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Pretreatment of seeds with plant regulators attenuates salt stress in pumpkin: effects on germination and initial seedling development1 1 Pesquisa financiada pela Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Código de Financiamento 001

O pré-tratamento de sementes com reguladores vegetais atenua o estresse salino em abóbora: efeitos na germinação e desenvolvimento inicial de plântulas

ABSTRACT

Pretreatment of seeds results in faster emergence of seedlings and uniform stand, especially under stress. Thus, the objective was to evaluate the action of plant regulators as stress attenuators during germination and initial development of pumpkin seedlings, cv. ‘Baiana Tropical’, irrigated with saline water. For this, a completely randomized design was established, in a 4 x 3 factorial scheme, with four replications. Treatments consisted of four types of water (W1 - 100% supply water; W2 - 100% fish farming effluent; W3 - 100% artesian well water; W4 - mixture of 50% fish farming effluent + 50% artesian well water) and three seed treatments (control, salicylic acid and gibberellic acid). The variables measured were germination, first germination count, shoot and root length, shoot and root dry mass, total soluble sugars, total amino acids and proline. The data were subjected to analysis of variance and Scott-Knott test. Pumpkin seedlings performed osmotic adjustment under saline conditions of W4 water. In addition, the treatment of pumpkin seeds with plant regulators (gibberellic and salicylic acids) favors the germination and initial development of seedlings under conditions of salt stress.

Keywords:
Cucurbita moschata ; Cucurbitaceae; Gibberellic acid; Salicylic acid; Stress mitigation

RESUMO

O pré-tratamento de sementes resulta em emergência de plântulas mais rápida e estande uniforme, principalmente, quando sob estresse. Sendo assim, objetivou-se avaliar a ação de reguladores vegetais como atenuantes de estresse durante a germinação e desenvolvimento inicial de plântulas de abóbora, cv. Baiana Tropical, irrigadas com água salina. Para isso, estabeleceu-se o delineamento inteiramente casualizado, em esquema fatorial 4 x 3, em quatro repetições. Os tratamentos foram constituídos de quatro tipos de água (A1 – 100% água de abastecimento; A2 – 100% efluente de piscicultura; A3 – 100% água de poço artesiano; A4 - mistura de 50% efluente de piscicultura + 50% água de poço artesiano) e três tratamentos de sementes (controle, ácidos salicílico e giberélico). As variáveis mensuradas foram germinação, primeira contagem de germinação, comprimento da parte aérea e raiz, massa seca da parte aérea e raiz, açúcares solúveis totais, aminoácidos totais e prolina. Os dados foram submetidos a análise de variância e teste de Scott-Knott. As plântulas de abóbora realizaram ajustamento osmótico em condições salinas da água A4. Além disso, o tratamento de sementes de abóbora com reguladores vegetais (ácidos giberélico e salicílico) beneficia a germinação e o desenvolvimento inicial de plântulas sob condições de estresse salino.

Palavras-chave:
Cucurbita moschata ; Cucurbitaceae; Ácido giberélico. Ácido salicílico; Mitigação de estresse

INTRODUCTION

Pumpkin (Cucurbita moschata Duchesne) is an annual vegetable-fruit with great socioeconomic importance. This species is cultivated in virtually all countries, with China holding the world’s highest production per year, 7.8 million tons (ATLASBIG, 2020ATLASBIG. Mapas e estatísticas do mundo e regiões. 2020. Disponível em: https://www.atlasbig.com/pt-br. Acesso em: 21 fev. 2021.
https://www.atlasbig.com/pt-br...
). In Brazil, its cultivation and use in the food of the population are quite traditional, with production around 500,000 tons per year, especially in the Northeast region (EMATER-GO, 2019EMATER-GO - Agência Goiana de Assistência Técnica, Extensão Rural e Pesquisa Agropecuária. Produção de abóbora em Rio Verde se torna referência nacional. Comunicação, 2019. Disponível em: https://www.emater.go.gov.br/wp/producao-de-abobora-em-rio-verde-se-torna-referencia-nacional. Acesso em: 17 mar. 2021.
https://www.emater.go.gov.br/wp/producao...
).

