Postharvest Quality of Cut Roses With the Application of Salicylic Acid

The objective of this work was to evaluate the effect of the application of salicylic acid (SA) on the maintenance of quality and longevity of cut roses cv. Vega. Cut roses were kept in a vase solution of SA and water at concentrations of 0; 0.5; 1.0; 1.5 and 2.0 mM. All treatments were kept at 8±2 C for 96 hours, simulating storage in flower shops; the flowers were then evaluated regarding loss of fresh matter and leaf chlorophyll content and were transferred to beakers containing distilled water at 25±2 oC for more 144 hours, simulating shelf life. At 24, 48, 72 and 96 hours from the beginning of the experiment, biochemical analyses of total proteins and the activity of the phenylalanine ammonia-lyase (PAL) and peroxidases (PO) were performed. Visual analyses were performed (stem curvature, turgescence and petal darkening) every 48 hour intervals until the end of the experiment. The treatments with SA allowed the maintenance of post-harvest quality, reducing the loss of fresh matter mass, lower stem curvature, greater turgescence and less darkening of the petals. The results showed that the application of SA increased total protein contents and FAL, which characterizes the activation of plant defense mechanisms to the senescence process.


Introduction
The market for flowers and ornamental plants is expanding, being considered one of the most promising sectors of agribusiness.Roses are one of the most commercialized species, especially as cut flowers.However, cut flowers have a reduced shelf life due to their intense post-harvest catabolic reactions, leading to rapid deterioration (Hardenburg, Watada, & Wang, 1988).Cut flowers are sensitive to microbial contamination at the stem base or in the vase solution, consequently were caused to shortening their vase life (Balestra et al., 2005).
Alternative methods to extend shelf life are being tested, such as refrigeration and maintenance of cut flowers in solution, also known as vase solutions.The latter contain substances which may be used singly or in combination to retard the senescence of the cut flowers.Salicylic acid (SA) is a natural compound that reduces the damage caused by ethylene during plant senescence (Geerdink, 2012), acting as an endogenous signalling molecule.The exogenous SA, when applied, induces the production of its precursor of methyl salicylate (Resende, Salgado, & Chaves, 2003), increasing the synthesis of SA in plant tissues, phenylalanine ammonia-lyase (PAL) and the production of proteins related to pathogenesis (PR-proteins) (Spletzer & Enyedi, 1999), inhibiting the synthesis of ethylene (Raskin, 1992).SA can prevent ACC-oxidase activity and decrease ROS (Reactive Oxygen Species) with increasing antioxidant enzyme activity (Canakci, 2008;Kalidage et al., 2009).
During evolution, plants developed defence mechanisms activated only in response to pathogen infection or treatment with certain biological or synthetic chemicals, called elicitors (Cavalcanti, Piero, Cia, Paschoalati, & Resende, 2005).This defence activation is called systemic acquired resistance (SAR), and it is characterised by the production of a signal from the infection site, causing necrosis and translocation of this signal to other parts of the plant, inducing defence reactions that will protect the plant against future aggression (Da Silva, Reis, Baldani, & Olivares, 2008).According to Leon-Kloosterziel et al. (2005) there are several enzymes related to induced resistance, such as peroxidases, poliphenol oxidases, PAL, β-1,3-glucanases and chitinases.When the plant is lead to induction, the activity of these enzymes in the area tends to increase when compared to plant tissues not exposed to the elicitors (Bettiol & Morandi, 2009).
Thus, the objective of this work was to evaluate the effect of exogenous SA on quality maintenance and longevity of cut roses.

