AbstractsEarth & Environmental Science

Results from two experiments on Grand Rapids, leaf lettuce are presented. Twelve nutrient solutions were used to grow the plants in sand cultures. Determinations of ascorbic acid concentration in the fresh tissues were made colourimetrically and the results analysed statistically. It was found that increased nitrogen gave highly significant increases in the ascorbic acid content of the plants in the winter experiment and non-significant increases in the spring experiment. Increased phosphorus and potassium gave non-significant results. The general effect in both experiments was for phosphorus to increase and potassium to decrease the concentration of vitamin C. Significant interactions between phosphorus and potassium in the winter experiment and between nitrogen and phosphorus in the spring experiment indicated that a balance between nutrients was as effective as the actual concentration of any element. From these studies it appeared that factors other than mineral nutrition are responsible for much of the variation in the ascorbic acid content of leaf lettuce.