The role of nanoparticles in plant biochemical, physiological, and molecular responses under drought stress: A review

Drought stress (DS) is a serious challenge for sustaining global crop production and food security. Nanoparticles (NPs) have emerged as an excellent tool to enhance crop production under current rapid climate change and increasing drought intensity. DS negatively affects plant growth, physiological and metabolic processes, and disturbs cellular membranes, nutrient and water uptake, photosynthetic apparatus, and antioxidant activities. The application of NPs protects the membranes, maintains water relationship, and enhances nutrient and water uptake, leading to an appreciable increase in plant growth under DS. NPs protect the photosynthetic apparatus and improve photosynthetic efficiency, accumulation of osmolytes, hormones, and phenolics, antioxidant activities, and gene expression, thus providing better resistance to plants against DS. In this review, we discuss the role of different metal-based NPs to mitigate DS in plants. We also highlighted various research gaps that should be filled in future research studies. This detailed review will be an excellent source of information for future researchers to adopt nanotechnology as an eco-friendly technique to improve drought tolerance.

Improving Drought Stress Tolerance in Ramie (Boehmeria nivea L.) Using Molecular Techniques

Ramie is one of the most significant fiber crops and contributes to good quality fiber. Drought stress (DS) is one of the most devastating abiotic factors which is accountable for a substantial loss in crop growth and production and disturbing sustainable crop production. DS impairs growth, plant water relation, and nutrient uptake. Ramie has evolved a series of defense responses to cope with DS. There are numerous genes regulating the drought tolerance (DT) mechanism in ramie. The morphological and physiological mechanism of DT is well-studied; however, modified methods would be more effective. The use of novel genome editing tools like clustered regularly interspaced short palindromic repeats (CRISPR) is being used to edit the recessive genes in crops to modify their function. The transgenic approaches are used to develop several drought-tolerant varieties in ramie, and further identification of tolerant genes is needed for an effective breeding plan. Quantitative trait loci (QTLs) mapping, transcription factors (TFs) and speed breeding are highly studied techniques, and these would lead to the development of drought-resilient ramie cultivars. The use of hormones in enhancing crop growth and development under water scarcity circumstances is critical; however, using different concentrations and testing genotypes in changing environments would be helpful to sort the tolerant genotypes. Since plants use various ways to counter DS, investigating mechanisms of DT in plants will lead to improved DT in ramie. This critical review summarized the recent advancements on DT in ramie using novel molecular techniques. This information would help ramie breeders to conduct research studies and develop drought tolerant ramie cultivars.

Hydrogen peroxide priming alleviates salinity induced toxic effect in maize by improving antioxidant defense system, ionic homeostasis, photosynthetic efficiency and hormonal crosstalk

BACKGROUND

Salinity stress (SS) is a serious detrimental factor for crop growth and productivity and its intensity it is continuously increasing which is posing serious threat to global food security. Hydrogen peroxide (H₂O₂) priming has emerged as an excellent strategy to mitigate the adverse impacts of SS. However, the role of H₂O₂ priming in mitigating the salinity induced toxicity is not fully explored.

METHODS AND RESULTS

Therefore, in this context the present study was conducted in complete randomized design (CRD) in factorial combination to determine the impact of H₂O₂ priming on germination, growth, physiological and biochemical traits, osmo-regulating compounds, hormonal balance and ionic homeostasis. The experiment was based on different levels of SS; control, 6 and 12 dS m^-1 SS and priming treatments, control and H₂O₂ priming (2%). Salinity stress significantly reduced the growth, leaf water status (- 15.55%), calcium (Ca²⁺), potassium (K⁺) and magnesium (Mg²⁺) accumulation and increased malondialdehyde (MDA: + 29.95%), H₂O₂ (+ 21.48%) contents, osmo-regulating compounds (proline, soluble sugars), indole acetic acid (IAA), anti-oxidant activities (ascorbate peroxidase: APX, catalase: CAT, peroxidase: POD and ascorbic acid: AsA) and accumulation of sodium (Na⁺) and chloride (Cl^-.). H₂O₂ priming effectively reduced the effects of SS on germination and growth and strengthen the anti-oxidant activities through reduced MDA (- 12.36%) and H₂O₂ (- 21.13%) and increasing leaf water status (16.90%), soluble protein (+ 71.32%), free amino acids (+ 26.41%), proline (+ 49.18%), soluble sugars (+ 71.02%), IAA (+ 57.59%) and gibberlic acid (GA) (+ 21.11%). Above all, H₂O₂ priming reduced the massive entry of noxious ions (Na⁺ and Cl^-) while increased the entry of Ca²⁺, K⁺ and Mg²⁺ thus improved the plant performance under SS.

CONCLUSION

In conclusion H₂O₂ priming was proved beneficial for improving maize growth under SS thorough enhanced anti-oxidant activities, photosynthetic pigments, leaf water status, accumulation of osmo-regulating compounds, hormonal balance and ionic homeostasis.

Improving crop productivity and nitrogen use efficiency using sulfur and zinc-coated urea: A review

Nitrogen (N) is an important macro-nutrient required for crop production and is considered an important commodity for agricultural systems. Urea is a vital source of N that is used widely across the globe to meet crop N requirements. However, N applied in the form of urea is mostly lost in soil, posing serious economic and environmental issues. Therefore, different approaches such as the application of urea coated with different substances are used worldwide to reduce N losses. Urea coating is considered an imperative approach to enhance crop production and reduce the corresponding nitrogen losses along with its impact on the environment. In addition, given the serious food security challenges in meeting the current and future demands for food, the best agricultural management strategy to enhance food production have led to methods that involve coating urea with different nutrients such as sulfur (S) and zinc (Zn). Coated urea has a slow-release mechanism and remains in the soil for a longer period to meet the demand of crop plants and increases nitrogen use efficiency, growth, yield, and grain quality. These nutrient-coated urea reduce nitrogen losses (volatilization, leaching, and N₂O) and save the environment from degradation. Sulfur and zinc-coated urea also reduce nutrient deficiencies and have synergetic effects with other macro and micronutrients in the crop. This study discusses the dynamics of sulfur and zinc-coated urea in soil, their impact on crop production, nitrogen use efficiency (NUE), the residual and toxic effects of coated urea, and the constraints of adopting coated fertilizers. Additionally, we also shed light on agronomic and molecular approaches to enhance NUE for better crop productivity to meet food security challenges.