Question 1

Which of the following statements best explains why plants cannot use atmospheric nitrogen ($N_2$) directly for their nutritional needs?

Accepted Answer

Plants lack the enzymes required to break the triple bond in $N_2$ molecules.

Question 2

A farmer notices yellowing of older leaves in his crop. Soil tests reveal low magnesium levels. Which process is most directly affected, leading to this symptom?

Accepted Answer

Chlorophyll production in the leaves

Question 3

Which of the following best describes the role of water in plant nutrition?

Accepted Answer

Water provides most of the hydrogen atoms incorporated into organic molecules.

Question 4

A plant growing in soil with low iron content develops chlorosis. Which of the following best explains this phenomenon?

Accepted Answer

Iron is required as a cofactor in chlorophyll synthesis.

Question 5

Which equation best represents the overall process of photosynthesis in plants?

Accepted Answer

$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$

Question 6

Which of the following is a micronutrient required by plants and functions as a cofactor in enzymatic reactions?

Accepted Answer

Iron

Question 7

Why do symptoms of a mobile nutrient deficiency, such as magnesium, appear first in older leaves?

Accepted Answer

Mobile nutrients are transported from older to younger tissues when in short supply.

Question 8

Which soil type is considered most fertile due to its balanced texture and composition?

Accepted Answer

Loam

Question 9

A botanist observes a plant growing on the branch of a tree, absorbing water and minerals from rain but not harming the host. What type of plant is this?

Accepted Answer

Epiphyte

Question 10

Which of the following best describes the mutualistic relationship between legumes and nitrogen-fixing bacteria?

Accepted Answer

Bacteria provide fixed nitrogen; plant supplies carbohydrates.

Question 11

Which process is responsible for the majority of water loss in plants?

Accepted Answer

Transpiration

Question 12

Which of the following elements is NOT a macronutrient for plants?

Accepted Answer

Zinc

Question 13

A plant growing in an acid bog supplements its nutrition by digesting insects. What is the primary reason for this adaptation?

Accepted Answer

To acquire nitrogen and minerals not available in the soil

Question 14

Which of the following best explains why crop rotation with legumes improves soil fertility?

Accepted Answer

Legumes fix atmospheric nitrogen, increasing soil nitrogen content.

Question 15

Which of the following is a function of mycorrhizae in plant roots?

Accepted Answer

Increase absorption of water and minerals from the soil

Question 16

If a plant is deficient in phosphorus, which of the following cellular processes would be most directly affected?

Accepted Answer

ATP synthesis

Question 17

Which of the following best describes the origin of most of the dry weight of a plant?

Accepted Answer

Assimilation of $CO_2$ from the atmosphere

Question 18

A plant is showing symptoms of stunted growth and poor root development. Soil analysis reveals a deficiency in potassium. Which function is most likely impaired?

Accepted Answer

Activation of enzymes and maintenance of osmotic balance

Question 19

Which of the following is a plausible consequence of excessive application of micronutrient fertilizers to crops?

Accepted Answer

Toxicity symptoms and possible plant death

Question 20

Which of the following best explains why the composition of minerals in a plant reflects the soil in which it grows?

Accepted Answer

Plants selectively absorb essential elements, but some non-essential elements are also taken up if present.

Plant Nutrition: Essential Elements and Uptake Mechanisms

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