Question

Question 27 (1 point) Photorespiration is favoured over photosynthesis when Conditions are cool and humid and stomata are open. Conditions are hot and dry and stomata are open. Conditions are hot and dry and stomata are closed. Conditions are cool and humid and stomata are closed.

Answer 1

Answer: option 3.

Photorespiration is favoured over photosynthesis when conditions are hot and dry and stomata are closed.

Photosynthesis is the process by which green plants and other organisms use sunlight to synthesize food for themselves using CO2 and water. It is a main process by which green plants fix carbon or energy.

Photo respiration is a reverse process by which plants take in oxygen in the presence of light and give out CO2. Therefore, this process generally wastes some amount of carbon or energy already fixed in the plants.

Rubisco is the very important ki design involved in the process of photosynthesis which generally preferred to as its substrate but under certain conditions it may also accept oxygen as a substrate which is when photo respiration takes place instead of photosynthesis.

This overtake of photo respiration by photosynthesis depends on two factors mainly:

1. Relative concentration of CO2 and Oxygen

2. Temperature.

Firstly when the stomata is closed then the uptake of CO2 and exit of oxygen cannot takes place and therefore there is a buildup of oxygen inside the stomata. At this point of time oxygen is preferred by rubisco enzyme and photo respiration would be favoured over photosynthesis.

Secondly it is an important point to be noted that at higher temperatures, Rubisco enzyme has a higher binding affinity to oxygen than to CO2. Where are Saturn normal temperature it has a higher binding affinity (80% more) to CO2 than to oxygen. Their food during hot and dry climatic conditions photo respiration would be favoured over photo synthesis.

As a justification of the two points listed above, we can say that hot and dry conditions and when the stomata is closed, the plants would favour photo respiration over photosynthesis.