Báo cáo lâm nghiệp: "Assessment of the effects of below-zero temperatures on photosynthesis and chlorophyll a fluorescence in leaf discs of Eucalyptus globulu"
Chia sẻ: Nguyễn Minh Thắng
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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:Assessment of the effects of below-zero temperatures on photosynthesis and chlorophyll a fluorescence in leaf discs of Eucalyptus globulus...
Nội dung Text: Báo cáo lâm nghiệp: "Assessment of the effects of below-zero temperatures on photosynthesis and chlorophyll a fluorescence in leaf discs of Eucalyptus globulu"
Assessment of the effects of below-zero temperatures
on photosynthesis and chlorophyll a fluorescence
in leaf discs of Eucalyptus globulus
L.F. Serrano, M.M. Chaves, M.H. Almeida J.S. Pereira
Inst. 1399 Lisbon Codex,
Sup. Agronomia, Portugal
measured slow fluorescence
Introduction and -5°C, we
kinetics of a and photosynthetic
chlorophyll
capacity at 25°C with saturating light and C0
2
concentration (provided by a bicarbonate/car-
The sensitivity of plants to low tempera-
bonate buffer, pH 8.7, giving rise to a C0 2
tures has been assessed by a number of concentration of approximately 5%), using an
methods, including measurements of LD-2 Hansatech oxygen electrode + fluoro-
meter. Leaf discs were illuminated with an LS-2
visible symptoms of injury, vital staining
Hansatech light source. Fluorescence was
techniques, protoplasmic streaming, plas- induced with red light at 650 mm and was
molysis and changes in the pattern of detected at 760 nm. Control discs were kept in
chlorophyll fluorescence kinetics (Baker the dark at 25°C for the same periods.
et al., 1983; MacRae et al., 1986). The When the methods of injury assessment
aim of our study was to test the possibility to be compared, whole plants were frozen
were
and the leaf discs collected for measurements
of using changes in photosynthetic capaci-
of photosynthetic oxygen evolution and fluores-
ty and in slow fluorescence kinetics in leaf cence. Tissue necrosis was expressed in terms
discs of Eucalyptus globulus to screen of mean % injury per leaf per plant.
resistance to below-zero temperatures,
which we compared with the classic tissue
necrosis method.
Results
The effects of the temperature treatments
Materials and Methods
on photosynthetic capacity (P of the
)
N
eucalypt leaf discs are shown in Fig. 1.
Leaf discs (10 )
2
cm of E. globulus potted plants Values of P measured either at 700 or
N
subjected to low temperature treatments.
were
2500 pmol quanta.m- are slightly
1
s-
’
2
They were placed in the dark, inside an alumi-
increased in treatments of 2 h at -2 and
num box floating in a 10 I bath containing ethyl-
- 3°C, whereas in treatments at -4 and
ene glycol. After 2 h of exposure at -2, -3, -4
- 5°C photosynthesis dropped to values with R being the depen-
0.71, P
The increasing delay of the fluorescence used as reliable screening tests for the
decrease kinetics to reach the final stea- detection of low temperature effects on
leaves of E. globulus.
dy-state fluorescence, which is well
expressed by the decrease in R values
fd
when treatment temperatures declined, is
in accordance with results reported by
References
several authors (MacRae et al., 1986;
Smillie et al., 1987). Such alterations in
the fluorescence kinetics indicate damage Baker N.R., East T.M. & Long S.P. (1983) Chil-
of the photosynthetic function. However, ling damage to photosynthesis in young Zea
mays. 11. Photochemical functioning of thyla-
we cannot tell whether the disturbances
koids in vivo. J. Cxp. Bot. 34, 189-197
occurred during the induction period, the
Lichtenthaler H.K. & Rinderle U. (1988) The
state I-state II transitions or the photo-
role of chlorophyll fluorescence in the detection
synthetic C0 fixation, since R values
2 td of stress conditions in plants. CRC Crit. Rev.
cover the whole process of photosynthesis Anal. Chem. 19 (suppl. 1 ), S29-S85
(Lichtenthaler and Rinderle, 1988). MacRae E.A., Hardacre A.K. & Fergusson I.B.
(1986) Comparison of chlorophyll fluorescence
These results obtained using leaf discs
with several other techniques used to assess
in agreement with earlier work with
are
chilling sensitivity in plants. Physiol. Plant. 67,
intact E. globulus plants. The degree of 659-665
correlation obtained between the percent-
Smillie R.M., Nott R., Hetherington S. & Oquist
age of tissue necrosis and either photo- G. (1987) Chilling injury and recovery in deta-
synthetic capacity or fluorescence quench- ched and attached leaves measured by chloro-
phyll fluorescence. Physio/. Plant. 69, 419-428
ing indicates that both techniques may be
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