Forest Research: Open Access
Open Access

Abstract

Anatomy and Functional Status of Haustoria in Field Grown Sandalwood Tree (Santalum album L.)

Rocha D, Ashokan PK, Santhoshkumar AV, Anoop EV and Sureshkumar P

To study the anatomy and functional status of sandal tree haustoria, two treatments of six year old field grown sandal tree growing with and without host Casuarina were investigated. Sandal tree was observed to form haustoria with host Casuarina and the wild grass grown around it. Sandal tree planted without host formed haustoria with the roots of nearby trees. However, maximum numbers of haustoria were observed in the sandal tree with host growing in the same pit. Anatomical studies of haustoria with host Casuarina reveals that vascular connections between the host and the sandal tree became so intimate that the host root and the parasitic root became almost a single physiological unit catering to the nutritional requirement of sandal tree. Furthermore, our investigations revealed that direct lumen-lumen xylem connections between the xylem of the host and the parasite were absent. Functional status of Sandal-haustoria was also studied by observing the translocation of radio-labelled phosphorus (32P) from host to sandal tree by labelling of hosts and wild grass with 32P and tracing it in sandal tree. After 2 h and 4 h of labelling Casuarina with 32P, no notable counts were observed. Higher counts of translocated 32P were observed in sandal tree after 6 h of labelling the host plant. There were marginal increase in 32P count in sandal tree with time and this increase continued upto 8 days and thereafter observed a reduction up to 16 days, which indicated the decay of already translocated 32P after 8th day. 32P count also observed in sandal tree when wild grass was inoculated with 32P. Translocations from the host plants other than Casuarina planted in the same pit were also investigated and its translocation observed varied with host species. The translocations from cocoa to sandal tree and Casuarina to sandal tree were the most efficient. The possible reverse translocation from sandal tree to host plant was also observed when 32P applied to sandal tree. The results from the radiotracer studies indicated that sandal tree forms a network of roots, connected through haustoria, between sandal tree and different hosts including the grass species growing around it. The implication of the these results is that the host plants need not be present in the same pit of sandal tree as it can extend its root to distance of 1.5 to 3 m to form haustoria on neighbouring plants.