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Article

Ornamental Traits and Sensory Analysis of ‘Biquinho Vermelha’ Pepper Treated with Paclobutrazol

by
Beatriz R. Morales
1,
Lucas C. Costa
2,
Marta R. Verruma-Bernardi
1,
Josiane Rodrigues
1,
Fernando C. Sala
1,
Fernando L. Finger
3 and
Christiane F. M. França
1,*
1
Agricultural Sciences Center, Federal University of São Carlos (UFSCar), Araras 13600-970, São Paulo, Brazil
2
Department of Botany, Institute of Biological Sciencies, University of Brasília (UnB), Brasília 70910-900, Distrito Federal, Brazil
3
Department of Agronomy, Federal University of Viçosa (UFV), Viçosa 36570-900, Minas Gerais, Brazil
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(1), 75; https://doi.org/10.3390/agronomy15010075
Submission received: 2 December 2024 / Revised: 27 December 2024 / Accepted: 28 December 2024 / Published: 30 December 2024
(This article belongs to the Section Crop Breeding and Genetics)
Browse Figures
Versions Notes

Abstract

:
This study investigated the impact of paclobutrazol (PBZ) concentrations and application protocols on ornamental quality and consumer preference. PBZ was applied at five concentrations using three different protocols: drench at transplanting, drench 30 days after transplanting, and immersion. At commercial maturity, plants were assessed based on growth parameters related to height, canopy structure, fruit and leaf characteristics, and sensory attributes. The results indicated that PBZ treatments led to darker green leaves and, in general, the drench method, regardless of time application, was more effective in modulating plant growth compared to the immersion protocol. Conversely, the sensory analysis showed a greater preference among evaluators for plants treated with PBZ at 2.5 and 5 mg L−1 via drench at 30 days after transplanting (D30DAT) or through immersion (IM), even though IM was not associated with any of the ornamental quality parameters evaluated. Likewise, the application of PBZ by drench during transplanting is not recommended as the plants showed a reduced number and size of fruits, which affected the ornamental value of the plants and global preference. Therefore, PBZ applied by D30DAT at concentrations of 2.5 and 5 mg L−1 produced ‘Biquinho Vermelha’ pepper plants with attractive ornamental characteristics; and thereby, should be considered an alternative method for producers of potted ornamental plants.

1. Introduction

The global market for flowers and ornamental plants is rapidly expanding regarding the decoration of indoor spaces [1], often by using potted plants. ‘Biquinho’ (Capsicum chinense Jacq.), a member of Solanaceae family, is one of the most common pepper varieties in Brazil and is traditionally cultivated in conventional systems to produce fruits that are consumed fresh or processed [2]; this variety also exhibits appealing traits that make it suitable for ornamental use. The success of cultivating these plants as ornamentals depends on their ability to attract consumers through features such as beauty, quality, vigor, the color, shape, and size of their fruits and leaves, as well as a well-balanced canopy [3]. ‘Biquinho’ pepper fruits are cuspidal and triangular; green when immature, orange during the maturation process, and red when mature. The main characteristic is the lack of pungency. This variety holds an intermediate growth, reaching an average of 60 cm in height and 1 m in canopy diameter [4]. Therefore, it may not adapt to cultivation in small pots, a necessary condition for its use to decorate indoor environments [5].
Paclobutrazol (PBZ) is an effective plant growth regulator that inhibits gibberellin synthesis by blocking the oxidation of ent-kaurene to ent-kaurenoic acid [6]. PBZ has been successfully used to reduce the height of various ornamental plant species, including roses, sunflowers, orchids, marigolds, platycodons, petunias, and peppers [7,8,9,10,11,12,13]. The ornamental quality of potted pepper plants, as defined by the standards of the Brazilian cooperative Veiling Holambra in São Paulo state, is evaluated based on several quality parameters which include plant height [5]. For optimal ornamental quality, these plants should exhibit dense foliage that fully covers the pot surface, supported by rigid stems. In addition, the plants should present an appropriate fruit set per plant, with fruits at the desired maturity stage, and free of phytotoxicity or nutrient deficiencies. The efficacy of PBZ and other plant growth regulators is influenced by several factors, including plant species, cultivar, application concentration, method, and timing [14,15].
The application of PBZ through drenching of cultivation substrate, or by immersion of the root/substrate system in the solutions, has been demonstrated to effectively reduce plant height and enhance the ornamental quality of various Capsicum species. However, these methods can also exhibit phytotoxic effects under certain conditions [5,10,16,17,18], depending on the concentration applied. The results of these studies show a clear genetic effect regarding the different quality parameters evaluated in response to PBZ applications.
Previous studies investigating the effects of PBZ on the ‘Biquinho’ pepper (Capsicum chinense) have yielded inconclusive results. However, research examining PBZ application at a concentration of 10 µM revealed that root system immersion was significantly more effective than foliar spraying. Foliar application, in contrast, was found to be ineffective as a method for regulating growth in this variety [16]. Furthermore, concentrations of 20 to 60 mg L−1 of PBZ when applied via drench at 15 DAT on ‘Biquinho’ pepper significantly reduced the number of fruits and intensely atrophied the plant growth, reducing its commercial and ornamental value [5]. These researchers studied concentrations and application methods separately; however these factors must be studied together to achieve a better ornamental result for plants. Thus, concentrations lower than 20 mg L−1 under different forms of application were proposed in the present work for ‘Biquinho’ pepper.
The objective of this research was to determine the effect of PBZ concentrations and application protocols on the ornamental quality and global preference of pepper plants of the commercial variety ‘Biquinho Vermelha’.