The Northeast region of Brazil is characterized by uneven rainfall regime and high evapotranspiration rates, causing the accumulation of solutes in the soil and in subsurface water sources (BEZERRA et al., 2020BEZERRA, R. U. et al. Produção e qualidade da abóbora maranhão sob influência de lâminas de irrigação e doses de nitrogênio. Irriga, v. 25, n. 1, p. 87-101, 2020.). Due to these characteristics, the availability and quality of water in this region are reduced (DINIZ et al., 2021DINIZ, G. L. et al. Irrigação com águas salinas e adubação silicatada no cultivo de maracujazeiro gigante amarelo. Revista Caatinga, v. 34, n. 1, p. 199-207, 2021.). Consequently, the practice of irrigated agriculture becomes limited, as the negative effects of salinity affect from seed germination to production, which can cause death of plants due to the toxicity of ions (DOURADO et al., 2020DOURADO, D. et al. Efeito de bioestimulante em sementes de cedro-rosa. Brazilian Journal of Development, v. 6, n. 5, p. 30306-30319, 2020.). Salt stress of 2.5 dS m−1 causes negative effects on Cucurbita pepo L., characterized by low biomass accumulation in the initial development of the seedlings of this species (CANJÁ et al., 2021CANJÁ, J. F. et al. Initial growth of zucchini irrigated with saline water in soil with biofertilizers. Revista Agro@ mbiente On-line, v. 15, n. 1, p. 1-15, 2021.).

Due to the scarcity of good quality water resources, the use of fish farming effluents is an alternative for the irrigation of agricultural crops with species relatively tolerant to salinity. These wastewaters are rich in minerals and organic matter; however, they may contain high salt contents (SIMÕES et al., 2016SIMÕES, W. L. et al. Beet cultivation with saline effluent from fish farming. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 20, n. 1, p. 62-66, 2016.). Thus, the adoption of certain management techniques, such as water dilution, can enable the use of saline waters in crops subjected to restrictive environmental conditions (LEITE et al., 2017LEITE, T. S. et al. The use of saline aquaculture effluent for production of Enterolobium contortisiliquum seedlings. Environmental Science and Pollution Research, v. 24, n. 23, p. 19306-19312, 2017.).

As techniques adopted to enhance the yield of species in stressful environments, plant regulators have been used (AMARO et al., 2020AMARO, H. T. R. et al. Tratamento de sementes com produtos à base de fertilizantes e reguladores de crescimento. Pesquisa Agropecuária Gaúcha, v. 26, n. 1, p. 222-242, 2020.). Among the most used are the gibberellic acid (GA3) and salicylic acid (SA). Gibberellic acid is a phytohormone considered a promoter of germination, acting on embryo growth and mobilization of energy reserves (PAIXÃO et al., 2021PAIXÃO, M. V. S. et al. Tratamentos pré-germinativos na emergência e desenvolvimento inicial de plântulas de graviola. Revistas Ensaios e Ciências, v. 25, n. 1, p. 72-76, 2021.), while salicylic acid is a phenolic hormone fundamental to plant development, acting as a signaling molecule and mitigator of biotic and abiotic stresses (OLIVEIRA et al., 2016OLIVEIRA, F. A. et al. Uso de bioestimulante como agente amenizador do estresse salino na cultura do milho pipoca. Revista Ciência Agronômica, v. 47, n. 2, p. 307-315, 2016.).

