Báo cáo lâm nghiệp: "Seasonal variations in photosynthetic activity of spruces as determined by chlorophyll fluorescence"

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Seasonal variations in photosynthetic activity of spruces as determined by chlorophyll fluorescence H.K. Lichtenthaler, U. Rinderle M. Haitz Botanisches Institut // (Plant Kaiserstr. 12, Physiology and Biochemistry), University of Karlsruhe, D-7500 Karlsruhe, F.R.G. height of the Rfd-values (measured in the Introduction 690 and 730 nm regions) reflects the potential photosynthetic activity of leaves as is demonstrated by parallel measure- In photosynthetically active, plant green ments of the net C0 rate P -assimilation 2 . N tissue (leaves, needles), the largest part of The Rfd-values are an indicator of the the light energy absorbed by the pigments intactness of the internal photosynthetic (chlorophylls, carotenoids) is used for apparatus. Though they usually parallel photosynthesis (photosynthetic quantum the net C0 rates, they are a -assimilation 2 conversion). A minor part is re-emitted as different parameter and independent of chlorophyll fluorescence, whose spectrum stomatal opening. exhibits maxima 690 and 735 near nm With an additional apparatus, the PAM al., 1986; Lichtenthaler (Lichtenthaler et fluorometer (Schreiber et al., 1986), one and Rinderle, 1988a). The light-induced can determine the photochemical Q- and in vivo chlorophyll fluorescence of a pre- the non-photochemical E-quenching and darkened green leaf or needle sample the rate of Q in the photosyn- -reoxidation A shows a transient which is known as fluo- thetic electron transport chain. Measure- rescence induction kinetics and variable ment of the chlorophyll fluorescence emis- fluorescence (Kautsky effect). Upon illumi- sion spectra enables the determination of nation, one observes a fast fluorescence further stress indicator: the ratio rise (ca 400 ms) to a maximum (f fol- ) max a F690/F735 of the 2 fluorescence maxima. lowed by a slow fluorescence decrease The height of F690/F735 mainly reflects (f to the steady state fluorescence (f ) d ). s the chlorophyll content of the needles and, The fluorescence decrease ratio (Rfd = to a lower degree, its photosynthetic activ- f Rfd-values at 690 nm), which in- ; s /f d ity (Rinderle and Lichtenthaler, 1988). The dicates the potential photosynthetic activ- registration of the different chlorophyll fluo- ity of a leaf area, has successfully been parameters (Lichtenthaler, 1987; established as a very suitable vitality index rescence Lichtenthaler et al., 1986; Lichtenthaler and stress indicator in plants (Lichtentha- and Rinderle, 1988) permits a fast screen- ler and Rinderle, 1988a, b; Lichtenthaler ing of seasonal and short-term variations et al., 1986; Strasser et aL, 1987). The
The differentiation between photochemical Q- in photosynthetic activity and in chloro- quenching and non-photochemical E-quenching phyll content of trees as well as damage using the new PAM fluorometer of A. Walz, to the photosynthetic apparatus. This is Effeltrich (Schreiber et al., 1986). In this new documented here for spruce trees of the fluorometer, the excitation light to measure Northern Black Forest by measurement of chlorophyll fluorescence is separately applied to the actinic light, which drives the photosynthetic the different fluorescence signatures of reactions. Ground fluorescence F is excited needles during a 1 yr period from 1987 to repetitively by 1 !s pulses of low intensity. 1988. The photosynthetic prenyl pigments (chloro- phylls and carotenoids) were extracted with 100% acetone and the pigments quantitatively determined using the newly established extinc- Materials and Methods tion coefficients of Lichtenthaler (1987). The determined at -assimilation 2 C0 rates were temperature and light saturation (2000 room The fluorescence signatures of different needle I1Em-2’s-1) using the 0-porometer /H 2 C0 sys- years, of mainly healthy (Althof, damage class tem of Walz al., 1967). (see Nagel et 0/1) and of damaged spruce trees (Mauzen- berg, damage class 3/4) were measured using 3 different fluorescence methods. 