ABSTRACT
Several technologies have been implemented to improve plant performance in irrigated crops, and one of them is the use of nanobiostimulants. Therefore, the aim of the present study was to explore the effects of applying different concentrations of a carbon-based biostimulant on the morphophysiology of cowpea plants subjected to varying electrical conductivities of irrigation water. The experiment was performed in a completely randomized design, in a 2 × 6 factorial scheme, with two electrical conductivities of irrigation water (ECw: 0.35 and 4.0 dS m-1) and six concentrations of nanobiostimulant applied through the leaves (0, 80, 160, 240, 320, and 400 mg L-1), with four replications. Growth and gas exchange variables were evaluated 31 days after sowing (V9 stage). Concentrations between 240 and 320 mg L-1 of carbon-based nanobiostimulant promoted greater increases in growth and physiological variables, but they caused decreases in non-photochemical quenching. Water electrical conductivity of 4.0 dS m-1 reduced the number of leaves (17.1%), stem diameter (10.0%), SPAD index (10.3%), net photosynthesis (10.9%), stomatal conductance (46.4%), transpiration (34.5%), instantaneous carboxylation efficiency (22.4%), and photochemical quenching (4.5%); in contrast, it increased the ratio between internal and ambient CO2 concentration (18.0%), leaf temperature (2.9%), water use efficiency (32.5%), and non-photochemical quenching (12.4%). Concentrations of 240 to 320 mg L-1 of the nanobiostimulant enhance the development and gas exchange of cowpea plants under non-stress conditions, whereas the concentration of 240 mg L-1 promotes the maximum increase in plant height under salinity.
Key words:
carbon dots; growth; gas exchange; salinity; Vigna unguiculata L.
HIGHLIGHTS:
Carbon-based nanobiostimulant stimulates the physiology of cowpea at concentrations of up to 320 mg L-1.
240 mg L-1 of the nanobiostimulant improves the growth of cowpea under salt stress.
Growth and gas exchange of cowpea are reduced by the electrical conductivity of irrigation wa-ter of 4.0 dS m-1.
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Means followed by the same letter do not differ at p ≤ 0.05 by Tukey’s test. *, ** - Significant at p ≤ 0.05 and p ≤ 0.01 by F test, respectively. Vertical bars indicate standard error (n=96)
Means followed by the same letter do not differ at p ≤ 0.05 by Tukey’s test. ** - Significant at p ≤ 0.01 by F test. Vertical bars indicate standard error (n=96)
Means followed by the same letter do not differ at p ≤ 0.05 by Tukey’s test. * - Significant at p ≤ 0.05 by F test. Vertical bars indicate standard error (n=96)
Means followed by the same letter do not differ at p ≤ 0.05 by Tukey’s test. *, ** - Significant at p ≤ 0.05 and p ≤ 0.01 by F test, respectively. Vertical bars indicate standard error (n=96)
Means followed by the same letter do not differ at p ≤ 0.05 by Tukey’s test. *, ** - Significant at p ≤ 0.05 and p ≤ 0.01 by F test, respectively. Vertical bars indicate standard error (n=96)