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INTRODUCTION
The root system is the main anchoring and nutrient absorption medium available to plants, consuming more than half of the carbon fixed annually by plants. Despite its obvious importance, the dynamics of live roots are poorly understood due to the inaccessibility of the root system (Benítez-Vega, 2007).
Plants produce small organic molecules of variable chemical identity that influence growth and development, known as phytohormones or growth regulators (Jaillais &y Chory, 2010). Compounds that play a more direct role in modulating maize root architecture include auxins, ethylene, brassinosteroids, and gibberellins.
The maize plant's root system is fasciculated and robust, serving the functions of anchoring the plant and nutrient absorption, with the presence of adventitious roots favoring these functions Ortigoza et al. (2019). Within agriculture, there is a significant interest in discovering mechanisms that certain species employ to counteract the negative impacts of climate change, particularly in the context of food production (Hunt & Elliott, 2002).
The use of bioestimulants that stimulate root development is one of the best alternatives for increasing productivity because they act directly on the roots, inducing the appearance of rootlets. This translates into an improvement in the absorption capacity of nutrients available in the soil, resulting in enhanced maize production (Morales, 2021).
The use of bioestimulants in agriculture is on the rise, aiming not to replace fertilization but to complement it by stimulating natural processes to improve nutrient absorption and efficiency. This has a positive impact on crop yield and quality while promoting plant development and providing resistance to various stress conditions caused by adverse weather or herbicide side effects (Van Oosten et al., 2017; Samudio-Cardozo, 2020).
Pectic oligosaccharides represent a promising alternative to boost the growth and productivity of various crops. They have shown a positive effect on vegetative and root development, accelerating and improving the flowering and fruiting process. Additionally, their application offers multiple ways to effectively increase yields (Falcón-Rodríguez et al., 2015; Lara-Acosta et al., 2018).
This research aimed to determine the effect of a mixture of pectic oligosaccharides on the development of the root system of maize plants.
MATERIALS AND METHODS
Location
This experiment was conducted at the Experimental Station of the Agricultural Innovation Institute of Panama, located in El Ejido, Los Santos Province, Republic of Panama. This area is characterized by an average annual temperature of 27.2ºC, average annual precipitation of 900 mm/year, average relative humidity of 75%, altitude of 25 meters above sea level, soil pH of 6.20, coastal plain topography, loam-clay soil texture, and wind speed of 1.2 m/s.
Experimental setup
The research was carried out in the field using polyethylene bags of different sizes (one pound for plants evaluated at seven DAP, twenty-five pounds for plants evaluated at twenty and forty DAP, and one hundred pounds for plants evaluated at sixty DAP (Figure 1). A drip irrigation system was implemented and the necessary plant nutrition was ensured through the application of fertilizers, following the guidelines proposed by Gordon (2021). The nutrient mixture was introduced into the irrigation system through a Venturi, thus guaranteeing its adequate distribution.
Experimental Design
A completely randomized design with three replicates was used, and two treatments were evaluated:
Sampling
Two crop cycles of hybrid maize ADV-9293 were grown. The treatments were evaluated at seven, twenty, forty, and sixty days after planting. The root system of the crop was washed to remove all substrate residues without affecting the root system (Figure 2). Aboveground plant evaluations were also performed.
Evaluated Variables
During the samplings, variables such as wet and dry weight of roots were measured using a digital scale, and the drying process was carried out in an oven at 75°C for forty-eight hours until reaching a constant weight. The number of roots was counted, and the length and diameter of the roots were measured using a graduated tape and a digital caliper, respectively (Figure 3).
FIGURE 3 Evaluation of the root system 40 days after planting, A: roots of corn plants treated with biostimulant, B: roots of corn plants without biostimulant.
Variables of the aerea part evaluated:
Plant height (cm): measured with a graduated ruler from the base of the stem to the last fully open leaf, and in the sixty-DAP sampling, it was measured up to the insertion of the ear.
Leaf area: determined using the equation applied by Razquin et al. (2017), by measuring the length and width of each leaf per plant. Three plants per treatment were measured using equation 1.
Stem diameter (cm): measured at the base of the stem using a digital caliper.
Biomass: aboveground biomass was determined by cutting and depositing the samples in labeled manila paper bags. Wet weight was measured with a scale, and then the samples were dried in an oven at 75°C for forty-eight hours to obtain dry weight.
Plant nutrition was carried out following the requirements indicated by Gordon (2021). The fertilizer solution was introduced into the irrigation system through a Venturi.
RESULTS AND DISCUSSION
The application of a bioestimulant based on pectic oligosaccharides through seed imbibition significantly influenced (P≤ 0.05) the length of the roots (Figure 4). The bioestimulant-treated group showed the highest values of root length during the four periods evaluated. This behavior may be due to the ability of pectic oligosaccharides to release auxins, which are plant hormones triggering various growth responses in plants. By promoting auxin synthesis, bioestimulants contribute to the elongation of plant roots. By increasing root length, plants can more efficiently explore and absorb soil resources, leading to greater development and resilience. Additionally, the interaction between bioestimulants and plants not only enhances root growth but can also protect plants against harmful pathogens and improve the availability of essential nutrients. These results align with those obtained by González & Fuentes (2017) in their study on the action mechanism of five plant growth-promoting microorganisms. Pectic oligosaccharides can stimulate protein synthesis in plant roots, favoring their growth and development.
