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Article

Chitosan Application Improves the Growth and Physiological Parameters of Tomato Crops

by
Juan José Reyes-Pérez
1,*,
Luis Tarquino Llerena-Ramos
1,
Wilmer Tezara
2,3,*,
Víctor Reynel
2,
Luis Guillermo Hernández-Montiel
4 and
Antonio Juárez-Maldonado
5
1
Universidad Técnica Estatal de Quevedo, Av. Quito, km 1.5 vía a Santo Domingo de los Tsáchilas, Quevedo 120501, Ecuador
2
Facultad de Ciencias Agropecuarias, Universidad Técnica Luis Vargas Torres, Esmeraldas 080102, Ecuador
3
Instituto de Biología Experimental, Universidad Central de Venezuela, Caracas 1041-A, Venezuela
4
Nanotechnology and Microbial Biocontrol Group, Centro de Investigaciones Biológicas del Noroeste, La Paz 23096, Baja California Sur, Mexico
5
Departamento de Botánica, Universidad Autónoma Agraria Antonio Narro, Saltillo 25315, Coahuila, Mexico
*
Authors to whom correspondence should be addressed.
Horticulturae 2025, 11(8), 878; https://doi.org/10.3390/horticulturae11080878
Submission received: 18 June 2025 / Revised: 16 July 2025 / Accepted: 23 July 2025 / Published: 28 July 2025
(This article belongs to the Special Issue Effects of Biostimulants on the Growth and Development of Horticultural Crops)
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Abstract

Tomato crops are treated with high concentrations of synthetic fertilizers and insecticides to increase yields, but the careless use of these chemicals harms the environment and human health and affects plant pathogen resistance. The effect of foliar spray of three concentrations of chitosan (500, 1000, and 2000 mg L−1) on plant growth, yield, fruit quality, and physiological performance in two tomato varieties (Floradade and Candela F1) was studied. Physiological traits such as photosynthesis, chlorophyll content, and leaf area index of the plants were positively affected by chitosan, an effective compound that biostimulates growth, with increases in biomass of organs with respect to the control treatment. Chitosan also improved tomato quality, such as increases in polyphenols, antioxidant capacity, flavonoids, carotenoids, vitamin C, and total soluble solids in both tomato varieties. Finally, yield increased by 76.4% and 65.4% in Floradade and Candela F1, respectively. The responses of tomato plants to chitosan application were different depending on the variety evaluated, indicating a differential response to the biostimulant. The use of chitosan in agriculture is a tool that has no negative effects on plants and the environment and can increase the productive capacity of tomato plants.

1. Introduction

Tomato (Solanum lycopersicum L.) is one of the most important horticultural crops in the world due to its industrialization, consumption, and nutritional and organoleptic properties [1,2]. It is cultivated in different soil and climatic conditions, both in open fields and greenhouses. Its demand continuously increases, and therefore so do its cultivation, production, and trade [3].
Currently, high doses of synthetic fertilizers and pesticides are used for tomato crop production to increase yields and control phytopathogens. However, synthetic fertilizers and pesticides cause damage to the environment, human health, and animal health, as well as resistance in phytopathogens [4,5]. Moreover, they impact soils, causing erosion, increased salinity, and the accumulation of heavy metals and nitrates. They also pollute the air through emissions of nitrogen oxides, contributing to the greenhouse effect [6,7,8]. Thus, there is a need to search for alternatives to synthetic chemical products that do not cause damage to the environment and increase crop yield [9,10]. One of the alternatives is the use of chitosan, due to its biocompatibility, biodegradability, and bioactivity [11]. Chitosan is extracted from chitin present in crustacean exoskeletons [12], fungal cell walls [13], and insect cuticles [14], among other sources.
The positive effects of chitosan in agriculture have been demonstrated in that it induces defense responses in plants, such as the production of proteins related to pathogenesis, phytoalexins, and lytic enzymes [11,15,16,17]. Chitosan has also been used to increase the antagonistic capacity of beneficial microorganisms [18], as well as crop growth, development, yield, and quality [19,20]. The foliar application of chitosan on different species (Zea mays, Sorghum bicolor, S. lycopersicum, and Cymbopogon flexuosus) has shown positive effects on chlorophyll and carotenoid content, total nitrogen content, and phosphorus content [21,22,23,24,25], improving chlorophyll fluorescence, carboxylation efficiency, and, therefore, net photosynthesis rate (A). Additionally, it affects stomatal conductance (gs), regulating transpiration rate (E) and water use efficiency (WUE) [25,26,27,28,29,30]; it also increases yield and improves tolerance to water deficit [30]. All these effects translate into an enhanced photosynthetic process and, consequently, an improvement in plant growth and development [18,31]. It has been suggested that the foliar application of chitosan could be used to stimulate tomato plants grown under salinity stress [32]. Soil and foliar applications of chitosan nanoparticles to Triticum aestivum [33], Catharanthus roseus [34], and Z. mays [35] mitigated the adverse effects of drought by increasing chlorophyll concentration, net photosynthesis rate, antioxidant enzyme activity, relative water content, yield, and biomass [35].
Chitosan alleviated photosynthetic limitations and enhanced enzymatic antioxidative defense that minimized salt-stress-induced oxidative damage, improving the overall development of C. flexuosus [29]. Reyes-Pérez et al. [36] have shown that chitosan increases seed germination, plant vigor, and agricultural yield. In addition, chitosan improves nutrient assimilation in plants [37]. The application of chitosan has increased the growth, development, germination, and yield of bell pepper, cucumber, lettuce, and carrot crops [38,39,40].
Numerous studies have documented the beneficial effects of chitosan on crop growth. Nevertheless, not much research has been conducted on how chitosan affects tomato hybrids (Candela F1) and pure varieties (Floradade). Due to the positive effects of chitosan on different plant species, the objective was to determine the impact of the foliar application of chitosan on the agronomic and physiological parameters of plants of two tomato varieties (Floradade and Candela F1) and to determine whether chitosan positively affects the growth, physiological performance, yield, and fruit quality of tomato plants. We predicted that the two genotypes would respond differently to chitosan spray.

