Elucidating ROS signaling networks and physiological changes involved in nanoscale zero valent iron primed rice seed germination sensu stricto.

Reactive oxygen species (ROS) play pivotal roles during seed dormancy and germination. Metabolically active cells of seeds generate ROS and successful germination is governed by internal ROS contents, maintained within an optimum "oxidative window" by several ROS scavengers. Although ROS was previously considered hazardous, optimum ROS generation in seeds can mediate early seed germination by acting as messengers for cell signaling involved in endosperm weakening, stored food mobilization, etc. Recent reports suggest that nanopriming can expedite seed germination rates and enhance seed quality and crop performances. However, nanoparticle-driven signal cascades involved during seed germination are still unknown. The present study is aimed to explore molecular mechanisms for promoting germination in nanoprimed seeds and to investigate the plausible role of nanoparticle-mediated ROS generation in this process. Here rice seeds were primed with 20 mg L -1nanoscale zero valent iron (nZVI) for 72 h and several biochemical and physiological changes were monitored at different time points (5, 10, 20, 40, 60, and 80 h). To gain insight into roles of ROS in germination rate enhancement, intercellular ROS inhibitor, diphenyleneiodonium (DPI) was taken as another priming agent. Seed priming with DPI impaired seed germination percentage, hydrolytic enzyme activities due to ROS imbalance. On the contrary, seeds primed with both DPI and nZVI could recover from deleterious consequences of DPI treatment. Although DPI impaired intercellular ROS generation, nZVI can generate ROS independently which was confirmed from ROS localization assay. In both nZVI and the DPI and nZVI co-primed sets, significant up-regulation in genes like OsGA3Ox2, OsGAMYB were observed which are responsible for regulating the activity of several hydrolases and mediates efficient mobilization of storage food reserves of seeds. Thus, nZVI priming has potential to regulate intracellular ROS levels and orchestrate all the metabolic activities which eventually up-regulates seed germination rate and seed vigour.

Nanopriming with zero-valent iron synthesized using pomegranate peel waste: A "green" approach for yield enhancement in Oryza sativa L. cv. Gonindobhog.

Nanopriming is a combination of nanoparticle treatment and a seed dressing technique that can increase seed quality, seedling vigour, yield and also imparts tolerance against biotic and abiotic stress. Here, nano-scale zero-valent iron (G-nZVI) was synthesized using fruit peel waste of Punica granatum L and their formation was validated from XRD and optical spectroscopic techniques. Later, the seeds were primed with G-nZVI at six different concentrations (0, 10, 20, 40, 80, and 160 mg L -1) to determine the dose which is optimum for increasing germination percentage and seedling vigour of rice (Oryza sativa L. cv. Gobindobhog). According to initial results, upon priming seeds with 40-80 mg L -1 G-nZVI highest growth rate was found. The early growth enhancement of seedlings was chiefly attributed to increased ROS generation, higher hydrolytic enzyme activities, and increased iron uptake in germinating seeds upon nanopriming. The effects of nanopriming were carried over to later stages of development. A field experiment was carried out where nanoprimed seeds and traditional hydroprimed control seeds were sown in plots and grown till maturity without the aid of any conventional fertilizers and pesticides and it was found that crop yield and grain nutrient concentrations were higher in nanoprimed sets. Compared to control hydroprimed sets, 1.53 folds higher crop yield was observed upon seed priming with 80 mg L -1 G-nZVI. Thus in the future, G-nZVI can be considered to be a novel low-cost, eco-friendly, food waste-derived seed treatment agent that has immense potential in increasing rice yield.