Phytotoxicity of Extracts of Argemone mexicana and Crotalaria longirostrata on Tomato Seedling Physiology

Phytotoxicity caused by secondary metabolites of botanical extracts is a drawback in agriculture. The objective of this study was to evaluate the phytotoxic effects of methanolic extracts of Crotalaria longirostrata and Argemone mexicana on the germination and physiological variables of tomato seedlings. The results indicated that high doses of both extracts (Clong500 and Amex500) inhibited tomato seed germination, while their mixture (Cl50 + Am50) promoted germination by 100%. At 30 days after transplanting (dat), the plant height increased by 15.4% with a high dose of C. longirostrata (Clong500) compared to the control. At 30 dat, the vigor index displayed a notable increase with Cl50 + Am50, reaching 29.5%. The root length increased with the mean dose of A. mexicana (Amex95) at 10, 20, and 30 dat (59.7%, 15.1%, and 22.4%, respectively). The chlorophyll content increased with Amex95 by 66.1% in 10 dat, 22.6% at 20 dat, and 19.6% at 30 dat. On the other hand, Amex95 had a higher nitrogen content throughout the trial. Amex95 produced the greatest increase in root dry weight by 731.5% and 209.4% at 10 and 20 dat. The foliage dry weight increased by 85.7% at 10 dat with Amex95 and up to 209.7% with Amex50 at 30 dat. The present investigation reveals the ability of the extracts to stimulate tomato growth at low and medium doses, though at high doses they exhibit allelopathic effects.


Introduction
Conventional agriculture focuses on the use of chemical pesticides (an estimated 2.5 million tons of synthetic active ingredients are used annually) to rapidly control pests and diseases of major crops produced worldwide.However, these pesticides reduce the diversity of non-target species, such as natural enemies of pests, and have toxic effects on ecosystems and human health [1,2].This is due to direct or indirect exposure to synthetic active ingredients that generate negative ecological impacts, in addition to risks to agricultural production due to damage to the soil microbiome [3].
To counteract the harmful effects generated by conventional agriculture, innovations in pest and disease management have emerged through agroecological systems for sustainable production that promote non-curative measures through preventive methods employing mechanical control and the use of biological or botanical pest control agents; these systems will limit the use of chemical pesticides through a spatial and temporal organization of agronomic and ecological concepts that avoid socioecological vulnerability [4,5].
For this reason, using plant extracts as an alternative to chemical pesticides is one solution, as these extracts have proved to be suitable alternatives for weed control, plant biostimulants, pest control, and the management of agricultural diseases [6,7].
