1. plants need to cool down when temperature is high.
transpiration ( which is a form of evaporation) cools the plants down.
2.Transpiration facilitates the ascent of sap as the water transpired produces a suction pull in the leaves which leads to the ascent of water through Xylem from roots to the leaves.
NOTE : If it is a 2 mark question WRITE BOTH POINTS.
If it is a 1 mark question WRITE SECOND POINT ONLY.
hope this helps you :)