ISHS Acta Horticulturae 464: International Postharvest Science Conference Postharvest 96
CELLULAR PHYSIOLOGY OF TEXTURAL CHANGE IN HARVESTED ASPARAGUS |
| Authors: | J.A. Heyes, V.M. Burton, L.A. de Vré |
| Abstract:
Asparagus spears were harvested and stored at 20°C either dry, standing in water or wrapped in perforated plastic bags. Water loss from dry-stored spears led to a rapid loss of rigidity as measured by a three-point bend technique. Standing spears in water increased spear rigidity but promoted stem rots. The textural impact of tip breakdown, a senescence disorder, was restricted to the tip itself. A tensile ring technique measured the cohesive properties of outer spear tissue 10 cm back from the tip. There was an increase in tissue strength in this region after harvest except when spears were stored standing in water. This may result from cell shrinkage rather than cell wall toughening. Detailed psychrometry of the tissues in the asparagus tip, when spears were stored in perforated bags, showed that bracts lost turgor within 48 h. Axillary buds and the central meristem retained turgor for over 96 h. Tissue water potential and solute potential fell in all tissues approximately linearly after harvest. Slight recovery of turgor in some tissues after 72 h may have resulted from accumulation of osmotically-active solutes such as asparagine. Immunolocalisation of the plasma membrane H+-ATPase in tissues after harvest confirmed that this activity was retained in vascular tissue. This activity may energise solute loading into the phloem for export from the tip. Water stress may prevent significant export, despite this loading. Attempts to determine turgor at the cellular level with a pressure probe were unsuccessful. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