Every year about 2000 plant species with a potential for pest and disease control in crops are discovered (as of 2015, 400,000 plant species were registered), and the use of plants as pesticides is possible due to the presence of secondary metabolites.There are more than 200,000 reported compounds among non-protein amino acids, anthocyanins, alkaloids, amines, glucosinolates, cyanogenic glycosides, terpenoids, phenylpropanoids, flavonoids, tannins, polyketides, saponins, coumarins, organic acids, and carbohydrates [8,9].It is believed that plant secondary metabolites do not induce resistance, cause low harmful effects to the environment, are safer for human health, and are more economical for farmers [10].
One plant that can be used for this purpose is Crotalaria longirostrata Hook.& Arn.(Fabaceae), colloquially known as chipilín, which is used as a food in southeastern regions of Mexico and Central America [11].The incorporation of C. juncea species into the substrate as solid fertilizer for crops such as beans and maize can increase nitrogen mineralization by up to 85% and carbon availability by 80% [12].Similarly, C. retusa leaf powder, used to grow Solanum lycopersicum, increased leaf biomass by 24.7% and root biomass by 34.1% [13].
However, allelopathic effects have also been reported for some species of this genus, such as C. retusa (used in a methanolic extract), which exhibits phytotoxic mechanisms at high doses of crude alkaloids on Phaseolus vulgaris, reducing germination by 69.3%, total protein by 81.7%, and leaf sugar by 62.3% [14].
Another plant with similar characteristics is the species Argemone mexicana Linn (Papaveraceae), known as chicalote, an annual weed present in Mexico and used as an indigenous medicinal plant [15,16].A. mexicana has demonstrated that it contains adequate levels of nitrogen and potassium for use as an organic fertilizer once it has been converted to vermicompost [17].On the other hand, a phytotoxic effect was reported when A. mexicana was used in a 1% w/v aqueous extract, inhibiting tomato and lettuce root germination and growth, while a 1% w/v methanolic extract reduced tomato root elongation by 48% [18].
Secondary metabolites present in plant extracts proved to be fundamental components in the induction of plant resistance to pathogen attack [19].However, their capacity to induce plant growth and improve the yield of certain crops is not well known [20].One example is saturated fatty acids, such as unsaturated fatty acids found in extracts of various organs of Moringa oleifera, which promote seed germination and plant development of Triticum aestivum L. [21].Aqueous extracts of Posidonia oceanica revealed that phenolic compounds, glycosides, and terpenes played a crucial role in the development of the roots and leaves of S. lycopersicum and Cucumis sativus [22].The methanolic extracts of C. longirostrata and A. mexicana used in this study contain secondary metabolites previously identified as significant components in these plants [23,24].
Although there are several studies on the effect of the A. mexicana species [25,26] and the genus Crotalaria [12,13,27] as plant growth stimulants, evidence of the effects of such plants is scarce.Therefore, the present work aimed to evaluate the phytotoxic effects of methanolic extracts of Crotalaria longirostrata and Argemone mexicana on the germination and physiological variables of tomato seedlings.

