FREEZING TOLERANCE AND BIOCHEMICAL-CHANGES IN WHEAT SHOOTS AS AFFECTED BY H2S FUMIGATION

Fumigation of winter wheat with H2S during low temperature acclimation substantially reduced the development of freezing tolerance of the leaves. After 6 weeks of low temperature exposure (3-degrees-C), the freezing tolerance was increased by 6 and 2-degrees-C at 0 and 0.25-mu-l l-1 H2S, respectively. Changes in levels of cellular constituents (c. g. amino acids, sugars), which are characteristic for an increased freezing tolerance, were much less pronounced upon H2S fumigation. Besides, H2S fumigation diminished shoot growth at low temperature. At 20-degrees-C, H2S fumigation did not affect both freezing tolerance of the leaves and shoot growth. The role of glutathione in the development of freezing tolerance was evaluated. Low temperature exposure resulted in a rapid increase in the water-soluble non-protein-sulfhydryl content (mainly glutathione) of the leaves: it was maximal after 3 days of exposure (two-fold). Fumigation of wheat with 0.25-mu-l l-1 H2S during low temperature exposure resulted in a further increase (up to six-fold) in the sulfhydryl content.