Introduction

The cut flowers are exported for a few days or within a week to various areas in the world. The cut flower market is recognized as a worldwide market. Thus, the quality of cut flowers will be considered their conditions through the transportation and the supply chain (Fig. 1) to pretend to fresh and longer vase life at the final customers (Reid and Jiang 2012). These maintenances are big critical problems, and they can be affected the cost-effective-significant cut flowers (Fanourakis et al. 2013). Currently, the horticultural export studies need to extend for reducing the quality loss and controlling the environmental condition in exporting packages (Kasso and Bekele 2018;Mengistie et al. 2017).

Meanwhile, the cut flowers can endure a lot of different stress considerations in the postharvest handling chain, such as insufficient temperature changes, dehydrated cause injury, mechanical impairment, fungi (Botrytis cinerea), and bacteria that arrangement the fresh quality and their vase life (Andrew et al. 2010;Goszczyńska and Rudnicki 1988;Luna-Maldonado et al. 2012;Reid and Jiang 2012;van Meeteren 2007;Woltering and van Doorn 1988). The longer vase life is one of the most important for estimation of cut flower quality because it can be provided more benefit money and happy vase life time for the final customer (Fanourakis et al. 2013;Reid and Jiang 2012). To develop the convenient methods for providing the longer vase life of cut flowers, some factors must be considered, such as the easy way to use, natural preservative solution for safety, and lower-cost compounded alternative, securing accessibility (Ha et al. 2020;In et al. 2016b;Lee et al. 2018).

To guarantee genuine quality of cut flowers from the growers to the final customers; the important factors should be recognized, the potential methods for standard handling techniques should be improved and developed, and the critical quality control should be investigated at each point of exporting chains (Fig. 1). In this review paper, we have extended the recommendation by including and summarizing all factors which affected postharvest quality and provided genuine postharvest handling tools in the flower industry.

Factors for improving postharvest quality in cut flowers

It has been well known that the potential vase life of cut flowers is affected by not only various postharvest factors but also preharvest conditions, such as genetic characteristics or environmental conditions (Gorsel 1993;Gudin 1992;In et al. 2007;In et al. 2016b;Meeteren et al. 2005;Paull et al. 1992;Sharma et al. 2016;Stamps et al. 1994). To identify the critical control points for quality management, the model should predict to what extent the care condition will affect the vase life and the economic value at the final consumers in postharvest chains as the processing and measuring to contribute the flow of agricultural products (Fig. 2).

Temperature

The most critical factor in postharvest chains is temperature condition which directly affects quality losses and previous studies for the temperature control in the flower industry have not been successfully yet (Choon Sea et al. 2012;Goszczyńska and Rudnicki 1988;Gupta and Dubey 2018;Meeteren 2009;Reid and Jiang 2012). It seems the constant temperature in the local short harvest chain is more important than a low temperature in whole postharvest chains including domestic and export distribution because it can keep the fresh quality and give longer vase life of cut flowers; however, the lower environmental temperatures under the critical point of each species have harmful effects (Reid 1991;2001). The hazard of Botrytis seems likely involved to grow with the high temperature (> 15°C) in the local harvest chain and going higher than the end of the exporting chain (Fanourakis et al. 2013;Gupta and Dubey 2018;Reid and Jiang 2012;). It depends on the relative environmental condition (Fanourakis et al. 2013). In several cases, the pathogen, physiological, and environmental factors are related opposite to the temperature response. In the wet harvest, the cut stems of flower shoots are moved into water in a short time and its temperature affecting through whole postharvest chains (Reid and Jiang 2012). In most cases, the forced air cooling method is used for cut flowers, and the vacuum cooling method is applied to the potted plants to be seen as very effective (Reid and Jiang 2012). In most case, the water temperature is lower than the air temperature and it is depended on the water source (mostly use tap water) (Shahri et al. 2011). The studies of fresh weight and water balance in cut roses were affected by the treated stem-end location with tap water of 0°C while the leaves and blooms are familiar with the normal environmental location (de Stigter and Broekhuysen 1983). In chrysanthemum, the stems were treated in water of 20°C showed that the hydraulic capacity was diminished 20% of the initial stem segment, meanwhile, the treated stems with 5°C were showed still 100% of the initial capacity of the stem segment in 24 h (van Meeteren 2007). When the flower stems are placed in water during the harvest, storage, and distribution, it is a good method for preventing their turgor water loss (Reid and Jiang 2012;van Meeteren 2007). However, the bacterial risks are existent in the stem-end because water introduces the bacteria from the stem-end surface to the xylem vessel (Fanourakis et al. 2013). In fact, low temperature condition of the air and water in postharvest makes to avoid the bacteria growth.

