140 J.E. FAUST, J.M. DOLE, AND R.G. LOPEZ
Rajapakse et al. 1996). Cuttings stored under light were darker green
and had a higher chlorophyll content compared to cuttings stored in
the dark. Leaf and stem dry weights increased for cuttings stored at 3◦C
under medium or high irradiance (23–34μmol⋅m−^2 ⋅s−^1 provided con-
tinuously during storage resulting in a DLI of 2–3 mol⋅m−^2 ⋅d−^1 ).
- Water.Depending on the packaging materials and design, cuttings
may lose water rapidly, resulting in leaf abscission, necrotic tissue, and
reduced rooting during propagation (Faust et al. 2006); however, the
presence of free water on cuttings will promote pathogenic infection.
Free water typically results from condensation that forms when cut-
tings transpire and the package of cuttings undergoes temperature fluc-
tuations during handling and shipping. Thus, a balance needs to be
achieved: cuttings should be turgid prior to shipping and storage, but
tissue surfaces should be dry. The use of antitranspirants has been stud-
ied, but were detrimental when applied prior to storage of geraniums
(Paton and Schwabe 1987). - Pathogens.Gray mold (Botrytis cinerea) and bacterial soft rot
(primarilyErwiniaspp.) are the primary pathogens that cause disease
problems during shipping and storage (Faust et al. 2006). Gray mold
is common within production greenhouses and spores can be readily
found on cuttings. Optimal conditions for gray mold spore germination
and infection are at 13–24◦C, greater than 93% relative humidity, and
8–12 h of free-water exposure. Disease development is maximized at
15–20◦C (Zhang and Sutton 1994; Sosa-Alvarez et al. 1995). Transpira-
tion from plant material packed in sealed boxes creates high-humidity
conditions in the postharvest environment. Spores will germinate if
there is water on the cuttings prior to packing or from condensation
during shipping and storage. - Ethylene. Ethylene can play an important, and often complicated,
role in the storage, shipping, and rooting of cuttings. Ethylene is used
to benefit stock-plant production through the use of ethephon appli-
cations, which reduces or prevents flowering and induces axillary
shoot development (Whipker et al. 2006). However, during shipping
and storage, ethylene can damage cuttings of many species by causing
leaf senescence and abscission. Finally, endogenous ethylene is often
required for root development during propagation.
Ethylene exposure can cause a variety of symptoms, many of which
look like stress or senescence responses. Loss of chlorophyll, or