7th Class Science Transportation in Animals and Plants Transpiration

       Transpiration

Plant use only 5% - 10% of the water, which is absorbed by the plant roots. Rest of the water is evaporated in the atmosphere through stomata. Evaporation of water through stomata is called transpiration. Transpiration actually helps in reducing pressure in the upper part of xylem. Reduction of pressure in the upper xylem pulls water in upward direction. Thus transpiration helps in water transportation.

     Water is absorbed by the roots, which are in the lower part of the plant. This water needs to be transported to the leaves of the plant, which is in the upper part of the plant. For absorption of water from lower to the upper part a force is required. Plants perform a process to acquire this force and thus water reaches its upper side. Name the process.

(a) Translocation                                             

(b) Transpiration

(c) Photosynthesis                         

(d) Respiration

(e) None of these

Answer: (b)

     Sieve plates formed in the phloem tube because

(a) End walls of the phloem cells are not completely broken down and they have small holes

(b) Pits of phloem cells are not in contact             

(c) Ends of the phloem cells are tapered

(d) End walls of the phloem cells are open

(e) None of these

Answer: (a)