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A field portable system for the measurement of gas exchange of leaves under natural and controlled conditions: examples with field‐grown Eucalyptus pauciflora Sieb. ex Spreng. ssp. pauciflora, E. behriana F. Muell. and Pinus radiata R. Don.
Author(s) -
KÜPPERS M.,
SWAN A. G.,
TOMPKINS D.,
GABRIEL W. C. L.,
KÜPPERS B. I. L.,
LINDER S.
Publication year - 1987
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11603690
Subject(s) - transpiration , photosynthesis , botany , humidity , compensation point , chemistry , cuvette , eucalyptus , carboxylation , horticulture , analytical chemistry (journal) , biology , thermodynamics , environmental chemistry , physics , optics , organic chemistry , catalysis
A field portable system is described which measures the response of gas exchange of one leaf to changes in environmental parameters under controlled conditions, and which simultaneously measures the gas exchange of another leaf as the climatic parameters vary naturally. The system consists of two independently operating cuvettes. It enables detailed studies of photosynthesis and stomata/transpiration of leaves attached to the plant in their natural position. It provides control of temperature, humidity, CO 2 and oxygen concentration (or, alternatively, of other gases) as well as of light. Infrared gas analyzers for CO 2 and H 2 O are used which allow similar time constants for the measurement of the two gases. Examples of a diurnal course of gas exchange of a leaf in its natural exposition and of experiments with steady‐state responses of gas exchange are presented. In Eucalyptus pauciflora Sieb. ex Spreng. ssp. pauciflora , a set of response curves of CO, assimilation ( A ) to CO 2 , as measured at various leaf temperatures and light levels, shows carboxylation efficiency to be light saturated at the lower photon irradiances the lower the leaf temperature is. Carboxylation efficiency is maximal at 25°C. At ambient CO, partial pressure stomata open in a way that CO 2 assimilation occurs at a rate found within the curvature region of the CO 2 response function of A. The light‐independent CO 2 compensation point as a function of temperature is presented. Applying a combined heat/low humidity pulse (15 or 60 min) on leaves of Eucalyptus behriana F. Muell. or Pinus radiata R. Don, respectively, leads to a lower level of intercellular carbon dioxide partial pressure ( C i ) during the decline in A and leaf conductance to water vapour ( g ). A lower C i level is maintained during recovery of A and g, A almost reaching the pre‐pulse level but not g. The existence of an after‐effect indicates that the response to the combined high temperature/low humidity pulse is a multi‐step process.