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

Abstract

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...

Chilling resistance of somatic hybrids of tomato and potato

“…The tomato variety used in these experiments is not the one used to produce the hybrids, as the mutant yellow green tomato parent is light-sensitive and was not available at the time of the experiments as comparable plants growing in the glass-house. The time course for changes in photosynthetic electron transfer activity at 0 ~ C in the hybrid variety Supravite is similar to other varieties of L. esculentum previously examined (14).…”

“…In intact leaves, these changes in photosynthetic electron transfer activity induced by severe chilling at 0 ~ C can be followed by monitoring light-induced changed in cytochrome f oxidation and reduction (14), absorbance changes at 518 rim, or chlorophyll fluorescence (R. M. SMmLm, unpublished experiments).…”

A photosystem I mutant in barley (Hordeum vulgare L.)

“…Photooxidation of cytochrome f in the intact leaf was measured as a decrease in absorbance at 554 nm (34,39). Cytochrome f is situated between the two photosystems.…”

“…The photooxidation of cytochrome f upon illumination of a segment of an intact leaf was measured as described previously (39). The spectrophotometer was operated in the dual wave-length mode and the changes upon illumination of the absorbance at 554 nm and 541 nm were measured (2).…”

Stress Tolerance and Stress-Induced Injury in Crop Plants Measured by Chlorophyll Fluorescence In Vivo

“…Leaves of the chilling-sensitive plant bean rapidly lost Hill activity when stored at 0°C (16 the extent of the decrease in Hill activity in chloroplasts isolated from chilled leaves of different species of tomato (27) and passionfruit (23) is related to plant chilling tolerance. Inasmuch as the inhibition develops on the photooxidizing side of PSII (16,27), which therefore results in a decrease in the yield of the induced Chl fluorescence (17), it should be feasible to use measurements of Chl fluorescence to follow the time course of chilling injury and determine the relative susceptibility of different species to chilling.…”