2. Materials and Methods

2.1. Plant Material and Crop Management

The commercial variety of pepper ‘Biquinho Vermelha’ (Capsicum chinense Jacq.) was selected for this study. The seedlings were produced from commercial seeds in a protected environment at the Federal University of São Carlos, in the city of Araras, state of São Paulo, Brazil (−22.3114976 latitude and 47.3847851 longitude; 685 m altitude). During the experiment, the mean, maximum, and minimum temperatures were 21.3 °C, 27.8 °C, and 16.6 °C, respectively. Sowing was carried out in trays of 128 cells filled with the commercial substrate Carolina Soil® (Kinston, NC, USA) on 23 January 2023. On 28 February 2023, when the seedlings reached 2 to 3 pairs of leaves, they were transplanted into pots number 15 (1.17 L in volume; 11 cm in height, 10.45 cm in basal diameter, and 14.5 cm in upper diameter) filled with a substrate based on Pine bark (Spagnhol®, Piracicaba, Brazil). Cultivation in pots was carried out in the same place where the seedlings were produced: in a greenhouse under natural light conditions. Irrigation was supplied to the plants intermittently with a micro-drippers system. Each plant received approximately 300 mL of the nutrient solution formulated by Furlani [19].

2.2. Experimental Design

The plants were treated with the plant growth regulator PBZ (CULTAR® 250 SC (Syngenta Crop Protection AG, São Paulo, Brazil)) following three application protocols: IM-Immersion, for 10 s, of the root-substrate of the seedlings in the PBZ solutions, immediately before the transplanting into pots; DT-Drenching of 250 mL of PBZ solutions to the cultivation substrate, applied immediately after transplanting the seedlings into pots; and D30DAT-Drenching of 250 mL of PBZ solutions to the cultivation substrate, 30 days after transplanting.
The concentrations used in each of the application protocols were 0; 2.5; 5.0; 7.5, and 10 mg L−1 of the commercial product. In control plants, application protocols were followed, replacing the PBZ solution with tap water. Thus, 15 treatments were applied (3 application protocols × 5 concentrations of PBZ).
When 50% of the plants in each treatment reached commercial maturity (at least 30% of ripe fruits) the plants were evaluated for the ornamental quality characteristics described below. In plants where the application was made by immersion and drenching at 30DAT (115DAT).

2.3. Ornamental Quality Traits

The plants heights were measured from the base of the stem to the apex of the canopy (considering the last leaf completely expanded) using a ruler and expressed in cm. The canopy’s longitudinal and transverse diameters were measured using a tape measure, observing the plant from above and at an angle of 90° to the stem. The canopy compactness was determined by the transverse and longitudinal diameter ratio, where values closer to one (1) indicate a more circular canopy [10].
The chlorophyll index (SPAD) was determined with the SPAD-502 chlorophyll meter (Spectrum Technologies Inc., Plainfield, IL, USA), using measurements from nine leaves, three from the basal part, three from the middle part and three from the upper part of each plant. The leaf color parameters were obtained in the same position using the Minolta® Chroma Meter—CM-25d spectrophotometer (Konica Minolta, Tokyo, Japan). Positive values of parameters a* and b* indicate red and yellow coloration and negative values of a* and b* indicate green and blue coloration, respectively. The L* parameter indicates luminosity (0 = black and 100 = white) and the hue angle (h°) shows where the color is located in the diagram, where 0° and 360° correspond to red, 90° to yellow, 180° the green color and 270° the blue color. The intermediate angles correspond to a combination of these colors. Chroma (C*) indicates chromaticity, the vivacity of the color, represented by the distance from the center to the end of the diagram, which varies from 0 to 60 [20].
The total number of leaves and fruits of each plant were counted. The length of the leaves was measured from the insertion of the petiole to the apex of the limbus in a longitudinal direction, with a ruler and expressed in cm. The width of the leaf was measured at the longest transverse length of the limb, also using a ruler and expressed in cm. The leaves used for length and width measurements were the same leaves on which the colorimetric and SPAD chlorophyll index measurements were carried out.
The length and diameter of the fruits were determined with a caliper using the average of measurements of nine fully ripe fruits per plant when available and chosen randomly from the canopy or the maximum number of fruits on each plant, when smaller than nine.
The aerial part of the plant was detached from the pot at the substrate level with pruning shears and its fresh weight was obtained on a scale. Plant fullness was determined by the relationship between the shoot fresh weight and the height of the plant. Throughout the cultivation of pepper plants, daily assessments were carried out on each plant to identify the day of the opening of the first flower, with the result expressed several days after transplanting for anthesis.

2.4. Sensory Analysis

The project was approved by the Research Ethics Committee, CAAE 74062923.0.0000.5504. The sensory analysis of the plants was carried out at the Sensory Analysis Laboratory of the Federal University of São Carlos. For this, one plant from each treatment was used, totaling 15 potted plants coded with three digits and presented to the evaluators all at once. All plants presented were at commercial maturity (at least 30% of ripe fruits). 125 participants responded to the global preference test, showing interest and availability using a seven-point structured hedonic scale (7-liked extremely; 6-liked a lot; 5-liked moderately; 4-neither liked/nor disliked; 3-disliked slightly; 2-disliked it very much; 1-disliked it extremely).

2.5. Statistical Analysis

A completely randomized design with five plants per treatment was used. Treatments were arranged in factorial scheme 3 × 5 (3 application protocols × 5 concentrations of PBZ). Data related to agronomic and sensorial variables were subjected to analysis of variance (ANOVA) and means were separated using Tukey’s and Scott-Knott’s tests, both at p ≤ 0.05 for agronomic and sensorial variables, respectively. A principal component analysis (PCA) was performed to assess the major vector variation among agronomic and sensorial traits associated with PBZ application protocols and concentrations. All assessments were accomplished with the R software (v. 4.3.2) [21]. The outputs were plotted using the R package ‘ellipse’ [22] considering the Euclidean distances at 95% confidence (p < 0.05). Traits loading contribution > 0.4 was set up as a minimum threshold for variable selection.

