Question

How does soil salinity affect plant growth?

• A. Promotes optimal growth
• B. Inhibits germination and growth
• C. Has no impact on plants
• D. Increases resistance to diseases

Hint:

• High soil salinity creates a stressful environment for most plants (except halophytes).
• Osmotic effect: Reduces water uptake by roots, causing water stress.
• Specific ion toxicity: Certain ions (e.g., Na$^+$, Cl$^-$) can be directly harmful to plant cells.
• Nutrient imbalance: Interferes with the uptake of essential nutrients.
• Collectively, these lead to poor seed germination, stunted growth, reduced yields, and even plant death.

Answer 1

The Correct Option is B

Soil salinity refers to the presence of excessive amounts of soluble salts in the soil water. High soil salinity can severely affect plant growth through several mechanisms: Option (A) Osmotic Stress (Water Stress): High salt concentration in the soil solution lowers the water potential of the soil. This makes it more difficult for plants to absorb water through their roots, even if the soil is physically moist. Plants experience physiological drought conditions. This can lead to reduced turgor, wilting, and stunted growth. Option (B) Ion Toxicity: Specific ions present in high concentrations (e.g., Na$^+$, Cl$^-$, SO$_4^{2-}$, sometimes Boron) can be directly toxic to plant cells. They can interfere with metabolic processes, enzyme activity, and damage cell membranes. Option (C) Nutrient Imbalance: High concentrations of certain ions (like Na$^+$) can interfere with the uptake and transport of essential nutrients (like K$^+$, Ca$^{2+}$) by competing for uptake sites or altering membrane permeability. This leads to nutrient deficiencies. These effects collectively lead to:

• Inhibition of Germination: High salinity can prevent seeds from imbibing enough water to germinate or can be toxic to emerging seedlings.
• Reduced Growth: Stunted root and shoot growth, reduced leaf area, and lower biomass production are common.
• Physiological Damage: Leaf burn, necrosis (tissue death), and premature leaf senescence can occur.
• Reduced Yield: For crop plants, salinity significantly reduces crop yields.

Option (a) is incorrect; salinity is generally detrimental. Option (c) is incorrect; it has significant impacts. Option (d) is incorrect; salinity stress often makes plants more susceptible to diseases, not more resistant. Therefore, soil salinity inhibits germination and growth. \[ \boxed{\text{Inhibits germination and growth}} \]