Answer:
a) The phloem is accountable for conducting food from the leaves to the rest parts of the plant, thus, in the absence of phloem, the plant will die.
b) Xylem tissue plays an essential role in the transportation of minerals and water from the roots to the leaves of the plant. It is this water, which is utilized in the process of photosynthesis and also plays a role in the process of transpirational pull. In case, due to the destruction of xylem tissues wilting of plants takes place as it loses turgidity and dies as water is not able to reach the leaves for the process of photosynthesis.