Even in an incipient way, research has been carried out on the exogenous application of gibberellic and salicylic acids in the germination performance of cucurbit seeds. Priming of Citrullus lanatus [(Thunb.) Matsum & Nakai)] seeds with gibberellic acid at 50 and 100 μg g−1 (SILVA et al., 2014SILVA, T. C. F. S. et al. Germinação de sementes de melancia sob diferentes métodos de tratamento com reguladores vegetais. Scientia Plena, v. 10, n. 3, p. 1-15, 2014.) and 1.0 mM salicylic acid (NÓBREGA et al., 2020NÓBREGA, J. S. et al. Emergência e crescimento inicial de melancia submetida a salinidade e doses de ácido salicílico. Revista Desafios, v. 7, n. 2, p. 162-171, 2020.) promoted higher germination and shoot length of seedlings, respectively. On the other hand, salicylic acid concentrations above 3 mM caused reduction in the germination and vigor of Cucumis sativus L. seeds (GASTL FILHO et al., 2017GASTL FILHO, J. et al. Ácido salicílico e potencial germinativo na germinação de sementes de pepino. Revista Inova Ciência & Tecnologia, v. 3, n. 2, p. 7-12, 2017.). Knowing the need for alternative techniques for the treatment of seeds and production of seedlings using wastewater, the objective was to evaluate the effects of gibberellic and salicylic acids as mitigators of salt stress during germination and initial development of pumpkin seedlings, cv. ‘Baiana Tropical’.

MATERIAL AND METHODS

Experimental design

The experiment was conducted under controlled laboratory conditions with pumpkin seeds, cv. ‘Baiana Tropical’, sold by the company Topseed® and acquired in the market of the city of Mossoró, RN, Brazil, in October 2018. The experimental design was completely randomized, with four replicates of 50 seeds. The treatments were arranged in a 4 × 3 factorial scheme, with four types of water (W1 - 100% supply water; W2 - 100% fish farming effluent; W3 - 100% artesian well water; W4 - mixture of 50% fish farming effluent + 50% artesian well water) and three seed treatments (control, gibberellic acid and salty acid), according to methodology of Guirra et al. (2020)GUIRRA, K. S. et al. Phytohormones on the germination and initial growth of pumpkin seedlings under different types of water. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 24, n. 12, p. 827-833, 2020..

Experimental conduction

The water used in the treatment of fish farming effluent (W2) was collected in tilapia (Oreochomis spp.) production tanks. The other treatments [100% artesian well water (W3) and 100% supply water (W1)] were also obtained on the campus of the Federal Rural University of the Semi-Arid Region, Mossoró, RN. In addition to these, well water (50%) and fish farming effluent (50%) were mixed in the treatment W4. The samples were collected in plastic pots and analyzed in the Water and Soil Laboratory of the same institution (Table 1).

Table 1
Result of water analysis with cation and anion concentrations, acidity (pH) and electrical conductivity (EC) found in the waters used in the experiment with pumpkin seeds, cultivar ‘Baiana Tropical’

The seeds were initially treated with a solution of gibberellic acid (GA3) at the concentration of 50 mg L−1 and salicylic acid (SA) at the concentration of 30 mg L−1 of H2O. For this, the seeds were placed to soak on paper towels (paper roll) previously moistened with the solutions of the acids in the proportion of twice their dry mass (BRASIL, 2009BRASIL. Ministério da Agricultura, Pecuária e do Abastecimento. Regras para análise de sementes. Brasília, DF: MAPA, 2009. 395 p.). Soon after, they were placed in moistened paper rolls and kept in the germination chamber at 25 °C for 24 hours (SILVA et al., 2019SILVA, J. E. S. B. et al. Ácido salicílico no condicionamento fisiológico de sementes de cebola submetidas a estresses hídrico e salino. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 23, n. 12, p. 919-925, 2019.). After this period, the seeds were removed, dried on paper towels and subjected to germination test in four replicates of 50 seeds. For this, the paper towel was initially moistened with the water treatments in the proportion of twice its dry mass. Then, they were placed in paper rolls and packed in plastic bags, which were kept in a germination chamber, at 25 °C, with a photoperiod of 12 h (BRASIL, 2009BRASIL. Ministério da Agricultura, Pecuária e do Abastecimento. Regras para análise de sementes. Brasília, DF: MAPA, 2009. 395 p.).

Physiological variables

Germination (G): evaluations of normal seedlings were performed at four and eight days, and the values were expressed as a percentage of normal seedlings (BRASIL, 2009BRASIL. Ministério da Agricultura, Pecuária e do Abastecimento. Regras para análise de sementes. Brasília, DF: MAPA, 2009. 395 p.).