Water temperature led to the extend vase life at a higher temperature during the storage (Cevallos and Reid 2001). The effect of water temperature at 0 - 10°C on vase life showed no significant difference between wet and dry storage treatments but ones at 12.5°C of wet storage have a few days longer vase life of some cut flower species, such as chrysanthemums, roses, tulips, gillyflowers, irises, and narcissuses (Cevallos and Reid 2001;Fanourakis et al. 2013). Cut carnation and Iris flowers survived at 15 and 20°C of water temperature during the wet storage (Cevallos and Reid 2001). In Gladiolus flowers, the temperature of dry storage for up to 36h at 5°C showed no affection with the relative water content (Costa et al. 2017). In cut rose (Rosa hybrida L.) ‘Sonia’ flowers, the low temperature (10°C) of vase water can be extended the stem water relation and provided 7.5 days longer vase life (Norikoshi et al. 2006).

Relative humidity

The proper postharvest method is related to control relative humidity (RH), which is the most important factor through the postharvest storage steps to extend maximum vase life and quality (Reid and Jiang 2012). Based on the vase life studies of cut roses postharvest, RH is actively interacted to keep long life of cut rose (In et al. 2016a). The function stomata are inhibited by pre-harvest in high RH (≥ 85%), and it reduced the vase life of cut roses (Carvalho et al. 2015). During the leaf development, a less-functional stomata can be enhanced with the high RH (Arve et al. 2017). During the storage and distribution, water loss from cut flowers was also increased under high RH condition through a regulation of stomatal opening rate, this led to decrease the vase life of cut flowers (Ahmad et al. 2011;In et al. 2016b). Previous study showed that the longest vase life of cut rose flowers is familiar with 90% RH in chamber and the shorted vase life in 60% RH. The bacterial population was developed and directly proportional to RH from 60% to 90% (Chamani and Wagstaff 2019). In chrysanthemum postharvest study, the recommended RH in plastic containers is 90% and the proper temperature is below 5°C (Silva et al. 2013;Vieira and Lima 2009;Vieira et al. 2014).

Water relation

Water relation is no less important factor to affect petal wilting in many cut flowers. Because the wilting stage can be precise due to a low water inherent potential of flower or stem. Its causes are related to blocking xylem in the decrease of water potential (van Doorn 2012). There are various factors that can affect the xylem blockage; however, the main reason is the bacterial proliferation in the stem end and the vase solution (van Doorn 2012). Xylem occlusions is the one of the major causes to diminish the postharvest quality of cut flowers due to the occurrence of flower dried stem-end before water placed likewise placing water immediately following harvest. The main reason for xylem occlusions is the development of bacterial growth in vase solution, and it includes bacterial stem-end in dry storage, and effects of non-sterile water prior to dry storage. The filling gas of xylem conduits can be caused by a cavitation event which has not been unclosed by the cutting methods (van Doorn 1995, 1997, 2012). This thing can occur in xylem conduits during the whole of the flowers stem (Cevallos and Reid 2001;Reid and Jiang 2012). Both wet and dry harvest showed that cavitation allows the water potential to turn into low enough (van Doorn 1997). Additionally, xylem occlusion can be found by wounding in wet harvest and dry harvest (van Doorn and Vaslier 2002).

