Answer:
a) i) Xylem
ii) Upper epidermis
iii) Stoma
iv) Chroloplast
v) Palisade cell layer
b) By a waxy layer on the cuticle of the leaf
Step-by-step explanation:
The plant's leaves have a large surface area that is capable of absorbing sunlight. The plant's waxy layer in the surface of the leaf protects it from the loss of water, as well as of diseases caused by the entry of microorganisms. The palisade cell's surface is a single layer of cells underneath the upper epidermis that is adapted to absorb light energy.
The waxy layer is a primary physical barrier composed of insoluble polymers and lipids whose function is to protect the leaves against the entry of harmful organisms including virus, bacteria and fungus. Moreover, the plant's waxy cuticle is also a barrier that prevents the loss of water and solutes.