Electrolyte Leakage Induced by Chilling in Passiflora Species Tolerant to Different Climates

104

An inhibitor of catalase accumulated when leaves of chilling-sensitive species were stored in the dark at 0°C. The inhibitor could be removed from crude extracts by passing them through a column of Sephadex G-25. After this treatment, the catalase activity of extracts of chilled tissues was found to be equal to that of extracts from unchilled leaves. When chilled tissues were incubated at 20°C, the inhibitor of catalase was lost, unless the tissues had been irreversibly damaged. It specifically inhibited plant catalase, and had no effect on mammalian catalase, plant malic dehydrogenase, or plant superoxide dismutase.Despite the presence of catalase inhibitor in extracts of chilled plants, no increase in the level of H202 in chilled tissues was found, suggesting either that the inhibitor is compartmentalized and not in contact with catalase in vivo, or that the level of H202 is controlled by means other than through catalase activity. Plant tissues normally contain H202 which is destroyed by catalase when they are damaged. After chilling, H202 leaking from already injured cells would not be so readily removed by the inhibited catalase, and could contribute to further injury by acting as a source of free radical oxidants.

Section: Resultsmentioning

confidence: 94%

An Inhibitor of Catalase Induced by Cold in Chilling-Sensitive Plants

Patterson¹,

Payne²,

Chen³

et al. 1984

104

“…A great deal of evidence has been accumulated to support this hypothesis (16,17). In addition, membranes may lose some of their semipermeability at temperatures below the phase transition point and become leaky (14,15).…”

Section: Discussionmentioning

confidence: 99%

Effects of Low Temperature on Respiration and Uptake of Rubidium Ions by Excised Barley and Corn Roots

Carey¹

1978

whe effect of temperature upon ion uptake and respiration was investigated with excised roots ofcorn ( Ze mays) and barley ( Horden_ vgae).A strong Iibition (Qlo -5 to 8) of ion uptake was observed at temperatures below 10 C. At It is well known that low soil temperatures may affect plant growth and that there are great differences among species in their tolerance of low soil temperature (2,(6)(7)(8)13 (approximately 0.07 ,uCi/,umol). This concentration of Rb was assumed to be rate-saturating for the low concentration isotherm mechanism (4). Separate samples of excised roots with a fresh wt of 200 to 300 mg in a "tea bag" (5) were conditioned for 20 min in a 0.5 mM CaSO4 solution at the measurement temperature. The "tea bags" were then transferred into 300 ml of labeled solution at the appropriate temperature for either 20 min below 15 C or 10 min above 15 C.After the uptake period, any 'Rb present in the readily exchangeable "free spaces" of the roots was removed by desorption in 0.05 mM RbNO3 and 0.5 mm CaSO4 at 0 C for I min and 30 min at 25 C. The 'Rb retained by the roots was determined by immersing the roots in 10 ml of liquid scintillation fluid (Toluene, Triton X100, Omnifluor, water, 1000:500:6.66:166) (Fig. 1). The data for ion uptake when graphed as an Arrhenius plot (Fig. 2)

“…Liebermann et aL (7) found 5 times as much potassium leakage from sweet potato roots after 10 weeks storage at chilling temperatures. There was also enhanced leakage of electrolytes from leaf tissue (3,11,19) and fruit tissue (16) at chilling temperatures. The results of Tatsumi and Murata (16) showed that fruit pitting, a symptom of chilling injury, was visible after 5 days whereas leakage did not increase until the 7th day.…”

mentioning

confidence: 99%

Temperature-Induced Leakage from Chilling-Sensitive and Chilling-Resistant Plants

Paull

1981

Leakage rates were determined from leaf cells loaded with rubidium and I'Hlleucine. There was a differential response between leucine and rubidium leakage depending upon the species used. The rate of leucine leakage shows a small decline below 5 C for two altitudinal variants of Lycopersicon hirsutum Humb. and Bonpl., whereas Lycopersicon escudentum L. showed a marked increase below 5 C. Rubidium showed a marked increase in leakage rate below 10 C with the altitudinal variants, with only a slight increase for the L escuientum species. A rough relationship existed between rubidium leakage rate at 1 C and the altitude of origin of the L hirsutum race, the low altitudinal forms having higher leakage rates than the higher altitudinal variants. The L esculentum lines show a rubidium leakage response similar to that of the high altitude L. hirsutum variants. Higher leakage rates were obtained if the calcium concentration in the medium was less than 1 millimolar and upon addition of metabolic poisons and detergents.The results are consistent with the view that chilling injury causes changes in the membrane and that cell leakage is an early symptom of this change in some species. Some chilling-sensitive species have increased leakage within 1 hour of exposure to chilling temperature.Changes in the physical state of membranes at chilling temperatures are thought to be responsible for the increased leakage of cell electrolytes from the tissue of chilling-sensitive plants (8,9). Liebermann et aL (7) found 5 times as much potassium leakage from sweet potato roots after 10 weeks storage at chilling temperatures. There was also enhanced leakage of electrolytes from leaf tissue (3,11,19) and fruit tissue (16) at chilling temperatures. The results of Tatsumi and Murata (16) showed that fruit pitting, a symptom of chilling injury, was visible after 5 days whereas leakage did not increase until the 7th day. This indicated that the injury was localized and the assay not sensitive enough to detect the earlier leakage changes that were visually apparent. Using narrow (1 x 3 mm) leaf strips which would avoid this problem, Patterson et al. (11) found two phases of ion leakage at 0 C: a relatively slow initial phase, followed by a rapid loss of most of the electrolyte. In the most chilling-sensitive Passiflora species used, the two phases could not be separated.