ISSN:
1573-9058
Keywords:
CO2 exchange
;
chlorophyll fluorescence in vivo
;
chloroplasts
;
heat shock granules
;
stress criteria
;
thermosensitivity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Effects of high temperatures on the leaves of Ranunculus glacialis were studied in plants taken from sites located between 2400-2550 m in the Central Alps. Changes in CO2 exchange rates, in vivo chlorophyll fluorescence, and cellular ultrastructure were investigated during and after an experimental heat exposure. The earliest heat stress effect was inactivation of the net photosynthetic rate at 38-39 °C. Between 40-42 °C, disorders appeared in the photosynthetic apparatus and in the tonoplast. Heat shock granules were observed at 42 °C in chloroplasts, and at 44 °C also in mitochondria. In this temperature range, the dark respiration rate was reversibly enhanced, and an increased number of polyribosomes indicated repair after the primary injury. Above 44 °C, the degradation progress entered the phase of chronic impairment leading to irreversible damage at 45-46 °C. An unusually wide temperature range from the start of reversible photosynthetic inhibition to incipient necrosis indicated a pronounced heat sensitivity, particularly in cellular functions, of this arctic-alpine species.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1006840623763
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