Effects of Cardboard Box Ventilation Hole Size During Forced-Air Precooling on Postharvest Quality and Physiological Properties in Cut Roses

Abstract

Forced-air cooling (FAC) is a method for rapidly reducing the temperature of horticultural products. However, its effects on the physiological properties and quality of cut flowers remain elusively unclear. This study investigated the impact of FAC with different vent hole diameters (4, 8, and 12 cm) on multiple metabolic pathways and the quality of cut rose flowers. Compared with controls with a conventional slow cooling method, FAC using 8 cm vent holes (FAC8) prolonged the vase life of cut roses by 3 days and reduced Botrytis cinerea incidence by 60%. The data revealed that FAC8 suppressed excessive transpiration in the late vase stages while it enhanced water uptake throughout the vase period. Additionally, FAC8 reduced the respiratory rate in cut roses, decreasing cumulative respiration by 15% versus controls. When detached leaves from cut roses were subjected to water loss treatment, FAC8 induced tighter stomatal closure, resulting in a 33% smaller stomatal aperture than that of controls after 2 h. Correlation analysis of measured indices demonstrated that FAC significantly contributed to the improvement of postharvest quality (p < 0.05) via the regulation of physiological properties. In conclusion, FAC enhances the postharvest quality of cut roses by maintaining stomatal regulatory ability.

1. Introduction

The rose (Rosa hybrida) is the world’s most widely-traded cut flower [1]. Cut roses possess extremely high ornamental and economic value [2]. The flower opening and senescence of roses are regulated by multiple factors [3]. After being harvested, cut flowers carry a large amount of field heat, which accelerates their senescence [4]. Once cut flowers are packaged, heat will accumulate within the limited packaging space, making it difficult for cut flowers to cool down [5]. Particularly since the cooling capacity of transport vehicles is limited, packaged cut flowers seldom achieve effective cooling during transit [6].

Forced-air cooling (FAC) allows cold air to rapidly pass through the packaging boxes through the suction effect [7], and it is widely utilized for the postharvest treatment of fruits and vegetables due to its high cooling capacity, rapid cooling speed, and low energy consumption [8]. It is also the most common and effective method for precooling cut flowers [8] and is especially an optimal precooling method for bundled packaged cut flowers [9].

For fruits and vegetables, FAC delays deterioration in appearance, texture, flavor, and nutritional quality [10,11]. In kiwifruit, it slows the loss of freshness and hardness [12]. In litchi, FAC mitigates declines in soluble solids content and anthocyanin levels [13]. For nectarines, mangoes, and apricots, it retards decreases in peroxidase activity, ascorbic acid content, and levels of other bioactive compounds, thereby delaying cellular senescence [10,14,15,16]. In broccoli, FAC attenuates the loss of antioxidant enzyme activity, preserving marketable quality [14].

The vase life of cut flowers is governed by complex metabolic processes [17,18]. Mitigating transpirational water loss is crucial for maintaining freshness [19,20], while preserving water uptake capacity delays wilting [21,22]. Cut flowers exhibiting a lower respiratory rate generally demonstrate extended vase life [23]. Stomata, functioning as regulators of plant physiological activity, coordinate gas exchange and transpiration, thereby influencing interconnected processes such as respiration, water transport, and water loss [24,25,26,27]. Variations in vase life under dehydration stress and longevity following cold storage are linked to the stomatal regulatory capacity for transpiration [19,28]. FAC has been shown to prolong vase life [29]; however, the underlying physiological and metabolic mechanisms of FAC action in cut flowers remain poorly understood.

Here, we aim to investigate the effect of FAC on the physiological metabolism and quality of cut rose flowers. We found that FAC prolongs the vase life of cut roses by influencing transpiration and respiration mainly through the regulation of stomatal aperture. Our findings elucidate the metabolic mechanisms underlying FAC-mediated vase life. They provide important guidance for optimizing other precooling technical parameters in cut flowers.