2. Materials and Methods

2.1. Study Site

The present research was carried out at La María Campus of the Quevedo State Technical University (UTEQ), Ecuador, with the following geographical coordinates: 79°27″ west longitude and 1°06″ south latitude. The altitude is 75 masl, average annual temperature 24 °C, relative humidity 84%, and average annual rainfall 2295 mm.

2.2. Experimental Design and Treatments

A completely randomized design with a bifactorial arrangement was used, where Factor A comprised the tomato varieties (Floradade and Candela F1), the certified seeds being acquired from Agrosad Productos Agropecuarios (Quito, Ecuador). These two varieties (Floradade and Candela F1) were chosen because they are widely used in Ecuador due to their productivity, vigor, and resistance to disease. Floradade is an open-pollinated variety, whereas Candela F1 is an F1 hybrid. Although Floradade is a well-known and respected variety, Candela F1 offers better traits in terms of vigor, yield, and resistance because it is an F1 hybrid. Factor B comprised three concentrations of chitosan (500, 1000, and 2000 mg L−1) (medium molecular weight; Sigma-Aldrich weight, catalog number C3646), plus a control, with a total of eight treatments and three replicates per treatment. The chitosan was dissolved in 1% glacial acetic acid and neutralized with 1N NaOH to pH 5.6. It was applied as a colloidal solution [22]. In addition, the chitosan powder had an average size < 100 µm according to supplier specifications.

2.3. Experiment Management

Seeding was carried out in plastic 2 mm-deep germination trays, using as substrate a mixture of four parts soil, two parts organic matter (compost), and one part sand. The trays were covered with plastic for 48 h to facilitate germination and growth. Transplanting was performed when the plants reached an average height of 15 cm in pots of approximately 8 kg, which contained the aforementioned substrate. The soil used had a loamy texture (32% sand, 48% silt, and 20% clay), an organic matter content of 3.8%, and a pH of 6.0. After transplanting, the crop was grown for 120 days. Floradade and Candela F1 are short-cycle cultivars (90 to 130 days) adapted to tropical environments, so the experimental duration was adequate to complete their productive cycle. According to Parvin et al. [19], these cultivars have been used in similar cycles in controlled tropical conditions.
Trellising was carried out 21 days after transplanting, whereby a stake was tied to the trellis-work 10 cm from the base of the plant to provide support. One plant was placed in each pot to ensure the success of the transplant. Once the plants were transplanted, daily irrigation occurred using drinking water to maintain soil moisture close to field capacity. This helps cover the evapotranspiration requirements of the plants and avoids water stress that could affect crop yield. Broken, diseased, and/or old leaves were removed every week.
The chitosan was applied at three concentrations of chitosan (500, 1000, and 2000 mg L−1) by spraying the leaves at 6, 12, and 25 days after transplanting, and water was used as a control treatment. The experiment consisted of 3 rows per plot, with 9 plants per treatment (36 plants per row) and a total of 108 plants per tomato variety, for a total of 216 plants.

2.4. Microclimate

Photosynthetic photon flux density (PPFD) was measured with a quantum sensor and light meter (LI-250, LI-COR Inc., Lincoln, NE, USA). Leaf temperature was measured with thermistors (YSI 409B) connected to a Switch Craft LN4153-405 (8402-10, Cole-Parmer Instrument Company, Vernon Hills, IL, USA) and a tele-thermometer (Yellow Springs Instruments Co., College Station, TX, USA). Air temperature and relative humidity in the greenhouse were measured with a HOBO Pro V2 logger, and data were stored in a HOBO Waterproof Shuttle (Onset Computer Corporation, Pocasset, MA, USA). The microclimatic variables were measured hourly between 07:00 and 17:00.

2.5. Morphometric Variables

The variables evaluated at 50 days after transplanting (DAT) were plant height (cm), stem diameter (mm), and root, stem, and leaf dry biomass (g). Plant height was measured from the base of the stem to the apex, and stem diameter was measured with a caliper. To obtain the dry biomass in all stages, the tissues corresponding to leaves, stems, or roots were placed in paper bags and placed in a drying oven (Shel-Lab®, model FX-5, series-1000203, Cornelius, OR, USA) at 80 °C until complete dehydration was achieved (approximately 72 h). They were then weighed on an analytical balance (Mettler® Toledo, AG204, Columbus, OH, USA), expressing the weight in grams of dry plant matter.
The number of bunches per plant was determined by counting five plants taken at random from each experimental unit, and the number of fruits per bunch was evaluated by counting plants taken at random from each experimental unit. As the fruits appear after between 30 and 40 days, the data of the clusters and fruits were taken 45 days after transplanting. In addition, the number of usable fruits was counted per plant within the useful area of each experimental unit in order to calculate the average per plant. For fruit weight, 10 randomly selected fruits were weighed, and their average was calculated. For the polar diameter of the fruit, all the fruits harvested from the plants of each treatment were measured with a tape measure to later obtain an average. The number of fruits harvested corresponds to the total number of fruits obtained per plant at the end of the cycle. The equatorial diameter of the fruit was measured in exactly the same way to obtain an average. The yield was calculated by extrapolating the average fruit weight per plant to the total experimental area and expressed in tons per hectare, a calculation that has been used by authors such as Hussain et al. [21]. Fifteen plants were evaluated in each treatment, and the yield (kg ha−1) was extrapolated according to the following equation:
Yield = number of fruits harvested × average weight of fruit (gr) × 55,556/1000
where 55,556 represents the number of tomato plants in one hectare.

