A Beneficial Effect of Cobalt on the Growth of the Rubber Plant (Hevea brasiliensis)

Abstract

WITHOUT adequate cobalt, ruminants will develop symptoms, sometimes referred to as enzootic marasmus or pining, and will die if not resuscitated with either cobalt or vitamin B₁₂ ^1,2. Cobalt has also been demonstrated to be an essential element required by certain blue-green algae³. However, while it has been demonstrated that cobalt will materially increase the elongation of stem segments in the presence of sugars^4,5, there is no conclusive proof that the element is essential to the growth of higher plants. Hewitt and Bolle-Jones⁶ failed to produce evidence that cobalt was essential for the growth of tomato, lettuce or sugar-beet. The evidence summarized here shows that a minute amount of cobalt supplied in nutrient solution to rubber plants grown in sand significantly improved growth. It shows that cobalt has a beneficial effect on the growth of a higher plant; but this, in itself, does not prove it to be an indispensable nutrient element.