An Approach of Colored Shade Nets on Photosynthetic Efficiency of Capsicum chinense and Capsicum frutescens

Abstract

This study aimed to assess the effect of red, pearl and aluminet shading nets on the photosynthetic efficiency of Capsicum chinense and C. frutescens. The experiment was carried in entirely randomized block design. C. chinense and C. frutescens were cultivated under red, pearl and aluminet with 35% shading and direct sunlight as control for 150 days. Leaf area, area duration and area ratio; specific leaf area and harvest index were higher in C. frutescens. Net CO₂ assimilation and stomatal conductance were higher in C. frutescens cultivated under red net and C. chinense cultivated under aluminet net. Transpiration was higher in C. chinense cultivated under the aluminet net. Water use efficiency and relative chlorophyll content and intrinsic water use efficiency were higher in C. frutescens cultivated under the red net. Initial and maximum chlorophyll were also higher in C. frutescens cultivated under red net. Maximum quantum efficiency and chlorophyll fluorescence rate decrease were lower in C. chinense cultivated under red net. Linear flux electron was lower in C. chinense cultivated in the control. PSII open centers fraction was higher in control, pearl net for C. frutescens. Non-photochemical extinction coefficient and dissipation of absorbed light were higher in C. chinense cultivated under red net. C. frutescens cultivated under red net had higher photosynthetic efficiency, considering water use efficiency in dry matter conversion and several mechanisms to maximize the photosynthetic process under shaded conditions.

Keywords:
chlorophyll fluorescence; dry matter conversion; photosynthetic process; shading; ornamental plants

HIGHLIGHTS

Colored shade nets contribute to the water use efficiency in dry matter conversion.

Peppers species showed different responses to different shading nets.

Red net contributes to chlorophyl efficiency.

Shading reduces the distance between palisade and lacunate parenchyma.

INTRODUCTION

Capsicum ssp. are widely cultivated like ornamental peppers [¹,²], due to their phenotypic diversity, such as architecture, coloration and positioning of fruits and flowers [³]. Besides their use as ornamental plants, peppers plants can also be used in medicine [⁴], pesticides in agriculture [²]; production of sweets and jellies in the food industry; and as pigments in the cosmetics industry [⁵].

Among to the species of Capsicum, C. chinense and C. frutescens are the most significant ornamentals. The C. chinense species stands out as having sizes between 50 to 100 centimeters (cm), oval leaves and slightly wrinkled surface, white flowers arranged in up 3 per node, and elongated fruits with 5 to 7 cm long with 2.5 to 3.0 cm in diameter and coloration between light green to orange [⁶]. C. frutescens can reach up to 1.2 meters (m) in height, have smooth and simple leaves, yellowish flowers, and small, pungent, erect, and slightly pointed fruits [⁶].

Ornamental peppers cultivated exposed to air temperatures of 35ºC and high solar radiation intensity [⁷] loses photosynthetic efficiency, i. e., conversion of light energy into usable biomass or material of economic importance (fruits) [⁸], due the reduction of photosynthetic process, blighting and abortion of flowers and fruits.

Additionally, ornamental peppers are C3 plants which have high complexity in the scope of photosynthetic and respiratory efficiency [⁸]. In the presence of heat, the solubility of carbon dioxide (CO₂) in water is higher than that of oxygen (O₂) resulting a in lower CO₂ /O₂ ratio in the cell, decreasing the concentration of CO₂ in the carboxylation site of Rubisco, which favors oxygenase activity and consequently, photorespiration [⁹,¹⁰]. In addition, excess energy can use photoinhibition, i.e., the photooxidative destruction of the photosynthetic apparatus a mechanism for regulating and eliminating heat, allowing balance between the energy reaching photosystem II (PSII) [¹¹].