3. Results

3.1. Ornamental Quality Traits

The analysis of variance presented in Table 1 showed a significant interaction between the concentrations and application protocols of PBZ for plant height, the height of first bifurcation, longitudinal and transverse diameters of the canopy, SPAD chlorophyll index, plant fullness, leaves length and width and for the C*, a* and b* parameters of the colorimetric analysis. The canopy compactness, fruit number and length, fresh weight of the aerial part, and the days to anthesis were significantly affected individually by the concentrations and application protocols of PBZ. The L* and h° parameters were significantly affected only by PBZ concentrations and the number of leaves and fruit diameter only by the application protocol.
All PBZ application protocols caused a reduction in plant height. This reduction was significant at all concentrations used as compared to the control when PBZ was applied by drench at transplanting (DT). However, when PBZ was applied via drench at 30DAT (D30DAT), a significant effect on height reduction was observed only from a concentration of 5 mg L−1 compared to the control. When applied as immersion (IM), PBZ was effective in significantly reducing plant height (24.4%) compared to control plants only at the highest concentration (10 mg L−1) (Table 2).
The application of PBZ by D30DAT produced significantly shorter plants when compared to IM at all concentrations of PBZ used, except for the control plants. The moment of the application of PBZ by drenching, whether at transplanting or 30DAT, did not significantly influence plant height (Table 2).
For the first bifurcation height, a significant difference was only observed in all concentrations relative to the control when PBZ was applied by DT. These plants showed a first bifurcation height, on average, 35.8% lower compared to D30DAT in all concentrations used except for the control. However, IM only produced plants with a first bifurcation height significantly lower than D30DAT at the highest concentration, 10 mg L−1 of PBZ (Table 2).
An increase in the SPAD chlorophyll index of leaves and plant fullness of plants treated with PBZ was observed. When PBZ was applied by DT, the leaves were greener, with a higher SPAD chlorophyll index compared to the leaves of control plants, regardless of the concentration used (Table 2). However, when applied by drenching 30 days later, this was only observed when the highest concentration was used (10 mg L−1 of PBZ). Leaves of plants treated with PBZ by DT were greener than when applied by IM and D30DAT in all concentrations except the control and the concentration of 5 mg L−1 of PBZ.
Plants treated with PBZ applied by DT showed improved plant fullness only at the lowest and highest concentrations compared to the control, not showing a direct relationship between the concentrations used and this characteristic (Table 2). However, when applied by D30DAT, better plant fullness was observed in all concentrations from 5 mg L−1. When the regulator was applied by IM, the increase in SPAD chlorophyll index and plant fullness was not significant (Table 2).
PBZ reduced the canopy longitudinal and transverse diameter of the canopy when applied by drenching, either at transplanting or at 30DAT. This reduction was significant when PBZ was applied by DT in all concentrations and from a concentration of 5 mg L−1 as compared to the control for the longitudinal diameter and transverse diameter of the canopy, respectively. D30DAT only significantly affected canopy longitudinal diameter from a concentration of 5 mg L−1 compared to untreated plants. However, the application of PBZ by IM did not have a significant effect on both diameters (Table 2).
Comparing the application protocols, there was no significant difference in the longitudinal diameter of the plants in which PBZ was applied by drenching at transplanting or 30DAT, except for the control. However, these two protocols produced plants with a longitudinal diameter significantly smaller than those in which PBZ was applied by IM (Table 2). The transverse diameter was significantly smaller than the control at a concentration of 5 mg L−1 when PBZ was applied by DT. In the other two protocols, no significant difference was observed between concentrations (Table 2).
Except for control plants, PBZ applied by DT from a concentration of 2.5 mg L−1 produced plants with smaller leaves in both length and width when compared to the D30DAT application protocol. Only at the highest concentration (10 mg L−1) was there a significant difference in leaf length between IM and D30DAT. At this concentration, IM produced plants with smaller leaves in length. For leaf width, comparing these last two protocols, there was only the exception of the control and for the concentration of 7.5 mg L−1. In the other concentrations, when applied by IM, the plants presented leaves smaller in width than those to which it was applied D30DAT (Table 2).
Based on instrumental color analysis, the leaves of all treatments were yellowish green, since all a* values were negative, indicating green color, and all b* values were positive indicating yellow color. The C* values were significantly lower in all concentrations used than the control when PBZ was applied by DT application protocol. The same was observed at concentrations of 5 and 10 mg L−1 when PBZ was applied by D30DAT and no effect was observed on the chromaticity of the leaves when PBZ was applied by IM. Comparing the application protocols, except for control plants, there was no significant difference in the chromaticity of the leaves between drenching at transplanting and at 30DAT, regardless of the concentration of PBZ used (Table 2).
A reduction in L* and an increase in h° values was observed with the application of PBZ. Except for the concentration of 7.5 mg L−1, all PBZ concentrations used were significantly lower than the control for these two parameters (Table 3).
The plant canopy became significantly more circular with increasing concentrations from the concentration of 7.5 mg L−1. Furthermore, increasing PBZ concentrations caused a significant delay in flowering beginning at a concentration of 5.0 mg L−1. This delay varied from three to four days at concentrations of 5, 7.5, and 10.0 mg L−1 compared to control plants (Table 3). However, although there was a delay in the beginning of flowering, this did not affect fruiting. The plants had, on average, 61.9 fruits. No significant difference was observed in the length of these fruits and the fresh mass of the aerial part when compared to the control in any of the PBZ-used concentrations (Table 3).
Drenching PBZ, either at transplanting or at 30DAT, produced plants with more circular canopy compared to plants in which PBZ was applied by IM (Table 4). The anthesis of plants in which PBZ was applied by DT was delayed by approximately 2 days compared to IM (Table 4). Plants in which PBZ was applied by DT had a significantly smaller number of fruits and these fruits were smaller in length than those of plants in which the other two protocols were applied. However, the D30DAT application protocol produced fruits significantly smaller in diameter than the fruits from plants in which PBZ was applied by IM and DT (Table 4).
The number of leaves was significantly lower in plants treated with PBZ applied by D30DAT compared to DT (Table 4). The fresh weight of the aerial part of the plants was significantly reduced when the application was made by drenching regardless of when this application was made (Table 4).