2.6. Physiological Variables

All physiological variables (Ψam, Ψpm, gas exchanges, LAI, and chlorophyll content) were taken between 38 and 58 days after transplanting, when the crop is in full development, with the first fruits appearing after between 30 and 40 days.

2.6.1. Leaf Water Potential

The morning leaf water potential (Ψam) was determined between 06:30 and 07:30 and the afternoon potential at 13:00 (Ψpm), using six fully expanded adult leaves of different plants from each treatment (n = 6) and a PMS 200 pressure chamber (PMS Instruments Inc., Corvallis, OR, USA).

2.6.2. Gas Exchange

Gas exchange was evaluated, including A, E, gs, intercellular CO2 concentration (Ci), and water use efficiency (WUE = A/E), using a CIRAS 2 portable infrared gas analyzer (PP Systems Inc., Amesbury, MA, USA). All measurements were performed on fully expanded and healthy adult leaves from 6 different plants in each treatment (n = 6) and the two tomato varieties. The conditions were as follows: ambient CO2 concentrations (Ca) of 420 ± 10 ppm, 21% O2, temperatures of 28 ± 1 °C, PPFD of 1000 ± 50 µmol m−2 s−1, and leaf–air water vapor pressure deficit (VPD) of 1.2–1.6 KPa. The gas exchange analysis was performed between 8:30 and 15:00.

2.6.3. Leaf Area Index Measurement

The leaf area index (LAI) of tomato plants from the two varieties in each treatment was determined using a plant canopy analyzer (LAI-2200 C, Li-COR, Lincoln, NE, USA). Six randomly chosen plants were measured for each treatment (n = 6), with a homogeneous canopy, using the plant canopy analyzer sensor wand, complemented with a 90° cover to block the equipment operator and the canopy of nearby plants. Measurements were taken with the sensor outside the canopy and below in the direction of the four cardinal points (north, south, east, and west).

2.7. Chlorophyll Content

Chlorophyll content was determined using a SPAD-502 Plus chlorophyll meter (Minolta, Tokyo, Japan). SPAD units are directly proportional to leaf chlorophyll content. Chlorophyll concentration was measured in 5 different leaves on 6 different plants for each treatment (n = 6).

2.8. Fruit Quality Indicators

According to the USDA’s color visual scale, fruits that were uniformly sized and free of physical damage were collected at stage 6 (light red) of maturity [41]. In order to evaluate the fruit quality attributes immediately, six fruits from each treatment were cleaned and used whole.

2.8.1. Polyphenol Content

Using the Folin–Ciocalteu reagent, polyphenols (mg Gallic acid g−1) were measured in accordance with Cumplido-Nájera et al. [42].

2.8.2. Antioxidant Capacity

The antioxidant capacity (μmol Trolox/g) was determined by bleaching of a preformed solution of the blue-green radical cation 2,2′-azinobis-(3-ethylbenzothizoline-6-sulfonic acid), as described by Henriquez et al. [43].

2.8.3. Flavonoid Content

Flavonoid content was determined by spectrophotometry, following the method of Zhishen et al. [44]. Flavonoids were expressed as mg Catechin g−1.

2.8.4. Carotenoids

Equation (1) was used to calculate β-carotene [μg g−1] in accordance with Naga and Yamashita [45], using the absorbance values of 453, 505, 645, and 663 nm.
β-carotene = 0.216 × Abs663 − 1.22 × Abs645 − 0.304 × Abs505 + 0.452 × Abs453

2.8.5. Vitamin C Content

According to Levine et al. [46], the colorimetric method was used to quantify vitamin C (mg 100 g−1) using 2,6 dichlorophenol, 1 g of fresh tissue, and 2% HCl.

2.8.6. Total Soluble Solids

The total soluble solids (TSS) in 10 mL of fruit pulp were measured using a digital refractometer (ATAGO, MASTER-100H model, Bellevue, WA, USA).

2.9. Statistical Analysis

Statistica version 10 software was used to perform the two-way analysis of variance (ANOVA), with factor 1 being chitosan concentration and factor 2 being tomato variety for the evaluated variables. Fisher’s least significant difference (LSD) a posteriori test was applied to determine the significance (p < 0.05) of differences observed in the variables studied. The SigmaPlot 11.0 program was used to create the corresponding graphs. In addition, a Pearson’s correlation analysis, hierarchical cluster analysis, and principal component analysis were performed using Origin software (v2016). For the hierarchical cluster analysis of the variables, the group average as the cluster method and Pearson’s correlation as distance type were used.

3. Results

3.1. Microclimate

The maximum PPFD values were observed in the afternoon, with values of 350 and 150 μmol m−2 s−1 above the canopy and below the crop, respectively. The lowest temperatures were found in the morning hours (23 °C). In the afternoon, the air and leaf temperature of Candela F1 was 36 °C, while in Floradade it was 34 °C (Figure 1). In the morning hours, the maximum RH (90%) was observed, while the minimum RH (44%) was recorded in the afternoon.