Alternative technologies are implemented to improve crop production in the scope of environment control, quality, and productivity. Colored shade nets are designed in different colors and shading density to improve cultivation of plants [¹²]. The spectral composition of the sunlight filtered by the coloration of shading nets and received by plants is modified due to the passage of sunlight through the net wires [¹²], resulting in photomorphogenetic and physiological modifications. Shading density of the nets is based on the interweaving of the polyethylene or propylene wires [¹²], and when too high, it can compromise the conversion of light energy into usable biomass, being necessary to evaluate which net density will provide the better effect in the cultivated species.

Therefore, colored shading nets can be an efficient option for maintaining the photosynthetic efficiency of ornamental peppers as they can contribute to dry matter production [⁷], as reported in several studies with vegetables, fruits, and other ornamental plants [¹³]. Growth analyses, associated with gas exchange and chlorophyll fluorescence aid in the detection of modifications caused by colored shading nets in photosynthetic efficiency of ornamental peppers by studying leaf development dynamic, fruit biomass production, gas exchange and sensitive indicators of photosynthetic processes subsequently, allowing their use in cultivation.

However, information on how different colored shade nets can affect the photosynthetic efficiency of ornamental peppers is scarce in the literature. To fulfill this gap, this study aimed to assess the effect of red, pearl and aluminet colored shading nets on the photosynthetic efficiency of C. chinense and C. frutescens plants.

MATERIALS AND METHODS

Experimental design

The experiment was carried out in complete randomized design in a 2x4 factorial scheme (2 species x 4 colored shading nets), with 8 netting treatments and five replications (one pot each). The treatments were: uncovered control (direct sunlight), red, pearl, and aluminet shading nets.

Location and conduction of the experiment

The experiment was located at the Floriculture Sector, Agronomy Department at the Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil. The experiment was carried out from February to August, 2021. Seedlings of C. chinense cv. Biquinho Iracema and C. frutescens cv. Etna were purchased from Isla Sementes^® (São Paulo, Brazil) and grown in rigid polypropylene trays filled with Tropstrato^® commercial substrate (Vida Verde, São Paulo, Brazil) in a greenhouse. The seedlings were transplanted when had two to three pairs of true leaves, into pots of 1.7 Liters (L) capacity, 14 cm height and 16 cm diameter, filled with the same substrate.

Wooden structures measuring 0.50x 0.50 x 0.70 m (width x length x height) were built for the shading nets and were arranged in the open environment 2.0 m apart in the rows and 3.0 m between rows to avoid shading from other treatments. These structures were covered in the sides and top with red, pearl, and aluminet shading nets of 35% shading factor (Ginegar, São Paulo, Brazil). As control treatment plants were exposed to direct sunlight (uncovered). The ornamental peppers were fertilized with 2 grams (g) of NPK 10-10-10 fertilizer, once a week, the irrigation was made until the substrate reach field capacity and weeds were removed manually when necessary.

Environmental data

Maximum and minimum temperature and relative humidity were recorded daily every one minute in each treatment using an AKSO AK-174 datalogger (AKSO, Rio Grande do Sul, Brazil) with a thermometer and hygrometer. The wavelength and solar radiation intensity intercepted by the colored nets were measured with a spectroradiometer model USB4000, Ocean Optics. The spectra were processed using SpectraSuite software. The wavelength was expressed in nanometers (nm) and the intensity in percentage (%). Means of monthly temperature, humidity, wavelength, and solar radiation intensity are shown in Table 1.

Growth analyses

One-hundred and fifty days after sowing, all the leaves from each experimental unit were collected and the leaf area (LA) was measured by the non-destructive method using a leaf area model AM350 (Marconi, São Paulo, Brazil). The results were expressed in centimeters squared (cm²).

From the leaf area data, leaf area duration (LAD) was measured by means of integral of leaf area over time of cultivation (150 days). The results expressed in cm² day^-1 and represents the time in which the leaf surface is kept photosynthetically active. Leaf area ratio (LAR) was measured by the ratio of leaf area by leaf dry mass. The results were expressed in decimeter squares per grams (dm² g^-1) and represents a reduction in the photosynthesizing leaf area due to shading. Specific leaf area (SLA) was measured by the ratio of leaf area to leaf dry mass, these results were expressed in dm² g^-1 and represents the cell size of the leaf mesophyll.

