Effects of Growth Temperature on the Thermal Stability of the Photosynthetic Apparatus of Atriplex lentiformis (Torr.) Wats.

Abstract

High growth temperatures induced a substantial increase in the thermal stability of the photosynthetic apparatus of Atriplex lentiformis. shrub that occurs in the hot interior deserts of California and possesses the C4 pathway of photosynthesis. Previous experiments in both the field and laboratory have shown that growth temperature has a substantial effect on the photosynthetic performance of these plants (19)(20)(21). Growth at high temperatures resulted in a substantially greater photosynthetic temperature optimum, increased rates of CO2 uptake at high temperatures, but decreased rates at low temperatures as compared to the responses of low temperature-grown plants. Differences in photosynthetic performance at low temperatures appear to be related principally to changes in RuDP carboxylase activity in the leaves (20). In this paper, we show that an important factor leading to a higher temperature optimum for CO2 uptake and the ability to maintain high CO2 uptake rates at high temperatures is an increase in the thermal stability of the photosynthetic apparatus of the high temperature-grown plants as compared to that of low temperature-grown plants, and we report studies of the physiological basis of this increased tolerance to high temperatures.The high summer temperatures of some deserts, which can often exceed 40 C and may reach 50 C or higher, can impose a severe constraint upon plant growth and productivity, even when adequate water is available. These temperatures are well above the thermal optimum for CO2 uptake for temperate zone plants as well as species predominantly active during the cooler seasons in the desert (3,8). It is becoming evident, however, that at least some summer active desert species have physiological adaptations that allow for high rates of CO2 uptake at high temperatures (7,21). For example, Tidestromia oblongifolia has a thermal optimum for CO2 uptake which exceeds 40 C. This species, however, is not capable of growth at cool temperatures and is not photosynthetically active during the mild spring and winter months (5).In contrast to species predominantly active during one season, evergreen desert species that are active throughout the year must possess a broad thermal tolerance or must be capable of acclimation to the seasonal changes in the temperature regime. Recent experiments have shown that many desert species that are active under seasonally variable temperatures possess a capacity to acclimate to the prevailing temperature regime (8, 16). Despite these observations, however, there is little in the literature concerning the mechanisms underlying temperature acclimation, particularly those involved in high temperature responses.Atriplex lentiformis (Torr.) Wats. is a phreatophytic evergreen

Chlorophyll fluorescence photography to detect mutants, chilling injury and heat stress

“…Heating of leaves can effect changes in the photosynthetic system that result in altered kinetics of light-indueed chlorophyll fluorescence (10,21,27). The variable fluorescence component, Fv, decreases as the electron transfer system becomes heat inactivated and there is an increase in Fo-fluorescence, the fluorescence rise taking place within the first nanosecond of illumination, as energy transfer from chlorophyll to the active centers is prevented.…”

“…The variable fluorescence component, Fv, decreases as the electron transfer system becomes heat inactivated and there is an increase in Fo-fluorescence, the fluorescence rise taking place within the first nanosecond of illumination, as energy transfer from chlorophyll to the active centers is prevented. This increase in Fo-fluorescence has been used to follow the onset of heat injury in plants and to rank plants for relative heat tolerance (21,23,31). Thus the heat-induced change in Fofluorescence generally is seen to occur at lower temperatures in arctic and cool temperate species than in tropical species (31).…”

“…Two areas in particular have benefitted from the development of practical measurements and screening procedures based on chlorophyll fluorescence. Firstly, the detection of photosynthetic mutants (1,11,15,26,32) and secondly, monitoring the development of injury to plant cells resulting from an applied stress including chilling (12,28), freezing (13,19), high temperatures (21,23,27,31), water (33) or oxygen (24) deficits, and ozone toxicity (25).…”

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)

“…An increased thermostability of the water splitting system in Atriplex lentiformis grown at high temperature has been reported earlier (19,20). Both in the case ofA.…”

Growth Temperature-Induced Alterations in the Thermotropic Properties of Nerium oleander Membrane Lipids

“…The temperature optimum for photosynthesis is between 35 and 40°C for plants grown in a 45°C/32°C (day/night) regime and between 25 prevailing temperature is probably an important adaptive mechanism for this and other desert evergreen species, such as Larrea divaricata (9) and A triplex lentiformis (12), which experience large seasonal differences in environmental temperature. The variation in fatty acid composition ofA.…”