Cu2+ inhibition of gel secretion in the xylem and its potential implications for water uptake of cut Acacia holosericea stems.
Maintaining a high rate of water uptake is crucial for maximum longevity of cut stems. Physiological gel/tylosis formation decreases water transport efficiency in the xylem. The primary mechanism of action for post-harvest Cu(2+) treatments in improving cut flower and foliage longevity has been elusive. The effect of Cu(2+) on wound-induced xylem vessel occlusion was investigated for Acacia holosericea A. Cunn. ex G. Don. Experiments were conducted using a Cu(2+) pulse (5 h, 2.2 mM) and a Cu(2+) vase solution (0.5 mM) vs a deionized water (DIW) control. Development of xylem blockage in the stem-end region 10 mm proximal to the wounded stem surface was examined over 21 days by light and transmission electron microscopy. Xylem vessels of stems stood into DIW were occluded with gels secreted into vessel lumens via pits from surrounding axial parenchyma cells. Gel secretion was initiated within 1-2 days post-wounding and gels were detected in the xylem from day 3. In contrast, Cu(2+) treatments disrupted the surrounding parenchyma cells, thereby inhibiting gel secretion and maintaining the vessel lumens devoid of occlusions. The Cu(2+) treatments significantly improved water uptake by the cut stems as compared to the control.
The University of Queensland, School of Agriculture and Food Sciences, Gatton, QLD, 4343, Australia. kamani.ratnayake@uqconnect.edu.au
Kamani
K
Ratnayake
Daryl C
DC
Joyce
Richard I
RI
Webb
D000045:Acacia / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D018533:Biomass; D003300:Copper / Q000633:toxicity*; D005782:Gels / Q000378:metabolism*; D018547:Plant Stems / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D014867:Water / Q000502:physiology*; D052584:Xylem / Q000166:cytology / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure
D005782:Gels; D014867:Water; D003300:Copper