Effect of Extracts on Tomato Seed Germination
The germination of tomato seeds after the application of methanolic extracts of C. longirostrata and A. mexicana (Table 1) was sensitive to high doses of both extracts (Clong500 and Amex500); the highest germination was observed with the mixture of the extracts Cl50 + Am50, with 100% germination; a promotion of germination was noted in comparison with the germination rate observed in the control seeds.

Greenhouse Test
At the beginning of the study, the tomato plants treated with the methanolic extracts were smaller than the control plants (Table 2); conversely, development responded favorably at 20 dat, showing greater growth with Clong500 and Amex95.Better results were obtained at 30 dat with the mixture of extracts (Cl50 + Am50), with growth increases of 14.9% and 15.4% with Clong500.After applying methanolic extracts to tomato plants at 10 dat, all treatments expressed a low vigor index (Table 3).At 20 and 30 dat, a slight increase in vigor index was recorded in the Amex95 treatment (4.5% and 6.8%) and a moderate increase in the Clong50 treatment (8.4% and 8.9%).After 30 dat, the Amex50 dose reached a vigor index of 10.7%, while the mixture of extracts (Cl50 + Am50) achieved the highest increase with 29.5%.
As shown in Table 4, treatment with Amex95 stimulated an increased root growth of the tomato plants throughout the trial (10.7, 17.5, and 29.5 mm, respectively).However, at 20 days post transplanting, the Clong500 treatment showed a similar increase (17.6 mm) to the Amex95 treatment.At the end of the trial, the Amex95 and Amex500 treatments similarly increased root length by 29.5 mm and 29.3 mm.The chlorophyll content in tomato leaves was higher with methanolic extracts (Figure 1A), and the chlorophyll content values for the first 10 dat were higher in Clong500 and Amex95 (44.9 and 45.1 SPAD, respectively).At 20 dat, the SPAD values increased in all treatments compared to the control, but the value was higher in all treatments compared to the first evaluation; the best treatments were Clong500 with 58.5 SPAD and Amex95 with 58.7 SPAD.At 30 dat, the increase was 67.7 and 67.6 SPAD with Clong95 and Amex50.Like chlorophyll, the nitrogen content increased at 10 dat in the Clong500 (14.4) and Amex95 (14.1) treatments; after 20 dat, it increased by 18.6 and 18.7, respectively.At 30 dat, the Clong95 (21.6) and Amex50 (21.4) treatments showed the highest nitrogen levels (Figure 1B).
After the application of Amex95 at 10 dat, the plant root dry weight increased by 0.74 g compared to the control (Figure 2A).Subsequently, at 20 dat the Amex95 treatment increased the root dry weight by 1.64 g, and Clong50 increased it by 1.69 g.At 30 days after transplanting, the Amex50 and Amex500 treatments showed a very similar increase in root dry weight (2.6 and 2.62 g, respectively), while Clong95 was superior with 2.75 g.Regarding the dry weight of the aerial part of the plant after receiving different doses of the extracts, the dry biomass showed a significant increase (Figure 2B).Through treatment with Amex95 it reached 0.65 g after 10 dat, and Amex500 obtained a dry biomass of 4.1 g at 20 dat.At the end of the trial (30 dat), Amex50 showed the greatest increase in dry biomass with 21.65 g, followed by Amex95 (20.86 g) and Amex500 (20.85 g).
(14.1) treatments; after 20 dat, it increased by 18.6 and 18.7, respectively.At 30 dat, the Clong95 (21.6) and Amex50 (21.4) treatments showed the highest nitrogen levels (Figure 1B).After the application of Amex95 at 10 dat, the plant root dry weight increased by 0.74 g compared to the control (Figure 2A).Subsequently, at 20 dat the Amex95 treatment increased the root dry weight by 1.64 g, and Clong50 increased it by 1.69 g.At 30 days after transplanting, the Amex50 and Amex500 treatments showed a very similar increase in root dry weight (2.6 and 2.62 g, respectively), while Clong95 was superior with 2.75 g.Regarding the dry weight of the aerial part of the plant after receiving different doses of the extracts, the dry biomass showed a significant increase (Figure 2B).Through treatment with Amex95 it reached 0.65 g after 10 dat, and Amex500 obtained a dry biomass of 4.1 g at 20 dat.At the end of the trial (30 dat), Amex50 showed the greatest increase in dry biomass with 21.65 g, followed by Amex95 (20.86 g) and Amex500 (20.85 g).

Discussion
Plant extracts derived from roots, leaves, stems, flowers, and seeds are sources of secondary metabolites that may produce stimulant or allelopathic effects [7].They are considered as an option to reduce losses in agriculture, given that when applied to leaves or seeds, they improve nutrient absorption capacities and strengthen resistance to abiotic and biotic stresses [6].
A metabolite with phytotoxic activity must become absorbed by the different plant tissues translocated through the phloem and xylem; therefore, its mode of action depends on the accepting plant species and the resources it limits (water, nutrients, light, ATP synthesis, gene expression, or damage to the cell cycle) [28].
Although studies on the possible phytotoxic properties of C. longirostrata are limited, other species of the Crotalaria genus have demonstrated allelopathic effects on seed germination.The aqueous extract of C. juncea leaves, at 1.5 and 3.3% w/v, significantly affected

