Abstract: The siam tulip is a relatively new exported cut flower that has become widely recognized for its attractive colorful pink bract. The main problem limiting this lovely flower’s value is its poor vase life after cutting. The objective of this study was to extend siam tulip’s shelf life by using a substance against ethylene action, 1-Methylcyclopropene (1-MCP). The experiment was arranged in a factorial completely randomized design, composed of two factors: 1-MCP concentration at four levels (0, 300, 600 or 900 ppb) and a period of fumigation at two levels (4 or 8 h) in a hermetically sealed plastic bucket (50 L) at 25°C. The results showed that flowers treated with 300 ppb 1-MCP for 8 h had maximal water uptake, preserved the highest anthocyanin content and the least occurrence of bract browning during postharvest life. No marked differences in weight loss of flowering stalk was observed.
INTRODUCTION
Siam tulip (Curcuma aeruqinosa Roxb.) is an ornamental plant specie in the family of Zingiberaceae and a relative newcomer to the world of cut flowers and ornamental plants (Top Tropicals Plant Catalog, 2009). Nowadays, the added value of siam tulip cut flowers is increasing due to their strikingly beautiful brilliant pink inflorescence that makes it a very appealing cut flower, potted plant or landscape addition (Phipps, 2009). Thai Horticulture (2009) reported that the siam tulip originated in Thailand. It has been classed as a tropical native tender perennial and has become a popular ornamental plant that grows well in warm and wet climates. Thus, the predominant production is located in Thailand. Nowadays, the Laddawan siam tulip is a F1 hybrid, a cross between Curcuma alismatifolia and Curcuma cordata. It is a popular variety for cut flowers that has high commercial demand (Tropical Nurseries, 2009). The end of vase life of this flower is partially determined by a browning appearance on their bracts (Bunya-Atichart et al., 2004). This disorder causes the flower to senescence and limits the length of postharvest life. Such changes have a major negative impact upon its salable value at market. Generally, the senescence of flower after cutting has been attributed mainly to ethylene. The presence of ethylene leads to flower senescence, shortening of life and loss of bright color (Jiang, 2000). A practical method to decrease this disorder is a great importance. Recently, an ethylene action inhibitor, the compound 1-methylcyclopropene (1-MCP), has been reported to prolong the display life in various cut flowers (Honghem et al., 2007). This compound is considered as non-toxic for human and the environment (Blankenship and Dole, 2003; Serek et al., 2006). Furthermore, 1-MCP is currently being considered for future use in applications to commercial cut flowers (Feng et al., 2000). At present, limited information have apparently been reported on the postharvest physiology of siam tulip. Thus, there is still a need for more information about 1-MCP application on post harvest of the siam tulip flower. The experiment outlined in the present research aimed to investigate the effectiveness of exogenous 1-MCP as a postharvest tool for extending the vase life and maintaining the quality characteristics of siam tulip cv. Laddawan, in order to assess the potential of 1-MCP as a pretreatment to extend the flower longevity and improve the qualities of this flower.
