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Xylem plugging and postharvest longevity of cut Acacia holosericea

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Ratnayake, K., Joyce, D. C. and Webb, R. I. (2015) Xylem plugging and postharvest longevity of cut Acacia holosericea. Acta Horticulturae, 1104 . pp. 287-293.

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Article Link: http://dx.doi.org/10.17660/ActaHortic.2015.1104.44


An inherently short vase life is a problematic characteristic of cut flowers and foliage for otherwise attractive native Australian Acacia spp. Reasons underlying the poor postharvest water uptake of cut acacia stems have been elusive. A. holosericea was used to investigate possible bacteria-induced and wound-induced xylem occlusion. The effects of bacterial-and wound-induced xylem blockage on water uptake were investigated by light and scanning and transmission electron microscopy. Observations were made on cut stems that stood into either deionised water (DIW; control) or 0.5 mM Cu2+ solution and on stems pulsed with 2.2 mM Cu2+ solution and then stood into DIW. The stem-end region of cut A. holosericea that stood into DIW or Cu2+ solution became covered with bacterial growth after 3 days. Regardless of the bacterial biofilm, the Cu2+ treated stems had improved water relations and vase life. Therefore, the biofilm had little or no effect on cut A. holosericea longevity. Further observations revealed presence of a vessel-occluding substance (gel) originating from axial parenchyma cells in direct physical contact with xylem vessels. The gel exuded into vessel lumens through pit membranes, evidently as a wound-response. Xylem occlusion by gels in A. holosericea may be especially problematic due to an abundance of secretory contact cells relative to xylem elements. Nonetheless, active wound response processes may be the key determinant of short postharvest longevity for this and possibly other cut Acacia spp. Cu2+ treatments, however, disrupted the secretory function of axial parenchyma cells thereby preventing vessel occlusion by the gels.

Item Type:Article
Business groups:Horticulture and Forestry Science
Keywords:Acacia Copper Cut Foliage Electron Microscopy Gel Vase Life Water uptake
Subjects:Science > Botany > Plant physiology
Agriculture > Agriculture (General) > Agricultural education > Research. Experimentation
Plant culture > Flowers and flower culture. Ornamental plants > Care and preparation of cut flowers and ornamental plants for market
Live Archive:12 Aug 2016 01:54
Last Modified:03 Sep 2021 16:50

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