Radiation‐induced improvement of the freeze‐resistance of a cold‐sensitive wheat variety: Freeze‐tolerance and fatty acid patterns

Abstract

Effects of 3–15 krad 60Co gamma radiation on cereal seeds were investigated with regard to the frost hardiness of leaves of 5–7‐day‐old seedlings. Comparative studies were carried out on the gas‐chromatographically determined distribution patterns of fatty acids in different pools (total fatty acid, total lipid, polar lipids) of a cold‐resistant (cv. Mironowskaya 808) and a cold‐sensitive (cv. Penjamo 62) cultivar of wheat (Triticum aestivum L.). Parallelism between fatty acid distribution pattern, empirical parameters suggested for quantitative measures of cold tolerance (the ratio unsat/sat and double‐bond index), and the low‐temperature behaviour of shoots grown from radiation treated seeds of ‘Penjamo 62’, was also examined. To monitor differences in the fatty acid syntheses of ‘Mironowskaya 808’and ‘Penjamo 62’, and to demonstrate radiation‐induced changes in fatty acid turnover a [1–14C]‐acetate incorporation technique was employed. The results of practical importance are: 1. A significant improvement in the frost‐resistance of the cold‐sensitive ‘Penjamo 62’variety could be achieved with 6–9 krad irradiation, the half‐freeze‐killing temperature dropping from −6 to about −18°C. 2. Freeze‐hardiness, no matter whether inherited or gained, could be abolished by gamma irradiation with higher dose. The following conclusions of theoretical interest can be drawn: 1. Low‐temperature behaviour of plant tissues is a dynamic property rather than a static one, not only the formation but also the breakdown of certain hydrocarbon chains may be of paramount relevance in cold‐tolerance. 2. Not the linolenic (18:3) component, but rather the overall distribution pattern of the C18 family seems to correlate with low‐temperature‐responses of shoots. 3. Empirical parameters investigated do not provide reliable quantitative measures of the susceptibility to freeze (and cold‐) injuries. 4. Changes in the syntheses of some key proteins (e.g. peroxidase, water‐soluble proteins, etc.) may also be important in adaptation to low‐temperature conditions.