The leaves, stems, flowers, flower buds, fruits and roots were collected, separated and packed in 3 Kg Kraft paper bags, and then placed in an oven with forced air circulation at 70ºC for three days. After dried, dry mass (leaves, stems, flowers, flower buds, fruits and roots) was weighed on a semi-analytical scale (Mark S2) (± 0.005g accuracy) and the results expressed in g. The harvest index (HI) was measured by the ratio between the dry mass of the fruits by the total dry mass of the plant and represents the conversion efficiency of photoassimilates into fruits.

Gas exchange

The net assimilation of CO₂ (A= μmol CO₂ m^-2 s^-1), stomatal conductance (gs= mol H₂O m^-2 s^-1) and transpiration (E= mmol de H₂O m^-2 s^-1) were measured with infrared gas analyzer (IRGA - model LCPro, ADC BioScientific Ltd.) on fully expanded leaves of the upper third, between 8 and 10 h. Water use efficiency (WUE= μmol CO₂ m^-2 s^-1/ mmol de H₂O m^-2 s^-1 ) was calculated by dividing net assimilation of CO₂ (A) by transpiration (E), and intrinsic water use efficiency (iWUE= μmol CO₂ m^-2 s^-1/ mol de H₂O m^-2 s^-1 ) was calculated by dividing net assimilation of CO₂ (A) by stomatal conductance (gs).

Photosynthetic parameters based on chlorophyll fluorescence

Leaf thickness, initial chlorophyll (F₀), maximum chlorophyll (F_m), relative chlorophyll content (SPAD), maximum quantum (F_v/F_m), linear electron flux (LEF), PSII open centers fraction (qL), chlorophyll fluorescence rate decrease (RFd), non-photochemical extinction coefficient (ΦNPQ), and non-photochemical dissipation of absorbed light energy (ΦNPQ_t) were measured with MultispeQ device [¹⁴], which is connected to the PhotosynQ platform (http:// www.photosynq.org).

Statistical analysis

The data were submitted to normality (Shapiro-Wilk) and homogeneity (Bartlett) tests of variances. Analysis of variance (ANOVA, F test) and means comparison tests (Tukey, p_value≤0.05) were performed in the R software version 3.6.3 [¹⁵]. Plots were made with SigmaPlot 10.0 program (Systat Software, Inc., San Jose, CA, USA). The results of the interactions are available in the supplementary material.

RESULTS

Environmental data

The red net reduced the maximum temperature by 4.1°C compared to control. In terms of relative humidity, this net increased the maximum and minimum temperature by 2.6% e 2.2%, respectively. The fraction of light passed through the wires of red, pearl and aluminet nets in the visible spectrum reached 588, 500 and 545 nm, respectively. The aluminet, red and pearl nets reduced the solar radiation by 28.8, 39.5 and 49.7%, respectively, compared to the control (Table 1).

Table 1
Mean monthly values of maximum temperature (MT), minimum temperature (MiT), maximum relative humidity (MRH), minimum relative humidity (MiRH), wavelength (W), solar radiation intensity (SRI) throughout the experiment

TREATMENT	MT (ºC)	MiT (ºC)	MRH (%)	MiRH (%)	W (nm)	SRI (%)
Control	36.2	12.4	95.4	32.9	710	80.2
Red	32.1	11.8	98.0	41.4	588	40.7
Pearl	34.6	9.4	95.9	33.0	500	30.5
Aluminet	33.0	9.4	95.0	36.0	545	51.4

Effects of colored shade nets on photosynthetic efficiency

Growth analysis

There was no interaction between the factors studied for growth analysis (p_value>0.05). Leaf area and leaf area duration were higher in C. frutescens (1520.1 cm² and 5.06 cm² day^-1) compared to C. chinense (1110.6 cm² and 3.70 cm² day^-1) (Figure 1 A and B). The opposite was observed for leaf thickness (Figure 1 C). Leaf area ratio (179.5 dm² g^-1), specific leaf area (179.5 dm² g^-1) and harvest index (0.27) were greater in C. frutescens compared to C. chinense (138.9 dm² g^-1, 146.8 dm² g^-1 and 0.16, respectively.) (Figure 1 D-F).