Material and Methods
Pink closed rose buds (Rosa sp.) cv.Vega from the Veiling in Holambra, of the commercial production of Holambra, São Paulo, Brazil, were maintained and transported under refrigeration to the Phytopathology Lab at the Federal University of Technology-Parana, campus Dois Vizinhos.Rose stems free from visible wounds or disease symptoms were selected and were trimmed to 40 cm-length using cutters.The cut roses were maintained at 8±2 °C in the first 96 hours simulating floriculture storage; and later, at 25±2 °C for 144 hours, simulating shelf life.The total duration of the experiment was 240 hours.
The stems were placed randomly in beakers containing 500 mL of SA solution at concentrations of 0; 0.5; 1.0; 1.5 and 2.0 mM (w/v) in distilled water for 96 hours.At 24, 48, 72 and 96 hours, standard 10 mm discs were collected from rose petals and frozen in liquid nitrogen and kept in a freezer at -20 °C.The material was used for biochemical analysis of total protein contents and enzymatic activity of Phenylalanine ammonia lyase (PAL) and Peroxidases (PO).
Protein contents were determined using the test proposed by Bradford (1976), with 0.2 Molar phosphate buffer 0.2 M pH 7.5 and reagent Bio-Rad ® .Readings were performed with spectrophotometer (630 nm); bovine serum albumin was the standard.PAL determination was performed by colorimetric quantification of trans-cinnamic acid from phenylalanine, according to Kuhn (2007).PO extraction and activity determination were done according to Matsuno and Uritani (1972).
At 96 hours, the cut roses were removed from the solution.The stem leaves were used to determine the Falker Chlorophyll Index (FCI) using the equipment ClorofiLOG ® model CFL1030, which gives values proportional to the absorbance of chlorophyll a, b and t (a + b), presenting high correlation index with values obtained by direct methods (Falker Automação Agrícola Ltda., 2008).Also, loss of fresh matter in each experimental unit was evaluated, obtained by the difference of fresh weight of the roses at the beginning of the experiment and weight at 96 hours, expressed as percentage.These evaluations were performed in the first 96 hours considering this period would be sufficient for SA activation and metabolic response.In addition, this is the maximum time roses are stored in flower shops, since they are replaced every four days-according to roses distributors.The stems were then placed in beakers containing distilled water until the end of evaluations.
Visual analysis of neck bending, turgescence and darkening of the petals was performed every 48 hours since the stems were placed in the SA solution until the end of the experiment, totalising 10 days or 240 hours-considering that the cut roses can last up to six days after being acquired from customers in flower shops All roses were analysed in the experimental unit, evaluating neck bending (grading notes: 1: > 90º, 2: ≤ 45º and 3: straight stem), turgescence (1: wilted, 2: slightly wilted and 3: turgid) and coloration of the petals (1: dark, 2: slightly dark and 3: without darkening), according to the methodology proposed by Geerdink (2012).
The experiment was conducted in a completely randomized design, with four replications and eight floral stems per experimental unit.
The collected data were submitted to analysis of variance (p ≤ 0.05) and presented as descriptive statistics (mean±standard deviation) and regression analysis (p ≤ 0.05) by the Assistat ® program (Silva & Azevedo, 2009).

Results and Discussion
Chlorophylls are the most abundant natural pigments in plants.They occur inside chloroplasts in leaves and other plant tissues, converting luminous energy into chemical energy (Elbe, 2000).These pigments are fundamental to maintain the visual and commercially desired characteristics in post-harvest.

Vega' mean
These qualitative characteristics found in the present work are probably related to the lower mass loss of fresh matter (Figure 1), since the stems treated with the highest concentrations of AS were the ones that obtained the lowest loss in relation to the others during the experiment.It is assumed that those that were longer turgid presented lower stem curvature and darkening of petals, since according to Cortes et al. (2011), working with 'Grand Gala' rose stems, state that high levels of tissue hydration are generally associated with increased vase life of cut flowers.This is corroborated by Geerdink (2012) who claims that qualitative characteristics are linked to the water balance of floral stems, since it is an important part for maintaining the cellular structures and consequently for visual appearance, since turgid petals become brighter, and thus more attractive to the consumer.
The goal is to maintain the quality of the roses, our service network, and obscuration of the petals, give by inhibition of post-harvest metabolism, respiratory or ethylene synthesis.As is the ethylene antagonist (Raskin, 1992), it is likely that inhibition of biosynthesis and ethylene action is suggested, which allows better roses when treated with AS.
Research to complement these results, referring to respiratory metabolic behavior with quantification of CO 2 and O 2 levels and ethylene production should be performed, since our collected data show that SA is promising for quality maintenance post-restoration of cut roses.

Conclusion
The different concentrations of SA did not interfere on the FCI in this experiment.Treatments with SA provided better quality cut roses in post-harvest, with reduced mass loss, neck bending, wilting and petal darkening.The application of SA also interfered on biochemical parameters.The life of cut flowers was significantly increased by treatment with SA irrespective of its concentration, when compared to the control.Therefore, SA an inexpensive that can also natural plant-derived compound has the potential to increase the vase-life of rose cut flowers.
Consider SA as a novel substance for commercial applications in the cut rose industry.However, further research is needed to optimize SA treatments for this purpose.
Figure 1 Figure 3. Q treated w