2. Materials and Methods

2.1. FAC Device

The experiment employed a custom-built FAC device composed of an axial flow fan, a fan speed controller, a static pressure chamber, and a canvas. The axial flow fan operated at 220 V, with an air volume of 14,900 m³·h⁻¹, a power rating of 550 W, and a rotational speed of 2800 rpm. The fan speed controller had an input voltage of 220 V and an output voltage ranging from 0 to 220 V. The static pressure chamber, constructed from tung wood, had internal dimensions of 1 m (length) × 0.9 m (width) × 1 m (height). The canvas served to seal the flower boxes, preventing airflow bypass during FAC treatment.

2.2. Plant Material and Treatments

The cut flowers used in this study were obtained from the cultivation base of Zhihui Horticulture Technology Co., Ltd. (Kunming, Yunnan, China). Vigorous pest- and disease-free cut roses (Rosa hybrida ‘Peach Avalanche’) harvested at commercial opening stage 3 [30] were selected for experiments.

After harvest, the cut roses were immediately transferred to the postharvest processing workshop. A fungicidal spray against Botrytis cinerea was applied (excluding flowers monitored for B. cinerea symptoms), followed by commercial packaging. Roses designated for FAC were packed in 0.3 cm thick single-wall corrugated cardboard boxes (100 cm × 45 cm × 20 cm) with mechanically-cut ventilation holes of nominal 4 cm, 8 cm, or 12 cm diameter (actual diameter tolerance: ±0.2 cm). The control group was packed in boxes with mechanically-cut 4 cm diameter holes (4 cm being the industry benchmark aperture). Each box contained 12 bunches (10 stems/bunch), arranged in a staggered configuration. All packed flowers were transferred to a cold storage room maintained at 2 °C (2 °C being the standard commercial rose storage temperature [5]). For FAC treatment, boxes were positioned adjacent to the mobile FAC unit. The fan speed was maintained at 2 m·s⁻¹ at box inlets throughout the fixed 2 h FAC treatment period, with actual cooling times to reach 8 °C simulated transport temperature (8 °C being a commercial transport temperature for roses [6]) being treatment dependent (see Figure S1). The control group employed the slow control cooling methodology and was positioned at least 3 m away from the FAC device to prevent any potential influence of accelerated airflow from the FAC unit. This configuration ensured that cooling in the control group occurred solely through gradual inward diffusion of cold air, achieving passive temperature reduction in cut flowers.

After precooling, the cut roses designated for stomatal analysis were transported within 30 min to the postharvest evaluation room at the National Phosphorus Resource Development and Utilization Research Center (Kunming, Yunnan, China). The room was maintained at 24 ± 1 °C and 70 ± 5% relative humidity, with 15 μmol·m⁻²·s⁻¹ photosynthetic photon flux density provided by light-emitting diode lighting under a 16 h photoperiod. Stem bases were trimmed underwater to a length of 50 cm, retaining leaves distal to the third pentafoliate node and removing basal foliage. Five stems per vase were placed in 1 L of deionized water for a 12 h light period rehydration prior to stomatal function assessment.

Additional cut roses for phenotypic and physiological assessments during the vase holding period were transferred to an adjacent cold storage chamber (6–8 °C) for 4 day simulated transport. At the beginning and end of simulated transportation, the fresh weight of the packaged cut roses was measured in cold storage. After simulated transport, the cut roses were transferred without hydration within 30 min to the aforementioned controlled-environment room. Stem bases were trimmed underwater to 50 cm, retaining leaves distal to the third pentafoliate node after basal foliage removal. Stems were placed in 1 L of a 150 mg·L⁻¹ 8-hydroxyquinoline solution (5 stems per vase) for vase life evaluation and physiological indicator monitoring.

