Effects of light, temperature and nitrogen treatments upon the fatty acid composition of galactolipids of young and older leaves from winter rape plants

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Abstract
The influences of light (1.5 W m−2, 24 W m−2), temperature (5°C, 15°C, 25°C) and nitrogen nutrition (1 mmol 1−1 NH4NO3, 2 mmol 1−1 NH4NO3, 8 mmol 1−1 NH4NO3) treatments on the fatty acid composition of galactolipids from young and older leaves of oil‐seed rape (Brassica napus L. var oleifera cv. Quinta) were tested. The linolenic acid (18:3) content of lipids from young leaves was mainly affected by light and temperature. However, older leaves reacted in the first instance on nitrogen and light. For young leaves a significant light/temperature interaction was obvious. The highest level of 18:3 (72%) was observed at 5°C/1.5 W m−2. Changes in the fatty acid composition in older leaves indicated a retarded senescence by an increased nitrogen‐supply. The 8 mmol 1−1 NH4NO3/24 W m−2 treatment resulted in the highest percentages of unsaturated fatty acids. The results are discussed in relation to the importance of the first‐order interaction of environmental factors to the galactolipid fatty acid composition. Additionally, the relevance of leaf‐age has been stressed.