Drift of Net Assimilation Rate in Plants

Abstract

IN a recently published note¹, the effect of age on net assimilation and relative growth-rates in the cotton plant is discussed. Although details² of the experiments have not reached me, it is evident from the note that O. V. S. Heath's results conflict with data already published^3,4 from this laboratory. In the experiments with cotton, no general rise or fall in the net assimilation rate (dry weight basis) was found up to the time of flowering and, although it is admitted that the absence of such a drift with time is not proved, Heath claims that his data confirm the findings of Gregory⁵. The latter found the net assimilation rate (area basis) to be independent of time up to maximum leaf area in barley, and he accounts for 80 per cent of the variation of his data in terms of the variation in external factors.