Abstract: Patumma is one of the most popular exported cut flowers in Thailand due to its attractive large pink bracts. Its export value, however is limited because of its poor vase life. The objective of this research was to extend patumma’s shelf life by using a substance against ethylene action, 1-Methylcyclopropene (1-MCP). The experiment was arranged in a Factorial in Completely Randomized Design, composed of two factors : 1-MCP concentration at three levels (0, 100 and 300 ppb) with period of fumigation at two levels (12 and 15 h) in a hermetically sealed plastic bucket (50 L) at 20°C. Afterwards, the treated and untreated flower stems were dipped in a plastic bottle filled with distilled water and stored in ambient temperature (27°C, 91% RH). Weight loss of flowering stalk, water uptake by flowering stem, vase life, anthocyanin content and bract colour were recorded every other day at ambient temperature. The results showed that flowers treated with 300 ppb of 1-MCP for 15 h had the least weight loss of the flowering stem and preserved the highest anthocyanin content at 8 DAV. For water uptake by the flowering stem, flowers treated with 100 ppb of 1-MCP for 12 h gave the highest water uptake from six to ten days after vase life (DAV), while the maximal vase life (10.25 days) of flowers treated with 100 ppb of 1-MCP for 12 h was observed. For bract colour, the results showed that treatment with 100 ppb of 1-MCP for 15 h gave the maximal L* and a* values at 12 DAV.
INTRODUCTION
Patumma (Curcuma alismatifolia), or Siam Tulip, is an annual monocotyledon crop which is considered a perennial like ginger in the family of Zingiberaceae. This plant is widely grown in the warm and wet climate of Thailand where no less than 30 species have been found. Curcuma alismatifolia is regarded as an appealing local ornamental plant and a popular cut flower with high popular commercial demand. Patumma typically form a lotus-like structure, containing a small flower bud and open flower surrounded by a large attractive bright pink bract (Olarn et al., 2007). Olarn et al. (2007) reported that after the flower was cut from its plant, the display life is relatively short at only seven days. Bunya-Atichart et al. (2004) reported that the end of vase life of the patumma flower is partially determined by a browning appearance on the flowers bracts which causes rapid loss of their attractive colour appearance and limits the length of their postharvest life. They also indicated that the shortened vase life of Curcuma alismatifolia var. Chiang Mai Pink may be related to ethylene. Ethylene is a plant hormone that accelerates the aging process leading to a shortened vase life in several flowers (Woltering and Van Doorn, 1988; Van Doorn, 2001; Serek et al., 2006). The compound 1-methylcyclopropene (1-MCP) has been found to be a very potent inhibitor of several ethylene-dependent processes in cutflowers. It prolongs the display life in commercial use (Feng et al., 2000) by competing with ethylene for the binding site on the ethylene receptor in plant tissue and controls ethylene biosynthesis and ethylene action (Sisler and Serek, 1997; De Wild et al., 1999; Muller et al., 2000; Mullins et al., 2000). Chutichudet et al. (2010a) indicated that 1-MCP fumigation for 8 h at high concentration of 600 ppb had the effect of lowering the flowering weight but not extending the vase life of the patumma flower cv. Chiang Mai Pink. This may be due to 1-MCP treatment at high concentrations of 600 and 900 ppb imposing a stress on the tissue of the flower. In an effort to extend the vase life of the patumma flower, they suggested the use of 1-MCP at a concentration lower than 600 ppb with a longer fumigation period. Furthermore, Chutichudet et al. (2010b) found that the Siam Tulip flowering stems in the treated group responded positively to 1-MCP application at 300 ppb for 8 h by promoting the tulip’s quality characteristics of high water uptake, best retention of anthocyanin content and low browning appearance during ambient storage compared to the untreated control group. However, 1-MCP had no effect in extending the postharvest life of patumma or the Siam tulip flowers. At the present time, not much information is available regarding the use of 1-MCP to extend the postharvest life and delay the senescence processes in the patumma flower. Therefore, there is still a need to experiment and study various concentrations of 1-MCP application and longer exposure periods of this substance in order to evaluate its ability as a postharvest tool for extending the potential vase life and regulating the quality characteristics of the patumma flower. The objectives of this study were to determine the efficacy of 1-MCP treatments at various concentrations and fumigation durations to evaluate the effects of 1-MCP in prolonging the post harvest life and maintain the flower’s qualities after harvesting.
