Green synthesis of Ag nanoparticles using plant metabolites

Nano-biotechnology is one of the most promising areas in modern nanoscience and technology. In this emerging area of research, nanoparticles (NPs) play an important role since the large-scale production and huge numbers of utilization. Gold and silver nanoparticles are among the most extensively studied nanomaterials, since they show high stability and low chemical reactivity in comparison to other metals. They are commonly synthesized using toxic chemical reducing agents able to reduce metal ions into uncharged NPs and/or high energy supplied procedures. The most commonly used method for the synthesis of NPs requires toxic chemicals like N,N-dimethyl formamide (DMF) or trisodium citrate, but recently a green technique, based on natural reducing agents, has been suggested to substitute the nature-unfriendly chemical methods. Many scientific works put in evidence the efficacy of plant extracts to reduce metal salts into the respective NPs, but this process lacks a clear control of NPs shapes and dimensions, since many different metabolites present into the extracts could participate to the process. This paper aims to clarify the reducing action of single pure natural compounds usually present in plant tissues and to obtain a stable and reproducible protocol for NPs synthesis

SURFACE NADH PEROXIDASES AND OXYLIPIN PATHWAY ARE INVOLVED IN THE RECOVERY FROM PHYTOPLASMA DISEASE IN APPLE.

Phytoplasmas are prokaryotic plant pathogens responsible for deterioration of several trees. In apple tree, the proliferation of the disease, caused by phytoplasmas, may undergo a spontaneous disappearance of symptoms, which are associated to hydrogen peroxide production in the phloem, a phenomenon called recovery. The aim of this work was to identify the biochemical pattern associated to the recovery by examining some enzymatic activities and metabolites in leaves from healthy, diseased and recovered plants. NAD(P)H oxidase/peroxidase, lipoxygenase, hydroperoxide lyase and phenylalanine ammonia lyase (PAL) activities were assayed. All these activities, except for PAL, were increased in leaves from recovered plants. Salicylate and jasmonate content was also determined, showing that the increase in recovered leaves was ascribed to jasmonate only. These results suggest that the activation of surface/plasma membrane redox systems is crucial in promoting the recovery process in apple tree, which then proceeds through the oxylipin pathway, leading to jasmonate. Conversely, salicylic acid appears to be involved only in the response to disease, but not in the subsequent recovery