MATERIALS AND METHODS
Siam tulip flowers (Curcuma aeruqinosa Roxb.) cv. Laddawan cut at the commercial stage were purchased from a commercial garden in Chiang Mai, in the North of Thailand. Each flower was wrapped with a foam sheath and packed carefully in fiberboard cartons then transported in an air-conditioned vehicle to Mahasarakham University. After they arrived at the laboratory, the flowers were selected again for uniformity in size, shape, initial bract color and freedom from external damage before being placed into chambers for fumigating with 1-MCP. Each flowering stem was recut with stainless steel scissors into 30 cm lengths. The experiment was carried out from June to August 2008 at the Division of Agricultural Technology, Faculty of Technology, Mahasarakham University, in the Northeast of Thailand. A Factorial Randomized Complete Block Design was arranged and composed of two factors: concentration of 1-MCP four levels (0, 300, 600 or 900 ppb) with two periods of fumigation time (4 or 8 h). While control flowers were sealed in identical chambers without added 1-MCP, different concentrations in combination with fumigation periods were used as treatments: 0 ppb 4 h, 300 ppb 4 h, 600 ppb 4 h, 900 ppb 4 h, 0 ppb 8 h, 300 ppb 8 h, 600 ppb 8 h and 900 ppb 8 h. Each treatment was carried out in ten replicates, one flower per replication. All treatments were taken in sealed 50 L plastic buckets of 50 L capacity containing distilled water and exposed to different concentrations of 1-MCP (0, 300, 600 or 900 ppb) with two periods of time (4 or 8 h) at 25°C. After the period of exposure, each flowering stem end was subsequently stood in 500 mL plastic bottle containing distilled water and stored in ambient temperature (27.5°C, 91% R.H.). The following determinations were recorded every other day for assessments of each flowering stalk weight loss as percentage. Water uptake by flowering stalk was measured as mL. Vase life (days) was considered terminated when 30% of the flowers on each stem wilted and lost color. Wilting was assessed as percentage by visual mean and scores were given ranging from 0 to 100%. Total anthocyanin content was determined according to the method of Ranganna (1997) that compared with absorbance value at wavelength of 535 nm by the use of spectrophotometer model V-325-XS, from China. Total anthocyanin content was expressed as mL per 100 g Fresh Weight (FW). Level of bract browning was assessed as percentage by visual mean and scores were given ranging from 0 to 100%. The collected data were statistically analyzed using the SPSS Computer Program, Version 6 (SPSS, 1999).
RESULTS
After exposure with different concentrations of 1-MCP (0, 300, 600 or 900 ppb) and various periods of time (4 or 8 h) and then kept in plastic bottle containing distilled water stored at ambient temperature, the results composed of:
| Table 1: | Weight loss of flowering stalk of siam tulip after fumigating with 1-MCP |
ns: Non significant | |
Weight Loss of Flowering Stalk
The results indicated that 1-MCP fumigation had no effect to the weight
loss of flowering stalk of siam tulip during vase life (Table
1).
Water Uptake
During postharvest life, the results began to show significant differences
in water uptake by flowering stem of siam tulip since, the sixth day. Both treating
with 1-MCP at 600 ppb for 4 h and 300 ppb for 8 h stimulated the highest water
uptake through flowering stem of 6.00 and 5.40 mL on 14 days after storage (DAS),
respectively (Table 2).
Vase Life
The result from Table 3 showed that flowers-exposed to
1-MCP at 300 ppb regardless of exposure duration increased the siam tulip’s
vase life by 12.90 days. While the interaction of different concentrations and
fumigation periods of 1-MCP had no significant effect on the vase life of siam
tulip flowers.
Wilting Percentage
Siam tulip flower showed a sharp increase the wilting incidence after storage.
The results showed that flower treated with 1-MCP at 300 or 600 ppb for 4 or
8 h appeared the least bract wilting, as measured by visual means at 8 DAS (Table
4).
Anthocyanin Content
The results from Table 5 showed that the concentrations
of anthocyanin gradually decreased during storage. Siam tulip flowers started
to show a highly significant difference of anthocyanin content after 6 DAS.
Flower-treated with 1-MCP at 300 ppb for 8 h retained the maximal anthocyanin
content of 32.95 mL per 100 g FW on 12 DAS.
| Table 2: | Water uptake by flowering stalk of Curcuma aeruqinosa Roxb. after fumigating with 1-MCP |
Letter(s) within columns indicate least significant differences (LSD) at *p = 0.05, **p= 0.01. ns: Non significant | |
| Table 3: | Vase life of siam tulip flower after fumigating with 1-MCP |
Letter(s) within columns indicate least significant differences (LSD) at *p = 0.05. ns: Non significant | |
Thus, 1-MCP treatment at 300 ppb for 8 h had a positive effect on anthocyanin pigment in flower bract.
| Table 4: | Wilting percentage of siam tulip flower after fumigating with 1- MCP |
Letter(s) within columns indicate least significant differences (LSD) at *p = 0.05, **p = 0.01. ns: Non significant | |
| Table 5: | Anthocyanin content in bract of siam tulip after storage |
Letter(s) within columns indicate least significant differences (LSD) at *p = 0.05, **p = 0.01. ns: Non significant | |
| Table 6: | Level of browning appearance of siam tulip’s bract after fumigating with 1-MCP |
Letter(s) within columns indicate least significant differences (LSD) at *p = 0.05, **p = 0.01. ns: Non significant | |
Level of Browning Appearance
The degree of bract browning on the flowers rapidly increased during storage.
