Effect of Silver Nanoparticles on In Vitro Shoot Regeneration of Banana

Abstract

Banana is propagated almost entirely by vegetative means, and shoot-tip culture on cytokinin-supplemented medium is the standard route to clean, uniform planting material. Two recurring problems of that route, microbial contamination and the loss of vigour that follows stress in the culture vessel, have made silver nanoparticles an attractive additive, since silver is antimicrobial and silver ions interfere with ethylene action. This narrative review asks what the published literature allows us to say about the effect of silver nanoparticles on in vitro shoot regeneration of banana. It draws on work on banana tissue culture, on the antimicrobial and plant biology of silver nanoparticles, and on oxidative stress and hormesis, and it reports no new data. Reports from other species describe both benefit and harm, with the outcome depending on dose, particle size, coating and the way the particles are delivered, and a pattern in which low exposure helps and higher exposure harms is plausible but not established for banana. Few of the studies we could draw on test banana directly, most describe particles poorly, and silver ions released from the particles are seldom separated from the particles themselves. The review concludes that a modest, narrow-window benefit is a reasonable hypothesis, sets out the controls a convincing banana experiment would need, and flags the questions of genetic stability and environmental release that any routine use would have to answer.