The effect of infection with tobacco-mosaic virus on the levels of nitrogen, phosphorus, protease, and pectase in tobacco leaves and on their response to fertilizers

The effect of nitrogen and phosphorus on the levels oftwo enzymes, pectase and protease, was also determined on the same material.3. Phosphorus increases the non-protein, or car- bohydrate, components of the leaf, while nitrogen increases the protein components.4. Nitrogen increases pectase levels, while phos-phorus decreases them.The reverse is true for protease.It is suggested that this may indicate the presence of different paths for the synthesis and breakdown of both pectin and protein.We wish to thank the Agricultural Research Council for grants and Mr F. J. Anscombe for advice on the statistical analysis.