Hydroponic cultivation of okra using saline nutrition solutions under application of salicylic acid

Sousa, Pedro F. do N.; Dantas, Maíla V.; Lima, Geovani S. de; Soares, Lauriane A. dos A.; Gheyi, Hans R.; Silva, Luderlândio de A.; Lopes, Kilson P.; Fernandes, Pedro D.

doi:10.1590/1983-21252023v36n419rc

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Agricultural Engineering • Rev. Caatinga 36 (4) • Oct-Dec 2023 • https://doi.org/10.1590/1983-21252023v36n419rc copy

Hydroponic cultivation of okra using saline nutrition solutions under application of salicylic acid

Cultivo hidropônico de quiabeiro utilizando soluções nutritivas salinas sob aplicação de ácido salicílico

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

The limited availability of low-salinity water for irrigation in the Northeastern semi-arid region has restricted food production, making it necessary to use strategies to reduce the effects of salt stress on plants. Among the alternatives, the foliar application of salicylic acid stands out. In this context, the objective of this study was to evaluate the effects of foliar application of salicylic acid in mitigating salt stress on the gas exchange, chlorophyll a fluorescence, photosynthetic pigments, and growth of ‘Canindé’ okra in a hydroponic system. The experiment was carried out in a greenhouse, in Pombal - PB, using the Nutrient Film Technique - NFT hydroponic system. The experimental design used was completely randomized in a split-plot scheme, with four levels of electrical conductivity of the nutrient solution - ECns (2.1, 3.6, 5.1, and 6.6 dS m^-1) as the plots and four concentrations of salicylic acid - SA (0, 1.2, 2.4, and 3.6 mM) as the subplots, with four replicates and two plants per plot. SA concentration of 3.6 mM was able to minimize the effect of nutrient solution salinity on chlorophyll a fluorescence and increase the synthesis of chlorophyll b in okra plants, 34 days after transplanting. Nutrient solution salinity above 2.1 dS m^-1 negatively affected gas exchange, relative water content, photosynthetic pigments, and growth and increased electrolyte leakage in the leaf blade of okra plants.

Keywords
Abelmoschus esculentus L; Salt stress; Phytohormone; NFT

Source of variation	DF	Mean squares
Source of variation	DF	gs	E	Ci	A	WUEi	CEi
Saline nutrient solution (ECns)	3	0.27^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	6.12^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	118222.53^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	1287.00^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	27.68^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.02^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}
Linear Regression	1	0.06^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	17.99^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	32320.86^{^* * ,}	3684.05^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	76.76^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.05^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}
Quadratic Regression	1	0.08^{^* * ,}	0.33^ns	3135.98^ns	102.98^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.00^ns	0.00^ns
Salicylic Acid (SA)	3	0.02^ns	0.65^ns	768.96^ns	1.00^ns	0.71^ns	0.00^ns
Linear Regression	1	0.01^ns	0.06^ns	1290.69^ns	0.47^ns	0.54^ns	0.00^ns
Quadratic Regression	1	0.01^ns	0.13^ns	802.78^ns	0.12^ns	1.07^ns	0.00^ns
Interaction (ECns × SA)	9	0.00^ns	1.94^ns	595.28^ns	13.58^ns	4.97^{^* * ,}	0.00^ns
Error 1	9	0.01	0.85	1321.87	4.32	1.54	0.00
Error 2	36	0.00	0.70	223.40	5.07	1.46	0.00
CV 1 (%)		24.63	21.37	24.75	9.10	23.04	28.58
CV 2 (%)		15.52	19.39	10.17	9.86	22.44	16.68

Source of variation	DF		Mean squares
Source of variation	DF	F₀	Fm	Fv	Fv/Fm
Saline nutrient solution (ECns)	3	162802^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	421126^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	276573^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.005^ns
Linear Regression	1	383550^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	1048168^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	765973^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.008^ns
Quadratic Regression	1	97170^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	161034^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	27225^ns	0.006^ns
Salicylic Acid (SA)	3	6891^ns	100303^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	80923^{^* * ,}	0.003^ns
Linear Regression	1	2840^ns	266325^{^* * ,}	231412^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.003^ns
Quadratic Regression	1	1175^ns	11944^ns	961^ns	0.007^ns
Interaction (ECns × SA)	9	11750^{^* * ,}	105222^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	121635^{^ , respectively not significant and significant at p ≤ 0.05 and p ≤0.01; CV - coefficient of variation; DF - Degrees of freedom.}	0.018^ns
Error 1		3528	13152	18821	0.012
Error 2		7376	23211	24290	0.009
CV 1 (%)		12	7.66	12.86	15.44
CV 2 (%)		17.79	10.18	14.61	13.51

Source of variation			Mean squares
Source of variation	NL	PH	SD	LA	AGR_LA	RGR_LA
Salinity levels (SL)	35.125^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	59.101^ns	1.004^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	21613.269^{^* * ,}	17.633^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	0.0001^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}
Linear regression	126.025^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	139.129^ns	3.378^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	78594.431^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	62.575^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	0.0003^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}
Quadratic regression	0.071ns	33.325^ns	0.437^ns	992.886^ns	3.698^ns	0.00007^{^* * ,}
NK combination	22.817^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	73.427^ns	1.070^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	33087.144^{^* * ,}	6.705^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	0.00007^{^* * ,}
Interaction (SL × NK)	4.608ns	57.186^ns	0.122^ns	4023.606^ns	1.741^ns	0.00002^ns
Blocks	15.250^{^* * ,}	237.622^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	0.437^{^* * ,}	47258.423^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}	2.609ns	0.00013^{^ , respectively not significant and significant at a p ≤ 0.05 and p ≤ 0.01, CV= coefficient of variation.}
Residual	5.273	35.736	0.1333	6035.59	2.1903	1.904e^-5
Mean	21.125	48.743	4.26	541.01	6.103	0.0159
CV (%)	10.87	12.26	8.57	14.36	24.25	27.44

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[1] Conflict of interest: The authors declare no conflict of interest related to the publication of this manuscript.