Figure 1
Leaf area (A), leaf area duration (B), leaf thickness (C), leaf area ratio (D), specific leaf area (E) and harvest index (F) of C. chinense and C. frutescens plants cultivated under colored shade nets. *Different capitalized letters indicate significant statistical differences by the Tukey test (p_value≤0.05).

Gas exchange

An interaction between the factors studied for gas exchange (p_value≤0.05) was observed, except for WUE (p_value=0.36) and iWUE (p_value=0.68). Net CO₂ assimilation (A) and stomatal conductance (gs) were higher in C. frutescens cultivated under red net (12.07 µmol CO₂ m^-2 s^-1 and 0.15 mol H₂O m^-2 s^-1) and C. chinense cultivated under aluminet net (11.30 µmol CO₂ m^-2 s^-1 and 0.23 mol H₂O m^-2 s^-1) compared to the control (Figure 2 A and B). Transpiration (E) was higher in C. chinense cultivated under aluminet (4.39 mmol H₂O m^-2 s^-1) net compared to the control (2.60 mmol H₂O m^-2 s^-1) (Figure 2 C). WUE was higher in the red net (4.18 µmol CO₂ m^-2 s^-1/ mmol H₂O m^-2 s^-1) compared to the control (2.74 µmol CO₂ m^-2 s^-1/ mmol H₂O m^-2 s¹) (Figure 2 D) and iWUE was higher in C. frutescens (72.56 µmol CO₂ m^-2 s^-1/ mol H₂O m^-2 s^-1) compared to C. chinense (58.74 CO₂ m^-2 s^-1/ mol H₂O m^-2 s^-1) (Figure 2 E).

Figure 2
Net CO₂ assimilation - A (A), stomatal conductance- gs (B), transpiration - E (C), efficiency - WUE (D) and intrinsic water use efficiency - iWUE of C. chinense and C. frutescens plants cultivated under colored shade nets.* Capitalized letters refer to comparison among colored shade nets, and lowercase letters compares ornamental peppers species. Different capitalized and lowercase letters indicate significant statistical difference by the Tukey test (p_value≤0.05).

Photosynthetic parameters based on chlorophyll fluorescence

Initial (F₀) and maximum chlorophyll (F_m) was higher in C. frutescens cultivated under red net (556 and 1869.25, respectively) (Figure 3 A and B) when compared to the control (415.8 and 1287.65, respectively). Maximum quantum efficiency (F_v/F_m) was lower in C. chinense cultivated under red net (0.52) (Figure 3 C) and relative chlorophyll content (SPAD) was higher on red net (69.55) compared to the others treatments.

Figure 3
Initial chlorophyll - F₀ (A), maximum chlorophyll - F_m (B), maximum quantum efficiency - F_v/F_m (C) and relative chlorophyll content - SPAD (D) of C. chinense and C. frutescens plants cultivated under colored shade nets. *Capitalized letters refer to comparison among colored shade nets, and lowercase letters compares ornamental peppers species. Different capitalized and lowercase letters indicate significant statistical difference by the Tukey test at p_value≤0.05.

