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A compact lighting system for use with portable leaf chambers to measure photosynthesis
Author(s) -
YOUNG A. T.,
HARRISON G. E.,
LAWLOR D. W.
Publication year - 1989
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/j.1365-3040.1989.tb01963.x
Subject(s) - irradiance , halogen lamp , solar irradiance , optics , radiation , radiant energy , photosynthesis , materials science , bundle , environmental science , physics , chemistry , atmospheric sciences , biochemistry , composite material
. A compact, portable lighting system, developed for the measurement of photosynthesis in the field with portable chambers and applicable to the laboratory, is described. The system consists of a miniature 50‐W, 12‐V tungsten‐halogen lamp and a light guide which is constructed with randomized fibre bundles and mounted above the window of a portable assimilation chamber. The light guide distributes light uniformly across the leaf surface; the photon irradiance at the leaf surface is monitored by measuring the irradiant emitted from one fibre‐optic bundle using a sensor connected to the body of the light guide. Up to 1600 μmol quanta photosynthetic active radiation m −2 s −1 may be achieved at the leaf surface; irradiance may be varied by wire mesh screens of different densities. Leaf temperature follows air temperature outside the chamber to within ±2 °C over the range 10–30 °C and within the range of photon irradiances from 0 to 1600/μmol quanta m −2 s. The power supply for the lamp is a 12‐V, 24‐A h lead‐acid battery and the photon irradiance at the leaf surface gradually decreases by c. 3% over 2.5 h of measurement. With this system, response of photosynthetic rate to irradiance and to CO 2 partial pressure at constant irradiance may be measured in the field, independent of natural variations in solar irradiance.