At longer storage times, the occurrence of bract discoloration proceeded. Bract
browning appearance of all treatments showed significantly different levels
while recording the data at two daily intervals. The results from Table
6 indicated that treating with 1-MCP at 300 ppb for 8 h resulted in the
least browning percentage of 12.20% on 10 DAS. Therefore, it is possible to
apply 1-MCP for control the bract browning in siam tulip flower.
DISCUSSION
To test the effect of 1-MCP on postharvest life and other postharvest characteristics of siam tulip flowers, Laddawan were treated with various concentrations of 1-MCP in combination with fumigation periods for 4 or 8 h. The results revealed that during storage, the weight loss of the siam tulip flower steadily declined throughout their vase life and were quite invariable among the treatments. A similar finding in a previous reported by Porat et al. (1999) found that 1-MCP did not affect weight loss in oranges, while Wu et al. (2009) reported that the treatment with 0.5 μl L-1 1-MCP significantly delayed weight loss of Chinese chive scapes flowers. The opposite result was confirmed by Chutichudet et al. (2010), who cited that patumma flowers treated with different concentrations of 1-MCP for 4 or 8 h affected to lower the weight more than that of untreated flowers. This was probably due to the fact that siam tulip flower was cut at a young stage and considered as a perishable product and susceptible to readily loosing a lot of water through transpiration immediately after cutting (Nakano et al., 2003). This caused the deleterious results and led to show the similar fresh weight of flowering stem between 1-MCP treated and untreated flowers (Ben-Yehoshua and Cameron, 1989).
The results of water uptake by flowering stalk showed that treatment with 1-MCP at 300 ppb for 8 h and 1-MCP at 600 ppb for 4 h remarkably increased water uptake through flowering stem more than in the control flowers. This indicated that a positive water balance in these flowering stems could be improved by 1-MCP application after cutting. However, there is a few published data reported in the role of 1-MCP related to postharvest physiological characteristics of the siam tulip flowers. While Chutichudet et al. (2010) found that 1-MCP fumigating had no effect on the water uptake of Patumma flowering stalk during vase life.
For the vase life of siam tulip flower, the results showed that the interaction of different exposure by 1-MCP at 0, 300, 600 or 900 ppb for 4 or 8 h had no effect on extending the flower longevity. This result is consistent with the findings of Chutichudet et al. (2010), who showed 1-MCP had no effect on the vase life of Patumma. The lack of these responses may have been due to plant tissues varying greatly in their ability to respond to the 1-MCP substance (Blankenship and Dole, 2003). In addition, another reason may be due to the efficacy of 1-MCP. It may have a transient ability to bind to ethylene receptors of the plant tissue in which their effects for blocking the ethylene produced at the later storage is not permanently attached, or it binds to other receptors (Sisler and Serek, 1997). This is in agreement with the previous data of Blankenship and Dole (2003), who found that the concentration of 1-MCP gas in fumigated plant material declined with time. Thus, after storage, the 1-MCP effect was almost completely lost. These caused to fail for blocking ethylene action in some species of cut flowers (Kim et al., 2007) such as several Australian native cut flowers (Macnish et al., 2000) because the diffusion of 1-MCP out of plant material after applying is rapid. Harima et al. (2003) also found that the length of the protection period by 1-MCP varies with plant species and tissues. These does not corresponded to the results of Able et al. (2002) and Yuan et al. (2010), who reported that 1-MCP treatment markedly increased the shelf life of broccoli (Brassica oleracea var. italica) florets and Mokara Jairak Gold (Honghem et al., 2007). However, at present there is limited research that has determined the effectiveness of 1-MCP to postharvest longevity in cut siam tulip. Additional experiments are needed to further investigate the effects of 1-MCP related to postharvest physiological characteristics of siam tulip flower.