Linear electron flux (LEF) was lower on C. chinense plants under the control treatment (30.97) (Figure 4 A). The PSII open centers fraction (qL) was higher in control (0.70), pearl net (0.60), and C. frutescens (0.66), compared to the other treatments (Figure 4 B and C). Chlorophyll fluorescence rate decrease (RdF) was lower in C. chinense cultivated under red net (0.64) compared to the other treatments (Figure 4 D). Non-photochemical extinction coefficient (ΦNPQ) and non-photochemical dissipation of absorbed light energy (ΦNPQ_t) were higher in C. chinense cultivated under red net (0.46 and 4.97, respectively) compared to the other treatments (Figure 4 E and F).

Figure 4
Linear electron flux - LEF (A), PSII open centers fraction - qL (B and C), chlorophyll fluorescence rate decrease - RFd (D), non-photochemical extinction coefficient - ΦNPQ (E), and non-photochemical dissipation of absorbed light energy -ΦNPQ_t (F) of C. chinense and C. frutescens plants cultivated under colored shade nets. *Capitalized letters compares colored shade nets, and lowercase letters compares ornamental peppers species. Different capitalized and lowercase letters indicate significant statistical difference by the Tukey test (p_value≤0.05).

DISCUSSION

Environmental data

Information in the literature has established that colored shading nets can reduce temperature during cultivation of horticultural and ornamental species by 1 to 5 ºC, with shading levels, colors and location being determinant factors [¹⁶]. For relative humidity, the opposite can be observed, in which colored nets resulted in increases ranging from 3.2 to 12.9% [¹⁷].

In our study, cultivation under the red net resulted in a maximum temperature of 32.1 ºC during the cultivation. This temperature is still viable for ornamental peppers, in which the optimum temperature ranges between 21 to 33 ºC. In the control, the temperature was much higher, reaching a maximum temperature of 36.1 ºC, resulting in blight symptoms in the leaves and fruits, and abortion of flowers and fruits. These conditions directly affect photosynthetic efficiency. In addition, the red net also stood out with the greatest increase in both maximum and minimum relative humidity, which is attributed to the formation of a microclimate with reduced temperature and incidence of solar radiation [¹⁷].

The fraction of light passed through the holes of the colored shade nets has its quality unchanged, but the fraction of light reached by the wires is spectrally modified [⁷]. The red net light transmittance is within red and far-red, the pearl transmits in blue, yellow, green, red, and infrared while in aluminet it is absent, which absorbs light in all spectral bands [⁷].

This information is essential because it might help to explain the biochemical and physiological processes observed during cultivation, such as those reported for the red net, which due to a higher proportion of red light, helps to activate phytochrome B and induces root formation via auxin signaling [¹⁸]. Pearl and aluminet nets have a higher proportion of far red and influence flowering through the photoreversibility of phytochrome C [¹⁷].

The CO₂ assimilation metabolism of pepper plants is of C3 type; hence it saturates in relatively higher irradiance in a typical cultivation day [¹⁹]. On the other hand, excessive radiant energy as obtained in the control treatment predisposes plants to photoinhibition and photorespiration [¹⁹] and consequently reduces the CO₂ net assimilation, the main source of carbohydrate substrate for growth and development [¹⁹]. The red, and pearl net kept the solar incidence radiation within the acceptable threshold, allowing full growth and development of C. chinense and C. frutescens plants.

Influence of colored shade nets on photosynthetic efficiency

Growth analysis

The leaf is the main photosynthesizing organ in the plant. A high plasticity to shading is usually attributed to leaves, mainly in area and thickness [²⁰]. The leaf area and leaf area duration were higher in C. frutescens, this might be attributed to an adaptative strategy of plants under shading environment, allowing optimization of light uptake to increase photosynthesis efficiency and consequently, more photoassimilates [²¹]. On the other hand, when plants are cultivated under direct sunlight they have greater photosynthetic capacity, due to the increased number of enzymes and greater stomatal conductance than those cultivated under shade [²⁰].

The thinner leaves observed on C. frutescens associated with a larger leaf area favors a greater CO₂ diffusion per area unit, given that the distance between stomata is reduced, due to the thickness of the palisade and lacunate parenchyma. These characteristics corroborate with the larger specific leaf area observed on C. frutescens plants, which allows the maximization of carbon gain unit leaf mass under shaded conditions [²²].