3.2. Sensory Analysis

The global preference test showed that participants had a greater preference for plants to which PBZ was applied using the IM and D30DAT application protocol in the two lowest concentrations, 2.5 and 5.0 mg L−1, as well as the control plant of D30DAT where PBZ was not applied (Figure 1 and Table 5). The ratings obtained by the 125 interviewees in all these treatments were presented as “moderately liked”. Furthermore, when the highest concentration (10 mg L−1) was applied by DT and D30DAT, the plants showed the lowest scores in terms of global preference together with those that were untreated and treated with 5 mg L−1 via the DT application protocol. All these plants were classified as ‘neither like nor dislike’. The plants to which concentrations of 2.5 and 7.5 mg L−1 were applied using the same method had intermediate grades (Table 5).

3.3. Principal Components Analysis (PCA)

From 24 inputs, 21 variables presented loading contributions higher than 0.4, which were delineated through two major components (PCA1 and PCA2). Together, such variables explained over 48%, 65%, and 56% of the total variation in IM, DT, and D30DAT, respectively (Figure 2A–C). Based on the PCA biplot, the clustering was better evidenced in both DT and D30DAT methods (Figure 2B,C). On the other hand, no marked discrepancy is observed in IM (Figure 2A). In DT, the biplot scaled two main clusters based on the vector of similarities. PCA1 positively scaled singularity for leaf color parameters (a*, SPAD, h°) and sensory analysis (GP) and negatively scaled with the growth parameters (Height, LDC, TDC, LW, and 1stBH). Such a response was closely associated with PBZ application or absence, respectively (Figure 2B). Likewise, in D30DAT, PCA1 positively scaled with leaf color (a*, SPAD, and h°), contrasting with growth parameters (LDC, Height, and TDC). However, it showed otherwise a singularity between growth traits and sensorial analysis parameters, which also varied over the range of PBZ concentrations. This was evidenced by three to four clusters displayed in the biplot (Figure 2).

