Pré-tratamento de sementes com nanobioestimulante na germinação e desenvolvimento inicial como estratégia de mitigação do estresse salino em algodão herbáceo

Abstract

Irrigation water salinity is a major constraint to production in semiarid irrigated agriculture because it impairs germination and early seedling establishment, which are decisive for stand formation in crops such as cotton. In this context, carbon dot–based nanobiostimulants (Arbolina®) have been investigated as an alternative to stimulate growth-related physiological responses and tolerance to abiotic stresses. This study evaluated the effects of Arbolina® seed treatment on cotton germination and early morphophysiological performance under saline and non-saline conditions. Two experimental stages were conducted: (i) a germination test in a BOD chamber on Germitest paper, in a completely randomized 2 × 7 factorial design (distilled water and 2.5 dS m⁻¹ × Arbolina® doses: 0, 20, 60, 100, 120, 180, and 220 mg L⁻¹), assessing first count (FC), final germination (FG), germination speed index (GSI), mean germination time (MGT), root length (RL), leaf area (LA), and fresh and dry biomass (FB and DB); and (ii) a greenhouse experiment in a 4 × 2 factorial design (0, 20, 60, and 100 mg L⁻¹ × 0.5 and 4.5 dS m⁻¹), including biometric traits, gas exchange, chlorophyll a fluorescence, leaf Na⁺ and K⁺ contents, Na/K ratio, electrolyte leakage (EL), and relative water content (RWC). In stage I, Arbolina® did not affect FC, FG, GSI, or MGT, while salinity reduced FC; however, early growth increased (RL, LA, and shoot biomass), especially under salinity, with better performance at 60 and 100 mg L⁻¹. In the greenhouse, salinity reduced growth and biomass traits. Arbolina® doses linearly increased A, gₛ, E, EiC, ΦPSII, and qP and promoted higher ETR (dose × salinity interaction), with emphasis on 100 mg L⁻¹, with no significant effects on Na⁺, Na/K ratio, EL, or RWC. Overall, Arbolina® did not change germination but improved early seedling growth under salinity and supported physiological and photochemical performance in the greenhouse assay.