If a leaf branch of a healthy potted plant is covered a polythene bag tiny water droplets are seen .why does this happen ? which part of the leaf is responsible ? what are the other function?

When the leaf branch is covered with a polythene bag, tiny water droplets are seen because of transpiration. The leaves lose access amount of water present in the plant through this process. Stomata ( small pores present on the surface) of the leaves are responsible for this.

This happens because when we give extra water to plants, they throw it out in form of water in a process called Transpiration. For this function to happen, stomata ( tiny pores on the surface of leaf) is responsible. This also helps in formation of clouds as they are formed from water vapour. 

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