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The ecofriendly nature of materials used in synthesis and their low cost make biosynthesized nanoparticles excellent stuff for a broad range of applications in bioscience. Green nanomaterials are progressively used in agriculture to deliver plant nutrients efficiently and effectively. The present work aimed to biosynthesize zinc oxide nanoparticles (ZnO NPs) utilizing Catharanthus roseus (L.) G. Don leaf extracts to use them as a nanopriming agent for improving seed germination and seedling growth in Eleusine coracana (L.) Gaertn (finger millet). UV-Vis spectroscopy, FTIR, FE-SEM, EDX, and TEM were used to characterize biosynthesized nanoparticles (NPs). The peaks at 362 nm characterized UV-Vis spectra of ZnO NPs. The FTIR absorption spectrum of ZnO NPs showed Zn-O bending at 547 cm−1. The size (44.5 nm) and shape (nonspherical) of ZnO NPs were revealed by TEM image analysis. XRD confirmed the hexagonal wurtzite phase of ZnO with an average particle size of 35.19. The seed germination results revealed that ZnO-nanoprimed seeds at 500 mg/L substantially improved all the seed germination parameters, viz., plumule length (23.4%), radicle length (55%), vigor index (41.94%), and dry matter production (54.6%) compared to hydropriming (control).

Modern agriculture is primarily focused on the massive production of cereals and other food-based crops in a sustainable manner in order to fulfill the food demands of an ever-increasing global population. However, intensive agricultural practices, rampant use of agrochemicals, and other environmental factors result in soil fertility degradation, environmental pollution, disruption of soil biodiversity, pest resistance, and a decline in crop yields. Thus, experts are shifting their focus to other eco-friendly and safer methods of fertilization in order to ensure agricultural sustainability. Indeed, the importance of plant growth-promoting microorganisms, also determined as “plant probiotics (PPs),” has gained widespread recognition, and their usage as biofertilizers is being actively promoted as a means of mitigating the harmful effects of agrochemicals. As bio-elicitors, PPs promote plant growth and colonize soil or plant tissues when administered in soil, seeds, or plant surface and are used as an alternative means to avoid heavy use of agrochemicals. In the past few years, the use of nanotechnology has also brought a revolution in agriculture due to the application of various nanomaterials (NMs) or nano-based fertilizers to increase crop productivity. Given the beneficial properties of PPs and NMs, these two can be used in tandem to maximize benefits. However, the use of combinations of NMs and PPs, or their synergistic use, is in its infancy but has exhibited better crop-modulating effects in terms of improvement in crop productivity, mitigation of environmental stress (drought, salinity, etc.), restoration of soil fertility, and strengthening of the bioeconomy. In addition, a proper assessment of nanomaterials is necessary before their application, and a safer dose of NMs should be applicable without showing any toxic impact on the environment and soil microbial communities. The combo of NMs and PPs can also be encapsulated within a suitable carrier, and this method aids in the controlled and targeted delivery of entrapped components and also increases the shelf life of PPs. However, this review highlights the functional annotation of the combined impact of NMs and PPs on sustainable agricultural production in an eco-friendly manner.

This chapter discusses the thermotolerant agriculturally important microorganisms, which play a pivotal role in improving crop performance under thermal stress conditions and diminish the effect of heat stresses on plants through production of exopolysaccharates and biofilm formation. These beneficial microorganisms include plant growth-promoting rhizobacteria, rhizosphere-competent fungi of the genus Trichoderma and arbuscular mycorrhiza fungi.

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