4. Discussion

4.1. Ornamental Growth Traits

Previous studies have shown that PBZ application via drenching was more effective in reducing plant height than the root-substrate immersion method, regardless of whether it was applied at transplantation or 30DAT. Drenching also proved to be an efficient method for controlling the growth of pepper plants, including the varieties ‘Pitanga’ and ‘Bode Amarela’, as well as several accessions from Germplasm Banks of C. annuum and C. chinense [5,16,17,18], in addition to other ornamental potted plants [7,9,11,13,23,24,25,26,27].
Unlike the plant height, a significant difference was observed in the height of the first bifurcation when comparing PBZ application by drenching at two different times: at transplantation and 30DAT (Table 2). When PBZ was applied at transplanting, the height of the first bifurcation was significantly lower. In Capsicum plants, branching follows a dichotomous model: when the plant reaches 15–20 cm in height, a young branch terminates with one or more flowers, forming the first bifurcation (two new vegetative branches). These branches emerge from the leaf axils and continue to grow until new flowers form. This vegetative process repeats throughout the plant’s growth cycle, regulated by apical dominance and hormonal signaling [28]. Therefore, when PBZ is applied 30 days after transplanting, the plant remains unaffected by the inhibitor of gibberellin synthesis for a longer period. As a result, the internode length is less reduced, allowing the first branch to grow taller before the occurrence of the first bifurcation.
The increased plant fullness observed in plants treated with PBZ at 30 days after transplanting (D30DAT) with a concentration of 5 mg L−1 prevents the substrate from being visible when the plants are viewed from above [10]. Despite the observed reduction in vegetative growth, the shoot fresh weight of plants treated with PBZ did not differ from that of the control plants, regardless of the concentrations applied. In contrast, Petunia plants treated with the regulator showed a significant reduction in shoot fresh weight [13]. According to these authors, plant fullness is a key indicator of overall plant quality, as the density of growth is an important attribute of visual appearance.
Plant fullness is determined by the ratio of shoot fresh weight to plant height. The absence of a significant effect of PBZ concentration on this trait in plants treated with the immersion method (IM) can be attributed to the lack of a notable impact on plant height in these plants. This is despite the greater shoot fresh weight observed in IM-treated plants compared to those treated with the other two protocols. The increased shoot fresh weight in IM-treated plants can be explained by the lower effectiveness of this treatment in reducing vegetative growth, relative to PBZ drenching applied either at transplantation or 30DAT.
The reduced longitudinal canopy diameter observed in plants treated with PBZ via drenching at all concentrations, as well as at a concentration of 5 mg L−1 when applied 30 days after transplanting (D30DAT), compared to untreated plants, supports similar findings reported for Pitanga, ENAS-5007, and ENAS-5032 pepper varieties [17,18] and in sunflower, zinnia, basil, and physalis grown in pots [23,26,29]. Canopy compactness is defined by the ratio of the transverse to longitudinal diameters. The smaller longitudinal diameter of plants treated with PBZ via drenching, either at transplanting or 30 days after transplanting (D30DAT), resulted in a more circular and compact canopy compared to plants treated with PBZ by immersion.
Higher values of canopy compactness were only observed at PBZ concentrations above 7.5 mg L−1. However, when applied at higher concentrations (20 to 60 mg L−1) via drenching at 15 days after transplanting (DAT) or at concentrations ranging from 25 to 75 mg L−1 by immersion in eight pepper accessions, PBZ showed no effect on canopy compactness in Biquinho Vermelha pepper plants [5,10].
The observed reduction in leaf length and width in plants treated with PBZ via drenching (DT) is expected, as these plants had an additional month of vegetative growth before they were subjected to the growth regulator, which inhibits gibberellin synthesis. A reduction in leaf length and width was also observed in plants treated with PBZ at concentrations ranging from 25 to 75 mg L−1, compared to control plants, in three out of the eight pepper accessions evaluated for leaf length and in four out of eight accessions evaluated for leaf width [10]. In ornamental pineapple, plants treated with PBZ had a 64% reduction in leaf length [27].
The reduction in the number of leaves in plants treated with PBZ by D30DAT, compared to those treated by drenching (DT), was visually proportional to the reduction in plant height without negatively affecting the ornamental appearance. Consistent with the findings of this study, research focused solely on PBZ application methods, without varying concentrations, found no significant difference in the number of leaves in ‘Biquinho’ pepper plants treated by drenching at transplant versus those treated by immersion. However, for the Bode Amarela variety, contrary to the results observed in this study, the immersion method was more effective, reducing the number of leaves by 68% compared to drenching at transplant [16].
Depending on the plant species, PBZ can delay or promote flowering [30]. In this study, flowering delays were observed in plants treated with PBZ at concentrations exceeding 5 mg L−1, compared to the control, as well as in plants treated by drenching (DT) versus those treated by immersion (IM). Similar delays in anthesis due to PBZ concentration have been reported in potted Zinnia and Sunflower plants [29]. In platycodon, there was no significant effect of anthesis compared to the concentrations of PBZ applied to the four varieties studied: ‘Blue’, ‘Lavander’, ‘Pink’, and ‘White’. In mango, the effect is usually the opposite, with reports of induction and/or advancement of flowering being common [31,32,33,34,35].
Although a delay in the onset of flowering was observed at concentrations as low as 5 mg L−1, this effect did not impact fruiting. However, it has been reported that at higher doses, PBZ caused a significant reduction in fruit number when applied by drenching to Biquinho Vermelha pepper plants at 15 days after transplanting (DAT) [5]. In contrast, the same study found no significant effect on fruit number in ‘Bode Amarela’ pepper or the 2345PB and 2334PB accessions, indicating that both genetic factors and PBZ concentration influence this characteristic. These variations in fruit set responses were also evident in eight pepper accessions treated with PBZ by immersion at concentrations ranging from 25 to 75 mg L−1 [10]. Regardless of the concentration used, the fruits of treated plants showed no change in length compared to untreated plants, which is a desirable characteristic for ornamental purposes. However, the application method is crucial, as PBZ applied by drenching (DT) reduced the number of fruits, and the fruits produced by these plants were smaller in length. Since the fruits are the primary decorative element of ornamental pepper plants, the application method significantly impacts their ornamental value [10] and, therefore, the number and characteristics of the fruits produced are relevant factors in evaluating the ornamental quality of these plants.

4.2. Ornamental Color Traits

Greener leaves with a higher SPAD chlorophyll index were also reported in sunflower plants, peppers ‘Biquinho Vermelha’, ‘Bode Amarela’ and ‘Pitanga’ [5,8,17]. However, this effect is dependent on the concentration used and the application method, with a significant impact observed when PBZ was applied at transplantation. When applied 30 days later, only the highest concentration was able to significantly increase the leaf chlorophyll index. PBZ is known to enhance cytokinin levels, which in turn stimulates chlorophyll synthesis and prevents its degradation [36]. The contrast between the color of leaves and fruits is a visual attraction for consumers of ornamental peppers [37]. Thus, the increase in chlorophyll content following PBZ application, which intensifies the green coloration of the plants, can enhance their visual appeal and contribute to their marketability.
The C* parameter, or color saturation, indicates the purity of the color and is used to measure the degree of difference between a given tone and a gray color of the same luminosity. Higher chroma values correspond to greater color intensity in the sample [38]. In general, plants treated with PBZ by drenching, based on chromaticity values, exhibited less intense green coloration, except for those treated at 30DAT with concentrations of 2.5 and 7.5 mg L−1. However, lower brightness (L*) and higher hue angle (h°) values indicated a darker shade of green and higher chlorophyll content in the leaves, respectively, compared to untreated plants. These changes were more subtle at the 7.5 mg L−1 concentration, where the difference was not statistically significant. The h° value correlates with chlorophyll content in leaves, where values near 180° indicate high chlorophyll content, and values near 90° suggest chlorotic leaves with low chlorophyll content [39].