3.2. Morphometric Variables

Chitosan (1000 mg L−1) only caused a significant increase in plant height in the Candela F1 tomato variety. In both tomato varieties, the highest results were obtained with the highest dose of chitosan (2000 mg L−1). In the Floradade variety, diameter was not affected by the 500 and 1000 mg L−1 doses of chitosan. However, in the Candela F1 variety, all chitosan treatments were superior to the control treatment. The dry biomass of all organs was higher in Floradade than in Candela F1; chitosan caused a significant increase in the dry biomass of all plant organs with respect to the control treatment. The Sh/R ratio was not affected much by chitosan in Floradade, while it caused a significant increase in Candela F1 (Table 1).
Both varieties showed an increase in yield with increasing chitosan concentrations. In Floradade, the yield increased from 51,844 kg ha−1 in the control to 91,452 kg ha−1 with 2000 mg L−1 of chitosan, showing an increasing trend with higher concentrations. Similarly, yield increased in Candela F1 from 29,293 to 48,456 kgha−1 under the same conditions. Furthermore, both tomato yields declined at 1000 mg L−1, with Floradade experiencing a more pronounced decrease than Candela F1. In terms of the total number of bunches, the Floradade variety experienced a significant increase from 2.07 in the control to 3.07 with 2000 mg L−1 of chitosan. The 2000 mg L−1 treatment was significantly different in this variable from the rest of the treatments. In the Candela F1 variety, there were no significant differences between the control and chitosan treatments for this variable (Table 2).
In the number of fruits harvested, the Floradade variety showed no differences between the control treatment and the various concentrations of chitosan. Candela F1, meanwhile, showed a significant increase in the number of fruits harvested with the highest chitosan concentration (2000 mg L−1). However, the 500 and 1000 mg L−1 treatments showed no significant differences with the control treatment. In polar and equatorial fruit diameters, both varieties showed an increase for both diameters as chitosan concentration increased. The greatest increase was obtained in the Floradade variety, where the polar diameter increased from 15.1 mm in the control to 21.2 mm with 2000 mg L−1 and the equatorial diameter from 16.7 mm to 23.6 mm (Table 2).

3.3. Water Potential

Morning leaf water potential (Ψam) at 38 DAT showed no significant difference between the two varieties in any of the treatments studied. The control-treatment plants had a higher Ψam, and when chitosan was applied at 1000 mg L−1, the values of Ψam were close to −0.2 MPa in both varieties. The afternoon leaf water potential (Ψpm) of Floradade for all treatments did not vary significantly, with a tendency to decrease in both varieties, the decrease being more accentuated in Candela F1. It is noteworthy that with applications of chitosan at 500, 1000, and 2000 mg L−1 in the afternoon, there was a significantly greater decrease in Ψpm in Candela F1, whose results were the opposite in the morning (Figure 2).
At 58 DAT, significant differences were only found for the Ψpm between both varieties when chitosan was applied at 2000 mg L−1 in the morning hours, with the difference in the same hours with respect to 38 DAT. The Ψpm of the plants at 58 DAT was lower, and with the dose of 2000 mg L−1 at 58 DAT, Candela F1 presented a lower Ψpm than Floradade. At 38 DAT, however, the Floradade variety had the lowest Ψpm. In the afternoon, there were no significant differences between the two varieties across all treatments, and an increase in plant Ψpm was generally observed in both varieties (Figure 2).

3.4. Gas Exchange

The net photosynthetic rate (A) and transpiration rate (E) at 38 and 58 DAT for the two tomato varieties plus the control showed significant differences between the three doses of chitosan applied and between the two varieties studied (Figure 3). At both 38 and 58 DAT, chitosan applications at the different doses did not cause significant variations in gs, Ci, or WUE between the two varieties, nor between treatments. At 58 DAT, E was lower in both varieties and for all treatments (Figure 3). Similar results were achieved for gs, Ci, and WUE. The distinctive feature for the latter was that at 58 DAT, there was an increase in WUE in the treatments compared to 38 DAT, which could be considered a consequence of the decrease in E at that age of the crop (Figure 3).

3.5. Leaf Area Index

The LAI at 38 and 58 DAT showed significant differences between the two vegetative phases evaluated in the two varieties and in the different doses of chitosan used in the research, whose values were between 2.0 and 2.5. At 38 DAT, the Floradade variety reached a significantly higher LAI than the Candela F1 variety in the control treatment, in which no chitosan was applied (Figure 4).
The application of the three dosages of chitosan stimulated the leaf development in the Candela F1 variety, which resulted in no significant differences in the LAI values with respect to the Floradade variety. At 58 DAT, when chitosan was applied at 1000 and 2000 mg L−1, there were significant differences in the LAI when comparing both varieties, in that Candela F1 reached higher LAI values, contrary to the results achieved at 38 DAT. The control treatment and the application of chitosan at 500 mg L−1 did not cause significant differences in this index between the two varieties (Figure 4).

3.6. Chlorophyll Content

Significant differences were found in chlorophyll content (SPAD) evaluated at 38 DAT among the varieties for the control treatment and the 500 and 1000 mg L−1 treatments, whereas with the 2000 mg L−1 dose, the Floradade variety significantly surpassed Candela F1. At 58 DAT, the same trend was observed, with the difference that with 2000 mg L−1 of chitosan, the chlorophyll content of Floradade was not statistically superior to that of Candela F1 (Figure 5).

