Báo cáo lâm nghiệp: Assessment of the effects of below-zero temperatures on photosynthesis and chlorophyll a fluorescence in leaf discs of Eucalyptus globulu

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...
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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 temperatureson photosynthesis and chlorophyll a fluorescencein leaf discs of Eucalyptus globulusL.F. Serrano, M.M. Chaves, M.H. Almeida J.S. PereiraInst. 1399 Lisbon Codex, Sup. Agronomia, Portugal measured slow fluorescenceIntroduction 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 2tures has been assessed by a number of concentration of approximately 5%), using anmethods, including measurements of LD-2 Hansatech oxygen electrode + fluoro- meter. Leaf discs were illuminated with an LS-2visible symptoms of injury, vital staining Hansatech light source. Fluorescence wastechniques, protoplasmic streaming, plas- induced with red light at 650 mm and wasmolysis and changes in the pattern of detected at 760 nm. Control discs were kept inchlorophyll 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 assessmentaim of our study was to test the possibility to be compared, whole plants were frozen were and the leaf discs collected for measurementsof 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 termsdiscs of Eucalyptus globulus to screen of mean % injury per leaf per plant.resistance to below-zero temperatures,which we compared with the classic tissuenecrosis method. Results The effects of the temperature treatmentsMaterials 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- ’ 2They were placed in the dark, inside an alumi- increased in treatments of 2 h at -2 andnum box floating in a 10 I bath containing ethyl- - 3°C, whereas in treatments at -4 andene 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 thedecrease kinetics to reach the final stea- detection of low temperature effects on leaves of E. globulus.dy-state fluorescence, which is wellexpressed by the decrease in R values fdwhen treatment tempera ...