2.3. Airflow Rate

At the start of FAC, an anemometer probe was positioned perpendicular to the airflow direction at the geometric center of the packaging box inlet vent to measure air velocity. This value represented inlet air velocity (v_in). The airflow rate at the packaging inlet was calculated as follows:

$${\mathrm{Q}}_{\mathrm{in}}={\displaystyle \frac{A_{\mathit{in}}\times v_{\mathit{in}}}{1000}}$$

(1)

where Q_in is the airflow rate at inlet (L·s⁻¹), A_in is the cross-sectional area of inlet vent (cm²), v_in is the air velocity at inlet (cm·s⁻¹), and 1000 is the unit conversion factor (cm³·s⁻¹ to L·s⁻¹).

2.4. Cooling Rate

After commercial packaging, temperature/humidity sensor probes were inserted into floral tissues at mid-height positions on both inlet and outlet sides of packaging boxes to monitor rose temperature during precooling and simulated transport. Using recorded temperature profiles, the average cooling rate (ACR, °C h⁻¹) was calculated as follows:

$$\mathrm{ACR}={\displaystyle \frac{T_i-T_f}{t}}$$

(2)

where T_i is the initial temperature of cut roses before precooling (°C), T_f is the target transport temperature (8 °C), and t is the time elapsed until core temperature of cut roses reached 8 °C (h).

2.5. Fresh Weight Loss Rate of Cut Roses

The fresh weight loss rate (FWLR, %) of cut roses during simulated transport was calculated as follows:

$$\mathrm{FWLR}={\displaystyle \frac{{\mathit{FW}}_i-{\mathit{FW}}_f}{{\mathit{FW}}_i-W_{\mathit{pa}}}}\times 100$$

(3)

where FW_i is the initial fresh weight of cut roses at the start of simulated transport (g), FW_f is the final fresh weight of cut roses at the end of simulated transport (g), and W_pa is the weight of the packaging materials used for commercial packaging (g).

2.6. Leaf Relative Water Content, Transpiration Rate, and Stomatal Aperture of Cut Roses

Following full rehydration, the third pentafoliate leaf (from the floral apex) was excised per treatment replicate. Its fresh weight was recorded as saturated weight (SW, g). Leaves underwent controlled dehydration (24 ± 1 °C, 70 ± 5% relative humidity) with fresh weights recorded at 20 min intervals. Dry weight (DW, g) was determined after oven-drying at 70 °C for ≥24 h.

Leaf relative water content (RWC, %) and transpiration rate (TR_leaf, mmol·m⁻²·s⁻¹) were calculated as follows:

$$\mathrm{RWC}={\displaystyle \frac{\mathit{FW}-\mathit{DW}}{\mathit{SW}-\mathit{DW}}}\times 100$$

(4)

$${\mathrm{TR}}_{\mathrm{leaf}}={\displaystyle \frac{(W_{t1}-W_{t2})\times 55.51}{A\times (t_1-t_2)}}$$

(5)

where FW is the fresh weight at measurement (g); W_t1 and W_t2 are the leaf weights at times t₁ and t₂ (g), respectively; A is the leaf area (m²); t₂ − t₁ is the time interval between measurements (s); and 55.51 is the molar mass conversion factor (converting g H₂O to mmol H₂O).

Stomatal morphology was examined after 2 h dehydration using microscopic analysis. Aperture assessment employed the epidermal imprint technique. A thin layer of neutral balsam was applied to the abaxial leaf surface using a clean brush. After polymerization, the film was excised with forceps, mounted on glass slides, and imaged using bright-field microscopy. Six stomata per leaf were randomly selected and measured for pore length (L_p) and width (W_p) using ImageJ 1.54k (NIH). The stomatal aperture index was calculated as W_p/L_p.

2.7. Water Uptake and Transpiration Rates of Cut Roses

At designated time points during vase holding, the total weight of the vase system (W_total, comprising the vase, solution, and cut flowers) was measured using an analytical balance. Immediately after this measurement, the flowers were removed, and the vase containing the residual solution was weighed (W_res). The fresh weight of cut flowers was calculated as FW = W_total − W_res.

