Stomata Function and Water Loss
Terrestrial plants use stomata, small pores primarily on the leaf surface, for essential gas exchange, allowing carbon dioxide (CO2) intake for photosynthesis and oxygen (O2) release. However, stomata are also the main sites of water loss through transpiration.
Adaptation to High Aridity
Having a reduced number of stomata on the leaf surface is a key adaptation for plants living in environments with high aridity (dry conditions). In such conditions, water is scarce, and excessive water loss through transpiration can be detrimental to the plant's survival.
- Fewer stomata mean less surface area available for water vapor to escape the leaf.
- This conserves the plant's limited water resources, crucial for maintaining turgor pressure and metabolic functions.
- Therefore, limiting stomatal density is an effective strategy to minimize transpiration and survive drought or arid climates.
Evaluating Other Options
- High pH: Soil pH affects nutrient availability but doesn't directly relate to the number of stomata for water conservation.
- Low UV radiation: While plants have mechanisms to cope with UV radiation, a low number of stomata is not primarily an adaptation to low UV levels. High UV might even influence stomatal density or behavior, but low UV doesn't necessitate fewer stomata for survival.
- Low soil nitrogen: Nitrogen is vital for plant growth, including the production of photosynthetic machinery and potentially stomata. Low nitrogen might affect overall growth, but fewer stomata are specifically linked to water conservation needs in arid conditions rather than nutrient deficiency.
The adaptation of having few stomata is most directly linked to minimizing water loss in dry environments.
Important Questions from Abiotic factors
The table below lists potential environmental conditions in future climates, related to atmospheric carbon dioxide concentrations ($CO_2$) and mean annual temperature (MAT).
The table also lists potential outcomes with respect to whether conditions will favour grasses with C3 or C4 photosynthetic pathways.
Assuming no other changes in environmental conditions, match the options in the two columns.Environmental conditions Outcomes (P) Increased $CO_2$, no change in MAT (i) C3 performs better than C4 (Q) No change in $CO_2$, increased MAT (ii) C4 performs better than C3 (iii) C3 and C4 perform equally - Mean global temperature since pre-industrial times has increased approximately by
- Some air-breathing marine vertebrates such as whales, seals and marine turtles possess adaptations for long, deep dives. Which one or more of the following is/are examples of such adaptations?
- Which one or more of the following is/are greenhouse gas(es)?
- You are a plant ecologist studying a plant in the genus Veronica. You notice that, at open rocky sites, Veronica grows as a creeper spreading low to the ground, whereas in grasslands, the stem stands upright. You collect seeds from multiple populations in each habitat type and grow them under uniform conditions in a greenhouse. You find that all the plants grown in the greenhouse have stems that stand upright. Which one or more of the following explanations best support(s) your observations?
