Leaf Temperatures in a Gas Exchange Chamber and in the Open Air

Abstract

Leaf temperatures in a Koch fully climatized gas-exchange chamber as designed by Siemens and in a similarly equipped open-air reference were measured with horizontally and vertically inserted thermocouples on Nerium oleander L. On a sunny day with only little air movement and an average air temperature of 20-4 °C, leaf over-temperatures in the gas-exchange chamber were lower on average by 2-2 K. The extent of reduction of over-temperature in the chamber is determined by the reduced global radiation in the chamber and the differences of wind velocities in chamber and reference. Differences in the ventilation intensity in the chamber have no demonstrable influence on the leaf over-temperatures. The over-temperatures of the reference leaves, on the other hand, depend to a large degree on air velocity. The changed radiation and air flow conditions in the chamber as compared with open-air conditions have consequences for the physiological reactions of the enclosed plant and must be taken into account when comparing results from gas-exchange measurements with open-air conditions. For further improvements of gas-exchange measurement equipment, air flow conditions and radiation quantity and quality might be starting points INTRODUCTION

Experiments on the control capacity of stomata of Picea abies (L.) Karst. after fumigation with ozone and in environmentally damaged material

“…This form of docutnentation has already been proved useful in earlier experiments (Koch & Maier-Maercker, 1986) because it is independent of the mistakes that unavoidably beset the usual calculations of leaf conductivity (for a detailed discussion, see Maier-Maercker & Koch, 1991). As leaf area and turbulences within the ehatnber, as well as the differences between leaf and air temperature, are identical in the ehatnber experiments at each point ofthe curve (Seibert, Koch & Eller, 1980), the regression of the curve foi; the same twig represents the behaviour of the stomata in the same way as the conductivity value. A piece of filter paper transpiring in the chamber yields a line parallel to the abscissa.…”