Mineral Nutrition of Sandalwood (Santalum spicatum)

Abstract

Acacia acuminata is a preferred host of the root hemiparasitic tree, Santalum spicatum (sandalwood). Comparison between nutrient content of adult trees of sandalwood and results for an earlier study of the mistletoe, Amyema preissii, on the same host species, A. acuminata, showed similar high levels of K and Na and low levels of Zn in both parasites compared with the host plants. Differences in K, Ca, N and Cu levels between parasitized and uninfected Acacias imply that the host plant contributes to the nutrition of sandalwood. The high K/Ca ratio in sandalwood confirms that K uptake in preference to Ca is a general feature of all categories of angiosperm parasites. Patterns of distribution of nutrients between various parts of sandalwood and A. acuminata depend on the type of nutrient, but levels are usually highest in leaves of both species and the haustoria. Although K, Ca and Na are much lower in the kernels than in vegetative parts of the parasite, only seedlings without supplementary Ca in a nutrient omission experiment failed to grow at all in the absence of hosts. Growth is not dependent on the level of K in the unattached plants but other evidence indicates it may have a role in water uptake in the attached plant. Calcium supply has a marked effect on internal Ca levels and growth of unattached plants. Compared with field plants, levels of Ca, and to a lesser extent Zn, were much higher in plants of the Ca/K treatment that produced greatest growth over 34 weeks. Haustorial formation is enhanced by the presence of A. acuminata roots. However, competition for nutrients, especially Ca, from co-planted A. acuminata seedlings results in suppression of growth of young sandalwood compared with their growth in the absence of the host species.