Ana Maria Mapeli

Longevity of Epidendrum ibaguense flowers as affected by pre-loading treatments and vase solution

Summary Post-harvest longevity of Epidendrum ibaguense cut flowers was maximum when treated for 6 h with 1 g m–3 Ethylbloc® [0.14% 1-methylcyclopropene; 1-MCP] followed, or not, by pulsing with 200 g l–1 sucrose for 12 h. This extended the vase-life from 5.5 d to at least 11 d. Cut inflorescences pulsed with 2.0 mM silver thiosulphate (STS) had reduced abscission of flowers, similar to the effect of 1-MCP. When inflorescences were pulsed with 200 g l–1 sucrose alone for 12 h, no effect was observed on the vase-life of the flowers. Flowers kept in a vase solution containing 20 g l–1 sucrose, 150 mg l–1 citric acid, and 200 mg l–1 8-hydroxyquinoline citrate did not influence the longevity of 1-MCP or STS pre-treated flowers, but the vase solution had a small influence on retarding abscission compared with flowers kept in distilled water. Adding 0.2 mM STS to the vase solution improved vase-life 1.74- and 1.45-fold compared with the longevity of flowers kept in distilled water or in vase solution alone, respectively. The presence of 0.3 mM AgNO3 alone, or mixed into the vase solution, had no affect on the vase-life of the flowers.

Dormancy breakage of Stylosanthes humilis seeds by aluminium.

Physiological dormancy of scarified seeds of Townsville stylo ( Stylosanthes humilis HBK) was released by acidic aluminium (Al 3+ ) solution. Antiethylenic substances inhibited germination of low-pH-stimulated dormant seeds, with a correspondingly low ethylene production and low activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase in seeds. On the other hand, antiethylenic substances did not decrease the germination of Al 3+ -stimulated seeds, but ACC oxidase activity and ethylene production by the seeds was decreased to a large extent. These data provide evidence that dormancy breakage by Al 3+ differs from that caused by low pH and is not associated with ethylene production. Similarly to Al 3+ action, methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of Townsville stylo seeds. Sodium selenate and N -acetyl cysteine, antioxidant compounds, largely decreased germination of MV- and Al 3+ -stimulated dormant seeds. Altogether these data point to oxidative radicals constituting key molecules in the chain of events triggered by Al 3+ leading to dormancy breakage.

Characterisation of respiration, ethylene production, and carbohydrate contents during flower opening in Epidendrum ibaguense

Summary The opening of flowers in Epidendrum ibaguense is characterised by continuous drops in respiration, ethylene production, and 1-aminocyclopropone-1-carboxylate (ACC) oxidase activity from the bud stage to fully open. Later, an increase in ethylene production and ACC oxidase activity occurred, suggesting autocatalytic production of ethylene, beginning at an early stage of senescence. Regardless of developmental stage, the main non-structural carbohydrates in flowers were non-reducing sugars [23.7% (w/w) fresh weight (FW)]. Starch accounted for 3.1% (w/w) FW and reducing sugars for 0.7% (w/w) FW. No depletion in the level of any carbohydrate was observed throughout senescence. At the beginning of floral senescence, a sharp increase occurred in the activities of acid and alkaline invertases, suggesting a role for both enzymes in the cleavage of sucrose. However, no major changes in sucrose synthase activity were found during flower development.

Action of ferric and aluminium ions on the dormancy breakage of Stylosanthes humilis seeds

Dormancy of scarified seeds of Stylosanthes humilis was broken by acidic Al3+ and Fe3+ solutions. Fe+3-stimulated seeds exhibited a high activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and produced great amounts of ethylene, which showed correlated with the germination process. In addition, specific inhibitors of ethylene biosynthesis and action largely depressed the Fe3+-stimulated germination, leading to the conclusion that the ion broke dormancy by triggering ethylene production by the seeds. By contrast, inhibitors of ethylene biosynthesis and action did not impair germination of Al3+-stimulated dormant seeds. Moreover, ethylene production and activity of ACC oxidase of Al3+-treated seeds was substantially decreased by inhibitors of ethylene biosynthesis, but germination kept large. Together these data suggest that ethylene biosynthesis was not required in the chain of events triggered by Al3+ leading to dormancy breakage. Methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of seeds to the same extent as Al3+ did. Germination of both Al3+- and MV-stimulated dormant seeds was inhibited by sodium selenate, an antioxidant compound; selenate, however had no effect on germination of Fe3+-stimulated seeds. Together these data indicate that the mechanisms underlying the germination of Al3+- and Fe3+-treated seeds are not the same.

