Zinc bionanocrystals enhance germination seedling vigor and metabolic activity in pearl millet seedlings

This study investigates the effect of seed priming with zinc bionanocrystals on germination and early seedling vigor in Pennisetum glaucum (pearl millet). Zn-bionanocrystals were synthesized using the ionotropic gelation method, yielding particles with a size of ~ 374–396 nm, a zeta potential of + 39.7 to + 44.6 mV, and an encapsulation efficiency of 84%. Priming with Zn-bionanocrystals (200–1000 ppm) significantly improved physiological and biochemical parameters, with 600 ppm identified as the optimal concentration. At this concentration, shoot and root lengths increased by 38% and 37%, respectively, compared to the control, resulting in a maximum seedling length of 31.2 cm. Germination frequency reached 92.5%, while seed vigor indices (SVI-I and SVI-II) increased by 44% and 46%, respectively. Enhanced metabolic activity was evidenced by a 1.8-fold increase in starch degradation rate and a 4.5-fold increase in α-amylase activity by day 5 post-germination. Protease activity increased 16.2-fold, accompanied by a 31% reduction in soluble protein content, indicating accelerated reserve mobilization. In addition, chlorophyll and carotenoid contents increased by 75%, suggesting improved photosynthetic potential. Overall, Zn-bionanocrystal priming enhanced germination performance, metabolic activity, and seedling vigor. These findings highlight the potential of Zn-bionanocrystals as an efficient seed priming agent for improving early-stage crop performance and provide a basis for their application in sustainable agriculture.