4.3. Sensory Analysis

The global preference test indicated that, despite the negligible effect on plant growth parameters, the immersion (IM) application of low PBZ concentrations (2.5 and 5 mg L−1) resulted in plants with characteristics that were equally appealing to the public as those treated with PBZ by drenching at 30 days after transplanting (D30DAT) at the same concentrations. The D30DAT control plants also received a relatively high preference score (5.42), likely due to their smaller average height (31.4 cm) compared to controls from other application protocols. The control plants treated with the IM protocol had an average height of 34.8 cm and a moderate score (4.82), while the control plants from the drenching (DT) protocol had an average height of 44.4 cm and the lowest preference score (4.02). The growth and development of all control plants were likely constrained by root growth limitations due to the pot size (1.17 L), which was consistent across all treatments and replications. However, the observed height differences among control plants could be attributed to environmental factors, such as light, which may have influenced the production of photoassimilates, thereby benefiting some plants’ growth over others, despite randomization within the greenhouse.
The ornamental quality analysis indicates that PBZ treatment had more pronounced effects on the characteristics of plants treated by drenching (DT). However, two of these plants received intermediate preference scores (4.85 and 4.63 for concentrations of 2.5 and 7.5 mg L−1, respectively), while three others received the lowest preference scores (0, 5, and 10 mg L−1). In a study on the acceptance and preferences of consumers for ornamental potted peppers, the color of the peppers was cited as the most important factor during purchase, followed by the overall appearance of the plant. In contrast, only 4% of respondents mentioned the plant’s shape, and only 2% cited “plant size” as a significant factor [37]. According to these authors, the presence of fruits at different stages of maturation on the same plant contributes to its ornamental appeal. This color variability is evident in ‘Biquinho Vermelha’ pepper plants at commercial maturity, where fruits display a range of colors—from green (immature) to yellow-orange (transitional phase) and red (ripe). This characteristic makes the species particularly attractive for ornamental purposes.
PBZ is classified as a low-toxic product (category 4) and has been used in commercial greenhouses for more than 20 years [29]; however, it is important to follow the recommendations printed on its labels for safe use in humans and the environment.

4.4. Interplay Between Ornamental Traits and Sensory Analysis

The contrast between the color of leaves and fruits has been indicated as a visual attraction for consumers of ornamental peppers [37]. In this study, untreated plants and those treated with the lowest concentration of PBZ via D30DAT exhibited the highest values for parameters associated with leaf color, particularly SPAD and h°, which indicate a more intense and darker green color, suggesting a higher chlorophyll content. However, the negative correlation between these parameters and the sensory analysis did not affect the participants’ preferences. Additionally, taller and less compact plants were preferred over shorter and more compact ones. These findings suggest that the overall appearance of the plant may be more important, with plant height and leaf color having limited significance when considered in isolation [37].
Plants treated with PBZ via drenching (DT) showed a positive correlation between interviewees’ preference and the more intense/darker green color of the leaves, while a negative correlation was observed with growth parameters. Smaller plants, characterized by reduced total height, first bifurcation height, canopy diameter, and leaf width, as well as greener leaves, were more preferred within the group of plants treated by DT. However, despite the positive correlation between reduced plant size and greener leaves with interviewee preference, the DT treatment resulted in the lowest preference scores when compared to all other application protocols. This response is likely due to the more significant reduction in plant growth parameters associated with the DT application. Taken together, these findings suggest that the DT application of PBZ is not recommended for this pepper variety.

5. Conclusions

Immersion protocol was not associated with any of the ornamental quality parameters evaluated and should not be recommended for this pepper variety. Likewise, the application of PBZ via drench during transplanting is not recommended as the plants showed a reduced number and size of fruits, which affected the ornamental value of the plants and evaluator preference. However, these results demonstrated that drench applications at 30 days after transplanting of 2.5 and 5 mg L−1 paclobutrazol for ‘Biquinho Vermelha’ potted plants not only controlled excessive plant growth but also showed a greater evaluator preference, producing plants with attractive ornamental characteristics and, therefore, it should be considered for producers of ornamental plants.

Author Contributions

Conceptualization, C.F.M.F. and F.L.F.; methodology: B.R.M., L.C.C.; M.R.V.-B., J.R., F.C.S., F.L.F. and C.F.M.F.; software, L.C.C., J.R. and C.F.M.F.; validation, B.R.M. and C.F.M.F.; formal analysis, B.R.M., L.C.C., M.R.V.-B., J.R., F.C.S. and C.F.M.F.; investigation, B.R.M.; resources, F.C.S.; data curation, B.R.M.; writing—original draft preparation, B.R.M.; writing—review and editing, B.R.M., L.C.C., M.R.V.-B., J.R., F.C.S., F.L.F. and C.F.M.F.; visualization, F.C.S. and C.F.M.F.; supervision, C.F.M.F.; Project administration, C.F.M.F. and F.C.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

