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 holosericeaA. Cunn. ex G. Don. Experiments were
conducted using a Cu2+ pulse (5 h, 2.2 mM)andaCu2+ 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
examinedover21daysbylightandtransmissionelectronmicroscopy.Xylem
vesselsofstemsstoodintoDIWwereoccludedwithgelssecretedintovessel
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
parenchymacells,therebyinhibitinggelsecretionandmaintainingthevessel
lumens devoid of occlusions. The Cu2+ treatments significantly improved
wateruptakebythecutstems ascomparedto thecontrol.