The shorter distance between the palisade and lacunate parenchyma promotes greater absorption of diffuse light from the shaded environment, as well as internal scattering between the chlorophylls of the chloroplasts [²²]. In addition to that, less thickness leaves allow greater light diffusion to the lower leaves and thus increase photosynthetic efficiency, which might be advantageous due to their light limitation caused by self-shading [²²]. It is worth mentioning that the leaf area ratio decreases throughout the cultivation, caused by the reduction in the leaf area duration [²³], and this was not observed in this study, probably because the colored shade nets reduced physical damage caused by blights in the leaves.

These morphological adaptations allow a greater investment of photoassimilates for dry matter production of fruits on C. frutescens [²²], demonstrating that the shading levels used in this study did not impair the photosynthetic efficiency of the plants. However, the potential acclimation due to shading is variable among species and an increase in the photosynthetic capacity through leaf plasticity may not occur as previously reported in C. chinense [²¹]. Therefore, it is important to assess the leaf development dynamic under colored shade nets throughout cultivation prior to its implementation in the cultivation system.

Gas exchange

The temperatures and solar radiation incidence percentage obtained for C. frutescens cultivated under red net and C. chinense cultivate under aluminet net were 32.1 ºC and 40.7%, and 33ºC and 51.4%, respectively. These values are within the optimum in which photoinhibition, or photorespiration processes do not occur. Furthermore, the higher concentration of carbon in carboxylation sites and increasing dry matter production was observed, with C. frutescens having a higher harvest index, corroborating with previous reports [²⁴].

The gs is lower when plants are under higher concentrations of CO₂ and shaded environments [²⁴]. In our study, the opposite was observed in C. frutescens plants cultivated under red net and C. chinense cultivated under aluminet net. A similar response was observed in cocoa plants in which the higher gs due to high CO₂ levels reflected the humid cultivation environment [²⁵]. A similar response was also observed in C. frutescens cultivated under red net, where 98% of maximum humidity was observed during cultivation. Contrary to the previous hypothesis, previous studies have evidenced that although rare, plants can present higher A and gs values at the same time [²⁶], but in a less humid environment it might indicate that these plants are adapted to hot and dry places, as observed in C. chinense plants cultivated under aluminet, which reached values of 95% of humidity.

In the presence of higher concentrations of CO₂ as observed in C. chinense plants cultivated under aluminet, it is expected a reduction of transpiration [²⁷]. Nevertheless, the opposite was observed, this is explained by the methods in which the experiment was conducted, with daily irrigations of the substrate until its field capacity, which might have mitigated the effects of high transpiration.

Despite the high gs, C. frutescens had the highest iWUE and WUE under the red net, respectively. This was probably an artefact by the IRGA measuring where the opening and closing of the stomas, which might be partially open or closed, but are not detected by the device. Thus, the stomata may have allowed sufficient CO₂ to enter for photosynthesis and higher iWUE, due to the lower temperature in the red net and less need for cooling of the leaf by loss of latent heat via transpiration [²⁷].

Photosynthetic parameters based on chlorophyll fluorescence

F₀ and F_m was higher in C. frutescens, due to its greater leaf area and reduced leaf thickness, and probably greater number of chloroplasts to maximize the light uptake process via chlorophylls [²⁸], improving the process of absorption, transfer, and utilization of energy through photosystem II [²⁸].

SPAD was higher in C. frutescens cultivated under the red net, because the shading associated with supplementation of red light caused by the net coloration is captured and directed to chlorophyll synthesis [²⁹]. This occurs because shaded leaves produce additional chlorophyll a and b to capture diffuse light [⁷]. In shaded tea plants supplement with red light, expression of the CsPOR-2 gene encoding the enzyme protochlorophyllide oxidoreductase (POR) is induced in response to shading by catalyzing the reduction of prochlorophyllide oxidoreductase to chlorophyllide, from which, chlorophyll is derived [²⁹,³⁰]. F₀, F_m and SPAD directly contribute to the increasing net photosynthetic rate, corroborating with the result observed for C. frutescens plants cultivated under the red net.

