The Question is from neet-botany photosynthesis-in-higher-plants , and it was created by the author Mr. NARESH KUMAR K

Question

How does water stress primarily affect the rate of photosynthesis?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Photosynthesis and its dependence on water
 **Related Topics**: Stomata, transpiration, CO2 uptake, water potential
 **Prerequisites**: Basic understanding of photosynthesis (light-dependent and light-independent reactions), stomatal function.
## SOLUTION PATHWAY
**Given Information**:
  The question asks about the primary effect of water stress on the rate of photosynthesis.
  Water stress implies a lack of sufficient water in the plant.
**Method & Steps**:
 1. Consider the role of stomata in photosynthesis.
  Reasoning: Stomata are tiny pores on the leaf surface that regulate gas exchange (CO2 uptake and O2 release).  They also play a crucial role in transpiration (water loss).
  Formula/Rule:  No specific formula is needed here, it's a conceptual understanding.
 2. Analyze how water stress affects stomatal opening.
  Working: When a plant experiences water stress, it closes its stomata to reduce water loss through transpiration. This is a protective mechanism to prevent wilting and desiccation.
  Key Point:  The closure of stomata is a primary response to water stress.
 3. Determine the impact of reduced stomatal opening on photosynthesis.
  Result: Reduced stomatal opening directly limits the uptake of CO2, a crucial reactant in the Calvin cycle (light-independent reactions) of photosynthesis.  This significantly reduces the rate of photosynthesis.
  Verification: This is a well-established fact in plant physiology.  Water stress is a major limiting factor for plant growth and yield because it directly impacts photosynthesis via stomatal closure.
 ## OPTION ANALYSIS
A :x: While water stress can indirectly impact chlorophyll production over time (due to reduced growth and overall plant health), it's not the primary immediate effect on photosynthesis rate.
B :x: Water stress can influence photorespiration (a competing process that reduces efficiency of photosynthesis), but stomatal closure is a more direct and immediate effect.
C ✓: This option correctly identifies the primary effect of water stress: reduced stomatal opening leading to limited CO2 uptake and thereby reduced photosynthesis.
D :x: Water stress can indirectly affect enzyme activity, but the primary impact is through stomatal closure, not direct enzyme denaturation.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the effects of water stress with other limiting factors (e.g., light intensity, nutrient availability): Water stress has a specific mechanism (stomatal closure).
  2.Overlooking the crucial role of stomata in gas exchange and water regulation: Understanding stomatal function is key to understanding water stress's impact.
 **Quick Tips**:
  1.Remember that stomata are the gatekeepers for CO2 entry during photosynthesis.
  2.Water stress = stomata closure = less CO2 = less photosynthesis.

Mr. NARESH KUMAR K · Answer

By directly inhibiting chlorophyll production

Mr. NARESH KUMAR K · Answer

By increasing the rate of photorespiration

Mr. NARESH KUMAR K · Answer

The correct Option is "By reducing stomatal opening, limiting CO2 uptake"

Mr. NARESH KUMAR K · Answer

By denaturing the enzymes involved in the Calvin cycle

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