MATERIALS AND METHODS
Patumma flowers (Curcuma alismatifolia) cv. Chiang Mai Pink were harvested at the commercial stage from a commercial garden in Chiang Mai in October 2009. Each flower was wrapped with a foam sheath and packed carefully in a fiberboard carton then transported in an air-conditioned vehicle to Mahasarakham University. During transport, buckets containing stems were covered with a plastic film shroud to minimize moisture loss. After they arrived at the laboratory, the flowers were selected again for uniformity of size, shape, initial bract colour and freedom from external damage before being placed into chambers for fumigating with 1-MCP. The stem end of each flower was recut with stainless steel scissors into 30 cm in length. The experiment was carried out from June to August 2009 at the laboratory of the Division of Agricultural Technology, Faculty of Technology, Mahasarakham University, in the Northeast of Thailand. A Factorial in Completely Randomized Design was arranged and composed of two factors: concentration of 1-MCP three levels (0, 100 and 300 ppb) with two periods of fumigation time (12 and 15 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, 100 and 300 ppb) with two periods of time (12 and 15 h) at the storage temperature of 20°C. While, control flowers were sealed in identical chambers without added 1-MCP and maintained under identical storage conditions. Following the treatments, each flowering stems was stood in the 500 mL plastic bottle containing distilled water and kept at ambient temperature at 27°C and 91% Relative Humidity (RH). The following determinations were assessed every other day for assessments of (1) weight loss of the flowering stalk was calculated as the percentage of the initial weight (%) (2) water uptake by the flowering stalk was measured as mL day-1 (3) vase life (days) was judged to have terminated when 30% of the flowers had withered. (4) 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 mg per 100 g fresh weight. (5) Bract colour was measured by using a Hunter Lab Model No. 45/0-L, Serial No. 7092, USA. CIE colour values L* (black = -100 and white = +100), a* (redness) (- = green and + = red) and b* (yellowness) (- = blue and + = yellow) were measured to describe the colour of flower’s bract. The collected data were statistically analyzed using the SPSS Computer Program, Version 6 (SPSS, 1999).
RESULTS AND DISCUSSION
After exposure with different concentrations of 1-MCP (0, 100 and 300 ppb) for various exposure periods (12 and 15 h), samples were then kept in plastic bottle containing distilled water and stored at ambient temperature. The recorded data composed of:
Flowering stalk weight: All patumma flowers decreased their weight as storage time prolonged. Weight loss of flowering stalk was greatly affected by 1-MCP treatments. Untreated control flowers exhibited a sharp decline in weight loss of the flowering stalk through vase life as compared to 1-MCP-treated flowers, except in the last 12 DAV. The minimum weight loss of flowers treated with 1-MCP at 300 ppb for 15 h was observed by 39.47% at 10 DAV (Table 1).
| Table 1: | Weight loss of patumma flowering stalk during vase life |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
| Table 2: | Water uptake by flowering stalk of patumma during vase life |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
Water uptake: Throughout the storage period, a marked reduction in water uptake by the flowering stalk was found in both the control group flowers and the flowers treated with 1-MCP. The results from Table 2 summarizes the water uptake trends in patumma flowers from day 2 to day 12 of storage. Highly significant differences in the water uptake during storage were observed. The most effective application of 1-MCP in promoting the distilled water uptake was found to be 100 ppb for 12 h.
Vase life: The results from Table 3 show that different 1-MCP fumigation periods have significant effect on vase life. Pretreatment flowers with 100 ppb 1-MCP for 12 h extended the longest vase life by 10.25 days, compared to the controls.
Total anthocyanin content: The results presented in Table 4 show that anthocyanin content in the bract tended to decline continually during storage. The significant difference in anthocyanin content, between treated flower and control, was presented during storage. Flower-treated with 300 ppb of 1-MCP for 15 h maintained the highest anthocyanin content (13.64 mg/100 g fresh weight) by the 8 DAV. Afterwards, all treatments showed no significant difference of anthocyanin content since 10 DAV.
Bract colour: The results indicated that flowers treated with 100 ppb of 1-MCP for 15 h retained the bract colour in terms of the highest L* and a* values throughout the storage. These indicated that flowers treated with 100 ppb 1-MCP for 15 h retained the highest brightness colour and redness (L* value 51.50, a* value 15.12) at the end of vase life by 12 DAV (Table 5, 6).
| Table 3: | Vase life of patumma after fumigation with 1-MCP |
| Letters within columns indicate least significant differences (LSD), at *p = 0.05, ns: Non significant | |
| Table 4: | Anthocyanin content of patumma after fumigating with 1-MCP |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
| Table 5: | Colour of patumma bract in term of L* value during vase life |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
For b* values, the results from Table 7 indicate that 1-MCP fumigation affected patumma bract’s colour in terms of the b* value only on the 4th DAV.