The results on wilting showed that no obvious differences in wilting occurrence between flowers of 1-MCP-treated and control treatment during vase life. A possible explanation for these effects of 1-MCP may be that bract wilting resulted from the failure of the cut stem to replace water lost mainly through transpiration (Bunya-Atichart et al., 2004). These brought about a hastening to eventually senescence of flower as the longer storage period evolved. A related observation that 1-MCP affected to delay the flower wilting as the result of promoting the more water uptake by flowering stem was observed particular at 8 DAS. While some researchers found the 1-MCP had no effect to delay the wilting of some flower, such as Patumma (Chutichudet et al., 2010) and Oriental hybrid lilies (Çelikel et al., 2002). However, these are not in line with the results of Celikel and Reid (2002), who found that 1-MCP could prevent the rapid wilting of carnation Sandra, alstroemeria (Alstroemeria), snapdragon, larkspur (Consolida ambigua), sweet william (Dianthus barbatus), stock (Matthiola incana) and penstemon Firebird (Serek et al., 1995a).
The results of anthocyanin content showed that anthocyanin content in the bract of flower declined continually until the end of the storage period, with those flowers treated with 300 ppb of 1-MCP had a greatest amount of anthocyanin (32.95 mL per 100 g FW). This result was also found to be true in Patumma flowers (Chutichudet et al., 2010). These may be due to the effects of 1-MCP depend on the plant species (Serek et al., 1995b). Generally, anthocyanin is considered in a group of plant flavonoids, which is often degraded after harvest, accompanied by flower browning (Underhill and Critchley, 1994). In some cases, anthocyanin degradations occur due to changes in the vacuoles that decrease the stability of the pigments and cause the chemical degradation of the anthocyanins, which result to senescence process (Oren-Shamir, 2009). Hershkovitz et al. (2005) cited that pretreatment with 1-MCP could reduce the damage of membrane in fresh product, which is an important factor involved in retaining bract discoloration. These results indicated that 1-MCP application had potential for commercial use to maintain the flower quality in term of pink color. The biochemical background of these effects, however, is still largely unknown, so properties of the 1-MCP involved in anthocyanin degradation require detailed characterization.
For browning incidence, the results showed that 1-MCP application at 300 ppb for 8 h dramatically affected to decrease the browning appearance. The flower-treated with 1-MCP at this treatment also exhibited significantly the highest water uptake and the maximal anthocyanin content during vase life. Generally, bract browning is a senescence symptom accompanied by decreasing the water uptake and degrading the anthocyanin in flower (Oren-Shamir, 2009). Able et al. (2002) found that 1-MCP treatment had an important role to decrease the color change in florets of broccoli. In addition, Tian et al. (2005) also found that water loss leads to change in anthocyanin pigment molecules, ultimately yielding brown pigments. Thus, the more water uptake by flowering stem, the higher anthocyanin level and the less browning of bract were observed which is consistent with the findings of Jiang et al. (2002). From the results, it may be possible to confirm the positive effect of 1-MCP treatments on alleviating the browning appearance. However, the specific mechanism of 1-MCP in reducing the browning incidence is still scarcely known. A better understanding of the mechanisms involved in improving the siam tulip’s qualities should be further investigated on the effects of 1-MCP at 300 ppb in conjunction with longer application period for extending the flower longevity and maintaining the postharvest characteristics.
In conclusion, it was found that siam tulip flowering stems responded positively to 1-MCP application at 300 ppb for 8 h by exhibiting to promote the quality characteristics of the highest water uptake, the best retention of anthocyanin content and the lowest browning appearance. However, the application of 1-MCP had no effect to the percentage of weight loss of siam tulip during vase life. Thus, 1-MCP at 300 ppb for 8 h has potential to slow the loss qualities of siam tulip during storage under ambient storage compared to the untreated control.
ACKNOWLEDGMENTS
This study was funded by the Mahasarakham University under project No. 5201087/2552. The authors wish to express their sincere thanks to the Financial Office for financial assistance and Mr. Paul Dulfer for his kindness to improve this manuscript. We appreciate the support of Dr. Sucharit Suanphairoch, who kindly provided the 1-MCP.