Nitrogen metabolism in harvested asparagus: No difference between light and dark storage at 20°C

Abstract

To extend our knowledge of nitrogen metabolism in asparagus after harvest we monitored protein, amino acid and ammonia levels and glutamine synthetase activity in tip sections (0–30 mm) of asparagus spears ( Asparagus officinalis L. cv. Limbras 10) stored for up to 48 h in continuous light or dark at 20°C. The patterns of change in light and dark were almost identical. Total protein content increased by 20% 12 h after harvest, before declining to harvest levels by 48 h. Ammonia increased slightly by 48 h. Glutamine synthetase activity increased 10–15% by 18 h then declined to 90% of harvest activity by 48 h. Glutamic acid and glutamine were the most abundant amino acids at harvest, accounting for 42% of the pool. Glutamine and proline levels fell rapidly. By 48 h most amino acids had increased substantially, with asparagine accounting for 28% of the pool. Glutamine levels fell steadily during storage, irrespective of the regime. Our results suggest that postharvest nitrogen metabolism in asparagus spear tips is not modulated by light.