ISHS Acta Horticulturae 415: VIII International Asparagus Symposium
MALATE ACCUMULATES IN TIPS OF HARVESTED ASPARAGUS SPEARS |
| Authors: | P.L. Hurst, D.E. Irving, P.J. Hannan |
| Abstract:
Freshly harvested asparagus spears held at ambient temperatures rapidly lose soluble carbohydrates from their tips. The key enzymes of the glyoxylate cycle, malate synthase (EC 4.1.3.2) and isocitrate lyase (EC 4.1.3.1), appear in some carbohydrate-starved and senescing plant tissues concurrent with the mobilisation of lipids and a decline in the respiratory quotient. To see if these events occur in harvested asparagus (Asparagus officinalis L.), we measured total lipid levels, respiratory quotients, and malate synthase and isocitrate lyase activities in 3 cm tip sections of whole asparagus spears stored at 20°C for up to 5 days. Within 24 h, the respiratory quotient dropped from near 1 to 0.65 before stabilising around 0.75 after 2 days. Over 5 days, nearly half of the total lipid in spear tips was lost. Malate synthase activity, which was absent at harvest, appeared after 1–2 days and continued to increase throughout the remainder of the storage period. Malate accumulated in the tips concurrently and reached 3- to 4-fold the harvest concentration by 4–5 days of storage. Isocitrate lyase activity was not detected at any time during the storage period. | |
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