Novel carbon nanoparticles derived from Bougainvillea modulate vegetative growth via auxin-cytokinin signaling in Arabidopsis

We present a green synthesis method of producing blue fluorescence emitting carbon nanoparticles (CNPs) through a simple and cost-effective single-step hydrothermal reaction. The synthesis utilized bract extracts and pollen grains from three Bougainvillea species: B. spectabilis, B. alba, and B. buttiana. The CNPs exhibited photoluminescence, with the highest emission observed in the ultraviolet region. Atomic force microscopy analysis revealed that the size of synthesized CNPs ranged from 23 to 83 nm. Fourier transform infrared analysis provided a comprehensive understanding of the CNP's surface functional groups, with carbon being the predominant group. X-ray diffraction analysis confirmed the amorphous nature of the synthesized CNPs. Zeta potential measurements indicated that the particles carried a negative charge, suggesting their colloidal stability. In experiments conducted with Arabidopsis thaliana seedlings, CNPs derived from B. alba pollen grains (Ba-POL) were found to promote leaf area expansion while simultaneously inhibiting primary root growth. In presence of 10 nM IAA, Ba-POL CNP treated seedlings displayed a significant reduction in primary root growth. RT-PCR analysis revealed substantial changes in the expression of auxin response genes in presence of Ba-POL CNP. Cytokinin levels were enhanced in the seedlings in the presence of Ba-POL CNP, as revealed increased expression of cytokinin reporter TCS::GFP. Our findings underscore the potential application of these novel CNPs in modulation of plant growth through its effects on auxin-cytokinin signaling.