Studies on sandal spike. Part II. Physiological significance of the disturbed iron balance in the spike disease of sandal (Santalum album Linn.)

Abstract

Chlorosis in spiked sandal leaves, as in the chlorotic eaves of other plants, is caused by a deficiency of iron. However, the deficiency appears to be not on account of reduced availability of this element in the soil, but a direct effect of the spike disease, since the soil iron content is normal and the pH of the soil is on the acid side (Table III). Like other chlorotic leaves, the spiked sandal leaves show an increase of amino nitrogen, oxalic and malic acids, and a decrease in calcium content. Thus chlorosis in sandal leaves, caused by spike-induced iron deficiency, bears resemblance to the chlorosis in other leaves which is caused by the reduced iron availability in soils. In spike-diseased plants there is a comparatively higher accumulation of iron in the roots than in the leaves, which suggests that probably the mechanism of translocation of iron in the plant is affected. The preponderance of iron over calcium in the spiked sandal roots, as evidenced by the much lower Ca/Fe ratio in them, seems to be responsible at least in part for the death of root ends and cessation of haustorial connections in the spiked sandal.