Heat Injury in Leaves of Alpine, Temperate and Tropical Plants

Abstract

Temperatures producing heat injury in leaves of 30 species were measured by following heat-induced changes in fluorescence of the leaf chlorophyll. Except for six alpine plants and four cereals, mainly leafy vegetables and leaves of young fruit trees were used. Dark-adapted leaves were heated at a rate of one Celsius degree per minute. Chlorophyll fluoroscence began to increase between 30 and 40°C and reached a peak around 50°C. The peak of fluorescence was reached at 47.1°C in an alpine plant Plantago glacialis, at 51.2°C in lettuce (Lactuca sativa) and at 57.6°C in pawpaw (Carica papaya). Similarly, in the cereals, the peak of fluorescence was reached at lower temperatures in the temperate ones (49.5°C in barley and 48.9°C in oats) than in the two from warm climates (55.2°C in maize and 53.5°C in sorghum). This difference in heat sensitivity between plants from the three groups did not hold for all plants surveyed and there was some overlapping between individual plants in different groups. However, the mean temperature, for the inital rise in fluorescence as well as for the peak of fluorescence, occurred at a lower temperature in the alpine group of plants and at a higher temperature in the tropical group of plants compared with the temperate group. The results demonstrate a relationship between heat resistance and temperature of the environment in which the plants evolved, and illustrate the potential use of the chlorophyll fluorescence method for in vivo measurements of heat sensitivity in green plants.

An ecological and evolutionary analysis of photosynthetic thermotolerance using the temperature-dependent increase in fluorescence

“…3 of Havaux 1993). Smillie and Nott (1979) report that T was 8.3, 6.8, and 7.8°C greater than T crit for almax pine, temperate and tropical plants respectively. Across 35 species in our study, T was on average +6.04°C max greater than T crit .…”

“…Prior to our study, the most extensive study of fluo rescence rise characteristics in relation to the native hab itat of species was that of Smillie and Nott (1979). They investigated T crit variation for 30 different species of al pine, temperate and tropical plants.…”

“…These observations have led to the hypothesis that species with warm climate distribu tions should have greater intrinsic photosynthetic thermotolerance and thus the temperature-dependent in crease in fluorescence should occur at higher tempera tures (Smillie and Nott 1979;Bilger et al 1984). While there has been considerable work on the photosynthetic thermotolerance of desert plants utilizing the temperature-dependent increase in fluorescence (Seemann et al 1979(Seemann et al , 1986Downton et al 1984) few comparative studies have been conducted across contrasting habitats or climates (but see Smillie and Nott 1979;Berry and Bjorkman 1980). As a result, the question still remains whether there is a correlation between photosynthetic thermotolerance and the temperature regime within a species' distribution.…”

Temperature Dependence of Photosynthetic Activities in Wheat Seedlings Grown in the Presence of BASF 13.338 (4-Chloro-5-Dimethylamino-2-Phenyl-3(2H)Pyridazinone)

“…Changes in the fluorescence yield of Chl a provide a sensitive indicator of changes in the physical state of the thylakoid membranes, and heat induced changes in the physical state of the thyalkoid membrane can be detected by monitoring the Chl a fluorescence temperature profile (23)(24)(25). In the Chl a fluorescence-temperature profile, at a given temperature, there is a sharp increase in the fluorescence yield and it has been shown that the acclimation ofphotosynthetic apparatus to different growth temperatures is reflected in the change of the temperature at which Chl a fluorescence rises (26,27).…”

Mutants of barley heat-sensitive for chloroplast development

“…This heat-induced rise in chlorophyll fluorescence can be measured in intact leaves and provides a means of ranking plants according to their heat sensitivity (14,18). Figure 8 shows fluorescence-heating curves for ts57 and wild type.…”