Discussion
Plant extracts derived from roots, leaves, stems, flowers, and seeds are sources of secondary metabolites that may produce stimulant or allelopathic effects [7].They are considered as an option to reduce losses in agriculture, given that when applied to leaves or seeds, they improve nutrient absorption capacities and strengthen resistance to abiotic and biotic stresses [6].
A metabolite with phytotoxic activity must become absorbed by the different plant tissues translocated through the phloem and xylem; therefore, its mode of action depends on the accepting plant species and the resources it limits (water, nutrients, light, ATP synthesis, gene expression, or damage to the cell cycle) [28].
Although studies on the possible phytotoxic properties of C. longirostrata are limited, other species of the Crotalaria genus have demonstrated allelopathic effects on seed germination.The aqueous extract of C. juncea leaves, at 1.5 and 3.3% w/v, significantly affected tomato seed germination by 12 and 100% [29].Also, a methanolic extract of C. juncea leaves (1 mg/mL) inhibited the germination of Vigna radiata by 50% [30].The extract containing chloroform fraction and leaves of C. retusa at concentrations of 10, 50, and 100 µg/mL reduced the germination ability of P. vulgaris by up to 60% [14], and a 15% (w/v) aqueous extract of C. juncea leaves inhibited the germination of Zea mays by up to 56.1% [31].However, the methanolic extract of C. juncea roots promoted up to 40% more germination [30].
The aqueous extract at 1% (w/v) of A. mexicana reduced the germination rate of tomato seeds by 90% [18].In Sorghum bicolor seeds, a 14 and 79.7% reduction in germination was observed when the aqueous extract was applied at doses of 5 and 25% (w/v) [32].Furthermore, an aqueous extract of A. mexicana at 50 g/L inhibited the germination of Brachiaria dictyoneura by 47.4% and that of Clitoria ternatea by 20.5% [33].The results obtained in this study showed that Clong500 and Amex500 inhibited tomato germination by up to 8.9%, and conversely, a mixture of the two extracts stimulated germination by up to 100% (Table 1).
Aqueous extracts of the leaves of C. brevidens, C. sessiliflora, and C. juncea (w/v) increased the growth of Triticum aestivum by 7.1 to 12.7% [34].The aqueous leaf extract of C. juncea (w/v) increased the stem height of Lactuca sativa by 7.7% [35].Likewise, a 50% w/v aqueous extract of A. mexicana stems stimulated the height of tomato plants by 18.5% [25].Namkeleja et al. reported that the aqueous extract of A. mexicana at 50 g/L promoted the development of B. dictyoneura (55.3%) and C. ternatea (32.5%) plants [33].These results are consistent with those observed in Table 2, where tomato plant height was greater when C. longirostrata and A. mexicana extracts were applied.
The seed vigor index indicates the relationship between environmental or genetic factors affecting seed quality, rapid and uniform plant emergence, plant weight, and/or plant growth rate under field or greenhouse conditions [36,37].As can be seen in Table 3, the highest vigor index was presented with Cl50 + Am50, suggesting that the extracts improve tomato seed and plant vigor.
There are several Crotalaria species (C.brevidens, C. juncea, C. lanceolata, C. pallida, C. sessiflora, and C. spectabilis) that have demonstrated their allelopathic effect when used as ground cover on T. aestivum, affecting root growth by up to 40.6% and the length of the longest root by up to 53.7% [34].However, an aqueous extract of C. juncea leaves at a low dose (7.5% w/v) increased the length of the longest root of Z. mays by 9.2% [31]; the use of C. juncea as a ground cover (500 g/m 2 ) increased the root development of Z. mays by 11.2% 24 days after emergence (dae) [38].The present results showed a similar increase in root length after Amex95 and Amex500 treatments.
A report showed that chlorophyll content increased when C. juncea species were applied as green manure in the Z. mays crop, by up to 35.6% at 56 dde [39], and in Oryza sativa by up to 25.5% [40].As shown in Figure 1, the increases in chlorophyll and nitrogen are closely related, and the treatments of C. longirostrata and A. mexicana also yielded a positive effect on tomato leaves.