First germination count (FGC): evaluated together with the germination test, in which normal seedlings were counted at four days after sowing according to the Rules for Seed Analysis (BRASIL, 2009BRASIL. Ministério da Agricultura, Pecuária e do Abastecimento. Regras para análise de sementes. Brasília, DF: MAPA, 2009. 395 p.), and the values were expressed as a percentage.

Shoot length (SL) and root length (RL): at the end of the germination test, ten normal seedlings of each repetition were randomly measured using a ruler graduated in millimeters, and the results were expressed in centimeters (cm).

Shoot dry mass (SDM) and root dry mass (RDM): normal seedlings were sectioned into shoots and roots, placed in paper bags and kept in a forced ventilation oven at 65 °C for 72 h. The dried material was weighed on a precision analytical scale (0.0001 g) and the results were expressed in milligrams (mg).

Determination of organic solutes

Total soluble sugars (TSS), total amino acids (TAA) and proline (PRL) were quantified in 0.2 g samples of fresh tissue from whole normal seedlings. These were automatically macerated in hermetically sealed tubes containing 3 mL of 80% ethanol. Subsequently, the tubes were kept in a water bath at 60 °C for 20 min. They were then centrifuged at 10,000 rpm for 8 min at 4 °C, and the supernatant was collected.

Total soluble sugars (TSS): determined by the anthrone method (YEMM; WILLIS, 1954YEMM, E. W.; WILLIS, A. J. The estimation of carbohydrates in plant extracts by anthrone. Biochemical Journal, v. 57, n. 3, p. 508-514, 1954.), with results expressed in mg of TSS g−1 of fresh mass (FM).

Total amino acids (TAA): determined by the ninhydrin method (YEMM; COCKING, 1955YEMM, E. W.; COCKING, E. C. The determination of amino-acids with ninhydrin. Analyst, v. 80, n. 948, p. 209-214, 1955.), with results expressed in μmol TAA g−1 of FM.

Proline (PRL): determined by the methodology proposed by Bates, Waldren and Teare (1973)BATES, L. S.; WALDREN, R. P.; TEARE, I. D. Rapid determination of free proline for water-stress studies. Plant and Soil, v. 39, p. 205-207, 1973., with results expressed in μmol PRL g−1 of FM.

Statistical analysis

The data were subjected to analysis of variance by the F test (p ≤ 0.05) and, in case of significance, subjected to the Scott-Knott test (p ≤ 0.05), using the statistical program System for Variance Analysis - SISVAR® (FERREIRA, 2011FERREIRA, D. F. Sisvar: a computer statistical analysis system. Ciência e Agrotecnologia, v. 35, n. 6, p. 1039-1042, 2011.).

RESULTS AND DISCUSSION

The treatments of pumpkin seeds with plant regulators and different types of water had significant interaction (p ≤ 0.05) for all variables, except for shoot length and root length.

Water salinity compromised seed germination; however, plant regulators, mainly salicylic acid (Figure 1A), favored germination in fish farming effluent (W2) and artesian well water (W3). In addition, in the supply water (W1), this plant regulator promoted higher germination than the other treatments, control and gibberellic acid. Seeds treated with gibberellic acid and subjected to the mixture of types of water (W4) had statistically superior results compared to those treated with salicylic acid for this same water. It was also verified that the seeds of the treatment without plant regulators under supply water had germination of 92%, which is approximately 9.5% higher than the values found in the other treatments.

Figure 1
Germination (A) and first germination count (B) of pumpkin seeds, cultivar ‘Baiana Tropical’, under salt stress. W1 = 100% supply water; W2 = 100% fish farming effluent; W3 = 100% artesian well water; W4 = mixture of 50% fish farming effluent + 50% artesian well water; C = control; GA3 = gibberellic acid; SA = salicylic acid

Means followed by the same lowercase letter (a, b, c) do not differ in the analysis of the water factor considering each plant regulator by the Scott-Knott test (p ≤ 0.05); means followed by the same uppercase letter (A, B, C) do not differ in the analysis of the plant regulator factor by the Scott-Knott test (p ≤ 0.05)


