- THE FLORICULTURE VEGETATIVE CUTTING INDUSTRY 143
sensitivity of ‘Beauregard’ (Villordon et al. 2012). MCP application
reduced zonal geranium root number and delayed adventitious root for-
mation of angelonia, bacopa (Sutera cordata), calibrachoa, New Guinea
impatiens, portulaca, and verbena (Leatherwood et al. 2016). These
rooting effects were partially overcome by subsequent exposure to ethy-
lene. MCP did not reduce rooting of lantana, indicating that ethylene
may not be involved in rooting of all species (Rapaka et al. 2007a,
2007b).
STS also reduced rooting of both stored and unstored pothos and
geranium cuttings, but MCP did not reduce rooting as compared with
untreated controls (Paton and Schwabe 1987; Muller et al. 1997; Serek
et al. 1998). The differential effect of STS versus MCP might be due to
toxicity from STS, which has been reported in other species (Kadner
and Druege 2004).
Purer and Mayak (1989) noted that GA could counteract the effect
of exogenous ethylene in geranium cuttings, which also prevented leaf
yellowing. GA neither reduced ethylene production nor had an effect
on carbohydrate partitioning, so ethylene sensitivity may have been
reduced.
Mutui et al. (2005, 2010) noted that exogenous ethylene increased
the number of geranium cuttings forming roots, but reduced the num-
ber of roots per cutting compared to untreated cuttings. Leatherwood
et al. (2016) noted that 1μL⋅L−^1 ethylene improved rooting of fuchsia
(Fuchsia triphylla) and begonia (Begoniahybrid).
- Carbohydrates.Subsequent rooting after storage is greatly affected
by carbohydrate levels within the cuttings (Druege et al. 2004; Enfield
2011). Naturally, the negative effects of storage and shipping on cuttings
can be linked to carbohydrate depletion. Druege et al. (2000) noted that
starch completely disappeared from leaves and to a large extent from
stems of chrysanthemum cuttings within 2 weeks of cold storage (0.5◦C
or 5◦C). Concentrations of glucose, fructose, and sucrose also decreased,
but to a lesser extent when cuttings were stored for 2, 3, or 4 weeks.
Rooting of cuttings in propagation depends on the endogenous levels
of carbohydrates in the cuttings at the time of harvest. Cuttings har-
vested from geranium stock plants grown under high light had higher
starch and soluble carbohydrates and rooted faster than those grown
under lower light levels (Forschner and Reuther 1984). Interestingly,
cuttings adapted to high light did best in a high-light propagation
environment and low-light-adapted cuttings performed best in a low-
light propagation environment. High-light-adapted cuttings rooted less
than low-light cuttings when propagated in a low-light environment,