3.7. Fruit Quality Indicators

The polyphenols, antioxidant capacity, flavonoids, carotenoids, vitamin C, and TSS for the two tomato varieties plus the control showed significant differences between the three doses of chitosan applied and between the two varieties studied (Figure 6). The application of the three doses of chitosan stimulated the tomato quality parameters in both varieties, which resulted in significant differences in the polyphenols, flavonoids, and TSS in Candela F1 with respect to the Floradade variety.

3.8. Multivariate Analysis

Pearson’s correlation analysis shows a positive correlation in most of the agronomic parameters (TC, NHF, FPD, FED, FY, RDW, SDW, LDW, and ShDW), as well as with Ψpm at 58 DAT, LAI at 38 DAT, A, A2, and SPAD units (Figure 7a). In contrast, LAI at 58 DAT (LAI2), Sh/R ratio, Ψpm at 38 DAT, Ci at 38 DAT, and WUE at 58 DAT (WUE2) were negatively correlated with agronomic parameters.
The results of the principal component analysis (PCA) of the evaluated variables show that the main axis of variation explained 45.9% of the data, while the second axis explained 17.0% (Figure 7b). The biplot shows four groups of treatments associated with different variables. One group comprises Candela F1 control (C-0) and Candela F1-500 mgL−1 (C-500), which are negatively associated with Ci at 38 DAT. Another group, formed by Candela F1-1000 mgL−1 (C-1000) and Candela F1-2000 mgL−1 (C-2000), is negatively associated with LAI2, Ψpm, WUE2, Sh/R, gs, and E. A group formed by the Floradade control (F-0) and Floradade-1000 mgL−1 (F-1000) treatments is positively associated with practically all agronomic and physiological parameters. And finally, the group including Floradade-2000 mgL−1 (F-2000) and Floradade-500 mgL−1 (F-500) is negatively associated with physiological variables at 58 DAT (A2, E2, gs2, Ψam2, and Ψpm2) and RDW (Figure 7b).

4. Discussion

Chitosan is a very interesting compound, with particular characteristics that make it a useful tool for agriculture. This research demonstrated that the foliar application of chitosan induced positive responses in growth (increase in plant height, stem diameter, and root, stem, and leaf biomass), yield, fruit quality, and physiological performance (net photosynthetic rate, chlorophyll content, and leaf area index) in the two tomato varieties studied. Therefore, chitosan application is an alternative to reduce the use of synthetic fertilizers and improve tomato yield. The responses of tomato plants to chitosan application were different depending on the variety evaluated, indicating a differential response to the biostimulant.
Similar to what was found in this study, an increase in tomato plant height with chitosan application has been reported by other authors [20]. Amirkhani et al. [47] reported that the application of biostimulants increased plant height compared to the control treatment in broccoli (Brassica oleracea). The increase in crop growth and development when chitosan is applied is related to the increased availability and uptake of nutrients and the photosynthesis process through the accumulation of metabolites and increased foliar pigments, as reported previously by Sharif et al. [48].
In agreement with our investigation, the application of chitosan as a biostimulant has induced positive responses in the growth of a variety of agricultural crops (S. lycopersicum, T. aestivum, Z. mays, Curcuma longa, Ocimum ciliatum, Ocimum basilicum, and Pisum sativum) [18,33,35,49,50,51,52]. The effects of chitosan on plant development have been linked to an increase in plant chlorophyll content after chitosan application [38,53]. The application of chitosan increased stem diameter in the tomato crop with respect to the control treatment, results that agree with those obtained by other authors [20,54,55].
Regarding biomass, the application of chitosan increased the biomass of organs with respect to the control treatment, similar results to those reported in tomato by Chanaluisa-Saltos et al. [56] and Torres Rodríguez et al. [57]. In bell pepper and tomato plants, an increase in fresh and dry biomass was obtained with the application of biostimulants including chitosan [58,59]. The rise in nutrient content in the soil through the application of biostimulants is reflected in an increase in the crops’ biomass and dry matter production [60]. When chitosan is applied to the soil, it positively influences plant nutrition, especially when combined with other fertilizers, with the great advantage of not affecting beneficial soil microorganisms [16]. This is because chitosan can function as a very efficient nutrient or biostimulant carrier [5]. This will also indirectly induce positive responses in plant growth and development.
The absence of significant differences in the number of clusters in the Candela F1 variety could be related to the lower sensitivity of this variety to the applied biostimulant, or to genetic factors that determine a lower number of reproductive structures compared to Floradade. This response is based on similar observations made by Parvin et al. [19], who reported differences in varietal sensitivity to chitosan. The lack of significant differences could be linked to the fact that fruit set is a variable influenced by hormone load, stable environmental conditions, and possible threshold effects of chitosan. This suggests that, in Floradade, chitosan did not exceed the threshold physiological response that stimulates fruit set. Similar results have been reported in a study by El Amerany et al. [18], where not all reproductive parameters were equally stimulated by chitosan.
In our work, a trend of increased SPAD units was observed with the application of chitosan, potentially indicating a higher chlorophyll content in the leaves, which would improve the photosynthetic process. Similarly, in Z. mays, T. aestivum, O. ciliatum, and P. sativum plants, an increase in chlorophyll content was observed with the foliar application of chitosan at concentrations of 0.01%, 0.2–0.4 g L−1, and 100 mg L−1, respectively [33,35,50,51]. The results suggest that the plants had an adequate supply of nutrients, so their availability was not a limiting factor for their normal development. Furthermore, it can be inferred that the photosynthetic system of the leaves maintained its integrity, which ensures favorable conditions for plant development.
In our study, no significant differences in stomatal conductance were observed between the chitosan treatments and the control; these results may be due to the fact that there was no water deficiency in the experimental environment. Nevertheless, it has been demonstrated that chitosan closes plant stomata, preventing water loss by transpiration [61]. When water is a limiting factor, the plant responds by closing its stomata to reduce water loss through transpiration, resulting in a reduction of stomatal conductance [62,63]. Chitosan-induced stomatal closure is more evident under water deficit conditions [64]. This reinforces that, in the absence of water deficiency, as was the case in our experiment, no significant changes in stomatal conductance have been observed.
The two tomato varieties treated with chitosan showed differences with the control treatment in A and E. However, there was no variation in gs, Ci, or WUE with respect to the control; these results indicate that the increase in CO2 assimilation at the expense of a large loss of water by transpiration generated a decrease in WUE, affecting the leaf water status. Chitosan did not significantly increase WUE in the two varieties studied. Under these conditions, chitosan would allow plants to use their natural and physiological mechanisms to rapidly recover maximum carbohydrate uptake, maintaining biomass production and yield [64]. The non-significant differences in WUE of chitosan-treated plants compared to the control suggest that A and gs change proportionally, reducing assimilated carbon as water consumption decreases [65]; however, it is important to bear in mind that WUE was evaluated in the leaves.
In both varieties examined, the addition of chitosan to tomatoes raised their levels of carotenoids, polyphenols, antioxidants, and vitamin C, which improves their quality and nutritional value. However, Candela F1’s fruit quality was superior to Floradade’s in terms of polyphenols, flavonoids, and total soluble solids. The use of biostimulants, like chitosan, promotes the synthesis of secondary metabolites, including lignin, alkaloids, phytoalexins, flavonoids, and compounds with protective properties. These compounds may cause cell thickening, which in turn may promote plant growth and development [66]. These compounds are beneficial to health and can improve the organoleptic properties of tomato [67].
In response to the foliar application of chitosan, both tomato varieties showed a higher yield and better fruit quality, associated with higher net photosynthetic rate, chlorophyll content, and LAI, which also explained the increase in tomato crop growth and development. Studies have been conducted on the molecular mechanisms of chitosan’s effects on plant growth and development [68]. However, it should be noted that more research into this approach and its effect on tomato quality are still needed.
The PCA with its two main axes explained 62.9% of the variation of all the data obtained. Four well-defined groups were found, which were corroborated by cluster analysis. These were (1) the Candela F1 control and Candela F1-500 mgL−1; (2) Candela F1-1000 mgL−1; (3) Candela F1-2000 mgL−1 and Floradade-1000 mgL−1 (negatively associated with the physiological variables LAI, Ψpm, WUE, gs, and E); and (4) Floradade control, Floradade-500 mg L−1, and Floradade-2000 mg L−1 (positively associated with virtually all agronomic and physiological parameters). This grouping supports the observation that depending on the tomato variety, a different agronomic and physiological response to chitosan application was obtained.