The presence of salts in the solution can cause ionic toxicity, leading to delays in germination and mobilization of reserves, besides reducing the viability of seeds (NÓBREGA et al., 2020NÓBREGA, J. S. et al. Emergência e crescimento inicial de melancia submetida a salinidade e doses de ácido salicílico. Revista Desafios, v. 7, n. 2, p. 162-171, 2020.). Nevertheless, the treatment of seeds with salicylic acid increased germination by 10.2% in fish farming effluent and 12.8% in artesian well water when compared to the control (supply water). Similarly, salicylic acid (0.5 mM) promoted a 40% increase in the germination of Vicia faba L. seeds under salinity conditions (90 mM of NaCl) (ANAYA et al., 2018ANAYA, F. et al. Influence of salicylic acid on seed germination of Vicia faba L. under salt stress. Journal of the Saudi Society of Agricultural Sciences, v. 17, n. 1, p. 1-8, 2018.). Thus, the interaction between salicylic acid and salinity can induce the activation of stress resistance genes and promote greater germination (JINI; JOSEPH, 2017JINI, D.; JOSEPH, B. Physiological mechanism of salicylic acid for alleviation of salt stress in rice. Rice Science, v. 24, n. 2, p. 97-108, 2017.).

Gibberellic acid promoted a 27.6% increase in germination in diluted water (W4). The present study also demonstrates that gibberellic acid has stress attenuating action, with benefits to seed germination, as emphasized by Khan et al. (2015)KHAN, M. I. R. et al. Salicylic acid-induced abiotic stress tolerance and underlying mechanisms in plants. Frontiers in Plant Science, v. 6, p. 17-23, 2015..

The results of first germination count were better in seeds treated with plant regulators, regardless of the water used (Figure 1B). When the seeds were exposed to saline waters, there was a reduction in this variable; however, the treatment of seeds with gibberellic and salicylic acids resulted in statistically higher values compared to untreated ones. In fish farming effluent (W2), the results were above 45.5% of normal seedlings with salicylic acid and 40% with gibberellic acid, compared to the treatment without plant regulator. Similar behavior was observed in artesian well water (W3) and in the dilution of these two waters (W4).

The results were quite significant when the seedlings were irrigated with supply water (W1). In the treatments with plant regulators, there were 77 and 86% of normal seedlings, respectively. These results can be explained by the cell elongation and division functions of the regulators used, which stimulate the growth and establishment of seedlings (TSEGAY; ANDARGIE, 2018TSEGAY, B. A.; ANDARGIE, M. Seed priming with gibberellic acid (GA3) alleviates salinity induced inhibition of germination and seedling growth of Zea mays L., Pisum sativum var. abyssinicum A. Braun and Lathyrus sativus L. Journal Crop Science Biotechnology, v. 21, n. 3, p. 261-267, 2018.). Similarly, the treatment of seeds with regulators mitigated the effects of water salinity, promoting the occurrence of a greater number of normal seedlings in the first count.

For the variables of length in both shoots and roots, there was no significant interaction. However, there were single effects of the regulators on these variables.

The treatment of seeds with gibberellic and salicylic acids promoted 28.9% and 36.6% higher shoot length compared to the control, respectively (Figure 2A). The beneficial effects of regulators were also verified in Oryza sativa L. seedlings under saline conditions, whose shoot length was higher with the application of gibberellin (CHUNTHABUREE et al., 2014CHUNTHABUREE, S. et al. Alleviation of salt stress in seedlings of black glutinous rice by seed priming with spermidine and gibberellic acid. Notulae Botanicae Horti Agrobotanici Cluj-Napoca, v. 42, n. 2, p. 405-413, 2014.). On the other hand, salicylic acid, for being involved in the stress defense mechanism, can influence the synthesis of gibberellins, hence leading to longer seedling lengths (TAIZ et al., 2017TAIZ, L. et al. Fisiologia e desenvolvimento vegetal. Porto Alegre: Artmed, 2017. 888 p.).