Regarding the dry weight, the results of the methanolic extract of A. mexicana increased the dry weight of the root and aerial part of the tomato plant compared to the extract of C. longirostrata (Figure 2).In L. sativa plants, there was an increase of 16.6% due to the use of the aqueous extract of C. juncea roots at 50 g/L [35], and an increase of up to 112.3% was observed in O. sativa plants at 60 days after emergency (dae) when using C. juncea as a ground cover [40].Likewise, a 50% (w/v) aqueous extract of A. mexicana stems increased the total dry weight of tomato plants by 38% [25].
In addition, the results of gas chromatography and mass spectrophotometry showed the presence of secondary metabolites in the extracts, which could be responsible for their capacity to stimulate plant growth.The methanolic extracts of A. mexicana and C. longirostrata presented a 72.6% and 79.9% abundance of these compounds, respectively; these metabolites belong to the groups of saturated and unsaturated fatty acids, amines, fatty alcohols, alkaloids, and cyanogenic glycosides [23,24].
Metabolites such as saturated and unsaturated fatty acids may promote plant growth for the synthesis of cellular constituents [41,42].These lipids act in the tricarboxylic acid cycle, contributing to enzyme activation, and may increase germination, root formation, photosynthesis, trichome number, and fruit yield [43,44].In the case of fatty acids, they are involved in jasmonic acid biosynthesis, fruit ripening, tuber formation, and pollen development [45,46].
Alkaloids are a group of secondary metabolites with a varied structure, mainly consisting of two carbon and nitrogen rings, with substituent groups at carbon 1 and 7 [8].The various modifications that nitrogen presents in the molecule (heterocyclic and nonheterocyclic) allow for arrangements in the chemical structure and its biological activity [47].Due to their carbon and nitrogen composition, alkaloids could potentially contribute to plant nutrition [48].
It is essential to consider that the secondary metabolites present in plant extracts can induce toxicity in the plant.The effects of low doses of the stimulus utilized can trigger an adaptive response in the organism, while high doses cause an increase in the organism's resistance or inhibition, referred to as hormesis [49].Hormesis establishes a dose-time-response connection that can vary depending on the individual and its characteristics, generating protective responses in plants by stimulating cellular defense mechanisms due to low doses or stress caused by high doses [50].The application of hormesis in plant growth and resistance using plant extracts faces significant challenges due to the need for more comprehensive investigations on the inheritance of hormesis transgenerational effects (HTE) across multiple plant generations [51].These studies should address the underlying epigenetic mechanisms that may generate phenotypic variability and the generation of new heritable epialleles in subsequent generations [52].
In addition, it has been observed that plants experience a hormetic response to low doses of exogenous agents for short periods, which drives photosynthesis through photosystem II; this process is activated by reducing the quenching of non-photochemical fluorescence, which dissipates excess energy and maintains a basal level of reactive oxygen responses [53,54].This phenomenon accounts for the positive increase in chlorophyll levels in the tomato plants treated with the methanolic extracts applied in this study (Figure 1A).Furthermore, plant secondary metabolites act as allelochemicals, stimulating plant growth at low doses, and acting as inhibitors at high doses [55].The effect of hormesis in plants, caused by applying plant extracts, was reported at a rate of 0.4%, in which 70% of the results obtained were favorable in plant growth, while 18% affected the increase in plant metabolism [56].The aqueous extract of M. oleifera has generated the adaptability of 12 secondary metabolites at a low dose of 2.5% (w/v); these metabolites are responsible for promoting Lepidium sativum shoot growth by 48%, but, at high doses of 10% (w/v), a significant inhibition in root length of 85% and shoot length of 38% was observed [57].
These results indicate that, when considering using plant extracts as plant growth promoters, it is necessary to consider studies that assess ecological risks.Moreover, it is required to investigate selective hormesis in populations (including plants, fungi, and insects), to apply statistical models that demonstrate the adaptive response of hormesis (characterized by a biphasic dose-response), and to analyze the impact on international regulations [49,58].