Preservative solution

8-Hydroxyquinoline (8-HQ) is well-known as a heterocyclic phenol to inhibit DNA replication and RNA synthesis by deceiving the separable cations Mn²⁺ and Mg²⁺; therefore, it is used for treatments of antiseptic, antibacterial properties, and disinfectant products. In most cases, 8-HQ is used as a preservative treatment for providing long vase life in cut rose flowers (van Doorn 2012). The effect of Hydroxyquinoline citrate (HQC) and low pH was tested in stems of cut rose flowers (Rosa hybrida L., CVS. Sonia, Ilona, Polka, and Frisco) to prevent vascular blockage by decreasing the number of bacteria (Doom and Perik 1990). Other preservatives, such as sodium dichloro- isocyanurate (DICA), Physan-20, and 8-hydroxyquinoline sulfate (HQS) with sucrose, improved the vase life of ‘Orange Sky’, ‘Red Local’, ‘Pinky Show’, and ‘Yellow Queen’ roses in room temperature condition (Ketsa and Chinprayoon 2007). Treatment with HQS (0.25 g L^-1) and 5% sucrose was the most effective in extanding the vase life and postharvest quality of cut ‘Red Local’ and ‘Orange Sky’ flowers. The combined application of DICA (0.03 g L^-1) and 5% sucrose also prolonged the vase life of cut ‘Pinky Show’ and ‘Yellow Queen’ flowers, compared to tap water. These solutions effectively improved solution uptake, fresh weight, and reduced bent neck symptoms of cut roses, compared to tap water (Ketsa and Chinprayoon 2007). Chlorine dioxide (ClO₂) is well-known for an antimicrobial chemical safety factor with vase life of exported cut roses. In the export processes of cut roses, the treatments with holding solution of ClO₂ with 2% sucrose and pulsing solution of ClO₂ was effective for 2 days after harvest and recommendable in high relative fresh weight in cut roses (Rosa hybrida L. ‘Beast’) (Lee and Kim 2019). Cut rose (Rosa hybrida L.) cv. Rote Rose was studied to extend the vase life with glucose, citric acid, isothiazolinoic germicide, and aluminum sulphate solution. The results showed that a combined solution with 10 g L^-1 glucose, 30 mg L^-1 citric acid, 0.5 mL L^-1 CMI/MI, and 50 mg L^-1 aluminum sulphate (GLCA) was effective in increase the vase life of 8 rose cultivars. Treatment with GLCA extended the vase life of all the tested cultivars more than glucose plus HQS (Ichimura et al. 2006). Hydraulic conductance of stem segments in the control ‘Rote Rose’ roses decreased rapidly after harvest, but those for GLCA and glucose plus HQS were maintained at near their initial levels. The treatment with GLCA was increased the vase life day of all experienced cultivars more than glucose plus HQS. The prolonged vase life of cut rose ‘Rote Rose’ was showed by the assignment to add GLCA, sugars, and the vascular-occlusion-suppression without toxicity (Ichimura et al. 2006). 8-hydroxyquinoline citrate, sucrose, and peroxidase inhibitors had the effect on delaying senescence and extending vase life in cut lisianthus flowers. The conbined application of peroxidase inhibitors (catechol, CH and p-phenylenediamine, PD), sucrose, and 8-HQC significantly delayed senescence of cut lisianthus flowers through an improvement of water uptake and suspension fresh weight loss (Sharifzadeh et al. 2014).

Precooling and storage

Precooling flowers is a very necessary step to keep the flower temperature down from the greenhouse or field to store them in a proper temperature condition (Reid 1991;2001;Reid and Jiang 2012). Forced-air cooling is the best practice for the actively forced cooling bunched-flower by fans (Reid 1991;2001;Reid and Jiang 2012). Especially, for long-distance transportation, it seems the precooling step is very important to bring fresh flowers from farms to customers (Reid 1991;2001). A cold storage with the proper temperature is often recommeded for both short and long distance transportation to reduced an early wilting in cut flowers after harvest (Reid 2001). The floral industry has long been experienced cool temperatures for storing and improving the quality of flowers which were arranged long-distance ornamental markets, as established by using a cooling room, and the application of forced air precooling (Reid 1991;2001;Reid and Jiang 2012). Nonetheless, the transportation facilities are not going together with the optimal temperatures (which is well-known at or near 0oC for most flowers), indicating that the appropriate temperature for precooling has not been sufficiently determined (Reid 1991;2001). In most cases, the enviromental temperatures are above the freezing point in transportation to increase the flower opening quickly, and decrease the vase life in various flowers (Reid and Jiang 2012). The affection of respiration during storage and residual vase life at room temperature (20oC) was studied deeply and suggested the relationships to the effected temperatures on residual vase life (Reid and Jiang 2012). The vase life study was conducted on Ranunculus asiaticus L. to screen the effect of different temperature during the storage on senescence and postharvest performance. The results showed that wet and dry storage of premature buds of R. asiaticus for 72 h at 5ºC, subsequently placed them in distilled water significantly improved the vase life of cut flowers, and this method can be used as the effective treatment for postharvest storage (Shahri et al. 2011). On the other hand, it takes a lot of cost and effects on the quality preservative method for removing the lag time between harvest and cooling by improving the field heat cooling-down to cause the rapid deterioration of some horticultural crops. The comparison for improving postharvest techniques between the effects of wet and dry storage practices must be considered for specialty cut flowers which are receiving the high profit of exporting values (Reid and Jiang 2012). The proper wet or dry storage condition belongs to each of species, while expanding the storage time, it is likewise to reduce vase life. Rose (Rosa hybrida) or marigold (Tagetes erecta) seems to decline less with dry storage; however, lisianthus (Eustoma grandiflorum) or zinnia (Zinnia elegans) is preferred to dry storage and provided a long vase life (Ahmad et al. 2012).