To the technicians from the laboratories, students, and experts from UFSCar who contributed to any of the evaluations, result analyses, or discussions, especially for the sensory analysis.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agronomy 15 00075 g001
Figure 1. Front view (A,C) and top view (B,D) of control plants and plants treated with PBZ via drench at 30 days after transplanting at concentrations of 2.5 and 5.0 mg L−1.
Figure 1. Front view (A,C) and top view (B,D) of control plants and plants treated with PBZ via drench at 30 days after transplanting at concentrations of 2.5 and 5.0 mg L−1.
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Figure 2. Principal component analysis biplot presenting major axes of variation for parameters related to ornamental traits and global preference (GP) in ‘Biquinho Vermelha’ pepper in three PBZ application protocols: (A) Immersion, (B), Drenching at transplant, and (C) Drenching at 30 DAT. The arrows are vectors of correlation among variables and ellipses; they represent delineated groups based on normally distributed data for the concentration of PBZ (0, 2.5, 5, 7.5, and 10 mg L−1) in each application method. The symbols are mean values with n = 5 per group. Captions: Height (plant height); 1stBH (first bifurcation height); LDC (canopy longitudinal diameter); TDC (canopy transverse diameter); CC (canopy compactness); NFr (fruits number); NLe (leaves number); DFr (fruits diameter); LFr (fruits length); Frw (shoot fresh weight); SPAD (SPAD index); PF (plant fullness); LL (leaves length); LW (leaves width); A (days after transplant to anthesis); L* (lightness); a* (the red/green coordinate); b* (the yellow/blue coordinate); C* (chroma) e h (hue angle); GP (global preference).
Figure 2. Principal component analysis biplot presenting major axes of variation for parameters related to ornamental traits and global preference (GP) in ‘Biquinho Vermelha’ pepper in three PBZ application protocols: (A) Immersion, (B), Drenching at transplant, and (C) Drenching at 30 DAT. The arrows are vectors of correlation among variables and ellipses; they represent delineated groups based on normally distributed data for the concentration of PBZ (0, 2.5, 5, 7.5, and 10 mg L−1) in each application method. The symbols are mean values with n = 5 per group. Captions: Height (plant height); 1stBH (first bifurcation height); LDC (canopy longitudinal diameter); TDC (canopy transverse diameter); CC (canopy compactness); NFr (fruits number); NLe (leaves number); DFr (fruits diameter); LFr (fruits length); Frw (shoot fresh weight); SPAD (SPAD index); PF (plant fullness); LL (leaves length); LW (leaves width); A (days after transplant to anthesis); L* (lightness); a* (the red/green coordinate); b* (the yellow/blue coordinate); C* (chroma) e h (hue angle); GP (global preference).
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Table 1. Analysis of variance for the ornamental quality traits of ‘Biquinho Vermelha’ pepper treated with solutions of PBZ at concentrations of 0; 2.5; 5.0; 7.5, and 10 mg L−1 applied in three different application protocols (AP): 1-Immersion, for 10 s, of the root-substrate of the seedlings in the PBZ solutions, immediately before the transplanting into pots; 2-Drenching of 250 mL of PBZ solutions to the cultivation substrate, applied immediately after transplanting the seedlings into pots and 3-Drenching of 250 mL of PBZ solutions to the cultivation substrate, 30 days after transplanting. Assessments were made at the commercial maturity of plants (when at least 50% of the plants in each treatment had 30% of the fruits ripe).
Table 1. Analysis of variance for the ornamental quality traits of ‘Biquinho Vermelha’ pepper treated with solutions of PBZ at concentrations of 0; 2.5; 5.0; 7.5, and 10 mg L−1 applied in three different application protocols (AP): 1-Immersion, for 10 s, of the root-substrate of the seedlings in the PBZ solutions, immediately before the transplanting into pots; 2-Drenching of 250 mL of PBZ solutions to the cultivation substrate, applied immediately after transplanting the seedlings into pots and 3-Drenching of 250 mL of PBZ solutions to the cultivation substrate, 30 days after transplanting. Assessments were made at the commercial maturity of plants (when at least 50% of the plants in each treatment had 30% of the fruits ripe).
Ornamental Quality TraitsPBZAPPBZ X AP
Plant height***
First bifurcation height***
Canopy longitudinal diameter***
Canopy transverse diameterNS**
Canopy compactness**NS
Fruit number**NS
Leave number NS*NS
Fruit diameterNS*NS
Fruit length**NS
Shoot fresh weight **NS
SPAD Index***
Plant fullness***
Leaf length***
Leaf width***
Days to anthesis**NS
Lightness (L*)*NSNS
Red/green coordinate (a*)***
Yellow/blue coordinate (b*)***
Chroma (C*)***
Hue angle (h°)*NSNS
NS, *, non-significant and significant at 5% probability, respectively.
Table 2. Effect of PBZ concentrations and application protocols on the ornamental quality traits of ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of 5 plants.
Table 2. Effect of PBZ concentrations and application protocols on the ornamental quality traits of ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of 5 plants.
Ornamental Quality TraitsApplication ProtocolPBZ Concentrations (mg L−1)CV (%)