Figure 2
Shoot length (A), root length (B), shoot dry mass (C) and root dry mass (D) of pumpkin seeds, cultivar ‘Baiana Tropical’, under salt stress. W1 = 100% supply water; W2 = 100% fish farming effluent; W3 = 100% artesian well water; W4 = mixture of 50% fish farming effluent + 50% artesian well water; C = control; GA3 = gibberellic acid; SA = salicylic acid

Means followed by the same lowercase letter (a, b, c) do not differ in the analysis of the water factor considering each plant regulator by the Scott Knott test (p ≤ 0.05); means followed by the same uppercase letter (A, B, C) do not differ in the analysis of the plant regulator factor by the Scott Knott test (p ≤ 0.05)


Salicylic acid proved to have greater action on root length, whose value was above 14 cm, resulting in growth up to 13.2% higher than that of the control (Figure 2B). On the other hand, in zucchini plants irrigated with saline water of 2.5 dS m−1, this stress caused a negative effect on plant development, with a decrease of approximately 14% in root length (CANJÁ et al., 2021CANJÁ, J. F. et al. Initial growth of zucchini irrigated with saline water in soil with biofertilizers. Revista Agro@ mbiente On-line, v. 15, n. 1, p. 1-15, 2021.). Plant metabolism is more stimulated to overcome the condition of stressful environment (LICHTENTHALER et al., 2021LICHTENTHALER, H. K. et al. Multi-colour fluorescence imaging of photosynthetic activity and plant stress. Photosynthetica, v. 59, n. 2, p. 4-20, 2021.). This behavior was verified in the present study, in which plant regulators acted together with the situation of salt stress because, as a response to adverse conditions, seedlings developed more their root system to find an appropriate environment for plant development.

The treatments of seeds with gibberellic acid and salicylic acid did not promote increments in shoot dry mass. On the other hand, salicylic acid hampered the shoot dry mass accumulation of seedlings grown from seeds treated with fish farming effluent (W2) (Figure 2C). In general, salinity compromised root dry mass. In supply water (W1), untreated seedlings accumulated more root dry mass than treated seedlings, while in W4, salicylic acid promoted higher root dry mass accumulations (Figure 2D). The use of salicylic acid in a stress situation promoted a 54.4% increase in root dry mass when compared to the control treatment. Likewise, salicylic acid promoted higher dry mass of Solanum lycopersicum L., Cucumis melo L. and Vicia faba L. seedlings under salinity conditions (ANAYA et al., 2018ANAYA, F. et al. Influence of salicylic acid on seed germination of Vicia faba L. under salt stress. Journal of the Saudi Society of Agricultural Sciences, v. 17, n. 1, p. 1-8, 2018.; LOPES et al., 2017LOPES, A. C. et al. Água salina e substratos no crescimento inicial do meloeiro. Irriga, v. 22, n. 3, p. 469-484, 2017.). This occurs because this plant regulator acts on physiological (germination and growth) and biochemical (synthesis of metabolites in response to stresses) processes in plants and can be used to improve their development under salinity conditions (RAFIQUE et al., 2011RAFIQUE, N. et al. Pre-sowing A4lication of ascorbic acid and salicylic acid to seed of pumpkin and seedling response to salt. Pakistan Journal of Botany, v. 43, n. 6, p. 2677-2682, 2011.).

To overcome the condition of abiotic stress, seedlings shifted their metabolism of shoot developmental to root growth. In seeds that were not treated, the salinity of the waters did not interfere in the accumulation of total soluble sugars. However, the treatments with gibberellic acid and salicylic acid, when subjected to dilution (W4), were superior to the control under the same condition, with accumulation of 19.5 μg g−1 FM and 22.4 μg g−1 FM, hence representing increments of 35.4% and 55.8%, respectively (Figure 3A).

Figure 3
Total soluble sugars (A), total amino acids (B) and proline (C) of pumpkin seeds, cultivar ‘Baiana Tropical’, under salt stress. W1 = 100% supply water; W2 = 100% fish farming effluent; W3 = 100% artesian well water; W4 = mixture of 50% fish farming effluent + 50% artesian well water; C = control; GA3 = gibberellic acid; SA = salicylic acid

Means followed by the same lowercase letter (a, b, c) do not differ in the analysis of the water factor considering each plant regulator by the Scott Knott test (p ≤ 0.05); means followed by the same uppercase letter (A, B, C) do not differ in the analysis of the plant regulator factor by the Scott Knott test (p ≤ 0.05)


