Nanoparticles in Agriculture: Characterization, Uptake and Role in Mitigating Heat Stress

Abiotic stresses like heat, drought, and salinity are among the major threats to sustainable crop production. These stresses induce numerous adverse effects in plants by impairing biochemical, physiological and molecular processes, eventually affecting plant growth, development and productivity. The rising temperature is one of the major causes of heat stress in agriculture. The variation in temperature during crop development has led to devastating agricultural losses in terms of yield. To adapt and mitigate these effects, germplasm scientists and agronomists aim to develop heat-tolerant varieties or cultivars. These efforts generally include the identification of alleles responsible for heat tolerance and their introgression into breeding populations through conventional or biotechnological methods. However, heat tolerance is a very complex physio-biochemical response of plants governed by a number of genes positioned at different loci. The accumulation of various additive gene effects into a single genotype is an extremely tedious and time-consuming process in both plant breeding and biotechnology. Recent advancements in agricultural nanotechnology have raised expectations for sustainable productivity without altering the genetic make-up of plants. In this milieu, the application of biologically active nanoparticles (NPs) could be a novel approach to enhance heat tolerance in crops. Recently, the NPs from silver, silicon, titanium and selenium have been proven valuable for plants to combat heat stress by altering their physiological and biochemical responses. Due to nano-scale size and the high surface area along with their slow and steady release, the NPs exert positive effects in plants through their growth-promoting and antioxidant capabilities. In this review, various technologies used for NPs characterization and their applications in agriculture have been discussed. The review further elaborates the uptake mechanism of NPs and their translocation in different plant parts along with the factors affecting them. This article also describes the role of metal or metal oxide NPs, as well as nano, encapsulated plant growth regulators and signal molecules in heat stress tolerance. The review will provide an insight to the scientists working in the area of agricultural sciences to explore new NPs to encounter different types of biotic and abiotic stresses.