The Carbohydrate Nutrition of Tomato Roots

The respiratory responses of substrate-depleted excised root tips to a range of sugars, sugar phosphates, and sugar alcohols have been determined by measuring oxygen uptake by the direct method of Warburg. Sucrose, dextrose, and laevulose are the only sugars which promote a high level of oxygen uptake. The effects of azide and DNP on the oxygen uptake promoted by sucrose and by dextrose are described. Mannose is a strong inhibitor of respiration. This inhibition is reversed by the simultaneous addition of those sugars which also reverse the growth inhibition caused by mannose. Mannose inhibits the respiration of sucrose and of glycolytic intermediates. Galactose is slowly respired and does not, even at high concentration, inhibit the respiration of sucrose. The results are discussed in relation to the growth effects of the sugars tested.