Comparative Study on the Effects of Silicon Nanoparticles and Cellulose Nanocrystals on Drought Tolerance in Tall Fescue (Festuca arundinacea Schreb.)

Tall fescue (Festuca arundinacea Schreb.) is a commonly used herbaceous species for slope ecological restoration in China. However, water scarcity often constrains its growth due to the unique site conditions of steep slopes and climate-induced drought stress. This study aims to compare the ameliorative effects of silicon nanoparticles (Si NPs) and cellulose nanocrystals (CNCs) on drought stress in tall fescue, and to elucidate their underlying mechanisms of action. The results indicated that drought stress impaired photosynthesis, restricted nutrient absorption, and increased oxidative stress, ultimately reducing biomass. However, Si NPs and CNCs enhanced drought tolerance and promoted biomass accumulation by improving photosynthesis, osmotic regulation, and antioxidant defense mechanisms. Specifically, Si NP treatment increased biomass by 48.71% compared to drought-stressed control plants, while CNCs resulted in a 33.41% increase. Transcriptome sequencing further revealed that both nanomaterials enhanced drought tolerance by upregulating genes associated with photosynthesis and antioxidant defense. Additionally, Si NPs improved drought tolerance by stimulating root growth, enhancing nutrient uptake, and improving leaf structure. In contrast, CNCs play a distinct role by regulating the expression of genes related to cell wall synthesis and metabolism. These findings highlight the crucial roles of these two nanomaterials in plant stress protection and offer a sustainable strategy for the maintenance and management of slope vegetation. Overall design: The experiment was conducted in a greenhouse at the College of Soil and Water Conservation Science and Engineering, Northwest A&F University, Yangling, China (34°27' N, 108°07' E), from July to September 2024. The temperature was maintained at 25 ± 5? and humidity at 70 ± 5%, with a light cycle of 16 hours of light and 8 hours of darkness. Uniform and plump tall fescue seeds were selected, with 50 seeds sown per pot (substrate: a mixture of peat, vermiculite, and perlite in a 1:1:1 ratio). After germination, 30 healthy seedlings per pot were kept for further cultivation. When the seedlings reached 15-20 cm, a 10-day concentration screening experiment was performed. The plants were divided into six treatments with the following experimental conditions: (i) Normal control (CK): Plants were sprayed with double-distilled water (DDW) and maintained at normal soil moisture (65-75% field capacity); (ii) Si NP treatments: Plants were sprayed with Si NPs solutions at concentrations of 50, 100, 200, 300, and 500 mg/L under normal soil moisture conditions; (iii) CNC treatments: Plants were sprayed with CNCs solutions at concentrations of 25, 50, 100, 200, and 300 mg/L under normal soil moisture conditions; (iv) Drought stress control (DS): Plants were grown under drought conditions (35-45% field capacity); (v) DS_Si NP treatments: Plants were sprayed with Si NPs solutions at the same concentrations as treatment (ii) and grown under drought conditions; (vi) DS_CNC treatments: Plants were sprayed with CNCs solutions at the same concentrations as treatment (iii) and grown under drought conditions. Each treatment was repeated three times. Before spraying, the nanomaterials were diluted with DDW and sonicated for 30 minutes. After adding 0.05% Tween-20, the solution was evenly sprayed on the leaves, with applications every three days. Soil moisture was replenished daily using the gravimetric method, and plastic film was used to cover the soil surface to prevent solution leakage. After 10 days, plant growth and physiological parameters were measured. The concentration screening results indicated that 300 mg/L Si NPs and 100 mg/L CNCs effectively promoted tall fescue growth and improved its physiological performance under drought conditions . These concentrations were selected for the final experiment. After an additional 10-day treatment (for a total of 20 days), samples were collected.