Field measurements of the photosynthetic rate of potatoes grown with different amounts of nitrogen fertilizer

Summary Three experiments are reported in which the photosynthetic rates of potatoes grown with various amounts of applied nitrogen (N) fertilizer were measured. Rates of photosynthesis in leaves of plants grown without applied N reached levels as high as those receiving N in all experiments. The rate of photosynthesis in the uppermost leaves of the variety Pentland Crown was found to increase during the season, whereas in Estima rates remained the same. Decline in the rate of photosynthesis with leaf age was more rapid in strongly shaded leaves than in less shaded leaves which were found to be photosynthetically active 8 weeks after expansion.