POSTHARVEST STUDIES ON THE CUT FLOWERS OF DAHLIA (Dahlia hybrida L.): II: EFFECT OF PREVENTING LATEX FLOW, PULSING, AND HOLDING SOLUTIONS ON VASE LIFE AND QUALITY.

The cut flowers of dahlia (Dahlia hybrids L.) Fam. Asteraceae tend to have a
very short vase life. which reduces their potential as a commercial cut (lower. Upon
cutting from the plant, the flower stem exudes a milky sap (called latex) that plugs the
conductive tissues at the cut base of the stem and prevents water uptake causing
rapid wilting and reduced vase life of the flower, A comprehensive postharvest study
on dahlia cut (lowers was carried out during the two successive seasons of
1995/1996 and 1996/1997, at the Veget. and Flof. Dept., Fac. of Agric., Mansoura
Univ. Three stepwise postharvest treatments were used in order to improve the vase
life and quality of cui dahlia. The first step included treatments to overcome the latex
problem (untreated control, dipping in ethanol, searing over a (lame, and dipping in
boiling water). followed by short term pulsing treatments {silver thiosulfate complex
(STS), an antibiotic complex. or 8-hydroxyquinoline sulfate (8-HQS». In the final
step, different components of the flower holding solutions (sucrose, boric acid, citric
acid, or cycocel (CCC)} were applied.
In part I, the effect of these treatments on water relations and the anatomical
structure of the flower stern were studied. In this part (Part II), the effects of these
treatments on vase life and quality of the flower were evaluated. Data were collected
on reducing sugars contents of the petals, vase life (days), maximum fresh weight
gain of the (lower, content of anthocyanin pigment in the petals, and flower opening
vetcclty.
The results showed that the higher the reducing sugars in the petals, the
longer the vase life of the flower Vias observed. Placing the base (5 em) of the stem in
ethanol alcohol (95%) for 5 minutes was the best method to prevent latex problem.
and that placinq the cut stem in 4 mM silver thiosulfate complex (STS) for 10 minutes
was the besl pulsing method. In addition. sucrose 1.5% was the test holding solution.
These three treatments resulted in higher reducing sugars content in the petals and
longer vase life of cut dahlia than the other comparable treatments. These treatments
also resulted in the best quality; measured as maximum fresh weight gain, highest
anthocyanin content, and lowest velocity of (lower opening. The combination of
ethanol treatment and STS pulsing treatment resulted in better quality than the other
combinations between preventing lalex flow and pulsing treatments in all quality
measurements. The results also showed that longest vase life of cut dahlia in both
seasons (8 days) was achieved by placing the stem of cut dahlia flowers in ethanol
(95%) for 5 minutes. fcHowed by 10 minutes pulse in 4 mM silver thiosulfate complex
(STS). The final step was placing the cut flower in a holding solution containing 1.5 %
sucrose.