Plants face a variety of abiotic stresses, which generate reactive oxygen species (ROS), and ultimately obstruct normal growth and development of plants. To prevent cellular damage caused by oxidative stress, plants accumulate certain compatible solutes known as osmolytes to safeguard the cellular machinery. The most common osmolytes that play crucial role in osmoregulation are proline, glycine-betaine, polyamines, and sugars. These compounds stabilize the osmotic differences between surroundings of cell and the cytosol. Besides, they also protect the plant cells from oxidative stress by inhibiting the production of harmful ROS like hydroxyl ions, superoxide ions, hydrogen peroxide, and other free radicals. The accumulation of osmolytes is further modulated by phytohormones like abscisic acid, brassinosteroids, cytokinins, ethylene, jasmonates, and salicylic acid. It is thus important to understand the mechanisms regulating the phytohormone-mediated accumulation of osmolytes in plants during abiotic stresses. In this review, we have discussed the underlying mechanisms of phytohormone-regulated osmolyte accumulation along with their various functions in plants under stress conditions.

https://www.mdpi.com/2218-273X/9/7/285/pdf

Phytohormones regulate accumulation of osmolytes under abiotic stress.

Biochar application for the remediation of salt-affected soils: Challenges and opportunities

How Plant Hormones Mediate Salt Stress Responses.

Drought and salt stress negatively affect soil fertility and plant growth. Application of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, ameliorates the negative effects of drought and salt stress on plants. The biochar application increased the plant growth, biomass, and yield under either drought and/or salt stress and also increased photosynthesis, nutrient uptake, and modified gas exchange characteristics in drought and salt-stressed plants. Under drought stress, biochar increased the water holding capacity of soil and improved the physical and biological properties of soils. Under salt stress, biochar decreased Na+ uptake, while increased K+ uptake by plants. Biochar-mediated increase in salt tolerance of plants is primarily associated with improvement in soil properties, thus increasing plant water status, reduction of Na+ uptake, increasing uptake of minerals, and regulation of stomatal conductance and phytohormones. This review highlights both the potential of biochar in alleviating drought and salt stress in plants and future prospect of the role of biochar under drought and salt stress in plants.

Biochar soil amendment on alleviation of drought and salt stress in plants: a critical review

Dietary fats are generally fatty acids that may play positive or negative roles in the prevention and treatment of diseases. In nature, fatty acids occur in the form of mixtures of saturated fatty acid (SFA), monounsaturated fatty acid (MUFA), and polyunsaturated fatty acid (PUFA), so their nutritional and/or medicinal values must be determined. Herein, we do not consider the classic indices, such as ∑SFA, ∑MUFA, ∑PUFA, ∑n-6 PUFA, ∑n-3 PUFA, and n-6 PUFA/n-3 PUFA; instead, we summarize and review the definitions, implications, and applications of indices used in recent years, including the PUFA/SFA, index of atherogenicity (IA), the index of thrombogenicity (IT), the hypocholesterolemic/hypercholesterolemic ratio (HH), the health-promoting index (HPI), the unsaturation index (UI), the sum of eicosapentaenoic acid and docosahexaenoic acid (EPA + DHA), fish lipid quality/flesh lipid quality (FLQ), the linoleic acid/α-linolenic acid (LA/ALA) ratio, and trans fatty acid (TFA). Of these nutritional indices, IA and IT are the most commonly used to assess the composition of fatty acids as they outline significant implications and provide clear evidence. EPA + DHA is commonly used to assess the nutritional quality of marine animal products. All indices have their advantages and disadvantages; hence, a rational choice of which to use is critical.

Nutritional Indices for Assessing Fatty Acids: A Mini-Review.

Application of biochar-based metal oxide nanocomposites can acquire new composites and combine the benefits of biochar with nanomaterials. For the first time, this research was conducted to evaluate the possible effects of solid biochar (25 g biochar kg−1 soil) and biochar-based nanocomposites (BNCs) of magnesium oxide (25 g BNC-MgO kg−1 soil), manganese oxide (25 g BNC-MnO biochar kg−1 soil) and combined use of these nanocomposites (12.5 g BNC-MgO + 12.5 g BNC-MnO kg−1 soil) on salt (non-saline, 6 and 12 dSm−1 NaCl salinities) tolerance of safflower plants (Carthamus tinctorius L.). Salinity reduced potassium, magnesium and manganese contents in root and leaf tissues, chlorophyll content index, photosynthetic pigments, maximum quantum yield of photosystem II (Fv/Fm) and relative photosynthetic electron transport rate (RETR), leaf water content and plant biomass, but increased the sodium content, reactive oxygen species generation (ROS), oxidative stress and antioxidants and ROS detoxification potential of safflower roots and leaves. Application of biochar and BNCs increased the contents of potassium, manganese and magnesium in plant tissues, photosynthetic pigments, Fv/Fm and RETR, leaf water content and reduced sodium accumulation, ROS generation and oxidative stress under saline conditions, leading to a higher plant biomass in comparison with control. The BNC-MgO + BNC-MnO was the superior treatment on reducing salt toxicity. This treatment reduced oxidative stress by enhancing photosynthetic pigments, Fv/Fm and RETR of safflower under salt stress. These results revealed that BNCs have a great potential for improving salt tolerance of plants through increasing RETR and decreasing sodium accumulation and ROS generation.

