Rice is an important staple crop produced and consumed worldwide. However, poor seed emergence is one of the main impediments to obtaining higher yield of rice especially in hot and dry ecosystems of the world that are ravaged by drought. Therefore, this study was carried out to evaluate the effects of potassium nitrate (KNO3), salicylic acid (SA) and silicon dioxide (SiO2) priming in improving emergence, seedling growth, biochemical attributes and antioxidant activities of FARO44 rice under drought conditions. Rice seedlings primed with 2.5% and 5% KNO3, 3% and 3.5% SiO2, and 1 mM and 2.5 mM SA were subjected to three drought levels of low, moderate and severe under the greenhouse. Seed emergence, seedling growth, biochemical attributes and antioxidant activities were thereafter evaluated. Seed priming experiments were laid in a completely randomized design with five replicates per treatment. The results found that rice seedlings responded differently to different priming treatments. However, all primed rice seedlings had significantly (P ≤ 0.05) improved emergence percentage (72–92%), seedling growth, seedling vigor, seedling fresh and dry biomass and shorter emergence time compared with controls. Likewise, total soluble protein content, activities of catalase, ascorbate peroxidase and superoxide dismutase, carbohydrate, soluble sugar and total chlorophyll contents of rice seedlings were increased by more than two-folds by seed priming compared with control. Salicylic acid showed less effect in increasing emergence, seedling growth, antioxidant activities and biochemical attributes of rice. Thus, this study established that seed priming with KNO3 (2.5% and 5%) and SiO2 (3% and 3.5%) were more effective in improving emergence, seedling growth, biochemical attributes and antioxidant activities of FARO44. Thus, priming of FARO44 rice with this chemical is recommended for fast emergence, seedling growth and drought resistance in dry ecosystems.

Rice is an important cereal consumed globally, however, poor germination and non-uniform seedling establishment are major causes of low rice yield in water-limiting arid ecosystems. Seed priming study with KNO3, SA and SiO2 to enhance germination and seedling growth was carried out with the objectives of (1) to determine the effects of seed priming on germination and early seedling growth, and (2) to evaluate effects of seed priming on physiological growth characteristics of rice seedling under drought stress simulated by polyethylene glycol (PEG6000). Under wellwatered conditions, rice seeds were primed with concentrations of KNO3 (2.5%, 5%, 10%, 15% and 20%), SiO2 (2.5%, 3%, 3.5%, 4% and 4.5%) and SA (0.5, 1, 1.5, 2, and 2.5 mM). While under drought stress, rice seeds were primed with 2.5% and 5% KNO3; 3% and 3.5% SiO2 and 1 mM and 2.5 mM SA. The results showed that all primed rice seedlings under both well-watered and drought stress conditions had significantly enhanced rice seedling growth parameters of seedling length, plumule length, root length, seedling vigor, seedling biomass and germination index and shorter germination time compared to unprimed controls. However, seed priming with concentrations of 2.5% and 5% KNO3; 3% and 3.5% SiO2, and 1 mM and 2.5 mM SA increased rice seedling growth parameters studied better than other concentrations. However, germination percentage was not significantly affected. Thus, priming of FARO44 rice with these concentrations of chemicals is recommended for fast germination, seedling growth and emergence in arid ecosystems.

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