Explanation: The products of light-dependent reactions in photosynthesis are ATP and NADPH and Oxygen. These high-energy molecules are generated through the absorption of light energy by chlorophyll and other pigments in the thylakoid membranes of chloroplasts.

34. Secondary xylem is produced by the activity of :

• A. Apical meristem
• B. cork cambium
• C. Vascular cambium
• D. intercalary meristem

Explanation: Secondary xylem, also known as wood, is a tissue produced by the vascular cambium during secondary growth. It is made up of tracheids, vessel elements, fibers, and parenchyma cells. These cells provide mechanical support to the plant and conduct water and minerals from the roots to the leaves.

35. Guard cells function as:

• A. The defense system
• B. Multisensory hydraulic valve
• C. Hydrostatic pressure
• D. All of these

Explanation: Guard cells are specialized cells found in the epidermis of leaves that surround and regulate the opening and closing of stomata, which are tiny pores used for gas exchange and act as multisensory hydraulic valves.

36. Which of the following nutrient is incorrectly paired with its function in plant?

• A. Iron-cytochromes and chlorophyll
• B. Molybdenum cell permeability
• C. Cobalt- Required by nitrogen fixers
• D. Calcium- formation of cell wall.

Explanation: Molybdenum is an essential component in two enzymes that convert nitrate into nitrite (a toxic form of nitrogen) and then into ammonia before it is used to synthesize amino acids within the plant. It is also needed by symbiotic nitrogen fixing bacteria in legumes to fix atmospheric nitrogen. So it cannot be used in cell permeability thus option b is incorrect.

37. Yellowing and brown end of leaf is because of deficiency of:

• A. Sodium
• B. Nitrogen
• C. Potassium
• D. Iron

Explanation: The correct answer is Potassium. Potassium is crucial for numerous plant processes, including water regulation and enzyme activation. A potassium deficiency often results in yellowing and browning of leaf margins and tips, a symptom not typically associated with other nutrient deficiencies. While nitrogen deficiency does cause yellowing, it affects older leaves more uniformly rather than just the edges. Sodium is not an essential nutrient for most plants, and iron deficiency results in yellowing between the veins but not browning at the leaf edges.

38. Which one of the following plants has modified bilobed leaves with a midrib between them, having long, stiff bristles along the margins of each lobe?

• A. Dionaea muscipula
• B. Drosera excelsa
• C. Drosera intermedia
• D. Nepenthes purpurea

Explanation: Dionaea muscipula, commonly known as the Venus flytrap, has highly specialised leaves that act as snap traps to capture and digest insects. Each leaf is divided into two lobes that hinge together and are lined with hair-like structures called trigger hairs. When an insect touches these trigger hairs, the lobes snap shut, trapping the prey inside. Digestive enzymes are then secreted to break down the insect and absorb nutrients, which help the plant survive in nutrient-poor soils. This adaptation allows the Venus flytrap to obtain nitrogen and other essential nutrients from its prey, supporting its growth in otherwise challenging environments.

39. The attraction between water molecules and cell wall of xylem is termed as :

• A. Adhesion
• B. Cohesion
• C. Capillary action
• D. Transpiration

Explanation: This is the correct answer. Adhesion refers to the attraction between molecules of different substances. In the case of xylem, the water molecules are attracted to the cellulose molecules in the cell walls. This adhesive force helps to pull water up the xylem vessels from the roots to the leaves.

40. Dark reaction of photosynthesis takes place:

• A. Grana
• B. Stroma
• C. Thylakoid
• D. Both grana and stroma

Explanation: Dark reactions (light-independent reactions) of photosynthesis take place in the stroma of chloroplasts.