Effect of Light and Chilling Temperatures on Chilling-sensitive and Chilling-resistant Plants. Pretreatment of Cucumber and Spinach Thylakoids <i>in Vivo</i> and <i>in Vitro</i>

Tomato leaves were detached and stored at 0 C for various periods of time. Chloroplasts were isolated from the leaves and their photoreductive activities were determined. Comparisons were made between two altitudinal forms of the wild tomato Lycopersicon hirsutum Humb. and Bonpl. (a tropical lowlands form and a highlands form adapted to growth at 3,100 meters), and two cultivars of the domestic tomato L. esculentum Mill. In each case the capacity of the isolated chloroplasts to photoreduce ferricyanide declined linearly with time of storage of the leaves at 0 C, but not at 10 C. This injury developed more slowly in the high altitudinal form of the wild tomato compared with the low altitudinal form and the two domestic cultivars indicating an enhanced resistance toward chilling injury in the tomato from 3,100 meters. Chioroplast activity declined in green tomato fruit held at 0 C, at about the same rate as in the chilled leaves.Measurements of photochemical activities in the isolated chloroplasts and in vivo measurements of cytochrome-554 photooxidation in chilled leaves showed that the site of action of the chilling effect was water donation to photosystem II.The chilling-induced impairment of photoreductive activity in chioroplasts provides a useful assay for detecting and measuring differences in the susceptibility of plants to chilling injury.Plant physiological studies of chilling resistance in plants, as well as the breeding and selection of varieties with enhanced cold tolerance, are hampered by the lack of assays which can detect and measure chilling-induced cellular changes well before obvious tissue damage occurs. Cellular membranes appear to be especially sensitive to chilling temperatures (6) and indeed the membranelocalized Hill reaction activity of chloroplasts declines rapidly in chilled leaves of chilling-sensitive plants (3,5,7,8). This suggests the possibility of using measurements of Hill activity to detect early changes caused by chilling and to measure differences in resistance to chilling injury in closely related species.Tomatoes, in common with most plants of tropical origin, are damaged by prolonged exposure to chilling temperatures. All stages of the plant's development are affected by chilling temperatures, including germination, growth, and fruit set (4). The harvested fruit are also susceptible to chilling injury and low temperatures can disrupt the normal ripening process. We have examined changes in the photoreductive activity of chloroplasts isolated from chilled, detached leaves of two cultivars of the domestic tomato, Lycopersicon esculentum, and high and low altitudinal forms of the wild tomato, L. hirsutum. In all cases activities declined linearly with the time that the leaves were exposed to a chilling temperature of 0 C. There was a clear distinction between the rate of decline in the high and low altitudinal forms of the wild tomato indicating a considerable adaptation to low temperature. A chilling-induced decline in photoreductive activity also took place in green...

Section: Resultsmentioning

confidence: 74%

Section: Cultivarsmentioning

confidence: 99%

mentioning

confidence: 99%

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Assay of Chilling Injury in Wild and Domestic Tomatoes Based on Photosystem Activity of the Chilled Leaves

Smillie¹,

Nott²

1979

“…1) showing a critical temperature between 10°and 150, mean 12°C. These critical temperatures are typical ofchillingsensitive tropical plants, such as cucumber (2,4). Chilling at a moderate PFD for 2 h, as distinct from chilling for up to 20 h (12) does not affect photosynthesis in chilling-insensitive plants (2,4).…”

Section: Discussionmentioning

confidence: 99%

Sensitivity of Altitudinal Ecotypes of the Wild Tomato Lycopersicon hirsutum to Chilling Injury