Materials and Methods
The authors of this study evaluated the experiment in the laboratory and greenhouse of the Parasitology Department of the Universidad Autónoma Agraria Antonio Narro in Saltillo, Coahuila, Mexico.

Sampling of Plants and Preparation of Extracts
The species C. longirostrata (Hook.& Arn.) and A. mexicana (Linn) have been taxonomically identified and included in the ANSM herbarium of the Universidad Autónoma Agraria Antonio Narro with record numbers 104040 and 103807, respectively.
For C. longirostrata, plant samples were collected in Chiapa de Corzo, Chiapas, Mexico, and only the leaves were dried in the shade for seven days.They were then milled in a blender (model 7011s, Waring Commercial, Torrington, CT, USA), left to macerate for 30 days (0.2 g dry matter/mL of 96% methanol), and finally filtered on Whatman paper No. 1 (Sigma-Aldrich, St. Louis, MO, USA) [59]. A. mexicana was collected in Saltillo, Coahuila, Mexico, obtaining only leaves, dried in the shade for ten days, and pulverized in a blender (model 7011s, Waring Commercial, Torrington, CT, USA).Maceration was carried out for seven days with continuous agitation at room temperature (0.1 g dry matter/mL of 96% methanol) and filtered through Whatman paper No. 1 [60].The two extracts were stored in dark flasks at 4 • C until use.

Plant Material
We used tomato (Solanum lycopersicum) seeds of the Rio Grande variety.The tomato seeds were immersed in a 6% sodium hypochlorite solution for 10 s, and then washed at least five times with sterile distilled water.We repeated this process twice to remove pesticide residues and disinfect the seeds.

Effect of Extracts on Tomato Seed Germination
The preparation of the concentrations followed that described by [23], where the relative density of each extract was obtained using a 25 mL Gay-Lussac pycnometer (16038, BRAND, Wertheim, Germany), and the density of water was taken as 0.997299 g/cm 3 at 24 • C for C. longirostrata and 0.997772 g/cm 3 at 22 • C for A. mexicana.
The lethal concentrations (LC) of C. longirostrata [23] and A. mexicana [24] have come from previous studies.Based on these concentrations, the treatments evaluated were for C. longirostrata an LC 50 of 4.78 mg/mL (Clong50) and an LC 95 of 14.52 mg/mL (Clong95), for A. mexicana an LC 50 of 7.63 mg/mL (Amex50) and a CL 95 of 107.98 mg/mL (Amex95), the doses of each extract at 500 mg/mL (Clong500 and Amex500), and the mixture of extracts with the CL 50 of each (Cl50 + Am50).To evaluate the phytotoxic or growth-stimulant effects on tomato plants.
For testing seed viability, 15 seeds were placed in each Petri dish with filter paper, which was moistened with 10 mL of the different concentrations of the methanolic extracts of C. longirostrata and A. mexicana, while the control was distilled water [61].Four replicates were established for each treatment and the absolute control.The Petri dishes were kept in the laboratory at a temperature of 25 • C, and the germinated seeds were counted after eight days (germinated seeds were considered those with visible radicle and hypocotyl).The test had a completely randomized design and four replications.The results were expressed in terms of germination percentage: where X is the number of seeds germinated in each treatment at eight days and Y is the number of seeds germinated in the absolute control at eight days.

Greenhouse Assay
Tomato seeds were germinated in 200-cavity polystyrene trays with peat moss as substrate and transplanted 30 days after emergence.Subsequently, they were placed in 10 L pots containing a mixture of perlite and peat moss (1:1).Plant nutrition was carried out with Steiner's nutrient solution [62], according to the phenological stage of the crop.Different doses of methanolic extracts were applied by spraying with the aid of an atomizer.The first application was made immediately after transplanting, the second application was made 10 days after transplanting (dat), and the third was applied at 20 dat.
The vigor index is a quality parameter that considers the germination capacity and viability of the same batch of seeds, and is calculated according to the formula [61]: where G is the germination rate obtained in the laboratory test and L is the length of the aerial part of the plant obtained in the greenhouse.
The plant aerial height in cm was recorded with a flexometer, the root length in mm was measured with a Vernier caliper, and the plant dry weight (root and foliage) in g was obtained with an analytical balance (Ohaus, Parsippany, NJ, USA); the chlorophyll index and nitrogen content were measured using the Minolta SPAD 502 plus a chlorophyll meter (Konica Minolta Holdings Co., Ltd., Tokyo, Japan) (which provides chlorophyll in SPAD units and the value of nitrogen present in the leaf) [63].Readings for all variables were taken at 10, 20, and 30 dat.

