The postharvest life of cut Eustoma grandiflorum flowers is limited by poor bud opening and bent neck in open flowers. Vase solutions containing up to 6% sucrose or glucose improved the quality and vase life of the flowers. The additional carbohydrate improved petal color, increased bud opening, strengthened pedicels, and extended overall inflorescence longevity by up to 8 days. The principal sugar in the petals of open flowers was glucose, with lower concentrations of sucrose and fructose. Presence of sugar in the vase solution greatly increased the concentration of sugars in the perianth of buds and open flowers. Eustoma flowers are affected by exposure to ethylene and pre-treatment with 1-MCP or STS delays final senescence of flowers that have been held in solutions containing sugar. IntroductionLisianthus, or the Texas gentian, Eustoma grandiflorum (Raff.) Shinn., native to the prairie states of North America, is now an important commercial cut flower (Halevy and Kofranek, 1984). Hybrids developed in Japan provide a wide range of colors, color patterns, and both single and double forms. Lisianthus has become very popular as a cut flower, because of the range of colors available, and the fact that each inflorescence comprises a long, straight stem bearing as many as 10 individual flowers. In addition, the plants (which may be annual or biennial depending on the growing environment) bear as many as 10 inflorescences over the production season (Tjia and Sheehan, 1986).Although there have b een many studies of the environmental conditions required for lisianthus production, there has been little examination of the postharvest characteristics of the flowers. Lisianthus is usually harvested commercially when the first one or two flowers on the stem have opened. A good quality inflorescence will usually have ten or more buds and flowers. If the flowers are placed in water, few if any of these buds open, and the longevity of the inflorescence is therefore determined by the life of the open flowers. Frequently, too, the life of the flowers is shortened by premature wilting and bending of the pedicels of the open flowers.In other bud-type cut flowers, it has long been known that bud opening (and consequently display life of the inflorescence) can b e enhanced by the addition of carbohydrate. This can be achieved either by using a postharvest pulse with a high concentration of sugar, as in gladiolus (Mayak et al., 1973) (Han, 1992). Halevy and Kofranek (1984) recommended a pulse with 5-10% sucrose for 24 hours to improve postharvest life of Lisianthus flowers, and Farina et al. compared a number of such pulses. They fo und that pulsing with Chrysal or TOG (with 4% sugar) was ineffective, but that TOG with 10% sugar or 8-HQS with 10% sugar were both effective pulses. Song et al. (1994) tested the effects of STS pre-treatment, and found a modest improvement in bud opening, but also showed that a standard holding solution containing biocides and 2% sugar increased flower life three-fold. Ichimura and Korenaga (199...
It is not known whether tepal senescence in Iris flowers is regulated by hormones. We applied hormones and hormone inhibitors to cut flowers and isolated tepals of Iris × hollandica cv. Blue Magic. Treatments with ethylene or ethylene antagonists indicated lack of ethylene involvement. Auxins or auxin inhibitors also did not change the time to senescence. Abscisic acid (ABA) hastened senescence, but an inhibitor of ABA synthesis (norflurazon) had no effect. Gibberellic acid (GA3 ) slightly delayed senescence in some experiments, but in other experiments it was without effect, and gibberellin inhibitors [ancymidol or 4-hydroxy-5-isopropyl-2-methylphenyltrimethyl ammonium chloride-1-piperidine carboxylate (AMO-1618)] were ineffective as well. Salicylic acid (SA) also had no effect. Ethylene, auxins, GA3 and SA affected flower opening, therefore did reach the flower cells. Jasmonates delayed senescence by about 2.0 days. Similarly, cytokinins delayed senescence by about 1.5-2.0 days. Antagonists of the phosphatidylinositol signal transduction pathway (lithium), calcium channels (niguldipine and verapamil), calmodulin action [fluphenazine, trifluoroperazine, phenoxybenzamide and N-(6-aminohexyl)-5-chloro-1-naphtalenesulfonamide hydrochloride (W-7)] or protein kinase activity [1-(5-isoquinolinesulfonyl)-2-methylpiperazine hydrochloride (H-7), N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide hydrochloride (H-8) and N-(2-aminoethyl)-5-isoquinolinesulfonamide dihydrochloride (H-9)] had no effect on senescence, indicating no role of a few common signal transduction pathways relating to hormone effects on senescence. The results indicate that tepal senescence in Iris cv. Blue Magic is not regulated by endogenous ethylene, auxin, gibberellins or SA. A role of ABA can at present not be excluded. The data suggest the hypothesis that cytokinins and jasmonates are among the natural regulators.
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