Abstract:
Early desiccation limits the vase life of Acacia cut flowers and foliage and may be attributable to poor hydraulic
conductivity (Kh) of the cut stems. Acacia holosericea A.Cunn. ex G.Don has been adopted as the test species to investigate
the postharvest water relations of the genus Acacia. To understand potential constraints on Kh, xylem conduits in cut
A. holosericea stems were anatomically characterised by light and scanning and transmission electron microscopy. Vessels
with simple perforation plates and tracheids were the principal water conducting cells. Bordered vestured intervessel pits
were present in xylem vessel elements. The majority of conduits (89%) were short at 1–5 cm long. Only 2% were 15–16 cm in
length. Mean xylem conduit diameter was 77 0.9 mm and the diameter profile showed a normal distribution, with 29% of
diameters in the range of 70–80 mm. Simple perforation plates can offer relatively low resistance to water flow. On the other
hand, bordered vestured pits and short xylem conduits can confer comparatively high resistance to water flow. Overall, the
presence of bordered vestured pits, together with a high proportion of short xylem conduits and high stomatal densities
(232 2 mm–2
) on unifacial phyllodes, could contribute to early dehydration of A. holosericea cut foliage stems standing in
vase water. Further research will relate these anatomical features with changes in Kh and transpiration of cut foliage stems.
