962
Japan). Ozone was generated by electric discharging and
analyzed by another gas tester system (GASTEC Co.
18L, Kanagawa, Japan). Chlorophyll contents were
measured by the method of Amon (1949). Some of the
rice leaves were preillummated by halogen light passed
through interference filters of 660 nm (17.5 W m' 2 ) and
700 nm (21.5 W m' 2 ) (Nippon Shinkuu Kogaku, Tokyo,
Japan), and by Ar (477 & 488 nm, 280 W m' 2 , NEC
GLG3028, Kawasaki, Japan) and He-Ne (633 nm, 450
W m" 2 , NEC GLG5360, Kawasaki, Japan) laser lights
while others were adapted to darkness.
Spectra of chlorophyll fluorescence were measured
by a multichannel spectrometer (Takahashi et al., 1991).
A leaf segment was fixed on a sample holder of the
apparatus, and projected by Ar (477 & 488 nm, 280
W m~ 2 ) and diode (693 nm, 110 W m~ 2 , Applied OptP
OptP burnin g Inc. STK-DP694-16G-155, Saitama, Japan)
laser lights. Induced fluorescences were introduced to
the spectrometer by an optical fiber and fluorescence
spectra were measured by a diode-array detector
Li I I _i J 1—
650 680 710 740 770 800
WAVELENGTH (nm)
Fig. 1 Spectral changes of chlorophyll fluorescence in
an intact leaf of rice wild-type plant with temperatures,
(a) 25°C, (b) 45°C and (c) 60°C. Fluorescences were
induced by the Ar laser light (477 & 488 nm) and spectra
were resolved into 5 main emitter components (F680,
F685, F695, F725 and F745) and one or two minor
components at the longer side. Chlorophyll content of
the leaf was 54.0 nmol cm" 2 .
equipped with an image intensifier (512 sampling points,
Tracor Northern TN6133, Wisconsin, U.SA.). Spectra
were measured at times when induced fluorescence
reached the maximum, approximately 1 s after initiation
of laser light projections. Measurements were carried
out at 25°C except for the experiments for effects of
temperature. Spectral data were transferred to a
multipurpose data processing system (Seki Technotron
SK-296, Tokyo, Japan) and subjected to correction of
sensitivity of the detector for wavelengths. Then spectra
were resolved into tentative fluorescence emitter
components of Gaussian peaks by curve fitting with a
micro-computer (NEC PC-980IRA, Kawasaki, Japan)
(Takahashi et al., 1991).
3. RESULTS
Effects of temperature on chlorophyll fluorescence
were examined. The fluorescence spectrum of a rice leaf
containing 54.0 nmol cm ' 2 chlorophylls showed two
peaks around 685 nm (Fn) and 740 nm (Fj) (Fig. la) as
reported for other intact leaves (Kocsanyi et al., 1988;
Rinderie & Lichtenthaler, 1988; Takahashi et al., 1991)
The Fn peak decreased against the Fi peak by raising
temperature up to 45°C (Fig. lb). The spectral shape
remarkably changed when the temperature was raised to
60°C (Fig. lc); a bend between the peaks grew shallow.
In order to analyze the change, the spectra were resolved
into 5 main tentative emitter components, F680, F 68 S,
F695, F725 and F745, and other one or two emitters
at longer wavelengths (F770 - F790). Changes in
proportions of emitters by raising temperature are shown
in Fig. 2. Proportion of F685 began to decrease al 40°C,
F680 at 45°C and F745 at 50°C, while those of F695 and
F725 increased above 50°C
Similar spectral changes of chlorophyll fluorescence
to those induced by high temperature were observed
when kidney bean leaves were fumigated with airFig.
airFig. 2 Changes of proportions of the emitters in
chlorophyll fluorescence with temperatures. The data
used were the same as Fig. 1. Symbols indicate • F680,
O F685, □ F695, OF725 and A F745.