5. Conclusions

According to our study’s data, chitosan increased net photosynthetic rate, chlorophyll content, leaf area index, and biomass, which led to considerably improved yields, demonstrating its efficacy as a biostimulant. Depending on the variety assessed, tomato plants responded differently to the application of chitosan, indicating a variable reaction to the biostimulant. Chitosan is an efficient compound to biostimulate the growth and development of tomato plants, in addition to positively modifying tomato physiology, which can potentially increase the yield of agricultural crops. Therefore, the use of chitosan in agriculture can be a useful tool to increase the productive capacity of crops, with the advantages of being an easily accessible compound and having no negative effects on crops or the environment.

Author Contributions

Conceptualization, J.J.R.-P.; methodology, J.J.R.-P., L.T.L.-R. and W.T.; software, W.T., V.R., J.J.R.-P., L.G.H.-M. and A.J.-M.; validation, W.T., V.R., L.T.L.-R. and A.J.-M.; formal analysis, J.J.R.-P., W.T. and L.G.H.-M.; investigation, J.J.R.-P., L.T.L.-R., V.R. and W.T.; resources, J.J.R.-P.; data curation, J.J.R.-P. and W.T.; writing—original draft preparation, J.J.R.-P. and W.T.; writing—review and editing, J.J.R.-P., W.T. and L.G.H.-M.; supervision, J.J.R.-P., L.T.L.-R. and W.T.; project administration, J.J.R.-P.; funding acquisition, J.J.R.-P. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Competitive Fund for Scientific and Technological Research (FOCICYT), grant number PFOC9-07-2023.

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

We are grateful to the State Technical University of Quevedo, for the support granted through the Competitive Fund for Scientific and Technological Research (FOCICYT) 9th Call, through the project PFOC9-07-2023, “Response of horticultural crops to selenium application under controlled conditions”.

Conflicts of Interest

The authors declare no conflicts of interest.

