Studies in the physiology of tobacco

Abstract

Effect of boron-nutrition on the rate of oxygen uptake by the root-tip and shoot tip and on the ascorbic acid content in young leaves of tobacco, K-49 have been investigated.

The effect of boron-nutrition on the rate of aerobic respiration of root and shoot-organs is different. Boron up to a concentration of 0·25 mg./kg. increases respiration in the case of roots whereas in the case of shoots a consistent decrease up to a concentration of 0·50 mg./kg. is in evidence. Increase in respiration in the boron-deficient shoots is suggested to be due to high sugar content in this region and not due to the increased polyphenoloxidase activity as suggested by Mac Vicar and Burris. Participation of ascorbic acid with respiration of the boron-sufficient plants is indicated. Ascorbic acid content of the tobacco young leaves definitely increases by boron feeding. The increase is slow up to 0·75 mg./kg. but further there is a rapid increase up to 1·5 mg./kg. which accounts for about 50% increase in the vitamin content. The highest concentration of 2·00 mg./kg. tried has, however, decreased it slightly though still keeping at a higher level than the control.