The transpiration in plants will be lowest :–When there is high humidity in the atmosphereThere is excess of water in the cellEnvironmental conditions are very dryHigh wind velocity

The transpiration in plants will be lowest when there is high humidity in the atmosphere.

Here's why:

1. Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere.

2. When the atmosphere is highly humid, it is already saturated with water vapor, and this reduces the concentration gradient for water between the leaf and the atmosphere. This means that water will be less likely to evaporate from the leaves, reducing the rate of transpiration.

3. In contrast, when environmental conditions are very dry, the concentration gradient for water between the leaf and the atmosphere is high, meaning water will be more likely to evaporate from the leaves, increasing the rate of transpiration.

4. Similarly, while having excess water in the cell can increase the rate of transpiration, it does not affect the atmospheric conditions that ultimately determine the rate of transpiration.

5. High wind velocity can also increase the rate of transpiration by removing the layer of humid air that forms around the leaf, maintaining a high concentration gradient for water between the leaf and the atmosphere.

So, the transpiration in plants will be lowest when there is high humidity in the atmosphere.