Pure biochemicals and nanomaterials as next generation biostimulants for sustainable agriculture under abiotic stress – recent advances and future scope

Sustainable agriculture faces major challenges under abiotic stress conditions owing to extensive application of chemical fertilizers which pollute water, soil and atmosphere. Biostimulants (BSs), comprising of naturally derived complex mixtures of uncharacterized biomolecules, pure biochemicals and nanomaterials, enhance nutrient use efficiency (NUE) and trigger crop’s natural defense mechanisms. While it is difficult to specify the metabolic effects of uncharacterized natural mixtures (seaweed extract, protein hydrolyzates, etc.), exogenous application of pure biochemicals and nanomaterials offers an edge as BSs since their physiological roles and mechanisms of action are decipherable. Foliar application or seed treatment of some amino acids, polyamines and biopolymers (chitosan, lipochitin oligosaccharides and thuricin 17) enable plants to overcome drought and salinity stress via activation of mechanisms for reactive oxygen species (ROS) scavenging, osmolyte regulation and chlorophyll accumulation. Interaction of nitric oxide (NO) with some vitamins and melatonin exhibits potential significance as BSs for mitigating stress by ROS scavenging and maintenance of intracellular ionic balance and membrane integrity. Near future is likely to see wide applications of nanoparticles (NPs) and nanomaterials (NMs) as BSs in view of their biphasic mode of action (bio-physical activation of membrane receptors followed by gradual release of BS into the plant cells)

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Not AvailableThe formation of adventitious roots (ARs) is primarily considered as a most crucial developmental phase for the vegetative propagation of plants. AR either originates naturally in whole plants, as a programmed developmental process, or develops in response to any stress or injury, for example, in cuttings. AR formation in plants is a complex and multistep process, regulated by several factors such as environmental stimuli and endogenous hormones. Availability of energy sources and supply of nitrogen and amino acid affect the pace and intensity of AR formation. Furthermore, significant alterations in enzyme activities and metabolite accumulation observed in plant cuttings suggest that the activity of specific enzymes and metabolites governs AR formation. Profiling of metabolites displays a significant increase in organic acids and several essential amino acids. There are major metabolic stages in AR formation: (1) sink establishment phase, (2) recovery phase, and (3) maintenance phase. However, available information regarding the molecular and physiological basis of AR formation is scarce and requires further investigations to unfold the precise mechanism of AR formation. Therefore, the present article is an attempt to provide a better understanding of AR formation in plant cuttings. Furthermore, the focus is also given to equate the corelation between varied actions of the aforementioned factors during AR formation.Not Availabl