How can biochar-based metal oxide nanocomposites counter salt toxicity in plants?

Paper description: Previous reports showed that biochar alleviates salt toxicity in different crops. In the current study, we explain the effects of biochar on root anatomy and morphology of mung bean plants, which has not been evaluated so far. Biochar, by changing root anatomy and increasing the indole-3-acetic acid content improves mung bean performance under salt stress. Abstract: To investigate the changes in the anatomical and physiological characteristics of mung bean roots in response to biochar treatment during salt stress, a pot experiment was conducted. Mung bean plants were subjected to three biochar concentrations (0, 50 and 100 g kg -1 soil) and three salinity treatments (0, 5 and 10 dSm -1 NaCl). Salinity decreased root growth, vascular cylinder (VC) and cortical parenchyma (CP) areas, affecting the VC/CP ratio, shoot dry weight, the relative water content (RWC) of roots and leaves, and the root indole-3-acetic acid (IAA) content. It increased specific root length, the shoot/root ratio and root abscisic acid (ABA), and 1-aminocyclopropane-1-carboxylic acid (ACC) contents. Plant growth, RWC, the shoot/root ratio, specific root length, total root area, VC and CP areas, and the IAA/ABA and IAA/ACC ratios were increased by biochar under saline media. Biochar improved xylem structure, the plant growth regulator IAA, and decreased stress hormones, ABA and ACC, which accelerate plant senescence, consequently increasing mung bean growth under salt stress. https://doi.org/10.2298/ABS181005014N Received: October 5, 2018; Revised: March 5, 2019; Accepted: March 12, 2019; Published online: March 18, 2019 How to cite this article: Nikpour-Rashidabad N, Tavasolee A, Torabian S, Farhangi-Abriz S. The effect of biochar on the physiological, morphological and anatomical characteristics of mung bean roots after exposure to salt stress. Arch Biol Sci. 2019;71(2):321-7.

/pdf/the-effect-of-biochar-on-the-physiological-morphological-and-4030tcra7j.pdf

The effect of biochar on the physiological, morphological and anatomical characteristics of mung bean roots after exposure to salt stress

Salicylic acid but not jasmonic acid improved canola root response to salinity stress

Effect of lignite on alleviation of salt toxicity in soybean (Glycine max L.) plants

Salicylic and jasmonic acids are classified as stress hormones, which can affect numerous physiological characteristics of plants such as electron transporting systems in thylakoid membrane under normal and stressful conditions. A greenhouse experiment was conducted with factorial arrangement based on a randomized complete block design with three replications to assess the possible effects of salicylic acid (1 mM) and jasmonic acid (0.5 mM) on different parameters of chlorophyll a fluorescence in safflower (Carthamus tinctorius L. cv. Goldasht) under salt stress [0, 4, 8, and 12 dS m−1 NaCl (about 0, 40, 80 and 120 mM NaCl, respectively)]. Leaf chlorophyll content index, relative water content, leaf area and seed yield were decreased with increasing salinity. Salinity caused a significant decrease in the variable fluorescence, the maximum quantum yield of photosystem II, efficiency of water-splitting complex on the donor side of the photosystem II and total performance index (PItotal). The highest time needed to reach maximum fluorescence was recorded at 12 dS m−1. Maximum fluorescence and PItotal were increased, but initial fluorescence and maximum fluorescence were significantly decreased by salicylic acid and jasmonic acid treatments under saline conditions. Salicylic acid and jasmonic acid considerably improved the variable fluorescence, maximum quantum yield of photosystem II, the efficiency of water-splitting complex, PItotal, physiological parameters and seed yield under salinity. In this way, foliar application of salicylic acid and jasmonic acid could play a key role in salt stress tolerance of safflower plants.

/pdf/chlorophyll-a-fluorescence-of-safflower-affected-by-salt-elq74wz7bv.pdf

Salar Farhangi-Abriz

Papers

How can biochar-based metal oxide nanocomposites counter salt toxicity in plants?

The effect of biochar on the physiological, morphological and anatomical characteristics of mung bean roots after exposure to salt stress

Salicylic acid but not jasmonic acid improved canola root response to salinity stress

Effect of lignite on alleviation of salt toxicity in soybean (Glycine max L.) plants

Chlorophyll a fluorescence of safflower affected by salt stress and hormonal treatments