Studies in the physiology of tobacco

Abstract

Dehydrogenase activities of tobacco K-49 in the absence of a designed supply of micro-nutrients (zero boron) were found to be reduced to 44% of the control and stepped up by the optimal boron concentration (0·75 mg./kg.) to 96 per cent. The activities were more or less equally favoured by boron concentrations from 0·75 to 1·50 mg./kg. The activities were maximum in middle leaves and minimum in old leaves; young leaves and young roots fall in between in this respect.

In the absence of micro-nutrients polyphenoloxidase activities were reduced by about 35% and with the supply of the optimal concentration of boron a recovery of 20% took place. Boron feeding increased this activity up to 0·50 mg./kg. and maintained it up to 0·75 mg./kg. Higher doses, however, up to 1·50 mg./kg. resulted in slight inhibition of this activity, with a further increase in boron up to 2·00 mg./kg., the decrease was considerable. It was noticed that polyphenoloxidase activity was low in the old leaves and high in the young leaves and young roots.

The significance of these results have been discussed.