Non-Metalbolized Cytonkinins For Improved Postharvest Performance of Ornamentals Progress Reports - June 2003
ANNUAL PROGRESS REPORT
JUNE 2003
Project Title:
Non-metabolized Cytokinins for Improved
Postharvest Performance of Ornamentals
Researcher/Institution Information:
Michael S. Reid, University of California, Department of
Horticulture, Davis, CA 95616 Phone: 530-754-6751 Fax: 530-754-6753 E-mail:
Ann I. King, University of California Cooperative Extension,
Half Moon Bay, CA
Phone: 650-726-9059 E-mail:
Industry Needs Addressed:
Postharvest leaf yellowing and senescence which occurs on
many species of cut flowers and potted plants reduces the quality and
postharvest longevity. Loss of leaves, due to premature yellowing or abscission,
is not only an aesthetic detraction, but also reduces photosynthetic activity
which is necessary to maintain postharvest growth, particularly in potted
plants.
Our preliminary research showed that application of
thidiazuron (TDZ), a substituted phenylurea which acts as a cytokinin analog,
reduced leaf yellowing in cut alstroemeria flowers and in potted poinsettia
plants. The hypothesis was that the TDZ acts as a long-lasting cytokinin to
prevent leaf yellowing, thereby maintaining photosynthesis under low light
conditions, but that it also has some effect on ethylene sensitivity.
If thidiazuron is widely effective in reducing leaf yellowing
in many species of potted plants and cut flowers, it could be of great benefit
to the ornamental industry as a postharvest treatment. It is easily applied as a
spray to potted plants prior to shipping, and is applied as a pulse treatment to
cut flowers prior to their being boxed and shipped.
During this last year, our proposal was to test thidiazuron
on a number of potted plant and cut flower species which are susceptible to leaf
yellowing to see if the yellowing could be reduced, and if it could have
commercial application. We proposed testing it at different concentrations on
many different plants. We also proposed starting initial work with commercial
growers to see if TDZ would fit into a commercial ornamental production system.
Research Conducted that Provides Specific Results and
Benefits to the Industry:
We tested TDZ (at different concentrations, applied as a
“preharvest” spray) on a number of potted plants, including: 2
cultivars of potted poinsettias, 3 cultivars of Euphorbia fulgens (the
same genus as poinsettia, but a very different-looking potted plant), 2
cultivars of potted Asiatic lilies, 1 potted chrysanthemum cultivar, and 3
cultivars of miniature potted roses. In addition, we used cut alstroemerias and
snapdragons as a model to test the efficacy and possible phytotoxicity of TDZ
when applied as a postharvest pulse treatment to cut flowers.
Additional species and cultivars which are currently being
evaluated include potted chrysanthemums, ferns, lilies, freesia, and cyclamen,
and cut snapdragon, asters, lilies, roses, and stock.
All plants and cut flowers were harvested fresh from
commercial producers, transported to UC Davis, treated with TDZ, and evaluated
in a standard postharvest room, using standard evaluation methods.
Results of TDZ treatment on potted plants are very promising.
In all cases (except chrysanthemum), TDZ reduced or delayed leaf yellowing
and/or senescence. TDZ also had the unanticipated benefit of greatly prolonging
the flower life on potted Euphorbia pulcherrima (poinsettia) and Euphorbia
fulgens, and to a lesser extent on potted roses and lilies. In
chrysanthemum, the control plants of the cultivar selected never yellowed, so we
did not see an improvement in postharvest life with TDZ. We are currently
testing additional chrysanthemum cultivars in which postharvest leaf yellowing
is a common problem.
The effect of TDZ on reducing leaf yellowing and greatly
prolonging the cyathea (flower) life on potted poinsettias has been very
well-received by a number of commercial poinsettia growers. There has been
interest in pursuing registration of TDZ as a commercial postharvest treatment.
Although only two cut flowers (alstroemeria and snapdragon)
were examined extensively for thidiazuron efficacy and phytotoxicity, very
different results appeared following TDZ pulses. TDZ was effective in prolonging
the postharvest life of alstroemeria, but TDZ caused abnormal stem growth on cut
snapdragons, and did not improve the postharvest life. Further tests are
underway to see if lower concentrations are effective, but not phytotoxic, and
to see if phytotoxicity occurs on other snapdragon cultivars or on other species
of cut flowers.
To test the effect of TDZ on prolonging photosynthetic
activity in leaves, detached alstroemeria leaves were placed on solutions of TDZ
or water. The leaves held in TDZ maintained higher chlorophyll levels than
leaves held on water, showing that TDZ may well have a beneficial effect in
maintaining postharvest photosynthetic activity.
Professional and/or Published Information:
Publications:
King, A.I., M. Yi, A. Ferrante, M. Reid. 2001. Thidiazuron
reduces leaf senescence and abscission in flowering potted plants. HortScience
36(3):599 (abst.).King, A.I., and M.S. Reid. 2002. Thidiazuron: A postharvest
material to reduce leaf yellowing & leaf drop. CORF News, Vol. 6, no. 2,
spring 2002, pgs 1, 5.King, A.I., M. Yi, M. Reid. 2003. Thidiazuron improves
display life of potted flowering plants. HortScience, article submitted.
