tailieunhanh - 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. | 617s Ann. Sci. For. 1989 46 suppl. 617S-62ŨS Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Assessment of the effects of below-zero temperatures on photosynthesis and chlorophyll a fluorescence in leaf discs of Eucalyptus globulus . Serrano . Chaves . Almeida and . Pereira Inst. Sup. Agronomia 1399 Lisbon Codex Portugal Introduction The sensitivity of plants to low temperatures has been assessed by a number of methods including measurements of visible symptoms of injury vital staining techniques protoplasmic streaming plas-molysis and changes in the pattern of chlorophyll fluorescence kinetics Baker et al. 1983 MacRae et al. 1986 . The aim of our study was to test the possibility of using changes in photosynthetic capacity and in slow fluorescence kinetics in leaf discs of Eucalyptus globulus to screen resistance to below-zero temperatures which we compared with the classic tissue necrosis method. Materials and Methods Leaf discs 10 cm2 of E. globulus potted plants were subjected to low temperature treatments. They were placed in the dark inside an aluminum box floating in a 10 I bath containing ethylene glycol. After 2 h of exposure at -2 -3 -4 and -5 c we measured slow fluorescence kinetics of chlorophyll a and photosynthetic capacity at 25 c with saturating light and co2 concentration provided by a bicarbonate car-bonate buffer pH giving rise to a co2 concentration of approximately 5 using an LD-2 Hansatech oxygen electrode fluorometer. Leaf discs were illuminated with an LS-2 Hansatech light source. Fluorescence was induced with red light at 650 mm and was detected at 760 nm. Control discs were kept in the dark at 25 c for the same periods. When the methods of injury assessment were to be compared whole plants were frozen and the leaf discs collected for measurements of photosynthetic oxygen evolution and fluorescence. Tissue necrosis was expressed in terms of mean injury per leaf per plant. Results The effects of the temperature .