FIGURE 4 Effect of the application of pectic oligosaccharide-based bioestimulant on root length in maize cultivation.
The results for root weight showed statistically significant differences (P≤ 0.05) in the evaluated periods (Figure 5). This increase in root weight is attributed to the fact that bioestimulants are growth promoters that enhance cell division and elongation, increase chlorophyll production, and improve the overall vigor of the plant. Pectic oligosaccharides can act as substitutes for auxins, plant hormones that promote root growth, resulting in increased root weight. This information is supported by the findings of Lemus-Soriano et al. (2021), indicating that the use of microorganisms and organic acids favors the vegetative and root growth of avocado crops. Sakthiselvan et al. (2014) have proposed that microorganisms can enhance plant development by exerting a beneficial impact on certain soil chemical properties. This translates into increased nutrient solubilization and greater absorption capacity by plants.
Maize plants treated with the bioestimulant differed significantly (P≤ 0.05) from untreated plants (Figure 6), exhibiting a greater number of roots in the different periods studied. In the study conducted by Posada-Pérez et al. (2016), a significant increase in the number of roots was observed in plants treated with a combination of Pectimorf® and AIB auxin (indole-3-butyric acid). This result highlighted the importance of these substances in promoting root development in plants. In general, bioestimulants stimulate natural processes that benefit nutrient utilization and increase resistance to stressful conditions, which could explain the increased number of roots in maize plants treated with bioestimulants.
The application of pectic oligosaccharides through seed imbibition had a significant impact (P≤ 0.05) on the increase in leaf area, plant height, and dry mass of maize crops. Plants treated with pectic oligosaccharides experienced an increase in leaf area, plant height, and dry mass due to the influence of certain hormones and their functions in the growth and development process of plants (Falcón-Rodríguez et al., 2020; Pérez-Díaz et al., 2023). This is attributed to the presence of certain hormones that participate in the process and contribute to the positive effects observed in plants treated with pectic oligosaccharides. Auxins are responsible for cell elongation and division, contributing to the increase in plant height; gibberellins promote stem elongation and cell division, also contributing to the increase in plant height; and cytokinins promote cell division and differentiation, contributing to the increase in leaf area (Pérez-Díaz et al., 2023). These hormones work together to regulate plant growth and development, and their presence in pectic oligosaccharides contributes to the observed effects in treated plants.
The bioestimulant-treated groups showed greater development in leaf area and dry mass. During the evaluation periods, leaf areas of 7.45, 573.34, 4414.44, and 9511.85 cm² were obtained, along with dry mass weights of 0.07, 8.52, 73.36, and 195.48 g, respectively (Table 1). These results are consistent with the previous findings of Soares et al. (2016) and Cargua-Chávez et al. (2019), who also observed a significant increase in leaf area and biomass in bean and soybean plants treated with a bioestimulant.
These results indicate a significant positive impact of the pectic oligosaccharide-based bioestimulant on leaf area, plant height, and dry mass in maize cultivation.
The application of pectic oligosaccharides through seed imbibition had a significant impact (P≤ 0.05) on plant height. This result aligns with the findings of Barreto- Zúñiga & Pinos-Rocel (2023), who also assessed maize production performance using three bioestimulants. Additionally, Blanco-Valdes et al. (2022) found that treatments imbibed with Quitomax® (a naturally sourced bioestimulant) resulted in increased plant height.
TABLE 1 Effect of pectic oligosaccharide-based bioestimulant application on leaf area, plant height, and dry mass in maize cultivation. El Ejido, Los Santos, Panama 2022
| Days After Sowing (DAS) | Leaf Area (cm²) | Plant Height (cm) | Dry Mass (g) | |||
|---|---|---|---|---|---|---|
| CB | SB | CB | SB | CB | SB | |
| 7 DAS | 7.45 a | 6.59 b | 6.56 a | 5.08 b | 0.07 a | 0.04 a |
| 20 DAS | 573.34 a | 386.24 b | 34.00a | 29.2 b | 8.52 a | 5.74 b |
| 40 DAS | 4414.44 a | 3875.87 b | 118.17 a | 110.33 a | 73.36 a | 60.58 b |
| 60 DAS | 9511.85 a | 8376.97 a | 223.67 a | 205.17 b | 195.48 a | |
CB= with bioestimulant SB= without bioestimulant
CONCLUSIONS
The application of pectic oligosaccharides through seed imbibition is beneficial for the root growth and development of maize crops, as these substances can influence the growth and development of plant tissues, increasing tolerance to abiotic stresses.
The use of bioestimulants based on pectic oligosaccharides constitutes an effective strategy to improve the production and vigor of maize crops.
