The Question is from neet-botany plant-physiology transpiration-and-photosynthesis-compromise, and it was created by the author Mr. NARESH KUMAR K

Question

Under conditions of high temperature and low humidity, which factor MOST directly exacerbates the transpiration and photosynthesis compromise?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Plant water relations and their impact on photosynthesis and transpiration.
 **Related Topics**: Stomatal regulation, vapor pressure deficit, water potential.
 **Prerequisites**: Understanding of transpiration, photosynthesis, and the role of stomata.
## SOLUTION PATHWAY
**Given Information**:
  High temperature and low humidity conditions.
  Compromise between transpiration and photosynthesis.
**Method & Steps**:
 1. Analyze the effect of high temperature and low humidity on plant processes.
  Reasoning: High temperature increases the rate of transpiration (water loss from leaves). Low humidity increases the vapor pressure deficit (VPD), which is the difference between the water vapor pressure in the air and the saturation vapor pressure at a given temperature.  A higher VPD further drives transpiration.
  Formula/Rule:  While no specific formula is directly applicable, understanding the relationship between VPD, temperature, and humidity is crucial.  Increased VPD = Increased transpiration rate.
 2. Consider how increased transpiration affects photosynthesis.
  Working: To cool themselves, plants close their stomata (pores on leaves) to reduce water loss during transpiration. However, this also limits CO2 uptake, which is essential for photosynthesis.  Therefore, a high transpiration rate leads to a compromise: more water loss but less CO2 uptake.
  Key Point: The compromise arises because the plant must balance the need for CO2 uptake for photosynthesis with the need to prevent excessive water loss through transpiration.
 3. Evaluate the given options.
  Result: Increased vapor pressure deficit (VPD) is the factor that most directly exacerbates this compromise because it directly drives the increase in transpiration rate, forcing the plant to close its stomata and reduce CO2 uptake.
  Verification: The other options are indirectly related or less significant under these specific conditions.  Reduced soil water potential contributes, but VPD is the immediate driving force for increased transpiration in the atmosphere.
 ## OPTION ANALYSIS
A :x: Decreased CO2 concentration is a consequence of stomatal closure to reduce transpiration, not the primary cause of the compromise.
B ✓: Increased vapor pressure deficit directly drives increased transpiration, forcing the compromise between water loss and CO2 uptake.
C :x: Reduced soil water potential can contribute to the problem but is less direct than VPD in this scenario.
D :x: Elevated atmospheric pressure has a negligible effect on transpiration and photosynthesis under these conditions.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing cause and effect:  Mistaking the reduced CO2 uptake as the primary cause instead of a consequence of increased transpiration.
  2.Overlooking VPD:  Failing to recognize VPD as the key driving force behind increased transpiration under low humidity conditions.
 **Quick Tips**:
  1.Remember the relationship between VPD, temperature, humidity, and transpiration rate.
  2.Understand that stomatal closure is a mechanism to regulate water loss, but it has a trade-off for photosynthesis.

Mr. NARESH KUMAR K · Answer

Decreased CO2 concentration

Mr. NARESH KUMAR K · Answer

The correct Option is "Increased vapor pressure deficit"

Mr. NARESH KUMAR K · Answer

Reduced soil water potential

Mr. NARESH KUMAR K · Answer

Elevated atmospheric pressure

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