The effects of different concentrations (0, 100 and 300 ppb) in combination with two fumigation periods (12 and 15 h) of 1-MCP on the vase life and other postharvest characteristics of patumma flower cv. Chiang Mai Pink was investigated.
For weight loss of the flowers, the results revealed that during storage, the weight of the patumma flower steadily declined. In general, loss of flowering weight is one of the most important causes responsible for flower quality deterioration. Flowers treated with 1-MCP started to show a significantly lower percentage of flowering weight loss than that of the control flowers from 2 DAS to 10 DAS. Throughout the vase life time, the least flowering weight loss received from treating with 1-MCP at 300 ppb for 15 h was observed. This observation is consistent with the findings of Wu et al. (2009) whom reported that the treatment with 0.5 μL L-1 1-MCP significantly delayed weight loss of Chinese chive scape flowers. The opposite result was confirmed by Chutichudet et al. (2010b), who found that 1-MCP had no effect on weight loss in Siam tulip flowers. This was probably due to the fact that the patumma flower has fresh reproductive organs which are 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; Bunya-Atichart et al., 2004). The reduction in weight loss of flowering stalk during storage life in 1-MCP-treated flowers may be due to 1-MCP interfering with the autocatalytic production of ethylene (Sisler et al., 1996), which in these cases may be depended upon the concentration applied as 1-MCP and fumigation time in order to bind the ethylene receptors.
| Table 6: | Colour of patumma bract in term of a* value during vase life |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
Thus, the decrease of flowering weight from treating with 1-MCP at 300 ppb for 15 h were observed during vase life (Lalel et al., 2003). However, mechanisms of 1-MCP for slowing the flowering loss in cut patumma have not been determined.
The results on water uptake by the flowering stalk showed a significantly different trend during vase life. This is due to the fact that after cutting at a young stage, patumma flowers have no renewable source of water to compensate for that lost through transpiration. Detached flowers therefore experience water stress, which might be involved in activating senescence (Apelbaum and Yang, 1981). In this study, flowers fumigated with 100 ppb of 1-MCP for 12 h continued to absorb the maximal distilled water since 6 DAV through 12 DAV. These data are consistent with those of Chutichudet et al. (2010b) indicated that the water uptake by flowering stalk of Siam Tulip 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 (Blankenship and Dole, 2003). In addition, these results are 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). While, Chutichudet et al. (2010a) found that 1-MCP fumigating had no effect on the water uptake of Patumma flowering stalk during vase life.
| Table 7: | Colour of patumma bract in term of b* value during vase life |
| Letters within columns indicate least significant differences (LSD), at **p = 0.01, *p = 0.05, ns: Non significant | |
For shelf life, flower longevity of patumma in this study showed a significant difference between treatments. 1-MCP at 100 ppb for 12 h notably had the longest vase life of 10.25 days. Generally, during storage, water uptake by flowering stalk was related to the shelf life. Relatively more water uptake by the flowering stems is often associated with extending the vase life of cut flower (He et al., 2006). These results suggest that there may be a longer vase life for flowers treated with 1-MCP at 100 ppb for 12 h because this treatment induced the flower to absorb the most water. This implies that 1-MCP, for full effectiveness, should be applied at a low concentration for a longer period (Serek and Sisler, 2001). This result is consistent with the findings of Valentines et al. (2005) who showed that a pre-treatment with 1-MCP at 1 nll-1 for 12 h was sufficient to extend the vase life of Lollypop flowers by 4 days. However, the effect of 1-MCP remains quite variable among the reported studies. Chutichudet et al. (2010a), for example, reported that after pre-treatment with a range of 1-MCP dosages (0, 300, 600 and 900 ppb) in two fumigation periods (4 and 8 h) no beneficial effect to the vase life of patumma flower was noted. A possible explanation for these effects of 1-MCP may be that the effective durations for 1-MCP application should be 12-24 h to achieve a full response (Blankenship and Dole, 2003). Sisler et al. (1996) demonstrated that 1-MCP completely protects senescence of carnations when given a 24 h exposure at 0.5 nll-1. These results could be explained by the fact that active concentrations of 1-MCP vary widely, as do fumigation periods (Fan et al., 1999). Thus, additional experiments, which apply 1-MCP for longer periods, are needed to confirm the effects of 1-MCP related to extending the vase life and other postharvest physiological characteristics of the patumma flower.