Water uptake rate (WUR, g H₂O·g⁻¹·d⁻¹) and transpiration rate (TR_flower, g H₂O·g⁻¹·d⁻¹) were calculated as follows:

$$\mathrm{WUR}={\displaystyle \frac{W_{\mathit{res,p}}-W_{\mathit{res,c}}}{{\mathit{FW}}_p\times t}}$$

(6)

$${\mathrm{TR}}_{\mathrm{flower}}={\displaystyle \frac{(W_{\mathit{res,p}}-W_{\mathit{res,c}})-({\mathit{FW}}_c-{\mathit{FW}}_p)}{{\mathit{FW}}_p\times t}}$$

(7)

where W_res,c is the W_res on the current measurement day (g), W_res,p is the W_res on the previous day (g), FW_c is the FW on the current day (g), FW_p is the FW on the previous day (g), and t is 1 day (time interval for calculation).

2.8. Respiration Rate and Cumulative Respiration Amount of Cut Roses

At designated time points during vase holding, the cut roses were placed in a 62 L sealed glass chamber for gas collection over a period of 1 h. Carbon dioxide concentrations in the chamber headspace were measured immediately before and after the collection period using a gas analyzer (Eranntex PTM600, Shenzhen, China). The respiration rate (RR, mg CO₂ kg⁻¹ h⁻¹) of the cut roses was calculated as follows:

$$\mathrm{RR}={\displaystyle \frac{(C_f-C_i)\times 0.111352}{t\times {\mathit{FW}}_c}}$$

(8)

where C_i is the initial CO₂ concentration (ppm), C_f is the final CO₂ concentration (ppm), t is the sampling duration (1 h), FW_c is the fresh weight of cut flowers on the current day (g), and 0.111352 is the conversion coefficient for 62 L headspace at 25 °C/101.325 kPa (converting ppm CO₂ to mg CO₂).

The cumulative respiration (CR, mg CO₂·kg⁻¹) of the cut roses was calculated as follows:

$$\mathrm{CR}={\sum }_{k=1}^n{\mathrm{RR}}_k\times 24$$

(9)

where RR_k is the respiration rate measured on day k during vase holding, and 24 is the number of hours per day.

2.9. B. cinerea Incidence and Vase Life of Cut Roses

B. cinerea incidence was recorded daily as the presence/absence of characteristic lesions on petals or leaves. Cut roses showing ≥1 typical lesion (water-soaked spots progressing to grey mold) were scored as infected. No severity scale was applied; evaluation was strictly binary (infected vs. non-infected). The incidence rate was calculated as the ratio of the number of infected cut roses to the total number of cut roses observed.

Vase life was defined as the duration from the start of vase holding until the onset of any of the following: irreversible wilting (≥50% petal collapse), senescence, discoloration, petal or leaf abscission, stem decay, or other signs indicative of loss of ornamental value.

2.10. Statistical Analysis

All measurements were performed with at least three replicates, and data are presented as means. Data were subjected to one-way analysis of variance (ANOVA), and means were separated by Duncan’s multiple range test using SPSS 17.0 (IBM Corp., Armonk, NY, USA) at a significance level of p < 0.05. SPSS 17.0 was used for the Pearson correlation analysis.

3. Results

3.1. Cooling Efficiency of FAC in Cut Roses

For FAC, the vent hole diameter in packaging boxes is an important parameter that affects the airflow rate. To evaluate the cooling performance of different vent hole diameters in FAC systems, we monitored the real-time temperature profiles of cut roses throughout the precooling process (Figure S1).

Compared to the control group (1.5 °C·h⁻¹), FAC significantly accelerated cooling, with the average cooling rate increasing by 9.7- to 16.3-fold. Increasing the vent hole diameter in packaging boxes from 4 cm to 8 cm enhanced the average cooling rate by 34% (from 14.5 °C·h⁻¹ to 19.5 °C·h⁻¹). However, further increasing the diameter to 12 cm yielded only 25% additional improvement (24.4 °C·h⁻¹), which was less than the improvement achieved when increasing from 4 cm to 8 cm vents (

Table 1. Cooling efficiency of cut roses.

