Question 1

Which soil layer is primarily responsible for the accumulation of minerals leached from above, and what is its main function in plant nutrition?

Accepted Answer

Subsoil; it stores minerals leached from the topsoil and provides a reservoir of nutrients for plant roots.

Question 2

According to the diagram of soil charge and ion transport, why do plants require active transport to acquire potassium ($$K^+) $$from the soil?

Accepted Answer

Because $$K^+$$ ions are attracted to the negative charge of soil particles and must be actively transported into root cells against a concentration gradient.

Question 3

Liebig’s Law of the Minimum states that plant yield is limited by:

Accepted Answer

The nutrient that is present in the smallest (most limiting) amount relative to plant needs.

Question 4

Which of the following is a micronutrient essential for plants, and what is its primary role?

Accepted Answer

Iron; involved in redox reactions and electron transport.

Question 5

A plant grown hydroponically in a solution lacking magnesium ($$Mg^{2+}) $$develops interveinal chlorosis in older leaves. This is because:

Accepted Answer

Magnesium is a mobile nutrient, so deficiency symptoms appear in older leaves first.

Question 6

Which equation best represents the process of nitrogen fixation by Rhizobium bacteria in legume root nodules?

Accepted Answer

$$N_2 + 8H^+ + 8e^- + 16$$ATP \rightarrow 2NH_3 + $$H_2 + 16$$ADP + 16P_i$$

Question 7

Why is leghaemoglobin important in root nodules of legumes?

Accepted Answer

It binds oxygen, maintaining a low oxygen concentration to protect nitrogenase activity.

Question 8

Which of the following best describes the role of mycorrhizal fungi in plant mineral nutrition?

Accepted Answer

They increase the surface area for nutrient uptake, especially phosphorus.

Question 9

A plant growing in acidic, nitrogen-poor soil is most likely to have which adaptation?

Accepted Answer

Development of carnivorous leaves to trap and digest insects.

Question 10

Which of the following symptoms would you expect in a plant with potassium ($$K^+) $$deficiency?

Accepted Answer

Yellowing and necrosis at the leaf margins, especially in older leaves.

Question 11

A hydroponic experiment shows that removing calcium ($$Ca^{2+}) $$from the nutrient solution causes new leaves to become distorted and necrotic. This is because:

Accepted Answer

Calcium is immobile, so deficiency symptoms appear in new growth.

Question 12

Which of the following best explains why plants cannot use atmospheric $$N_2$$ directly for amino acid synthesis?

Accepted Answer

Plants lack the enzymes to break the triple bond in $$N_2$$ and must rely on ammonia ($$NH_3) or $$nitrate ($$NO_3$$^-$$) forms.

Question 13

Which of the following is a real-world example of a plant using a special nutritional strategy to obtain nitrogen?

Accepted Answer

A Venus flytrap capturing and digesting insects to supplement nitrogen intake.

Question 14

A plant with interveinal chlorosis (yellowing between veins) in older leaves is most likely deficient in which nutrient, and why?

Accepted Answer

Magnesium, because it is a mobile nutrient and a component of chlorophyll.

Question 15

Which of the following best describes the function of phosphorus ($$P) in $$plants?

Accepted Answer

It is important for energy storage and transfer as part of ATP.

Question 16

Which process is used to experimentally determine if a mineral element is essential for plant growth?

Accepted Answer

Growing plants hydroponically in a complete solution, then transferring them to a solution lacking the suspected nutrient and observing for abnormal growth.

Question 17

Which of the following is NOT a function of mycorrhizal associations in plants?

Accepted Answer

Fixing atmospheric nitrogen.

Question 18

A parasitic plant that lacks chlorophyll and taps into the vascular tissue of a host plant is best described as:

Accepted Answer

A non-photosynthetic parasite, such as Indian pipe, that obtains nutrients from its host.

Question 19

Which of the following best explains why adding more nitrogen fertilizer to a field already sufficient in nitrogen does not increase crop yield, according to Liebig’s Law of the Minimum?

Accepted Answer

Yield is limited by the nutrient in shortest supply relative to need, so adding more of a non-limiting nutrient has no effect.

Soil and Plant Mineral Nutrition: Essential Elements and Special Nutritional Strategies

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