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Horticulturae 11 00878 g001
Figure 1. Microclimatic variables measured in the greenhouse: photosynthetic photon flux density (PPFD) above and below the tomato plants; air temperature (T air, black circles) and leaf temperature for Floradade (white circles) and Candela F1 (green circles).
Figure 1. Microclimatic variables measured in the greenhouse: photosynthetic photon flux density (PPFD) above and below the tomato plants; air temperature (T air, black circles) and leaf temperature for Floradade (white circles) and Candela F1 (green circles).
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Figure 2. Leaf water potential in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated in the morning (Ψam) and afternoon (Ψpm) at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
Figure 2. Leaf water potential in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated in the morning (Ψam) and afternoon (Ψpm) at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
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Figure 3. Net photosynthetic rate (A) and transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and water use efficiency (WUE) in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
Figure 3. Net photosynthetic rate (A) and transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), and water use efficiency (WUE) in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
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Figure 4. Leaf area index (LAI) in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
Figure 4. Leaf area index (LAI) in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
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Figure 5. SPAD units in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
Figure 5. SPAD units in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 (A) and 58 (B) days after transplanting. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
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Figure 6. Polyphenols (A), antioxidant capacity (B), flavonoids (C), carotenoids (D), vitamin C (E), and total soluble solids (F) in two evaluated tomato varieties (Floradade and Candela F1) treated with chitosan. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
Figure 6. Polyphenols (A), antioxidant capacity (B), flavonoids (C), carotenoids (D), vitamin C (E), and total soluble solids (F) in two evaluated tomato varieties (Floradade and Candela F1) treated with chitosan. Different letters per column indicate significant differences between treatments according to Fisher’s test (p < 0.05).
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Figure 7. (a) Pearson correlation of the response variables, and (b) biplot of the treatments and response variables in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 and 58 days after transplanting. Abbreviations: SPAD 2 (chlorophyll content, 58 DAT); SPAD (chlorophyll content, 38 DAT); WUE 2 (water use efficiency, 58 DAT); Ci2 (intercellular CO2 concentration, 58 DAT); GS 2 (stomatal conductance, 58 DAT); E2 (transiration rate, 58 DAT); A2 (net photosynthetic rate, 58 DAT); WUE (water use efficiency, 38 DAT); CI (intercellular CO2 concentration, 38 DAT); GS (stomatal conductance, 38 DAT); E (transiration rate, 38 DAT); A (net photosynthetic rate, 38 DAT); LAI2 (leaf area index, 58 DAT); LAI (leaf area index, 38 DAT); PH NOON 2 (Ψpm, 58 DAT); PH AM 2 (Ψam, 58 DAT); PH NOON (Ψpm, 38 DAT); PH AM (Ψam, 38 DAT); SH/R (shoot/root); ShDW (shoot dry weight); LDW (leaf dry weight); SDW (stem dry weight); RDW (root dry weight); Fruit yield; FED (equatorial diameter of the fruit); FPD (polar diameter of the fruit); AFW (average fruit weight); NHF (number of harvested fruits); TC (total clusters).
Figure 7. (a) Pearson correlation of the response variables, and (b) biplot of the treatments and response variables in two tomato varieties (Floradade and Candela F1) treated with chitosan and evaluated at 38 and 58 days after transplanting. Abbreviations: SPAD 2 (chlorophyll content, 58 DAT); SPAD (chlorophyll content, 38 DAT); WUE 2 (water use efficiency, 58 DAT); Ci2 (intercellular CO2 concentration, 58 DAT); GS 2 (stomatal conductance, 58 DAT); E2 (transiration rate, 58 DAT); A2 (net photosynthetic rate, 58 DAT); WUE (water use efficiency, 38 DAT); CI (intercellular CO2 concentration, 38 DAT); GS (stomatal conductance, 38 DAT); E (transiration rate, 38 DAT); A (net photosynthetic rate, 38 DAT); LAI2 (leaf area index, 58 DAT); LAI (leaf area index, 38 DAT); PH NOON 2 (Ψpm, 58 DAT); PH AM 2 (Ψam, 58 DAT); PH NOON (Ψpm, 38 DAT); PH AM (Ψam, 38 DAT); SH/R (shoot/root); ShDW (shoot dry weight); LDW (leaf dry weight); SDW (stem dry weight); RDW (root dry weight); Fruit yield; FED (equatorial diameter of the fruit); FPD (polar diameter of the fruit); AFW (average fruit weight); NHF (number of harvested fruits); TC (total clusters).
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Table 1. Morphometric variables (height, stem diameter, root dry weight, leaf dry weight, stem dry weight, shoot dry weight, and shoot/root ratio) of two tomato varieties (Floradade and Candela F1) at 50 days after transplanting. The plants were subjected to different concentrations of chitosan. Different letters between rows indicate significant differences for p < 0.05 according to Fisher’s least significant difference (LSD). Values show the mean ± standard error.
Table 1. Morphometric variables (height, stem diameter, root dry weight, leaf dry weight, stem dry weight, shoot dry weight, and shoot/root ratio) of two tomato varieties (Floradade and Candela F1) at 50 days after transplanting. The plants were subjected to different concentrations of chitosan. Different letters between rows indicate significant differences for p < 0.05 according to Fisher’s least significant difference (LSD). Values show the mean ± standard error.
VariableVarietyControl 500 mg L−11000 mg L−12000 mg L−1
Height (cm)Floradade106.5 ± 3.0 a114.27 ± 2.1 a117.20 ± 2.1 ab116.53 ± 1.8 a
Candela F1120.02 ± 2.5 b123.47 ± 2.1 bc125.9 ± 1.8 bc130.47 ± 1.9 c
Stem Diameter (mm)Floradade9.40 ± 0.3 ab9.67 ± 0.2 ab9.67 ± 0.2 ab10.13 ± 0.4 ab
Candela F18.20 ± 0.3 a10.30 ± 0.2 b10.30 ± 0.3 b10.80 ± 0.21 b
Root Dry Weight (RDW) (g)Floradade52.8 ± 7.1 cd56.7 ± 5.4 de58.3 ± 6.5 de70.3 ± 6.5 e
Candela F128.3 ± 2.0 a36.7 ± 4.7 ab38.7 ± 4.7 abc48.2 ± 1.9 bcd
Leaf Dry Weight (LDW) (g)Floradade38.0 ± 2.5 ab42.0 ± 3.7 bc42.7 ± 2.1 c44.0 ± 1.9 c
Candela F132.2 ± 3.7 a36.7 ± 1.7 ab37.2 ± 2.8 ab39.3 ± 2.4 b
Stem Dry Weight (SDW) (g)Floradade23.8 ± 1.6 bc26.0 ± 1.3 c27.2 ± 1.9 c27.0 ± 0.7 c
Candela F115.5 ± 1.1 a18.7 ± 1.9 ab21.2 ± 2.2 bc23.8 ± 1.6 bc
Shoot Dry Weight (ShDW) (g)Floradade64.8 ± 4.6 ab65.8 ± 3.3 ab69.8 ± 3.7 b71.0 ± 2.3 b
Candela F150.7 ± 4.5 a55.8 ± 4.1 ab57.8 ± 3.5 ab63.2 ± 3.2 ab
Shoot/Root (Sh/R)Floradade1.0 ± 0.2 a 1.2 ± 0.1 a1.3 ± 0.1 a1.4 ± 0.1 a
Candela F11.1 ± 0.2 a1.6 ± 0.3 ab2.1 ± 0.4 b2.1 ± 0.2 b
Table 2. Production parameters (yield, number of bunches, number of harvested fruits, FPD, and FED) of two tomato varieties (Floradade and Candela F1) subjected to different concentrations of chitosan. Letters between rows indicate significant differences for p < 0.05 according to Fisher’s least significant difference (LSD). Values show the mean ± standard error.
Table 2. Production parameters (yield, number of bunches, number of harvested fruits, FPD, and FED) of two tomato varieties (Floradade and Candela F1) subjected to different concentrations of chitosan. Letters between rows indicate significant differences for p < 0.05 according to Fisher’s least significant difference (LSD). Values show the mean ± standard error.
VariableVarietyControl 500 mg L−11000 mg L−12000 mg L−1
Yield
(Kg ha−1)		Floradade51,844 ± 6680 ab71,882 ± 11,812 bc43,119 ± 7675 a91,452 ± 17,580 c
Candela F129,293 ± 5927 a31,915 ± 8826 a28,011 ± 3406 a48,456 ± 6594 ab
Total Clusters (TC)Floradade2.07 ± 0.2 d2.5 ± 0.2 c2.87 ± 0.2 b3.07 ± 0.2 a
Candela F11.47 ± 0.1 a1.47 ± 0.1 a1.27 ± 0.1 a2.0 ± 0.2 ab
Number of Harvested Fruits (NHF)Floradade4.87 ± 0.3 b5.53 ± 0.5 b3.93 ± 0.4 ab5.73 ± 0.6 b
Candela F12.87 ± 0.3 b2.8 ± 0.3 b2.93 ± 0.3 b4.13 ± 0.4 a
Polar Diameter of the Fruit (FPD)Floradade15.1 ± 1.3 bc17.3 ± 1.3 b20.8 ±1.8 a21.2 ± 2.5 a
Candela F19.5 ± 1.0 c11.5 ± 1.4 b11.6 ±1.3 b15.4 ± 1.3 a
Equatorial Diameter of the Fruit (FED)Floradade16.7 ± 1.5 c20.1 ± 1.4 b22.7 ± 1.9 b23.6 ± 2.6 a
Candela F111.2 ± 1.1 c13.1 ± 1.5 b13.4 ± 1.5 b17.5 ± 1.4 a
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MDPI and ACS Style

