Green Toxicology refers to the application of predictive toxicology in the sustainable development and production of new less harmful materials and chemicals, subsequently reducing waste and exposure. Built upon the foundation of “Green Chemistry” and “Green Engineering”, “Green Toxicology” aims to shape future manufacturing processes and safe synthesis of chemicals in terms of environmental and human health impacts. Being an integral part of Green Chemistry, the principles of Green Toxicology amplify the role of health-related aspects for the benefit of consumers and the environment, in addition to being economical for manufacturing companies. Due to the costly development and preparation of new materials and chemicals for market entry, it is no longer practical to ignore the safety and environmental status of new products during product development stages. However, this is only possible if toxicologists and chemists work together early on in the development of materials and chemicals to utilize safe design strategies and innovative in vitro and in silico tools. This paper discusses some of the most relevant aspects, advances and limitations of the emergence of Green Toxicology from the perspective of different industry and research groups. The integration of new testing methods and strategies in product development, testing and regulation stages are presented with examples of the application of in silico, omics and in vitro methods. Other tools for Green Toxicology, including the reduction of animal testing, alternative test methods, and read-across approaches are also discussed.

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Leaf elongation in monocotyledonous plants is sensitive to drought. To better understand the sequence of events in plants subjected to soil drying, leaf elongation and transpiration of maize seedlings (Zea mays L.) of 4 cultivars were monitored continuously and the diurnal courses of the root and leaf water relations were determined. Results from this study indicate the following sequence of drought response: Leaf elongation decreased before changes in the leaf water relations of non‐growing zones of leaf blades were detected and before transpiration decreased. Reductions in leaf elongation preceded changes in the root water potential (ψw). Root ψw was not a very sensitive indicator of soil dryness, whereas the root osmotic potential (ψs) and root turgor (ψp) were more sensitive indicators. The earliest events observed in drying soil were a significant increase in the largest root diameter class (1 720 to 1 960 gm) and a decrease in leaf elongation (P= 0.08) 2 days after withholding water. Significant increases in root length were observed 2 days later. Soil drying increased the number of fine roots with diameters of <240 µm. Slight increases in soil strength did not affect leaf elongation in the drying soil.

Abstract:Global climate change is likely to increase the risk of frequent drought. Maize, as the principal global cereal, is particularly impacted by drought. Nutrient supply may improve plant drought tolerance for better plant establishment during seedling growth stages. Thus, this study investigated the interactive effects of drought and the application of the nutrients N, P and K either individually or in combination. The maize seedlings were harvested between 12 and 20 days after sowing, and the leaf area, shoot fresh and dry weight and root dry weight were determined, and shoot water content and root/shoot dry weight ratio were calculated. Among the N, P and K fertilization treatments applied individually or in combination, the results showed that there was generally a positive effect of combined NPK and/or NP nutrient supply on shoot growth such as leaf area, shoot fresh and dry weight at day 20 after sowing under both well-watered and drought conditions compared with no nutrient supply. Compared with the effect of N and P nutrient supply, it seems that K was not limiting to plant growth due to the mineralogical characteristics of the illitic-chloritic silt loam used, which provided sufficient K, even though soil tests showed a low K nutrient status. Interestingly, the root/shoot ratio remained high and constant under drought regardless of NPK application, while it decreased with NPK applications in the well-watered treatment. This suggests that the higher root/shoot ratios with N, NP, PK and NPK under drought could be exploited as a strategy for stress tolerance in crop plants.

Many physiological mechanisms associated with nutrient supply have been implicated as improving plant growth under drought conditions. However, benefits to plant growth under drought might derive from an increased recovery of soil water through osmotic adjustment in the shoots and especially in the roots. Thus, experiments were carried out to investigate the effects of the nutrients N, P and K applied singly or in combination, on the osmotic adjustment and turgor maintenance in the roots and leaves of maize seedlings. The seedlings were harvested between 18 and 37 days after sowing according to the soil matric threshold potentials. Soil matric potentials and shoot and root biomass were determined at harvest. Turgor pressure and osmotic adjustment of the leaves and roots were estimated by measurements of their water and osmotic potentials. Results showed that plants with either of the combined fertilisation treatments NPK or NP grew faster at a given level of drought stress than those with no fertilisation, N, P or K applied individually or the combined nutrient treatments PK and NK. Among the fertiliser applications with either a single or two combined nutrients, plants treated with any of N, P or NP grew faster than those with either K or NK. The association between the interactive effects of nutrients and drought stress on the osmotic adjustment and turgor maintenance in roots may partially explain the role of nutrients in drought tolerance of maize seedlings. In particular, the roots exhibited a higher osmotic adjustment than the leaves for all nutrient treatments, suggesting that shoot growth shows a higher sensitivity to water deficit compared to root growth. We conclude that the maintained turgor of roots under drought stress obtained with an optimal nutrient supply results in better root growth and apparently promotes overall plant growth, suggesting that osmotic adjustment is an adaptation not only for surviving stress, but also for growth under such conditions.