Guard cell and subsidiary cell sizes are key determinants for stomatal kinetics and drought adaptation in cereal crops.

Climate change-induced drought is a major threat to agriculture. C4 crops have a higher water use efficiency (WUE) and better adaptability to drought than C3 crops due to their smaller stomatal morphology and faster response. However, our understanding of stomatal behaviours in both C3 and C4 Poaceae crops is limited by knowledge gaps in physical traits of guard cell (GC) and subsidiary cell (SC). We employed infrared gas exchange analysis and a stomatal assay to explore the relationship between GC/SC sizes and stomatal kinetics across diverse drought conditions in two C3 (wheat and barley) and three C4 (maize, sorghum and foxtail millet) upland Poaceae crops. Through statistical analyses, we proposed a GCSC-τ model to demonstrate how morphological differences affect stomatal kinetics in C4 Poaceae crops. Our findings reveal that morphological variations specifically correlate with stomatal kinetics in C4 Poaceae crops, but not in C3 ones. Subsequent modelling and experimental validation provide further evidence that GC/SC sizes significantly impact stomatal kinetics, which affects stomatal responses to different drought conditions and thereby WUE in C4 Poaceae crops. These findings emphasize the crucial advantage of GC/SC morphological characteristics and stomatal kinetics for the drought adaptability of C4 Poaceae crops, highlighting their potential as future climate-resilient crops.

Stomatal Responses of Two Drought-Tolerant Barley Varieties with Different ROS Regulation Strategies under Drought Conditions.

Drought stress is a major obstacle to agricultural production. Stomata are central to efforts to improve photosynthesis and water use. They are targets for manipulation to improve both processes and the balance between them. An in-depth understanding of stomatal behavior and kinetics is important for improving photosynthesis and the WUE of crops. In this study, a drought stress pot experiment was performed, and a transcriptome analysis of the leaves of three contrasting, cultivated barley genotypes Lumley (Lum, drought-tolerant), Golden Promise (GP, drought-sensitive), and Tadmor (Tad, drought-tolerant), generated by high-throughput sequencing, were compared. Lum exhibited a different WUE at the leaf and whole-plant levels and had greater CO2 assimilation, with a higher gs under drought stress. Interestingly, Lum showed a slower stomatal closure in response to a light-dark transition and significant differences compared to Tad in stomatal response to the exogenous application of ABA, H2O2, and CaCl2. A transcriptome analysis revealed that 24 ROS-related genes were indeed involved in drought response regulation, and impaired ABA-induced ROS accumulation in Lum was identified using ROS and antioxidant capacity measurements. We conclude that different stomatal ROS responses affect stomatal closure in barley, demonstrating different drought regulation strategies. These results provide valuable insight into the physiological and molecular basis of stomatal behavior and drought tolerance in barley.

Quantitative System Modeling Bridges the Gap between Macro- and Microscopic Stomatal Model.

An understanding of stomatal function is vital for the carbon and water cycle in nature. In the past decades, various stomatal models with different functions have been established to investigate and predict stomatal behavior and its association with plants' responses to the changing climate, but with limited biological information provided. On the other hand, many stomatal models at the molecular level focus on simulating and predicting molecular practices and ignore the dynamic quantitative information. As a result, stomatal models are often divided between the microscopic and macroscopic scales. Quantitative systems analysis offers an effective in silico approach to explore the link between microscopic gene function and macroscopic physiological traits. As a first step, a systems model, OnGuard, is developed for the investigation of guard cell ion homeostasis and its relevance to the dynamic stomatal movements. The system model has already yielded a series of important predictions to guide molecular physiological studies in stomata. It also exhibits great potential in breeding practice, which represents a key step toward "Breeding by design" of improving plant carbon-water use efficiency. Here, the development of stomatal models is reviewed, and the future perspectives on stomatal modeling for agricultural and ecological applications are discussed.

OsFTIP7 determines metallic oxide nanoparticles response and tolerance by regulating auxin biosynthesis in rice.

The widely application of metallic oxide nanoparticles (NPs) has led to an increase in their accumulation in farmland. Previous studies have found that the metallic oxide NPs have negative effect on plants development and growth. Nonetheless, the underlying mechanism of response to metallic oxide NPs in rice remains elusive. In this study, we show that rice FT-INTERACTING PROTEIN 7 (OsFTIP7) plays an essential role in NPs of CuO and ZnO-mediated physiological and biochemical changes in rice. Loss of function of OsFTIP7 reduced the toxicity of the NPs of CuO and ZnO to the seedlings by accumulating more biomass and chlorophyll contents. Furthermore, after high exposure to metallic oxide NPs, more indole-3-acetic acid (IAA) were determined in Osftip7 with higher expression of auxin biosynthetic genes than the control seedlings. What's more, IAA-treated seedlings displayed the similar phenotype as Osftip7 under high concentrations of NPs of CuO and ZnO. Taken together, the results substantiate that OsFTIP7 is involved in metallic oxide nanoparticle-mediated physiological and biochemical changes by negatively regulating auxin biosynthesis in rice.

