Climate change and human activity have led to an increase in salinity levels and the toxicity of chromium (Cr). One promising approach to modifying these stressors in plants is to use effective nanoparticles (NPs). While titanium dioxide nanoparticles (TiO₂ NPs) and hydroxyapatite (HAP NPs) have been demonstrated to increase plant tolerance to abiotic stress by enhancing antioxidant capacity, lipid peroxidation, and secondary metabolites, it is unknown how these two compounds can work together in situations when salt and Cr toxicity are present. The objective of the current study was to determine the effects of foliar-applied TiO₂ NPs (15 mg L⁻¹) and HAP NPs (250 mg L⁻¹) separately and in combination on growth, chlorophyll (Chl), water content, lipid peroxidation, antioxidant capacity, phenolic content, and essential oils (EOs) of Solidago canadensis L. under salinity (100 mM NaCl) and Cr toxicity (100 mg kg⁻¹ soil). Salinity was more deleterious than Cr by decreasing plant weight, Chl a + b, relative water content (RWC), EO yield, and increasing malondialdehyde (MDA), electrolyte leakage (EL), superoxide dismutase (SOD) activity, and catalase (CAT) activity. The co-application of TiO₂ and HAP NPs proved to be more successful. This was evidenced by the increased shoot weight (36%), root weight (29%), Chl a + b (23%), RWC (15%), total phenolic content (TPC, 34%), total flavonoid content (TFC, 28%), and EO yield (56%), but decreased MDA (21%), EL (11%), SOD (22%) and CAT activity (38%) in salt-exposed plants. The study demonstrated the effective strategy of co-applying these NPs to modify abiotic stress by enhancing phenolic compounds and EO yield as key results.

气候变化和人类活动导致盐度水平和铬（Cr）毒性增加。改变植物中这些应激源的一种有前途的方法是使用有效的纳米颗粒（NP）。虽然二氧化钛纳米粒子 (TiO ₂ NPs) 和羟基磷灰石 (HAP NPs) 已被证明可以通过增强抗氧化能力、脂质过氧化和次生代谢物来提高植物对非生物胁迫的耐受性，但尚不清楚这两种化合物如何在以下情况下协同工作：存在盐和铬毒性。本研究的目的是确定叶面施用 TiO ₂ NP (15 mg L ^-1 ) 和 HAP NP (250 mg L ^-1 ) 单独和组合对生长、叶绿素 (Chl)、水分含量、盐度（100 mM NaCl）和铬毒性（100 mg kg ^-1土壤）下加拿大一枝黄花的脂质过氧化、抗氧化能力、酚类含量和精油（EO）。盐度比 Cr 更有害，它会降低植物重量、叶绿素 a + b、相对含水量 (RWC)、EO 产量，并增加丙二醛 (MDA)、电解质渗漏 (EL)、超氧化物歧化酶 (SOD) 活性和过氧化氢酶 (CAT) ） 活动。 TiO ₂和HAP NPs 的联合应用被证明更为成功。这通过增加芽重 (36%)、根重 (29%)、叶绿素 a + b (23%)、RWC (15%)、总酚含量 (TPC，34%)、总黄酮含量 (TFC) 来证明，28%）和 EO 产量（56%），但在盐暴露植物中降低了 MDA（21%）、EL（11%）、SOD（22%）和 CAT 活性（38%）。 该研究证明了共同应用这些纳米粒子通过提高酚类化合物和环氧乙烷产量来改变非生物胁迫的有效策略，作为关键结果。