THECOMMERCIALGREENHOUSEGROWER
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JANUARY 2017
22
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R
ESEARCHDIARY
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observedwhen P or s-ABA
was applied.With P
increasing shelf life of
impatiens and african
marigold by 1 and 1.3 days
comparedwith control plants,
respectively. The application
of P at 2×wasmore effective
at delaying visual wilting than
at lower rates (0.5× and 1×)
in africanmarigold.
Applications of s-ABA
delayedwilting by 1.3 to 3.7
days in all cultivars. The shelf
lives of impatiens and petunia
treatedwith s-ABA at 2×
were extended themost, by
3.7 and 3.0 days compared
with control plants,
respectively. A rapid
reduction of stomatal
conductancewas observed
within 4 hours of P or s-ABA
application in plants showing
delayedwilting symptoms. s-
ABA treatment appeared to
causemarginal leaf chlorosis
in impatiens, whereas
application of P damaged
the opened flowers in all
cultivars. The application of
VP or SACs did not extend
shelf life in any treated plants.
Foliar application of P on
selected species and
treatment with s-ABA on
most of specieswould allow
bedding plants towithstand
water deficit during shipping
and/or retailing.
Plants use sunlight for
photosynthesis and are
exposed to ultraviolet (UV)
radiation that is present in
sunlight.
UV radiation is divided into
3 classes: UV-A, UV-B, and
UV-C. The Ultraviolet-C (UV-
C) region of the UV
spectrum includes
wavelengths below 280 nm;
these highly energetic
wavelengths are absorbed
by ozone and are not
present in the sunlight at the
earth’s surface therefore
under normal growing
conditions, effects of UV-C
light are not seen on plants.
Research at Cornell
University examined the
effects of applying
ultraviolet-C irradiation (UV-
C) on greenhouse
ornamental plants and
demonstrated very
promising uses of UV-C as a
treatment to increase
branching and reduce the
height of plants, and in
some situations, affect the
rate of flowering (Acta
Horticulturae 1134).
Several conclusions have
beenmade from this
research that are consistent
withmultiple plant species.
First, the amount of UV-C
light that a greenhouse plant
receives is critical to its
response. The proper weekly
dosage, for as little as 15
min a week, will control a
plant’s growth response. In
addition, too high a dosage
of UV-C irradiationwill burn
plants and too lowwill have
no effect. Second, proper
applications of UV-C light
decreases final plant height.
Several plant species have
responded to applications of
UV-C light by growing
shorter than the control
plants that receive normal
greenhouse lighting. Third,
UV-C light increases
branching of greenhouse
plants.
At appropriate dosage
rates, UV-C light increases
branching on some species
and increases the number of
flowers that are produced.
This avoids the need to
pinch plants and to apply
plant growth regulators.
Fourth, the application of
UV-C light can affect
flowering time. The
application of UV-C
irradiation can either delay
flowering or cause earlier
flowering depending on
plant species and dosage
rate. In some cases, the
increased branching is
accompanied by delayed
flowering.
Water stress during shipping
and retailing can reduce the
post-production quality and
marketability of bedding
plants. Anti-transpirants can
temporarily prevent plants
fromwilting by either
physically blocking stomata
or physiologically inducing
stomatal closure, limiting
water loss by transpiration.
Researchers atWest Virginia
University evaluated the
efficacy of commercially
available anti-transpirants on
enhancing temporarywater
stress tolerance in bedding.
Two physical anti-
transpirants [ -pinene polymer
( P) and vinyl-acrylic polymer
(VP)], and three physiological
anti-transpirants [two sugar
alcohol-based compounds
(SACs) and a biologically
active form of abscisic acid
(s-ABA)] were applied to
begonia, new guinea
impatiens, impatiens, petunia,
africanmarigold and french
marigold. Physical anti-
transpirantswere sprayed on
foliage and physiological anti-
transpirantswere drenched
to themedia. All anti-
transpirantswere applied at
half. equal to or twice the
manufacturer’s
recommended rate
(HortTechnology).
Extended shelf lifewas
Anti-transpirants andwater stress in
bedding plants
Using ultraviolet-C (UV-C) irradiation
as a growth regulation