Raison

Brown²

1989

The transition temperature of the leaf polar lipids and the critical temperature for chill-induced inhibition of photosynthesis was determined for three altitudinal ecotypes of the wild tomato Lycopersicon hirsutum. Photosynthesis was measured as C02-dependent 02 evolution at 25°C after leaf slices were exposed to chilling temperatures for 2 hours at a moderate photon flux density of 450 micromoles per square meter per second. The transition temperature of the leaf polar lipids was detected from the change in the temperature coefficient of the fluorescence intensity of trans-parinaric acid. Chill-induced photoinhibition was evident in the three tomato ecotypes when they were chilled below a critical temperature of 100, 110, and 130C, respectively, for the high (LA1777), mid (LA1625), and low (LA1361) altitudinal ecotypes. The temperature differential, below the critical temperature, required to produce a 50% inhibition was also similar for the three ecotypes. A transition was detected in the leaf polar lipids of these plants at a temperature similar to that of the critical temperature for photoinhibition. The results show that the three tomato ecotypes are similar with respect to their critical temperature for chilling-induced photoinhibition and the rate of their response to the chilling stress. They are, thus, similarly sensitive to chilling.Altitudinal ecotypes of the wild tomato Lycopersicon hirsutum have been used extensively in comparative studies of the susceptibility ofplants to chilling (1,10,12,18 It is important to note that in the terminology adopted here a distinction is being made between the terms 'sensitivity' to chilling and 'response' to a chilling stress. The basis for the distinction is that described by Raison and Lyons (15). For tropical plants that are sensitive to chilling there is usually a critical temperature below which injury develops and this can vary from about 70 to 1 5C depending on the species (7, 13). For plants with a critical temperature near 15°C and chilled at 0°C the chilling stress, determined as the temperature differential below the critical temperature, will be greater than that for plants with a critical temperature near 7°C. The term response is used in relation to the time or rate of symptom development. For any plant this will depend on the chilling stress (1), the type of tissue (19), its metabolic state prior to chilling (9), the time in a day/night cycle when chilling commences, the chilling temperature (9), and a number of environmental factors such as humidity (20). From the available data, it is not clear whether the tomato ecotypes adapted to the lower temperatures at high elevation are less sensitive to chilling, i.e. have a lower critical temperature, or are more resistant to the stress and thus show a slower response.Differences have been noted in both the response and sensitivity of photosynthetic reactions of plants to chilling for a few hours at a moderate PFD of less than 500 ,umol m-2 s-' (2, 4). For plants sensitive to chilling, such as olea...

“…Furthermore, specific effects have been reported such as an inactivation of photophosphorylation (9,14). There is also a possibility that certain protective responses may not be fully effective at low leaf temperatures.…”

mentioning

confidence: 99%

Zeaxanthin Synthesis, Energy Dissipation, and Photoprotection of Photosystem II at Chilling Temperatures

Adams¹,

Winter²,

Krüger³

et al. 1989

When leaves of a mangrove, Rhizophora mangle, were exposed to an excess of light at chilling temperatures, synthesis of zeaxanthin through violaxanthin de-epoxidation as well as nonphotochemical fluorescence quenching were markedly reduced. The results suggest a protective role of energy dissipation against the adverse effects of high light and chilling temperatures: leaves of R. mangle that had been preilluminated in 2% 02, 0% CO2 at low photon flux density and showed a high level of zeaxanthin, and leaves that had been kept in the dark and contained no zeaxanthin, were both exposed to high light and chilling temperatures (50C leaf temperature) in air and then held under control conditions in low light in air at 250C. Measurements of chlorophyll a fluorescence at room temperature showed that the photochemical efficiency of PSII and the yield of maximum fluorescence of the preilluminated leaf recovered completely within 1 to 3 hours under the control conditions. In contrast, the fluorescence responses of the predarkened leaf in high light at 5°C did not recover at all. During a dark/light transient in 2% 02, 0% CO2 in low light at 50C, nonphotochemical fluorescence quenching increased linearly with an increase in the zeaxanthin content in leaves of R. mangle. In soybean (Glycine max) leaves, which contained a background level of zeaxanthin in the dark, a similar treatment with excess light induced a level of nonphotochemical fluorescence quenching that was not paralleled by an increase in the zeaxanthin content.Exposure of many plants to temperatures in the chilling range (0-12C) increases the sensitivity of PSII to photoinhibition (1,10,(23)(24)(25) the formation of zeaxanthin and the development of nonphotochemical fluorescence quenching are much slower at 5°C than at 20°C. Leaves were pretreated to contain either high or low levels of zeaxanthin and were then subjected to a combination of high light and chilling temperatures. The experiments show that leaves which contain high zeaxanthin levels and which are in a low fluorescence state exhibit a decreased sensitivity to sustained reductions in the photochemical efficiency ofPSII. Furthermore, the decreased rapidity of the development of fluorescence quenching at 5°C is used to separate two components of fluorescence quenching with different induction kinetics. MATERIALS AND METHODSPlant material, growth conditions, analysis of pigments as well as continuous recording of Chl a fluorescence with a pulse amplitude modulation fluorometer (26) in leaves were as described earlier (6), with the exception that soybean (Glycine max) plants were taken straight from the growth cabinet. To determine fluorescence in the light, leaves were sealed into a gas exchange chamber in darkness and leaf temperature was either kept at 20°C or was brought to 5°C within 15 to 20 min. The dew points of the incoming gas streams (2% 02,0% C02) were 15 and 0C, respectively. After 25 min at 20C or 5 min at 5°C leaf temperature in the dark, the (control) fluorescence yield was dete...