KNO₃ Priming and Temperature Effects on Seedling Emergence and Seed Surface Micromorphology of Passiflora Species

This study aimed to determine the effects of KNO₃ priming and emergence temperature (25 and 32°C) on seedling emergence and quality in three Passiflora species comprising five genotypes. KNO₃-treated and untreated seeds were sown in a peat:perlite (3:1) medium at 25 and 32°C after priming in 3% KNO₃ solution at 25°C for 48 h. Seed morphological characteristics and surface micromorphology were also evaluated using scanning electron microscopy (SEM). Emergence rate (ER), mean emergence time (MET), seedling survival, seedling height, stem diameter, leaf number, chlorophyll content, and photosynthetic performance (%Φ) were determined. At 25°C, ER ranged from 0 to 76%, with the highest value recorded in control seeds of P. edulis 1 (76%), followed by KNO₃-treated seeds (68%). At 32°C, the highest ER was 82% in KNO₃-treated P. edulis 1. In contrast, KNO₃ reduced ER in P. ligularis from 76% to 25% at 32°C and resulted in 0% emergence in P. edulis 2. KNO₃ increased ER in P. caerulea 1 and P. caerulea 2 at 25°C and in P. caerulea 1 at 32°C. The shortest MET among treatments with successful emergence was 9.75 days in KNO₃-treated P. caerulea 2 at 25°C and 20.2 days in KNO₃-treated P. edulis 1 at 32°C. Seedling quality and physiological responses also varied among species, genotypes, priming treatments, and temperatures. Overall, the effects of KNO₃ priming and temperature were species- and genotype-dependent.