Salicylic acid does not relieve salt stress on gas exchange, chlorophyll fluorescence, and hydroponic melon growth

Fátima, R. T.; Dantas, M. V.; Lima, G. S.; Oliveira, V. K. N.; Soares, L. A. A.; Silva, A. A. R.; Gheyi, H. R.; Guedes, M. A.; Nóbrega, J. S.; Fernandes, P. D.

doi:10.1590/1519-6984.274595

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Brazilian Journal of Biology

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Original Article • Braz. J. Biol. 83 • 2023 • https://doi.org/10.1590/1519-6984.274595 copy

Salicylic acid does not relieve salt stress on gas exchange, chlorophyll fluorescence, and hydroponic melon growth

O ácido salicílico não alivia o estresse salino nas trocas gasosas, fluorescência da clorofila e crescimento hidropônico do meloeiro

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The objective of this study was to evaluate the salicylic acid applications in attenuating the harmful effects of saline nutrient solution on the physiology and growth of 'Gaúcho' melon cultivated in the NFT hydroponic system. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil. The cultivation system used was the Nutrient Film Technique - NFT hydroponics. A completely randomized split-plot design was used, with the plot referring to four levels of salinity in the nutrient solution - ECns (2.1 control, 3.2, 4.3, and 5.4 dS m^-1) and the sub-plot four concentrations of salicylic acid (SA) (0, 1.5, 3.0, and 4.5 mM), applied via foliar spray, with six replications. Nutrient solution of 4.3 and 5.4 dS m^-1 electrical conductivity promotes higher maximum and variable fluorescence, respectively. The stomatal conductance, transpiration, stem diameter, main branch length, leaf dry mass, and stem dry mass of ‘Gaúcho’ melon plants decrease with the increase in salinity of the nutrient solution. Salicylic acid increases the initial fluorescence and the main branch length of ‘Gaúcho’ melon plants in hydroponic cultivation. Salicylic acid at a concentration of 1.5 to 4.5 mM did not attenuate the effects of salt stress on the internal CO₂ concentration, CO₂ assimilation rate, and root dry mass of 'Gaúcho' melon plants.

Keywords:
Cucumis melo L.; phytohormone; phytomass; salinity; plant physiology; nutrient film technique

Fertilizer	Quantity g 1000L^-1
KH₂PO₄	136.09
KNO₃	101.10
Ca(NO₃)₂.4H₂O	236.15
MgSO₄.7H₂O	246.49
H₃BO₃	3.10
MnSO₄.4H₂O	1.70
ZnSO₄.7H₂O	0.22
CuSO₄.5H₂O	0.75
(NH₄)₆Mo₇O₂₄. 4H₂O	1.25
CuSO₄	0.75
EDTA - Na	13.9
FeSO₄	13.9

Sources of variation	DF	Mean squares
Sources of variation	DF	gs	E	A	Ci
Nutrient solution salinity (ECns)	3	0.08^ = significant at ≤ 0.01.	5.92**	442.71**	1743.44**
Linear Regression	1	0.20**	17.00**	1286.84**	5227.20**
Quadratic Regression	1	0.02ns	0.38^ns	19.41^ns	1.50^ns
Residual 1	15	0.005	0.56	22.22	110.05
Salicylic acid (SA)	3	0.01^ns	0.14^ns	17.86^ns	2834.41**
Linear Regression	1	0.01^ns	0.0009^ns	0.0002^ns	6885.67**
Quadratic Regression	1	0.003^ns	0.22^ns	53.53^ns	1617.04**
Residual 2	60	0.005	0.37	13.42	225.42
Interaction (ECns × SA)	9	0.009^ns	0.78^ns	52.45**	501.36^* * = significant at p ≤ 0.05.
CV 1 (%)		13.37	13.45	13.70	6.35
CV 2 (%)		13.93	10.92	10.65	9.09

Sources of variation	DF	Mean squares
Sources of variation	DF	F₀	Fm	Fv	Fv/Fm
Nutrient solution salinity (ECns)	3	8633.15ns	148894.30^ ,= significant at ≤ 0.01.	90161.56**	0.0010^ns
Linear Regression	1	755.00^ns	332432.13**	144699.07**	0.0000^ns
Quadratic Regression	1	20242.04^ns	104940.37^ns	86400.00*	0.0003^ns
Residual 1	15	3819.61	43800.17	22760.74	0.0014
Salicylic acid (SA)	3	13075.01^* * = significant at p ≤ 0.05.	48232.69^ns	4720.15^ns	0.0017^ns
Linear Regression	1	28152.03**	117876.00^ns	9594.40^ns	0.0043^ns
Quadratic Regression	1	7776.00^ns	1650.04^ns	1962.04^ns	0.0001^ns
Residual 2	60	3320.59	29415.02	19055.98	0.0021
Interaction (ECns × SA)	9	4664.64^ns	58827.25^ns	27466.97^ns	0.0022^ns
CV 1 (%)		12.41	10.24	9.77	4.95
CV 2 (%)		11.57	8.39	8.94	6.01

Sources of variation	DF	Mean squares
Sources of variation	DF	NL	SD	MBL	RDM	LDM	SDM	R/S
Nutrient solution salinity (ECns)	3	59.95ns	11.46^ ,= significant at ≤ 0.01.	3835.81**	15.03**	1212.30**	474.77**	0.0222**
Linear Regression	1	176.41^ns	30.74**	11116.87**	31.34**	2693.74**	36.455**	0.0627**
Quadratic Regression	1	2.34^ns	3.60^* * = significant at p ≤ 0.05.	315.37^ns	11.55*	0.68^ns	0.57^ns	0.0003^ns
Residual 1	15	20.21	0.69	213.18	3.49	128.96	27.36	0.0013
Salicylic acid (SA)	3	63.28^ns	1.33^ns	474.48*	1.03^ns	242.44^ns	85.14^ns	0.0029^ns
Linear Regression	1	59.50^ns	0.01^ns	1074.00*	0.06^ns	456.10^ns	125.11^ns	0.0012^ns
Quadratic Regression	1	23.01^ns	1.58^ns	117.04^ns	2.84^ns	204.10^ns	130.29^ns	0.0071^ns
Residual 2	60	26.76	0.60	159.71	2.18	89.47	40.68	0.0023
Interaction (ECns × SA)	9	11.05^ns	0.89^ns	160.11^ns	6.74**	94.09^ns	56.52^ns	0.0009^ns
CV 1 (%)		13.18	10.36	6.49	25.95	28.22	27.69	26.03
CV 2 (%)		15.16	9.65	5.62	20.50	23.51	33.77	35.08

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