1) The red laser-induced chlorophyll fluorescence kinetics (determination of Rfd-values as a vitality index Results of needles) measured near 690 and near 730 nm in a portable field fluorometer (Lichtenthaler and Rlnderle, 1988b). 2) The chlorophyll fluor- Rfd-va/ues and net C0 -assimilation 2 escence emission spectra at room temperature induced by blue light (470 ± 30 nm) recorded with a Shimadzu MPS 5000 spectrometer under fluorescence decrease The height of the steady-state conditions of the chlorophyll fluor- ratio 730 nm) (Rfd-values 690 escence (5 min after onset of illumination). 3) at or
spruce, the 1987 needles showed, how- reflects the photosynthetic activity P as , N shown for several needle years of the ever, a much lower increase in the new vegetation period than the older needle healthy and damaged spruces (Table I). years and those of the healthy, fully green This is valid for normal physiological conditions during summertime, when the spruce. stomata are open and can be regulated. The photosynthetic activity of the spruce The Rfd-values in the needles of damaged needles (P measured with a CO 0 2 H i N trees were also very high and only slightly porometer) decreased in October and lower than those of healthy spruces. The November from original values of 4-8 high Rfd-values thus indicated that the pmol C0 to very low values in 1 S M - 2 chlorophyll in the needles of damaged December (frost period; values of 0-2 trees, though lower in content, was photo- pmol C02!m-2!s-!) with some recovery in synthetically active. Under water stress a rather warm January. In March 1988, the conditions and in wintertime when the sto- P increased again to reach maxi- -values N mata are closed, the Rfd-values (e.g., mum values at the end of April (6—8 pmol values of 2.5--4) indicated that the internal C0 just before the new shoots ), I ’S 2 - 2’M photosynthetic apparatus was functional, were formed. Thereafter, the P showed N though the net C0 rates -assimilation 2 lower values again. These characteristics were very low or even zero. Photosynthe- were found at the Althof and the Mauzen- tic quantum conversion then depended berg sites. The low P values in winter N upon the C0 set free by respiration. 2 appear to be mainly due to closed stoma- Needles from fully green healthy ta, but in part also to damage of the photo- spruces possessed a higher chlorophyll from the synthetic apparatus seen as content per needle area unit than the cor- lower Rfd-values. responding needle years of damaged In contrast, the Rfd-values as a vitality spruces, which were light green and often index and as an index of the intactness of showed yellowish-green parts at the the photosynthetic apparatus, showed a upper needle part. Net photosynthesis PN different behavior. There was a clear per needle area unit was therefore always decrease of the values in December, with higher for green control needles than for considerable increase in January and needles of damaged trees (Table I). again a decrease in March 1988. There- after, higher values between 4 and 5 were reached (Fig. 1). These characteristics Seasonal variations were found in the 1986 and 1987 needles at the Althof and Mauzenberg sites. The very high Rfd-values of 6-7 were only The chlorophyll content of summer 1987 reached in the very young current year decreased in the spruce needles in the needles. The decrease of the Rfd-values winter months of 1988 up to 25% in the in December and March indicated damage older needles and to a somewhat lower of the photosynthetic apparatus, the degree in the youngest needle year 1987. increase in January (during a warm pe- With the start of the new vegetation pe- riod) demonstrated the fast regeneration riod, the chlorophyll content increased rate of the photosynthetic apparatus. again. This increase was particularly With the new PAM-fluorometer, one can strong in the 1987 needles, which in the determine the fluorescence kinetics with 1st yr still had a very low chlorophyll saturating light-pulses. The resulting fluo- content. In the case of the damaged
