The seeds of Sapindus mukorossi were collected from trees with the ideal phenotypical characters of good height, large crown and medium aged with abundant seed production. The fresh seeds were collected manually and the extracted seeds were cleaned and thoroughly hand mixed to improve the homogeneity during the sampling. The seeds based on their diameter were graded into three classes i.e. small (L 1 ) (<1.2 cm), medium (L 2 ) (1.2-1.4 cm) and large (L 3 ) (>1.4 cm). The graded seeds were subjected to five different pre-sowing treatments for germination viz., Control (T 1 ) (untreated seeds), Cold water treatment for 72 hours (T 2 ), Cow dung treatment for 7 days (T 3 ), Concentrated H 2 SO 4 for 20 minutes followed by rinsing under running tap water (T 4 ) and Hot water treatment (80 0 C) followed by 24 hours soaking (T 5 ). The graded and treated seeds were kept in seed germinator for four week. Watering and spray of fungicide was carried out manually when necessary. The effects of seed size and pre-sowing treatments on germination of seeds were explored periodically through counting the germinated seeds. The study revealed that seed parameters of the Sapindus mukorossi were significantly influenced by seed size categories. The weight of 100 seeds was recorded maximum (210.23 g) in large size (L 3 ) seed category which is significantly differed from L 2 (medium) and L 1 (small). However no significant difference has been observed among seed viability. The highest germination per cent (68.52%), germination capacity (74.07) and germination energy (41.48%) was recorded in concentrated H 2 SO 4 for 20 minutes followed by rinsing under running tap water (T 4 ) pre-sowing treatment while the lowest germination per cent (56.66%), germination capacity (64.07%) and germination energy minimum (30.74%) in T 1 (control). All treatments were significantly different from each other. On the other hand, among three seed category, large seed category (L 3 ) was recorded maximum per cent germination (76.22%), germination capacity (83.55%) and germination energy (47.77%) while the minimum germination per cent (46.22%) germination capacity (54.44%) and germination energy (25.33%) was found in small seed category (L 1 ). But all three seed size categories differed significantly from each other. Among the treatment combinations, germinability parameters were recorded maximum in T 4 L 3 (concentrated H 2 SO 4 for 20 minutes followed by rinsing under running tap water+ large seed category). The seed size and pre sowing treatments often controls the germination and initial seedling growth in many tree species. Pre-sowing treatment methods are employed for overcoming seed dormancy and are used not only to ensure the rapid germination but it also decreases labour, cost and time for nursery production.

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