Measuring and testing – Simulated environment
Patent
1987-02-03
1988-09-06
Noland, Tom
Measuring and testing
Simulated environment
73336, 356432, 374142, G01N 3348, G01N 2164
Patent
active
047683902
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
1. Field of Invention
The present invention is concerned with an instrument for measuring the photosynthetic activities and capacities of plants. More particularly it is concerned with an instrument for measuring simultaneous chlorophyll fluorescence emission, CO.sub.2 assimilation rate and, if desired, transpiration rate, parameters which are all characteristics of a plant's general metabolic and health status.
Recent demonstrations that changes in chlorophyll fluorescence emission during the induction of photosynthesis are closely related to the rate of carbon dioxide assimilation have increased the interest in the application of fluorescence as a convenient monitor of leaf photosynthetic activity.
2. Description of Prior Art
Apparatus and techniques for measuring chlorophyll fluorescence emission from leaves in the laboratory are known. Chlorophyll fluorescence emission is indicative of the light reactions of photosynthesis, and is the first detectable parameter to indicate a change in photosynthetic activity. It has been found that the level of photosynthetic activity of the leaf as evidenced by the fluorescence emission can provide not only evidence of the general health of the leaf but also how the leaf responds to changes in its environment. The response may be rapid and provide an indication of the leaf's activity well in advance of any visible physical change in the leaf.
Simultaneous measurements of CO.sub.2 assimilation rate of a leaf and continuous fluorescence signals have previously been made under laboratory conditions. To date, apparatus for measuring CO.sub.2 assimilation rate and the fluorescence signals have employed the continuous means of using white light fitted with a red-removing filter, so that continuous fluorescence induction curves may be generated by the red-deficient light, and by detecting the fluorescence of the leaf, which is emitted as red light, with a continuous detector fitted with suitable filters so that only red light, all of which is derived from fluorescence of the leaf is detected. This method of detecting fluorescence gives a measure of the fluorescence induced when light deficient in the red portion of the spectrum is incident upon the leaf.
In field conditions white light contains red light ie the part of the spectrum which would be eliminated by the red removing filter. Some of the light, which would not be present in the red-deficient light is capable of driving photosynthesis. The continuous method described above is not representative of the activity of the plant when white light is incident upon it, as under field conditions. Therefore, it was desirable to develop a system for measuring the fluorescence response of a leaf which is exposed to white light, simultaneously with the measurement of CO.sub.2 assimilation by the leaf.
SUMMARY OF THE INVENTION
An instrument has now been devised which can be used to simultaneously measure CO.sub.2 assimilation and parameters of chlorophyll fluorescence by the leaf induced by white light eg sunlight or artificial white light.
According to the present invention an instrument (2) for simultaneously measuring a plurality of parameters indicative of photosynthetic activity of a leaf (5) in vivo comprises
(a) a gas tight chamber (4) for the leaf (5),
(b) means (10) for illuminating the leaf with modulated light of insufficient intensity to drive photosynthesis,
(c) means (14) for detecting modulated fluoroescence emission from the leaf,
(d) means for illuminating the leaf with photosynthetically active light,
(e) means (43) for measuring the light absorbed by the leaf,
(f) and means (32) for measuring the rate of uptake of carbon dioxide gas of the leaf.
The term leaf in the present specification includes a part of a leaf and also more than one leaf. The term leaf also refers to any part of a plant capable of photosynthesis.
Plant photosynthetic activity can be measued directly by assessing CO.sub.2 uptake. Infra-red spectroscopy provides a rapid non-destructive means of assessing CO.sub.2 upta
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"The Relationship Between Carbon Dioxide Fixation and Chlorophyll a Fluorescence During Induction of Photosynthesis in Maize Leaves at Different Temperatures and Carbon Dioxide Concentrations"; Planta, vol. 160, pp. 550-558; 1984; C. R. Ireland et al.
"Chlorophyll a Fluorescence: Can It Shed Light on Fundamental Questions in Photosynthetic Carbon Dioxide Fixation?"; Plant, Cell and Environment; vol. 8, pp. 439-448; 1985; Mirta N. Sivak et al.
Baker Neil R.
Long Stephen P.
Noland Tom
The British Petroleum Company p.l.c.
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