02.55.07.510.0
Plant height (cm)IM34.8 Ba32.8 Aab29.9 Aab30.7 Aab26.3 Ab
DT44.4 Aa20.6 Bbc25.5 ABb26.5 ABb14.3 Bc16.2
D30DAT31.4 Ba25.1 Bab19.0 Bb20.3 Bb17.7 Bb
First bifurcation height (cm)IM8.1 Aa7.8 ABa6.8 ABa7.6 ABa6.1 Ba
DT9.2 Aa6.4 Bb5.2 Bb5.7 Bb4.1 Bb19.2
D30DAT8.5 Aa8.9 Aa8.0 Aa8.0 Aa8.4 Aa
SPAD chlorophyll IndexIM52.6 Aa56.6 Ba57.2 Aa55.6 Ba58.8 Ba
DT51.3 Ac67.0 Aab62.8 Ab65.8 Aab72.1 Aa6.9
D30DAT53.6 Ab53.9 Bab60.0 Aab56.9 Bab60.9 Ba
Plant fullness (g·cm−1)IM3.3 Aa3.5 Ba3.6 ABa3.7 ABa3.7 Ba
DT2.2 Ab5.0 Aa3.0 Bb3.1 Bb6.0 Aa20.4
D30DAT2.9 Ab4.0 ABab4.7 Aa4.8 Aa4.5 Ba
Canopy longitudinal diameter (cm)IM43.6 Aa38.6 Aa39.0 Aa43.1 Aa36.2 Aa
DT45.3 Aa30.2 Bb30.5 Bb30.4 Bb22.6 Bb14.7
D30DAT34.10 Ba29.3 Bab25.4 Bb25.2 Bb24.4 Bb
Canopy transverse diameter (cm)IM24.9 Ba30.3 Aa29.4 Aa35.0 Aa29.1 Aa19.3
DT34.4 Aa22.0 Bab26.4 Ab25.3 Bb20.8 Bb
D30DAT28.4 ABa23.7 ABa22.7 Aa22.4 Ba21.7 ABa
Leaf lenght (mm)IM59.0 Aa57.2 Aab53.1 ABab55.4 ABab50.7 Bb6.9
DT56.0 Aa48.6 Bb48.2 Bb50.4 Bab47.2 Bb
D30DAT55.6 Aa61.6 Aa57.9 Aa56.5 Aa57.4 Aa
Leaf width (mm)IM39.0 Aa35.5 Bab33.3 Bb36.3 Aab32.1 Bb7.9
DT36.1 Aa31.0 Cb30.4 Bb31.6 Bab29.1 Bb
D30DAT38.3 Aa41.1 Aa39.1 Aa39.1 Aa39.7 Aa
Chroma (C*)IM19.4 ABa19.3 Aa17.2 Aa17.8 Aa16.4 Aa11.0
DT21.5 Aa13.0 Bbc15.4 ABb15.4 Ab11.6 Bc
D30DAT18.4 Ba16.6 Bab14.0 Bb15.8 Aab13.6 Bb
Means followed by the same lowercase letter in the rows and uppercase letters in the columns do not differ from each other using the Tukey test at 5% probability.
Table 3. Effects of PBZ concentrations on canopy compactness (CC), number of fruits (NFr), fruit length (LFr), leaf lightness (L*), leaf hue angle (h°), shoot fresh weight (FrW), and days after transplantation for anthesis (A) in ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of five plants.
Table 3. Effects of PBZ concentrations on canopy compactness (CC), number of fruits (NFr), fruit length (LFr), leaf lightness (L*), leaf hue angle (h°), shoot fresh weight (FrW), and days after transplantation for anthesis (A) in ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of five plants.
PBZ (mg L−1)L*h°CCFrW
(g)		ANFrLFr (mm)
038.8 a114.8 b0.7 b101.2 ab38.1 c67.9 a22.5 ab
2.537.1 b115.9 a0.8 ab103.3 a39.9 bc64.0 a23.5 a
5.037.0 b116.1 a0.8 ab89.6 ab41.1 ab56.3 a21.8 ab
7.537.7 ab115.5 ab0.9 a95.1 ab42.4 a64.7 a21.7 ab
10.036.7 b116.3 a0.9 a86.1 b41.5 ab56.5 a21.0 b
CV (%)3.20.914.015.85.619.79.7
Means followed by the same letter in the lines do not differ from each other using the Tukey test at 5% probability.
Table 4. Effects of PBZ application protocols on canopy compactness (CC), number of fruits (NFr), number of leaves (NLe), fruit diameter (DFr), fruit length (LFr), and days after transplanting for anthesis (A) in ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of five plants.
Table 4. Effects of PBZ application protocols on canopy compactness (CC), number of fruits (NFr), number of leaves (NLe), fruit diameter (DFr), fruit length (LFr), and days after transplanting for anthesis (A) in ‘Biquinho Vermelha’ pepper. The data were collected between 8 and 22 June 2023 and represents the average of five plants.
Aplication ProtocolCCANFrLFr (mm)DFr (mm)NLeFrW (g)
IM0.7 b39.6 b69.7 a22.7 a12.5 a118.5 ab108.1 a
DT0.8 a41.7 a53.7 b20.9 b13.0 a128.2 a85.4 b
D30DAT0.9 a41.0 ab62.2 a22.7 a11.2 b101.3 b91.6 b
CV (%)14.05.619.79.710.123.015.8
Means followed by the same letter in the lines do not differ from each other using the Tukey test at 5% probability.
Table 5. Results of overall preference test of ‘Biquinho Vermelha’ pepper plants treated with PBZ.
Table 5. Results of overall preference test of ‘Biquinho Vermelha’ pepper plants treated with PBZ.
Application ProtocolPBZ
(mg L−1)		Global Preference
Immersion04.82 b
2.55.18 a
5.05.54 a
7.54.89 b
10.04.70 c
Drenching at transplanting04.02 d
2.54.85 b
5.04.14 d
7.54.63 c
10.04.42 c
Drenching at 30DAT05.42 a
2.55.33 a
5.05.03 b
7.54.78 b
10.04.36 c
CV (%) 27.4
Means followed by the same letter do not differ from each other using the Scott–Knott test at 5% probability.
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Morales, B.R.; Costa, L.C.; Verruma-Bernardi, M.R.; Rodrigues, J.; Sala, F.C.; Finger, F.L.; França, C.F.M. Ornamental Traits and Sensory Analysis of ‘Biquinho Vermelha’ Pepper Treated with Paclobutrazol. Agronomy 2025, 15, 75. https://doi.org/10.3390/agronomy15010075

AMA Style

Morales BR, Costa LC, Verruma-Bernardi MR, Rodrigues J, Sala FC, Finger FL, França CFM. Ornamental Traits and Sensory Analysis of ‘Biquinho Vermelha’ Pepper Treated with Paclobutrazol. Agronomy. 2025; 15(1):75. https://doi.org/10.3390/agronomy15010075

Chicago/Turabian Style

Morales, Beatriz R., Lucas C. Costa, Marta R. Verruma-Bernardi, Josiane Rodrigues, Fernando C. Sala, Fernando L. Finger, and Christiane F. M. França. 2025. "Ornamental Traits and Sensory Analysis of ‘Biquinho Vermelha’ Pepper Treated with Paclobutrazol" Agronomy 15, no. 1: 75. https://doi.org/10.3390/agronomy15010075

APA Style

Morales, B. R., Costa, L. C., Verruma-Bernardi, M. R., Rodrigues, J., Sala, F. C., Finger, F. L., & França, C. F. M. (2025). Ornamental Traits and Sensory Analysis of ‘Biquinho Vermelha’ Pepper Treated with Paclobutrazol. Agronomy, 15(1), 75. https://doi.org/10.3390/agronomy15010075

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