The results on anthocyanin content of patumma flower were relatively affected by treatment with 1-MCP during vase life, from 2 DAV to 8 DAV. Flowers fumigated with 1-MCP at 300 ppb for 15 h had an extreme anthocyanin content of 13.64 mg/100 g FW) at 8 DAV. The effect of 1-MCP on anthocyanin content has been consistent with the results of Chutichudet et al. (2010a) whom revealed a pretreatment of patumma flowers with 1-MCP at 600 ppb for 4 h and 900 ppb for 8 h was effective in controlling anthocyanin degradation, a similar response that has been previously documented by Chutichudet et al. (2010b). They found that Siam Tulip flowers treated with 1-MCP at 300 ppb for 8 h benefited by retaining the maximal anthocyanin content of 32.95 mL per 100 g FW on 12 DAS. From this study, the results indicated that the application of 1-MCP, especially at concentration of 300 ppb for 15 h, clearly influenced anthocyanin degradation in patumma’s bract. Generally, anthocyanin pigment is often degraded after harvest (Underhill and Critchley, 1994) due to the deterioration in membrane function of bract (Jiang and Chen, 1995; Jiang et al., 2004). These results suggest that 1-MCP plays a significant role in controlling the senescence of the patumma flower. Therefore, commercial use of 1-MCP may enhance patumma quality under postharvest conditions. A possible explanation for the effects of 1-MCP being beneficial for maintaining the anthocyanin stability may be that pretreatment with 1-MCP could reduce damage to the membrane in fresh product, which is an important factor involved in retaining the pink colour of the bract in the patumma flower (Hershkovitz et al., 2005). Unfortunately, the activity of degrading enzymes and other biochemical and physiological parameters were not analyzed during storage. However, the possibility that the mechanism by which 1-MCP exerts its activity may be through the direct inhibition of anthocyanin degradation is unclear at present. Furthermore, with respect to detailed knowledge available on anthocyanin degradation, very little is known about its stability and catabolism in patumma flower. Further investigation on the effect of 1-MCP related to this characteristics is warranted.
For bract colour, a significant change of colour in terms of L* and a* values were observed during storage. The changes in L* value tended to decline with further storage resulting in the bract colour becoming darker. The reduction in a* values resulted in the patumma’s bract changing to a lower intensity of red. The application of 1-MCP at 100 ppb for 15 h significantly maintained the bract colours both in terms of L* and a* values compared to untreated control flowers, except b* value at 12 DAV. Bract of flower fumigated with 1-MCP at 100 ppb for 15 h preserved the best colour retention in terms of brightness and redness of bract. This may be due to the response of patumma flower to exposure times to 1-MCP at different concentrations (Serek et al., 1995b). This behavior seems to be a general effect of 1-MCP in most of the studied flowers, such as patumma (Chutichudet et al., 2010a) and the Siam tulip (Chutichudet et al., 2010b). Both studies cited a positive effect of 1-MCP treatments on preserving the flower colour. Therefore, patumma flower exposed to 100 ppb of 1-MCP showed a potential trend to preserve better bract colour during vase life. However, the cause of this 1-MCP effectiveness in colour retention has been limited. In addition, the specific mechanism of 1-MCP in maintaining the colour of patumma bract is still scarcely known. To understand 1-MCP efficacy for maintaining the bract colour, analysis of the enzyme level of pigment degradation will be required.
In conclusion, it was found that the efficacy of 1-MCP application for extending the vase life and maintaining patumma quality is influenced by concentration dose and treatment duration. Patumma flower treated with 1-MCP at 300 ppb for 15 h exhibited the least weight loss and the best retention of anthocyanin content. While, flowers treated with 1-MCP at 100 ppb for 12 h activated the highest water uptake and the longest flower longevity. Treatment with 100 ppb 1-MCP for 15 h showed the best colour retention of flowering bract in terms of L* and a* values. Thus, 1-MCP treatment may be a promising technique for extending the vase life and maintaining postharvest quality of the patumma flower during storage.
ACKNOWLEDGMENTS
This research was funded by the Mahasarakham University under project No. 5301043/2552. The authors wish to express their sincere thanks to the Financial Office for financial assistance, Ms. Janya Tuengsrangpan for her assistance. In addition, we also thank Mr. Paul Dulfer for his kindness in improving this manuscript. We appreciate the support of Dr. Sucharit Suanphairoch, who kindly provided the 1-MCP substance.