Reyes-Pérez, J.J.; Llerena-Ramos, L.T.; Tezara, W.; Reynel, V.; Hernández-Montiel, L.G.; Juárez-Maldonado, A. Chitosan Application Improves the Growth and Physiological Parameters of Tomato Crops. Horticulturae 2025, 11, 878. https://doi.org/10.3390/horticulturae11080878

AMA Style

Reyes-Pérez JJ, Llerena-Ramos LT, Tezara W, Reynel V, Hernández-Montiel LG, Juárez-Maldonado A. Chitosan Application Improves the Growth and Physiological Parameters of Tomato Crops. Horticulturae. 2025; 11(8):878. https://doi.org/10.3390/horticulturae11080878

Chicago/Turabian Style

Reyes-Pérez, Juan José, Luis Tarquino Llerena-Ramos, Wilmer Tezara, Víctor Reynel, Luis Guillermo Hernández-Montiel, and Antonio Juárez-Maldonado. 2025. "Chitosan Application Improves the Growth and Physiological Parameters of Tomato Crops" Horticulturae 11, no. 8: 878. https://doi.org/10.3390/horticulturae11080878

APA Style

Reyes-Pérez, J. J., Llerena-Ramos, L. T., Tezara, W., Reynel, V., Hernández-Montiel, L. G., & Juárez-Maldonado, A. (2025). Chitosan Application Improves the Growth and Physiological Parameters of Tomato Crops. Horticulturae, 11(8), 878. https://doi.org/10.3390/horticulturae11080878

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