Treatment	Control	FAC4	FAC8	FAC12
Parameter
Qin (L·s−1)	0	2.51	10.05	22.62
Ti (°C)	19.8 a	19.7 a	20.1 a	19.8 a
ACR (°C h−1)	1.5 b	14.5 ab	19.5 a	24.4 a

Note: Forced-air cooling (FAC) using packaging boxes with vent hole diameters of 4 cm (FAC4), 8 cm (FAC8), and 12 cm (FAC12). Q_in represents the airflow rate at the inlet of the packaging boxes. T_i represents the initial temperature of cut roses before precooling. ACR represents the average cooling rate. Data are shown as means (n = 3). Different lowercase letters indicate significant differences according to one-way analysis of variance (ANOVA) and Duncan’s multiple comparison test (p < 0.05).

).

3.2. Effect of FAC on Vase Life and B. cinerea Incidence in Cut Roses

The ultimate objective of FAC treatment of cut flowers is to extend their vase life. Since vase longevity is primarily governed by both the intrinsic senescence rate and B. cinerea infection, we evaluated vase life and B. cinerea incidence in cut roses to determine FAC efficacy.

Compared with the control group, FAC delayed wilting onset (Figure 1A). After precooling treatment, vase life increased progressively in the following order: control < FAC4 < FAC12 < FAC8 (Figure 1A,B). Without the B. cinerea control, FAC-treated roses exhibited less severe symptoms than the controls on day 5 (Figure 1C). Throughout the vase holding period, disease incidence in all FAC groups was lower than in the control group. Among FAC groups, FAC4 showed the highest infection rate, FAC12 intermediate, and FAC8 the lowest (Figure 1D).

3.3. Effect of Forced-Air Cooling on Respiration, Transpiration, and Water Uptake Rates of Cut Roses

The most crucial factors resulting in vase life reduction include water stress and insufficient available carbohydrates. In order to investigate the effects of precooling on the physiological parameters of cut roses, the transpiration rate, water uptake rate, and respiration rate of cut roses during the vase holding period were measured.

During early vase days (days 1–5), FAC-treated roses exhibited higher transpiration and water uptake rates than controls. In late vase days (days 5–9), a significant decline in water uptake rate coincided with a reduced transpiration rate in FAC-treated cut roses, while controls showed an elevated transpiration rate (Figure 2A,B). On day 1, FAC-treated roses had a higher respiration rate than the controls. During days 2–5, their respiration rate dropped below that of controls, followed by a more gradual increase through days 5–9 (Figure 2C). Throughout the vase holding period, FAC-treated cut roses had lower respiratory activity than the controls. Among FAC treatments, FAC8 decreased cumulative respiration by 15% compared with the control group (Figure 2D).

3.4. Effect of FAC on Stomatal Function in Cut Roses

Water issues comprise one of the most detrimental factors affecting the vase life of cut flowers. In cut roses, water relations are primarily mediated through the stomatal function of leaves. To investigate the effects of FAC on stomatal function in cut roses, the stomatal apertures in leaves were observed after precooling. Subsequently, rehydrated leaves were subjected to a water loss treatment to examine the stomatal response to dehydration stress. Concurrently, leaf relative water content and transpiration rate were monitored throughout dehydration.

After FAC treatment, leaves exhibited significantly smaller stomatal apertures than in the control group (p < 0.05). Among FAC treatments, FAC8 induced the strongest stomatal closure, with apertures significantly smaller than those in FAC4 and FAC12 (aperture size: FAC4 > FAC12 > FAC8; Figure 3A,B). During simulated transport, FAC-treated cut flowers demonstrated a significantly lower fresh weight loss rate compared to the controls. FAC8 showed the lowest fresh weight loss, followed by FAC12 and FAC4 (highest loss; Figure S2). During water loss treatment, FAC-treated leaves exhibited significantly smaller stomatal apertures than the controls (p < 0.05; Figure 3A,B). Consistent with post-FAC stomatal aperture measurements, FAC8 induced the strongest stomatal closure (stomatal aperture: FAC4 > FAC12 > FAC8). As leaf relative water content decreased, FAC groups exhibited significantly lower transpiration rates than the control group in both the stomatal transpiration phase (uninhibited stomata) and cuticular transpiration phase (stomatal suppression) during dehydration. Among FAC treatment, the transpiration rates were in the order of FAC4 > FAC12 > FAC8 across both phases (Figure 3C). Compared to the controls, FAC-treated leaves showed a slower relative water content decline and lower transpiration rate during water loss treatment (Figure S3).

