12. Anatomy of Indian Sandalwood (Santalum album L.)

Indian sandalwood (Santalum album L.) is one of the most valuable tropical hardwoods in the world, known for its fragrant heartwood and essential oil. Due to its overexploitation in the past, it is categorized as ‘vulnerable’ and listed in International Union for Conservation of Nature Red List of threatened species. The global shortage and high market price of sandalwood have always been a reason for frequent adulteration and import of cheaper substitutes of this prized material. To resolve adulteration problems, wood identification techniques using light microscopy and image analysis have always been essential tools for timber authentication and utilization. Besides wood (stem and root) anatomy, anatomical features of bark and haustoria could be essential components in understanding the issues of forest forensic and functional attributes of sandalwood haustorial–host interactions, respectively. In this chapter, the anatomical characteristics of bark, stem wood, root wood and haustoria are described based on the investigation carried out on the availability of sandalwood trees and xylarium samples in the Navsari Agricultural University, Gujarat, India. The study showed that stem wood and root wood in S. album look alike apart from vessel diameter in root wood, which appeared to be slightly more prominent and more frequent than vessel diameter in stem wood. However, ray frequency and fibre length in stem wood were higher than root wood. Interestingly, in the bark, distinct oil cells were observed without oil globules associated with ray parenchyma. However, there are no reports on distinct oil cells in stem wood and root wood. The oil globules in stem wood were observed in lumens of procumbent ray cells and axial parenchyma. Ray cells were heterogeneous types in stem wood and root wood while homogeneous in the bark. In stem wood, occasional rhomboidal crystals were seen in chambered cells of axial parenchyma only, while in root wood, these were observed in ray cells and axial parenchyma both. However, in the bark, occasional crystals were observed in cortical cells and axial parenchyma. Considering haustorial anatomy, the initiation of penetration peg at sandalwood haustorium and host root interface confirmed young haustoria's transition to mature haustoria.