Answer: Small, xerophytic type leaves.
Xerophytes are plants specially built to survive in places where water is scarce. Common features include small leaves, thick waxy coatings, and sometimes thorns instead of broad leaf blades, all of which reduce water loss.
In contrast, trees in wetter regions of India tend to have large, broad leaves since water is not a limiting factor there. Rajasthan's dry climate forces its native trees to rely on these smaller, tougher leaves to survive long dry spells.