Question 1

Which of the following best explains why plants require nitrogen from the soil?

Accepted Answer

Nitrogen is required for the synthesis of amino acids, nucleic acids, and chlorophyll, which are vital for plant growth and metabolism.

Question 2

A farmer notices that his crops have yellowing leaves with stunted growth. Soil tests reveal a deficiency in a macronutrient. Which element is most likely deficient, and what is its primary function?

Accepted Answer

Nitrogen; it is essential for the synthesis of proteins, nucleic acids, and chlorophyll.

Question 3

Which process allows plants to absorb mineral cations from the soil, and how does soil pH affect this process?

Accepted Answer

Cation exchange; lower pH increases H+ ions, which displace mineral cations from clay particles, making them more available to roots.

Question 4

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

Accepted Answer

They increase the surface area for water and mineral absorption, and secrete growth factors that stimulate root growth.

Question 5

A plant growing in alkaline soil (pH 8) is showing signs of iron deficiency. Which of the following best explains this observation?

Accepted Answer

At high pH, iron becomes less available to plants, even though calcium may be more available.

Question 6

Which of the following is a consequence of excessive use of commercial fertilizers on farmland?

Accepted Answer

Leaching of excess minerals into water bodies, causing algal blooms.

Question 7

Which of the following equations represents the conversion of atmospheric nitrogen to ammonia by nitrogen-fixing bacteria?

Accepted Answer

$\mathrm{N_2 + 8H^+ + 8e^- \rightarrow 2NH_3 + H_2}$

Question 8

Which of the following best describes the function of root nodules in leguminous plants?

Accepted Answer

They house nitrogen-fixing bacteria that convert atmospheric nitrogen into forms usable by the plant.

Question 9

A plant is found to be potassium-deficient. Which physiological process is most likely to be directly affected?

Accepted Answer

Regulation of stomatal opening and closing

Question 10

Which of the following statements about the nitrogen cycle is correct?

Accepted Answer

Soil bacteria convert atmospheric nitrogen into ammonium ($\mathrm{NH_4^+}$) and nitrate ($\mathrm{NO_3^-}$), which plants can absorb.

Question 11

Which of the following is a distinguishing feature of arbuscular mycorrhizae compared to ectomycorrhizae?

Accepted Answer

Arbuscular mycorrhizae penetrate the cell walls of root cortical cells, forming arbuscules inside the cells.

Question 12

Which of the following best explains why loam soils are considered the most fertile for plant growth?

Accepted Answer

They have a balanced mixture of sand, silt, and clay, providing optimal texture and nutrient availability.

Question 13

A plant growing in soil with low magnesium content is likely to show which of the following symptoms?

Accepted Answer

Chlorosis (yellowing) of older leaves due to magnesium's role in chlorophyll.

Question 14

Which of the following best describes the ecological role of carnivorous plants?

Accepted Answer

They supplement their nutrient intake by digesting insects, especially in nutrient-poor soils.

Question 15

Which of the following is a micronutrient essential for the synthesis of chlorophyll and is required in the smallest amounts by plants?

Accepted Answer

Molybdenum ($\mathrm{MoO_4^{2-}}$)

Question 16

Which of the following best explains why soil mismanagement can lead to reduced agricultural productivity?

Accepted Answer

Soil mismanagement can deplete essential nutrients, disrupt soil structure, and reduce microbial activity, all of which are critical for plant growth.

Question 17

A plant is growing in soil with a high concentration of sodium ions ($\mathrm{Na^+}$). Which of the following is a likely consequence for the plant?

Accepted Answer

Reduced uptake of potassium ions ($\mathrm{K^+}$) due to competition at the root surface.

Question 18

Which of the following best describes the function of rhizobacteria in the rhizosphere?

Accepted Answer

They enhance nutrient availability by exchanging chemicals with plant roots and decomposing organic matter.

Question 19

Which of the following is a real-world consequence of improper fertilizer application in agriculture?

Accepted Answer

Eutrophication of lakes and rivers due to nutrient runoff, leading to algal blooms and oxygen depletion.

Plant Roots and Nutrient Acquisition: Soil, Essential Elements, and Symbiotic Relationships

Study Guide - Practice Questions

Study Guide - Flashcards