Regarding the total amino acid contents, the treatment of seeds with gibberellic acid promoted 2.8 times more accumulation in seedlings under diluted water (W4) compared to the control (Figure 3B). In relation to the increase in the concentration of amino acids, Paiva et al. (2018)PAIVA, E. P. et al. Germination and biochemical components of Salvia hispanica L. seeds at different salinity levels and temperatures. Acta Scientiarum. Agronomy, v. 40, n. 1, p. 393-396, 2018. also found a similar response in Salvia hispanica L. seedlings under salinity conditions. However, in Cucumis sativus L. seedlings prepared from osmoprimed seeds, it was found that the amino acid content was increased when plants were subjected to fish farming effluent (EC = 5.5 dS m−1), in which case osmotic adjustment is suggested (MATIAS et al., 2015). On the other hand, the treatment with fish farming effluent (W2) of the present study showed no significant difference when compared to the control.

Thus, for the maintenance and performance of cellular functions, it can be understood that plants in general maintain balance through the accumulation of metabolites, allowing their development under conditions of abiotic stresses. This was not found partially in the present study, because pumpkin seedlings, cv. ‘Baiana Tropical’, were not able to perform osmotic adjustment in the waters from fish farming and artesian well. It is evident that in situations of restriction of water with more adequate quality for seedling production, one could use W4 water, referring to the dilution of fish farming effluent and well water, combined with the treatment with plant regulators, without damage to germination and vigor.

In the evaluation of proline content, the gibberellic acid promoted 31% greater accumulation in seedlings maintained in fish farming effluent + artesian well water, when compared to the treatment without regulator for this same type of water (Figure 3C). The accumulation of this organic solute as osmoprotectant was also observed in seedlings of Salvia hispanica L. when exposed to salinity (PAIVA et al., 2018PAIVA, E. P. et al. Germination and biochemical components of Salvia hispanica L. seeds at different salinity levels and temperatures. Acta Scientiarum. Agronomy, v. 40, n. 1, p. 393-396, 2018.).

Faced with salt stress, plants develop adaptation strategies to maintain their growth metabolism. Among the strategies, the osmotic adjustment stands out, which consists of the accumulation of biomolecules such as sugars, proteins and amino acids in cells, to reduce the water potential inside them (NÓBREGA et al., 2020NÓBREGA, J. S. et al. Emergência e crescimento inicial de melancia submetida a salinidade e doses de ácido salicílico. Revista Desafios, v. 7, n. 2, p. 162-171, 2020.). From the results obtained and in view of plant metabolism in situations of abiotic stress, it can be verified that the use of gibberellic acid is efficient in mitigating salt stress in germination and that the use of salicylic acid is also beneficial to the initial development mainly of the root system under salt stress.

CONCLUSIONS

Treatment of pumpkin seeds, cv. ‘Baiana Tropical’, with plant regulators (gibberellic and salicylic acids) favors the germination and initial development of seedlings under conditions of salt stress.

ACKNOWLEDGMENTS

This study was carried out with support from the Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Financing Code 001.

REFERENCES

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  • ANAYA, F. et al. Influence of salicylic acid on seed germination of Vicia faba L. under salt stress. Journal of the Saudi Society of Agricultural Sciences, v. 17, n. 1, p. 1-8, 2018.
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    » https://www.atlasbig.com/pt-br
  • BATES, L. S.; WALDREN, R. P.; TEARE, I. D. Rapid determination of free proline for water-stress studies. Plant and Soil, v. 39, p. 205-207, 1973.
  • BEZERRA, R. U. et al. Produção e qualidade da abóbora maranhão sob influência de lâminas de irrigação e doses de nitrogênio. Irriga, v. 25, n. 1, p. 87-101, 2020.
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Profa. Riselane de Lucena Alcântara Bruno Riselane bruno - lanebruno.bruno@gmail.com

Publication Dates

  • Publication in this collection
    06 Dec 2021
  • Date of issue
    2022

History

  • Received
    06 Aug 2020
  • Accepted
    02 Sept 2021
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