3.5. Correlation Analysis of Measured Indices

To determine whether stomatal functional changes induced by FAC significantly affected the physiological properties and commercial quality of cut roses, we performed correlation analyses among the measured indices.

The results demonstrated that the vase life of FAC-treated cut flowers was significantly correlated with the fresh weight loss rate during simulated transportation, B. cinerea incidence, water uptake rate, transpiration rate, cumulative respiration, stomatal aperture, transpiration rate of leaves, and relative water content of leaves. Notably, the strongest correlation for vase life was observed with stomatal aperture after precooling and after a 2 h water loss treatment, exhibiting a correlation coefficient as high as 0.93. In addition to their significant correlation with vase life, stomatal aperture after precooling and after a 2 h water loss treatment were also significantly correlated with the fresh weight loss rate during simulated transportation, B. cinerea incidence on the 5th and 9th days of the vase holding period, water uptake rate on days 1 and 5, transpiration rate on days 1 and 5, respiratory rate on day 9, cumulative respiration on day 9, transpiration rate of leaves after a 280-min water loss treatment, and relative water content of leaves after 280 and 540 min water loss treatment. This high degree of overlap between indicators significantly correlated with vase life, and those correlated with stomatal aperture after precooling and after a 2 h water loss treatment indicated that the vase life of FAC-treated cut flowers is strongly correlated with stomatal aperture-related parameters (Figure 4).

4. Discussion

4.1. Influence of Vent Hole Diameter on Commercial Quality of FAC-Treated Cut Roses

FAC is a prevalent precooling technique in horticultural preservation [31,32]. FAC has been shown to impact the quality and cooling efficiency of fruits and vegetables by adjusting crucial parameters [31,33], such as vent hole diameter and airflow velocity [34]. In the realm of cut flower preservation, vase life and the incidence of B. cinerea are key indicators of commercial quality [35,36]. The cooling efficacy of forced-air cooling for cut flowers is primarily governed by the volumetric flow rate of cold air convectively exchanging heat with flowers and the temperature of the cooling air. The temperature of the cooling air is typically maintained at the optimal storage temperature (2 °C) for cut flowers [5]. Previous studies have shown that FAC can delay bent neck and petal wilting in cut roses by increasing airflow velocity [29]. Our preliminary experiments established 2 m·s⁻¹ as the suitable airflow velocity for achieving rapid and uniform cooling in cut flowers. However, no studies to date have investigated the impact of vent hole diameter on precooling effectiveness for cut flowers, nor the effect of FAC on B. cinerea incidence in cut flowers. Therefore, this study employed vent hole diameter as the variable regulating the forced-air cooling treatment rate to investigate the effects of forced-air cooling on cut roses. Our study fills these voids by demonstrating that the vent hole diameter exerts a profound effect on both the vase life and the incidence of B. cinerea in FAC-treated cut roses. Following FAC with three vent hole diameters (4 cm, 8 cm, and 12 cm), cut roses in the FAC group with the 8 cm vent hole exhibited optimal commodity quality. This result suggests that there exists an optimal balance in the design of packaging ventilation for FAC that maximizes the preservation of cut flower quality. These results demonstrate that employing packaging boxes with appropriately sized vent holes for FAC application to cut flowers effectively enhances the commercial quality of cut flowers.