Statistical Analysis
The obtained data were processed with an analysis of variance, and means were compared with Tukey's test (p ≤ 0.05) under a completely randomized design.All analyses were performed with the Statistical Analysis System (SAS) version 9.0 statistical software.

Conclusions
We found that methanolic extracts of A. mexicana and C. longirostrata leaves at high doses showed phytotoxic activity on S. lycopersicum, which affected germination, plant height, and vigor index.On the other hand, the two combined extracts showed the ability to stimulate seed germination.These methanolic extracts showed active properties as a plant growth promoter in S. lycopersicum cultivation and as a possible insecticide, suggesting their application to reduce the use of synthetic molecules.

Figure 1 .
Figure 1.Effect of methanolic extracts of C. longirostrata and A. mexicana on tomato plants.(A) Chlorophyll content, and (B) nitrogen content in the leaves of the tomato plants treated with the extracts.The capital letters in each bar indicate statistical difference (ANOVA, Tukey HSD, p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL50 of C. longirostrata, Clong95 = represents the CL95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL50 of A. mexicana, Amex95 represents the CL95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL50 of both extracts.

Figure 1 .
Figure 1.Effect of methanolic extracts of C. longirostrata and A. mexicana on tomato plants.(A) Chlorophyll content, and (B) nitrogen content in the leaves of the tomato plants treated with the extracts.The capital letters in each bar indicate statistical difference (ANOVA, Tukey HSD, p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL 50 of C. longirostrata, Clong95 = represents the CL 95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL 50 of A. mexicana, Amex95 represents the CL 95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL 50 of both extracts.

Figure 2 .
Figure 2. Effect of methanolic extracts of C. longirostrata and A. mexicana on tomato plants.(A) Leaf dry weight response, and (B) root dry weight response of tomato plants treated with the extracts.The capital letters in each bar indicate statistical difference (ANOVA, Tukey HSD, p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL50 of C. longirostrata, Clong95 represents the CL95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL50 of A. mexicana, Amex95 represents the CL95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL50 of both extracts.

Figure 2 .
Figure 2. Effect of methanolic extracts of C. longirostrata and A. mexicana on tomato plants.(A) Leaf dry weight response, and (B) root dry weight response of tomato plants treated with the extracts.The capital letters in each bar indicate statistical difference (ANOVA, Tukey HSD, p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL 50 of C. longirostrata, Clong95 represents the CL 95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL 50 of A. mexicana, Amex95 represents the CL 95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL 50 of both extracts.

Table 1 .
Effect of methanolic extracts of C. longirostrata and A. mexicana on tomato seed germination.Clong50 stands for the CL 50 of C. longirostrata, Clong95 represents the CL 95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL 50 of A. mexicana, Amex95 represents the CL 95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL 50 of both extracts.

Table 2 .
Response of tomato plant height to methanolic extracts of C. longirostrata and A. mexicana.

Table 3 .
Vigor index of tomato plants treated with methanolic extracts of C. longirostrata and A. mexicana.Means with the same letter in the same column are not significantly different by Tukey's test (p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL 50 of C. longirostrata, Clong95 represents the CL 95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL 50 of A. mexicana, Amex95 represents the CL 95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL 50 of both extracts.

Table 4 .
Response of tomato plant root length to methanolic extracts of C. longirostrata and A. mexicana.
Means with the same letter in the same column are not significantly different by Tukey's test (p ≤ 0.05).Control refers to the absolute control group, Clong50 stands for the CL 50 of C. longirostrata, Clong95 represents the CL 95 of C. longirostrata, Clong500 corresponds to a concentration of C. longirostrata of 500 mg/mL, Amex50 stands for the CL 50 of A. mexicana, Amex95 represents the CL 95 of A. mexicana, Amex500 corresponds to a concentration of A. mexicana of 500 mg/mL, and Cl50 + Am50 refers to a mixture of the CL 50 of both extracts.