Q. Which tree's heartwood is used for extracting catechu (kattha) in paan?
Answer: Senegalia catechu
Notes: Senegalia catechu, called Khair, yields catechu (kattha) from its heartwood. Catechu is used to flavor and color betel leaves (paan). The tree is common in dry deciduous forests, especially in Uttar Pradesh. It is also noted for tannins and traditional medicinal value.