Abstract
The use of ornamental sunflower as a cut flower has been increasing due to the advent of new cultivars and the demand of the flowergrowing market for new products. However, there are few studies related to postharvest of this species. The objective of this research was to evaluate the water balance and durability of ‘Sunbright Supreme’ sunflower collected at three different harvest stages and submitted or not to a pulsing with sucrose. The flower stalks were collected fully open, at an intermediate opening stage and also closed; they were then standardized at 50 cm and stored in water or 4% sucrose solution during 24 hours. After this period, stalks were maintained in sealed bottles containing 500 mL of water. Fresh matter, water consumption, flower opening, complete durability and visual quality of stems were evaluated every three days, considering a rating scale of color, turgescence and stalk bending. Rates of absorption and transpiration were calculated considering the fresh matter and variation in water volume. There was an increase in fresh matter and high water consumption in inflorescences until the seventh day; after this period, there was a reduction in weight and increased transpiration rates. Stems collected closed, closed with pulsing and at an intermediate stage treated with pulsing were maintained in commercial quality about four days longer than the open harvested (with and without pulsing) and intermediate without pulsing. Sucrose pulsing leads to flower opening of stalks collected at all harvest stages. The positive water balance was observed until the seventh day and contributes to the maintenance of commercial quality in ornamental sunflower. The early harvest of ornamental sunflower ‘Sunbright Supreme’ is recommended, besides the application of 4% sucrose pulsing.
Highlights
As a result of breeding programs, new varieties of ornamental sunflower have been made available to the flower market, presenting reduced size and different shades
These varieties have made the sunflower a prominent product in the composition of arrangements, due to its exotic shape and the different shades of flowers, which add life and dynamism to the environments (Andrade et al, 2012). As it is a new product in the floriculture market and since sunflower is normally produced for food or energy purposes, there is little research on procedures and postharvest for this species, when produced with ornamental purposes
The use of sucrose pulsing affected the fresh matter of stems collected at the open stage, which showed superiority to those that did not receive this treatment (Figure 2)
Summary
As a result of breeding programs, new varieties of ornamental sunflower have been made available to the flower market, presenting reduced size and different shades. Several physiological processes occur, causing the deterioration of plant products, the exhaustion of reserves by the breathing process and the wilt of the floral structures due to water loss by transpiration and reduction in absorption due to the occlusion of conducting vessels, deposition of chemicals or bacterial proliferation (Nowak and Rudnicki, 1990, Sonego and Brackmann, 1995) In this context, the optimization of water relations is one of the factors that most contribute to the control of senescence and increase the post-harvest durability of cut flowers (Finger et al, 2004; Sales et al, 2015), being influenced by the post-harvest procedures adopted. Water balance is based on the relationship between transpiration and water absorption by the flower stems (Bellé et al, 2004) and is related to the visual quality of the flowers, since it reflects the turgescence characteristic of the flower stems
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