A calmodulin antagonist protects in vitro raspberries against disturbed photosynthesis caused by constant light and cytokinin

Abstract Leaf chlorosis is often a problem in micropropagated Rubus idaeus , which makes successful acclimatization difficult. We found that leaf bleaching becomes extreme when in vitro plants are exposed to continuous fluorescent light in the presence of 6-benzyl adenine (BA) or isopentenyl adenine (2iP). These cytokinins had a profound negative effect on the photosynthetic apparatus measured by the chlorophyll index (ChlIdx), photosystem II efficiency (Fv/Fm) and anthocyanin reflection index (AriIdx). Since calmodulin plays a role in the regulation of photosynthesis, we investigated the impact of calmodulin antagonist Chlorpromazine hydrochloride (CPZ) on this harmful bleaching effect. In cytokinin plus CPZ treated plants, ChlIdx was three times greater and Fv/Fm was increased 50% than in only cytokinins treated plants. while plants in hormone-free control medium had the highest ChlIdx and Fv/Fm. This study illustrates how drugs for humans, like the antipsychotic medication CPZ, can also be useful in other biological systems, such as in this case, where CPZ contributes to the quality of in vitro plants.