Packing and transporting

Cut flowers are graded and parked in streamed card-board boxes, and they are lined with polythene film and hold with moist tissue paper shavings (Reid 2009). In Korea, the exported companies are usually using the plastic container with water- or preservative solution-carried end of the box to keep the stems are easy used water or preservative solution. In rose flower packing, the blooms are commonly packed in bundles of 20 each and tied with string or rubber band (Reid 2009). In orchids packing, these flowers are picked and kept in cardboard boxes, and entered to the packing room where they will be cleaned and graded color-wise, size, and quality-wise (De et al. 2014). Each of individual flowers is inserted in a plastic vial containing water or preservative solution (De et al. 2014;Reid 2009). These are then transferred to a designed box with each box carrying around 5-10 bunches and touched with cotton packed clot to be protected from transit shock (De et al. 2014;Reid 2009). Ethylene scrubbers with KMnO or Purafil may also be installed in the box (De et al. 2014). In chrysanthemum flower packing, these are packed in sleeves and are packed in designed boxes (Senapati et al. 2016). The flowers are evaluated according to bloom grades (Senapati et al. 2016). If blooms are abundant and loose, a pillow made of corrugated paper or a small plastic nest should be covered under the neck of the bottom layer a teaching end of the box (Senapati et al. 2016). Two flowers are kept on the opposite side to one another which is along the length of the box that the flower bud faces are in the side of the box and the stem end towards are in the center (Senapati et al. 2016).

LED light

Ha et al. (2020) studied on the light-emitting diode (LED) light to screen the effects of LED light on postharvest quality of cut roses ‘Lovely Lydia’. The treatments were performed under ultraviolet + LED light (UV+LED) inside the cardboard boxes with 4 ± 1°C and 50% RH after harvest. The control flowers were established without lighting systems. Morphological and physiological characteristics of cut rose flowers were measured after 48 h of transport condition. Treatment with UV+LED effectively prolonged vase life of cut flowers by 2.9 days, compared with the control flowers (10.6 days). UV+LED also significantly improved flower diameter, prevented the bacterial population at cut stem ends, and increased water uptake rate, fresh weight, and water balance of cut rose ‘Lovely Lydia’. These results also indicated that UV+LED light decreased the stomatal opening rate of cut roses, and consequently prevented the leaf transpiration after harvest, therefore, they can improve the longevity of cut roses. The lighting system is an impressive method to develop postharvest quality and provide long vase life of cut flowers which are exported overseas or long transportation (Ha et al., 2020).

Further investigation for handling postharvest mechanization in flower industry

The future investment tools for handling of cut flowers for export in the flower industry will be managed by the various factors which were displayed in this manuscript. On the other hand, the upgraded high quantity machine seems to prefer and apply in the near future, such as the automatic planters, the mobile controlling sprayers, rotary tillers, harrows, smart watering systems, drones for detecting insects, …, which are need a nd investigate t o smart farm p roject i n the F ourth Industrial Revolution (Nguyen et al. 2019). The use of smart techniques is a challenge for suggestion as a great opportunity to improve flower productivities and to increase vase life of cut flowers, and the florist technician can design to use new technology and software. In the further of handling postharvest mechanization goals, there are various expectation objections to prolong vase life and low operating-harvest and -postharvest cost: first, the improvement of smart operators for controlling florist farm must be investigated carefully; second, the use of preservative solution need to familiar with eco-friendly environment, sustainability and resource use must be raised efficiently; third, the education and training course for florist farmer must be attributed importantly; fourth, the innovated research on the preservative solution is needed for the high grade of vase life by suggesting the harvest and postharvest model.

Conclusion

Viewed by various tools as proper for handle development in cut flower export, this review paper is not only to help the florists and scientists to understand the postharvest technologies but also to provide the practical steps for keeping long vase life of cut flowers. The investigation of the preservative solution for cut flower must be continuing, the pre-cooling and cooling step need to innovate, the postharvest mechanization should be upgraded, and the reduce of transported time is the proper choice for flower export.