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The soybean is a legume that is widely cultivated in many countries due to the high levels of protein and oil contained in its seed, and is used for human and animal nutrition. However, salinity affects more than 800 million hectares worldwide, limiting global agricultural production. • The aim of this research was to evaluate the structural behaviour of the roots and stems under progressive salt stress, detailing the possible anatomical modifications to these organs in soybean plants during this stress. The plants were randomized into five treatments (0, 50, 100, 150 and 200 mM NaCl). • All the root regions studied and exposed to 100 mM Na + exhibited increases in the epidermis and endodermis and formation of lysogenic aerenchyma with increasing salinity, revealing the protective roles of these structures in reducing Na + influx. In the stem, increases in the cortex and pith in the first internode subject to 100 mM Na + suggest anatomical responses that aim to minimize oxidative stress. • Soybean plants subjected to progressive salt stress (>50 mM Na +) avoided cavitation and loss of function linked to vessel elements, reducing the metaxylem in all the root and stem regions analysed. Finally, our results confirm anatomical changes to the roots and stems.

Salicylic acid (SA) is an interesting messenger in plant metabolism that modulates multiple pathways, including the antioxidant defence pathway, and stimulates anatomical structures essential to carbon dioxide fixation during the photosynthetic process. The aim of this research was to determine whether pre-treatment with exogenous SA can alleviate the deleterious effects induced by water deficit on production components, biomass and gas exchange, measuring reactive oxygen species, antioxidant enzymes, variables connected to photosynthetic machinery, anatomical

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Water deficit is the most limiting abiotic stress to plants because it affects several physiological and biochemical processes. Brassinosteroids, including 24-epibrassinolide (EBR), are steroids that regulate growth and positively act on gas exchange. This research aims to determine whether EBR can attenuate the negative effects of water deficit, revealing possible contributions of this steroid on photosynthetic machinery of young Eucalyptus urophylla plants under water deficit. The experiment had a completely randomized factorial design with two water conditions (control and water deficit) and three levels of EBR (0, 50, and 100 nM EBR). Water deficit caused a decrease in the levels of total chlorophyll and carotenoids, but these photosynthetic pigments increased by 135 and 226%, respectively, in plants sprayed with EBR when compared to the water deficit + 0 nM EBR treatment. Regarding the antioxidant system, 100 nM EBR induced significant increments in superoxide dismutase (42%), catalase (52%), ascorbate peroxidase (147%), and peroxidase (204%).Steroid application in E. urophylla plants exposed to water deficit increased the effective quantum yield of the photosystem II (PSII) photochemistry and electron transport rate. However, interestingly, it decreased the nonphotochemical quenching and relative energy excess at the PSII level, indicating improvements related to PSII efficiency. This research revealed that application of 100 nM EBR attenuated the negative effects caused by water deficit, being explained by the positive repercussions on antioxidant enzyme activities, chloroplastic pigments, PSII efficiency, electron flux, and net photosynthetic rate. | INTRODUCTIONThe genus Eucalyptus has more than 700 species, distributed across more than 20 million hectares of the world's temperate and tropical regions (Mora et al.

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Micronutrient elements such as zinc, boron copper, iron, manganese, molybdenum, and chlorine are frequently responsible by the regulatory activity of the cell organelles, being nutrients that are absorbed and found in lower concentrations in plant tissues, they also contribute to supply the nutritional exigency of the plant. Study with Zea mays plants exposed to Zn toxicity + Si presented significant increases in stomatal conductance, net photosynthetic rate, transpiration rate, and water use efficiency, respectively, in comparison with treatment only with Zn. In relation to chlorophylls a, b and total and carotenoids presented non-significant increases, when compared to plants exposed to Zn toxicity. This study revealed the positive contribution of the Si on gas exchange and reduction of the negative effects provoked on chlorophylls and carotenoids in maize plants under Zn toxicity. Other results described that prolonged exposure to excessive Cu resulted in serious toxic effects on the rice seedlings. In contrast, Tre pretreatment has been shown to be beneficial in alleviating Cu toxicity, which was mainly attributed to the ability of Tre to restrict Cu uptake and accumulation to maintain Cu homeostasis, and to induce production of antioxidant and Gly enzymes to alleviate excessive Cu-triggered oxidative stress. Stress caused by the excessive supply of micronutrients to plants frequently promotes repercussions on oxidant system, inducing the overproduction of reactive oxygen species. The oxidative damage is a situation characterized by the large ROS accumulation and insufficient detoxification promoted by antioxidant enzymes, such as catalase and glutathione peroxidase. Different mechanisms have been proposed to explain the tolerance of plants to toxicity induced by micronutrients, as uses of other elements and substances, in which it can positively act with specific transporters, metal ion homeostasis and compartmentalization of micronutrients into the vacuole. Keywords: gas exchange, antioxidant metabolism, metals, photosynthetic pigments © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. . IntroductionLarge amounts of minerals and organic materials can be found in soil [ ] and some of these materials have great significance in the anatomical development and plant morphology. The soil fertility is an important factor of agronomic order. It is related to provision of essential elements in the soil, where the plant will absorb adequate levels of important substances to work with its metabolism [ ]. The nutrients are arranged in ionic form, which can interact with the root system of plants via three mechanisms interception root, diffusion, or mass flow [ ].The plants require basic conditions to develop and supply the essential elements to aid with the metabolism ...