Non-structural carbohydrate metabolism and postharvest conservation of gerbera flowers

The species Gerbera jamesonii Adlam has great economic importance in the ornamental sector, due to exuberance of floral stems. However, florists face some challenges such as postharvest handling and difficulty of conservation. Therefore, this study aimed to characterize the non-structural carbohydrate content in different floral stages of G. jamesonii var. Dawn and evaluate the effect of preservative solutions during the postharvest storage of this species. For this purpose, it was quantified TSS, RS and NRS from the seven stages of gerbera stems ontogeny (E1, E2, E3, E4, E5, E6 and E7). The preservative solutions used were: T1) distilled water; T2) citric acid (100 mg L-1); T3) glucose (20 g L-1); T4) gibberellic acid (GA3 , 5 mg L-1); T5) calcium chloride (CaCl2 , 20g L-1) and T6) Sodium Thiosulphate (STS, 20 mM). The effect of preservative solutions were assessed daily, considering the longevity of flowers, variation in the absorption of preservative solution, pH of the solution and fresh mass variation. The experimental design was completely randomized with four replicates. There was a difference in carbohydrate metabolism during floral opening and senescence. In the orange bracts there was a lower TSS content, while in the inflorescences it was observed a reduction in the yellowish, greenish-green and greenish stages. The content of RS increased in the bracts, whereas in the inflorescence there was no difference. The NRS content was higher in the orange bracts, showing lower rates in the inflorescences in yellowish and yellowish greenish stages. The preservative solutions had an impact, on the floral stem longevity, varying according to the solutions used, i.e. CaCl2 and STS reduced the durability of gerbera flower in 9.25 and 11.5 days, respectively, compared to stems kept in distilled water. The glucose solution did not promote a significant difference compared to water. Therefore, we conclude that there is variation in the metabolism of non-structural carbohydrates during the floral development of G. jamesonii var. Dawn and the tested solutions were not effective in promoting postharvest conservation of gerbera.

Longevidade de inflorescências de Epidendrum ibaguense tratadas com aminoetoxivinilglicina

Abstract – This work evaluated the influenceof the aminoethoxyvinylglycine (AVG), an inhibitor of ethylene synthesis, when applied in pulsing solution or sprayed, on the abscission and longevity of cut star orchid ( Epidendrum ibaguense Kunth) inflorescences.The cut stems were placed in solutions with 0, 0.5, 1, 1.5 and 2 mM AVG concentrations immediately after the harvest for periods of 6, 12, 18 and 24 hours. The same treatment concentrations were sprayed on the inflorescencesuntil runoff. The experiment had a randomized complete block design with factorial treatments of rate and duration plus rate of application to the flowers, with fivereplicates, with three stems per experimental unit. Regardless of the way the AVG was applied, the inhibitor extended the flowers’ longevity in approximately 70% compared to the control treatment, reaching maximum effect at 1.5 and 2 mM AVG. The percentage of abscissed flowersdiminished in all treatments containing AVG, with higher efficiencywhen sprayed over the inflorescence,decreasing the abscission by 80% at concentrations between 1 and 2 mM AVG.Index terms: AVG, pulsing, spraying.

Longevidade de inflorescências de Epidendrum ibaguense Kunth tratadas com ácido aminooxiacético

O objetivo deste trabalho foi avaliar a influencia sobre a longevidade de inflorescencias de Epidendrum ibaguense do inibidor da sintese de etileno – acido aminooxiacetico (AOA) – aplicado em solucao de condicionamento e pulverizacao. As hastes foram colhidas e imediatamente condicionadas em 0,0; 0,5; 1,0; 1,5 e 2,0 mM de AOA por 6, 12, 18 e 24 h, ou pulverizadas com as mesmas solucoes ate o molhamento completo da inflorescencia. Independentemente do tempo e da concentracao de AOA, o condicionamento das hastes nao prolongou a longevidade das flores em vaso. A pulverizacao das inflorescencias de E. ibaguense com AOA fez com que sua vida de vaso fosse prolongada em aproximadamente 26% em comparacao ao tratamento de condicionamento e ao controle; a pulverizacao com 1,5 mM de AOA contribuiu para uma vida de vaso de 8 dias.