rescence spikes (distance g-h in Fig. 2), calquenching (qE) (see Schreiber et al., which indicate the reoxidation capacity of 1986; Lichtenthaler and Rinderle, 1988). The the primary photosynthetic quencher O were more or less the , A qQ-values in summer and winter (values of were higher for the normal green needles same (Althof) than those of the Mauzenberg 0.83-0.96 at the Althof and Mauzenberg site. The height of the spikes decreased in sites). In contrast, the qE-values (energy the cold winter months together with the quenching), which contain information, Rfd-values. e.g., of the light-mediated formation of From the kinetics of the PAM-fluorome- proton gradient across the mem- a ter, one can calculate the coefficients for brane, were higher in winter (values of 0.55-0.68) than at the time of highest pho- photochemical (qQ) and non-photochemi-
tosynthetic activity, e.g., in springtime about 20% in the winter months, which (values of 0.35-0.45). paralleled a lower chlorophyll content and photosynthetic activity. The ratio of the chlorophyll fluorescence intensity at the 2 maxima near 690 and 735 nm (F690/F735) was about 0.98- 1.08 in normal green needles and ca 1.2- Conclusion 1.6 in the light green or yellowish-green needles of the damaged spruces. The dif- The photosynthetic activity of spruce ferences, mainly due to the differing chlo- needles undergoes seasonal variations rophyll content of the needles, were larger with a maximum in springtime (April), in summer than in winter. The values for before and at the time of the formation of the ratio F690/F735 tended to increase by
References the new year’s needles. The current year needles reach their maximum in May and June. The chlorophyll fluorescence signa- Lichtenthaler H.K. (1987) and Chlorophylls tures of the needles of spruces (Rfa! carotenoids, the pigments of photosynthetic bio- values as well as the values for qE and membranes. Methods Enzymol. 148, 350-382 the ratio F690/F735) are very suitable to Lichtenthaler H.K. & Rinderle U. (1988a) The describe the seasonal variation in photo- role of chlorophyll fluorescence in the detection of stress conditions in plants. CRC Crit. Rev. synthetic activity. These fluorescence Anal. Chem. 19 (,’3uppl 1), S29-S85 signatures reflect the intactness of the Lichtenthaler H.K. & Rinderle U. (1988b) Chloro- internal photosynthetic apparatus even at phyll fluorescence as vitality indicator in forest closed stomata and are much better para- decline research. In: Applications of Chloro- meters to describe the internal photosyn- phyll Fluorescenc!a. (Lichtenthaler H.K., ed.), Klu- thetic activity than measurements of net wer Academic Publishers, Dordrecht pp. 133-139 C0 alone. -assimilation 2 Lichtenthaler H.K., Buschmann C., Rinderle U. & Schmuck G. (1986) Application of chlorophyll fluorescence in ecophysiology. Radiat Envi- ron. Biophys. 25, 297-308 Acknowledgments Nagel E.M., Buschmann C. & Lichtenthaler H.K. sponsored by a grant from the This work (1987) Photoacoustic spectra of needles as an was PEF, Karlsruhe, which is gratefully acknowledged. indicator for the activity of the photosynthetic
apparatus of healthy and damaged conifers. non-photochemical chlorophyll fluorescence Physiol. Plant. 70, 427-437 quenching with a new type of modulation fluoro- meter. Photosynth. Res. 10, 51-62 Rinderle U. & Lichtenthaler H.K. (1988) The Strasser R., Schwarz B. & Bucher J. (1987) chlorophyll fluorescence ratio F690/F735 as a Simultane messungen der chlorophyll possible stress indicator. In: Applications of fluoreszenz-kinetik bei verschiedenen Chlorophyll Fluorescence. (Lichtenthaler H.K., wellenlangen als rasches verfahren zur ed.), Kluwer Academic Publishers, Dordrecht, friihdiagnose immissionsbelastungen von pp. 176-183 waidbdumen. Ozoneinwirkung auf an Schreiber U., Schliwa U. & Bilger W. (1986) buchen und pappein. Fur. J. For. PathoL Continuous recording of photochemical and 17, 149-157