Variation in response of five identical steady‐state porometers

Abstract. Variation in response was measured for live identical steady‐state porometers manufactured and calibrated by Li‐Cor, Lincoln, NE, U.S.A. Mean values for relative humidity, air and leaf temperature, transpiration and leaf conductance were compared in two experiments, one with random measurements among a population of leaves and the other using paired observations on the lateral sides of individual leaves. Comparisons were made using young newly expanded leaves of potato (Solarium tuberosum, cv. Norland) plants grown under controlled environmental conditions in the Biotron at the University of Wisconsin‐Madison. Average mean differences among porometers were 5, 11 and 12% for relative humidity, leaf conductance and transpiration, respectively.