Increase in Linolenic Acid Is Not a Prerequisite for Development of Freezing Tolerance in Wheat

Abstract

Seedlings of winter wheat ( Tnticum aestivum L. cv. Kharkov) were acclimated at 2 C in the dark in the presence of two inhibitors of linolenic acid synthesis, 4-chloro-5(dimethylamino)2-phenyl-3(2H)pyridazinone-(BASF 13-338) and 4-chloro-5(dimethylamino)-2(a,a,a-trifluoro-m-tolyl)-3(2H)pyridazinone (Sandoz 6706). Although the increase in the proportion of linolenic acid generally observed at low temperature was completely inhibited, the development of freezing tolerance was unaffected. These results demonstrated that an enrichment in linolenic acid is not a prerequisite for low temperature acclimation. Willemot (16) observed that when wheat plants were pretreated with an inhibitor of linolenic acid synthesis (BASF 13-338)2 prior to cold acclimation, both the accumulation of linolenic acid and the development of freezing tolerance were completely inhibited. He concluded that low temperature stimulation of linolenic acid synthesis was a necessary prerequisite to the development of freezing resistance even though it was not the factor responsible for the difference in tolerance observed among the various strains of wheat studied previously (3, 17). Willemot (16) also found that BASF 13-338 inhibited the increases in both dry weight and phospholipid content generally associated with low temperature hardening (13). This observation, coupled with the considerable evidence (6, 11) demonstrating that pyridazinone herbicides inhibit chloroplast function, may be an indication that a reduced level of photosynthetic carbon, and not the inhibition of linolenic acid synthesis, is the causal factor inhibiting cold hardening. The

Correlation between Cold- and Drought-Induced Frost Hardiness in Winter Wheat and Rye Varieties

“…Samples were seeded with ice crystals at -3°C to avoid supercooling. Frozen samples were thawed at 2°C for 1 h. Survival of shoots or of excised epicotyls was then assessed by the following methods: (a) vital staining with neutral red followed by observation of protoplasmic streaming; (b) detection of ability to plasmolyze and deplasmolyze in salt solution (6); (c) greening in White's solution (13) + 1% Agar-Agar after 2 days at room temperature or in White's solution + 0.2% sucrose after 2 weeks at 2°C (epicotyls developing into a leaf); (d) measuring the relative release of amino acids (10) and; (e) manually evaluating the relative turgidity (personal assessment on a scale of 1-10). All assessments were performed in duplicate.…”

Chemical and Biophysical Changes in the Plasma Membrane during Cold Acclimation of Mulberry Bark Cells (Morus bombycis Koidz. cv Goroji)

“…However, no preferential increase in phospholipid unsaturation could be detected in black locust (17) and poplar (29) which are both extreme cold hardy species. These findings have led to the conclusion that membrane unsaturation or fluidity is not related to the development of cold hardiness (6,14,17).…”

“…However, no preferential increase in phospholipid unsaturation could be detected in black locust (17) and poplar (29) which are both extreme cold hardy species. These findings have led to the conclusion that membrane unsaturation or fluidity is not related to the development of cold hardiness (6,14,17).In many of the studies relating lipid unsaturation to hardiness, total lipids were investigated rather than the plasma membrane which is considered to be the primary site of injury. This has been primarily due to the lack of methods to isolate sufficient quantities of pure plasma membrane from plant tissues.…”

“…Many plants capable of cold hardening exhibit an increase in lipid unsaturation (24) and an increased level of phospholipids during hardening (6,16,17,23,26,29). This has led to the speculation that the enhanced fluidity of the membrane by lipid unsaturation is related to cold hardiness.…”

Spin-label Studies of Membranes in Rye Protoplasts during Extracellular Freezing

“…Unsaturation of the phospholipid fatty acids in the membranes might be important in increased membrane tolerance to freezing, but recent evidence indicates that this is probably not the case (3,5,18,22,24).…”