Optimized Protocol for OnGuard2 Software in Studying Guard Cell Membrane Transport and Stomatal Physiology.

Stomata are key innovation in plants that drives the global carbon and water cycle. In the past few decades, many stomatal models have been developed for studying gas exchange, photosynthesis, and transpirational characteristics of plants, but they provide limited information on stomatal mechanisms at the molecular and cellular levels. Quantitative mathematical modeling offers an effective in silico approach to explore the link between microscopic transporter functioning and the macroscopic stomatal characteristics. As a first step, a dynamic system model based on the guard cell membrane transport system was developed and encoded in the OnGuard software. This software has already generated a wealth of testable predictions and outcomes sufficient to guide phenotypic and mutational studies. It has a user-friendly interface, which can be easily accessed by researchers to manipulate the key elements and parameters in the system for guard cell simulation in plants. To promote the adoption of this OnGuard application, here we outline a standard protocol that will enable users with experience in basic plant physiology, cell biology, and membrane transport to advance quickly in learning to use it.

Alteration of Crop Yield and Quality of Wheat upon Exposure to Silver Nanoparticles in a Life Cycle Study.

As a result of the rapid development of nanotechnology, metal-based nanoparticles (NPs) are inadvertently released into the environment and may pose a potential threat to the ecosystem. However, information for food quality and safety in NP-treated crops is limited. In the present study, wheat ( Triticum aestivum L.) was grown in different concentrations of Ag-NP-amended soil (20, 200, and 2000 mg kg-1) for 4 months. At harvest, physiological parameters, Ag and micronutrient (Fe, Cu, and Zn) contents, and amino acid and total protein contents were measured. Results showed that, with increasing the exposure doses, Ag NPs exhibited severe phytotoxicity, including lower biomass, shorter plant height, and lower grain weight. Ag accumulation in roots was significantly higher than that in shoots and grains. Decreases in the content of micronutrients (Fe, Cu, and Zn) in Ag-NP-treated grains suggested low crop quality. The results of amino acid and protein contents in Ag-NP-treated wheat grains indicated that Ag NPs indeed altered the nutrient contents in the edible portion. In the amino acid profile, the presence of Ag NPs significantly decreased the contents of arginine and histidine by 13.0 and 11.8%, respectively. In summary, the effects of metal-based NPs on the edible portion of crops should be taken into account in the evaluation of nanotoxicity to terrestrial plants. Moreover, investigation of the potential impacts of NP-caused nutrient alterations on human health could further our understandings on NP-induced phytotoxicity.

Phytotoxicity of CeO2 nanoparticles on radish plant (Raphanus sativus).

Cerium oxide nanoparticles (CeO2 NPs) have been considered as one type of emerging contaminants that pose great potential risks to the environment and human health. The effect of CeO2 NPs on plant-edible parts and health evaluation remains is necessary and urgently to be developed. In this study, we cultivated radish in Sigma CeO2 NP (<25 nm)-amended soils across a series of concentration treatments, i.e., 0 mg/kg as the control and 10, 50, and 100 mg/kg CeO2 NPs. The results showed that CeO2 NPs accelerated the fresh biomass accumulation of radish plant; especially in the treatment of 50 mg/kg CeO2 NPs, root expansion was increased by 2.2 times as much as the control. In addition, the relative chlorophyll content enhanced by 12.5, 12.9, and 12.2% was compared to control on 40 cultivation days. CeO2 NPs were mainly absorbed by the root and improved the activity of antioxidant enzyme system to scavenge the damage of free radicals in radish root and leaf. In addition, this study also indicated that the nanoparticles might enter the food chain through the soil into the edible part of the plant, which will be a potential threat to human health.

Iron Oxide Nanoparticles as a Potential Iron Fertilizer for Peanut (Arachis hypogaea).

Nanomaterials are used in practically every aspect of modern life, including agriculture. The aim of this study was to evaluate the effectiveness of iron oxide nanoparticles (Fe2O3 NPs) as a fertilizer to replace traditional Fe fertilizers, which have various shortcomings. The effects of the Fe2O3 NPs and a chelated-Fe fertilizer (ethylenediaminetetraacetic acid-Fe; EDTA-Fe) fertilizer on the growth and development of peanut (Arachis hypogaea), a crop that is very sensitive to Fe deficiency, were studied in a pot experiment. The results showed that Fe2O3 NPs increased root length, plant height, biomass, and SPAD values of peanut plants. The Fe2O3 NPs promoted the growth of peanut by regulating phytohormone contents and antioxidant enzyme activity. The Fe contents in peanut plants with Fe2O3 NPs and EDTA-Fe treatments were higher than the control group. We used energy dispersive X-ray spectroscopy (EDS) to quantitatively analyze Fe in the soil. Peanut is usually cultivated in sandy soil, which is readily leached of fertilizers. However, the Fe2O3 NPs adsorbed onto sandy soil and improved the availability of Fe to the plants. Together, these results show that Fe2O3 NPs can replace traditional Fe fertilizers in the cultivation of peanut plants. To the best of our knowledge, this is the first research on the Fe2O3 NPs as the iron fertilizer.