The F_v/F_m is an indicator of plant adaptation to abiotic stress such as high temperature and solar radiation [³¹]. Plants cultivated under direct sunlight showed reduced values of F_v/F_m, indicating that the chlorophyll is reemitted via heat or the PSII reaction center malfunctions due to photoinhibition [³¹]. In this study, this was not observed in the control treatment because the temperature and intensity of the solar radiation were probably not enough to cause photoinhibition in the plants [²⁸] or, if they did, it was temporary, resulting in no damage.

The maximum values of F_v/F_m are reached under temperatures between 36 to 39 ºC according to reports in the literature, corroborating to the data obtained in this study [²⁸]. A decrease in the values of F_v/F_m from 40 ºC onwards is usually observed, but C. chinense cultivated under the red net showed the lowest value with a maximum cultivation temperature of 32.1ºC, this might indicate photoinhibition, associated with the lower valuer of E [²⁶].

Reduced LEF in C. chinense in the control treatment implies a decrease in intercellular CO₂ and ability to use the reducing power of NADPH and ATP in plants, an adjustment mechanism of the operational efficiency of PSII [¹⁴], due to exposure to high temperature and incidence of solar radiation.

The higher qL associated with reduced LEF in the C. frutescens occurred because the energy obtained by solar radiation under shaded conditions was enhanced and used by photosystem II [²⁸]. The higher qL associated with high F_v/F_m in the control treatment, occurred because it may have not produced Reactive Oxygen Species (ROS) by means of excess energy on the reaction centers [³²]. On the other hand, the higher qL observed on plants under the pearl net occurred to balance the PSII and PSI energy flow, because this screen has a red to distant (FR) light ratio compared to red (R), allowing more absorption and light transmission. The lower RdF, qL and F_v/F_m in C. chinense cultivated under red net implies the reduction of solar radiation energy on photosystem II, due to reemission via ΦNPQ and ΦNPQt, a mechanism to prevent the accumulation of ROS in the plant due to heat, because, E was lower, i. e., with little reemission of latent heat [¹⁴].

CONCLUSION

The use of shading nets caused a modification of morphological and physiological parameters in the leaves of C. frutescens, favoring the conversion of solar energy into higher photosynthetic efficiency. In addition, photosynthetic parameters based on chlorophyll fluorescence showed that C. frutescens cultivated under red net used several mechanisms to maximize the photosynthetic process under shaded conditions and had higher photosynthetic efficiency assessed by the water use efficiency and dry matter conversion. On the other hand, when the same parameters were evaluated in C. chinense, it did not obtain photosynthetic efficiency, which does not justify the adoption of colored nets for its cultivation.

Acknowledgments

The research was partially funded by the Brazilian Federal Agencies: “Fundação de Amparo à Pesquisa do Estado de Minas Gerais” (FAPEMIG), “Conselho Nacional de Desenvolvimento Tecnológico” (CNPq) and “Coordenação de Aperfeiçoamento Pessoal de Nível Superior” (CAPES) for the financial support (Process number: 88882.349320/2019-1) - funding code 001.

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• Supplementary Material:
  Supplementary materials are available in https://www.documentador.pr.gov.br/documentador/pub.do?action=d&idInc=eca69196-c738-4a4e-874a-b20ec11c67b4

Edited by

• Editor-in-Chief:
  Bill Jorge Costa

• Associate Editor:
  Adriel Ferreira da Fonseca

Publication Dates

• Publication in this collection
  11 Oct 2024
• Date of issue
  2024

History

• Received
  27 Oct 2023
• Accepted
  23 July 2024