4.2. FAC Prolongs Vase Life Through Regulation of Respiration and Transpiration Properties in Cut Flowers

Vase life in cut flowers is primarily governed by postharvest physiological metabolism [37]. Key factors resulting in vase life reduction include water stress and insufficient available carbohydrates [20,38,39]. Excessive respiratory activity during the vase holding period depletes stored nutrients prematurely, thereby shortening vase life [40]. During dry storage after harvest, the cessation of water supply coupled with excessive transpiration negatively impacts vase life [41]. Upon transfer to vases, transpirational pull directly influences water uptake [42]. The equilibrium between transpiration and water uptake constitutes a key determinant of wilting [21,43]. When transpirational water loss exceeds uptake capacity, cut flowers experience water stress, exhibiting symptoms such as wilting and discoloration that lead to loss of ornamental value [44,45]. While the efficacy of FAC in prolonging vase life of cut roses is established, its underlying physiological mechanisms remain poorly understood. In this study, FAC-treated flowers exhibited a higher respiratory rate than the controls on the 1st day of the vase holding period, potentially facilitating the recovery of normal physiological functions. Subsequently, the respiratory rate declined rapidly and rose gradually during later vase stages, probably helping to reduce nutrient depletion and delaying senescence. During the initial vase holding period, FAC-treated cut roses maintained an elevated transpiration rate, potentially facilitating rehydration and flower opening. As senescence progressed in later stages, the reduced respiration rate minimized water loss, sustaining hydraulic balance. Notably, FAC-treated cut roses consistently demonstrated a higher water uptake rate throughout the vase holding period compared to the controls, indicating that FAC likely enhances hydration by modulating transpiration. In summary, our findings demonstrate that FAC prolongs vase life in cut flowers by regulating respiratory and transpirational properties.

4.3. Stomatal Function Modulation by FAC Regulates Physiological Properties in Cut Flowers

Stomata serve as critical channels for gas exchange and water transport in plants [46,47], fulfilling essential functions that include regulating photosynthetic and respiratory gas exchange [48], modulating transpiration to maintain water balance [49], and influencing plant stress responses [28,50,51]. Cut flowers actively regulate the stomatal aperture to control water loss under dehydrating conditions [19]. It has been demonstrated that cut flower vase life after storage is strongly dependent on leaf stomatal functionality [28]. Although stomatal function is recognized as pivotal for postharvest physiological properties in cut flowers [19], the impact of FAC on stomatal behavior remains unclear. In this study, after FAC treatment, the leaves of FAC-treated groups maintained significantly tighter stomatal closure, and cut roses in these groups exhibited a lower fresh weight loss rate during simulated transport compared to the controls. Meanwhile, the leaves of FAC-treated groups also exhibited significantly tighter stomatal closure during water loss treatment compared to the control, leading to a reduced transpiration rate and mitigating fresh weight decline. Combined with the findings of this study regarding FAC’s effects on respiratory properties and water balance, these results collectively revealed FAC’s influence on stomatal function. Critically, stomatal functionality indicators showed a significant correlation with physiological and metabolic markers. These findings indicate that FAC8 treatment enabled cut roses to maintain superior stomatal regulatory capacity compared to the control group and FAC4 and FAC12 treatments. This enhanced physiological function resulted in improved water economy and a reduced respiration rate during vase life, along with tighter stomatal closure during water deficit stress, collectively contributing to better preservation of postharvest quality.

5. Conclusions

The current study compared the effects of FAC and a controls treatment using a conventional slow cooling method on the cooling performance, physiological properties, and commercial quality of cut roses. It was observed that FAC cooled cut roses more rapidly than the control treatment. FAC affected the stomatal function in leaves, reduced postharvest fresh weight loss, decreased the respiration rate during the vase holding period, enhanced water balance between transpiration and water uptake, mitigated B. cinerea incidence, and prolonged the vase life of cut flowers. These measured indices were all significantly correlated across treatment groups. The overall findings suggest that FAC modulates the stomatal aperture in cut roses, thereby regulating respiratory and transpirational properties to ultimately extend vase life. Future studies should elucidate the signaling mechanisms by which FAC enhances the stomatal closure capacity in cut roses.