Abstract:
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
Cu2+ treatments in improving cut flower and foliage longevity has been
elusive. The effect of Cu2+ on wound-induced xylem vessel occlusion was
investigated for Acacia holosericea A. Cunn. ex G. Don. Experiments were
conducted using a Cu2+ pulse (5 h, 2.2 mM) and a Cu2+ 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, Cu2+ treatments disrupted the surrounding
parenchyma cells, thereby inhibiting gel secretion and maintaining the vessel
lumens devoid of occlusions. The Cu2+ treatments significantly improved
water uptake by the cut stems as compared to the control.
