Experimental Studies of the Relation between Carbon Assimilation and Stomatal Movement

Abstract

Two purely physical sources of error in the ‘resistance porometer’ as ordinarily used are considered to be of appreciable importance, viz. that due to the flow through the leaf being augmented with water vapour which is removed again by a drying agent before the air passes through the standard capillary, and that due to the leaf temperature differing from the capillary temperature. In a bad case the total error might amount to 10 or 15 per cent. of the ‘leaf resistance’. Modifications to deal with these sources of error and with the more important errors due to the responses of the enclosed stomata to variations in CO₂ supply are described.