Stresses, Volume 2, Issue 2 (June 2022) – 6 articles

Yam (Dioscorea alata) is a tropical plant that is considered critical for food security. The use of high fertilizer, low soil fertility, and insect pest infestation reduce yam tuber yield and quality. The present study was performed to determine the effect of potassium silicate and arbuscular mycorrhizal fungi (AMF) on yam cultivated under salinity stress. This study revealed that the combination of Rhizophagus irregularis (AMF) and Potassium silicate was more effective than their individual application on yam and were beneficial for overall analyzed characters. We observed the days to emergence and the average days to first leaf emergence decreased by 33.46% and 26.78%, respectively, the number of leaves increased by 45.23%, number of sprouts per seed tuber by 50%, vine length by 60.8%, vine length at harvest by 40.53%, the average leaf width by 53.79%, petiole length by 31.74%, tuber length by 43.84%, average diameter of tuber by 56.58%, and average number of tuber per vine by 46.15% in T5 treated plants. We also recorded that starch content increased by 21.89%, ascorbic acid by 61.51%, average moisture by 8.36%, TSS by 50%, and total sugar by 69.53% in T5 treated plants. The total phenol was found to be 1.53% higher in T3 applied plants, while the dry matter was 36.37% higher in T5 treatment. Furthermore, the enzymatic evaluation of MDA in leaves was found to be enhanced by 142% in T2. The enzyme 8-OHdG from the leaves sample was reported to be increased after T5 by 621.15%. Moreover, the amount of CAT was higher by 53.46% in T2 treated plants. Likewise, the amount of enzyme SOD and POX in leaves of D. alata enhanced by 30.91% and 51.15% T2 treatments respectively. Full article

Vitamin E and dietary flavonoids are natural substances with antioxidant and anti-inflammatory activities, showing little or no side effects. Fruit and vegetable diets based on flavonoids and vitamin E provide a benefit to hypertensive subjects by regulating blood pressure. However, the exact mechanism of their anti-inflammatory properties has not been chemically explained. It has been proposed that their anti-oxidant and anti-inflammatory properties may be related to their ability to scavenge free radicals. We here describe the chemical considerations that flavonoids and tocopherols required to act as potential scavengers of the ^•NO₂ radical, a key radical in the cellular oxidative process. Moreover, we provide a theoretical study of the energy content of the nitrated compounds in the different possible positions. With this analysis, it was predicted that five flavonoids from different families (quercetin (flavanol), naringenin (flavanone), luteolin (flavone), catechin (flavanol) and aurantinidin (anthocyanin)) and three tocopherols (β-, γ-, and δ-tocopherol, but not α-tocopherol) could act as potential scavengers of the harmful ^•NO₂ radical. These results may help to explain their beneficial effect on cardiovascular health through its antioxidant role. To validate our theoretical considerations, we also examined uric acid, a well-known ^•NO₂-scavenger. We hope this study could help to elucidate the potential scavenging activity of other dietary antioxidants. Full article

The non-essential metalloid arsenic (As) is widely distributed in soil and underground water of many countries. Arsenic contamination is a concern because it creates threat to food security in terms of crop productivity and food safety. Plants exposed to As show morpho-physiological, growth and developmental disorder which altogether result in loss of productivity. At physiological level, As-induced altered biochemistry in chloroplast, mitochondria, peroxisome, endoplasmic reticulum, cell wall, plasma membrane causes reactive oxygen species (ROS) overgeneration which damage cell through disintegrating the structure of lipids, proteins, and DNA. Therefore, plants tolerance to ROS-induced oxidative stress is a vital strategy for enhancing As tolerance in plants. Plants having enhanced antioxidant defense system show greater tolerance to As toxicity. Depending upon plant diversity (As hyperaccumulator/non-hyperaccumulator or As tolerant/susceptible) the mechanisms of As accumulation, absorption or toxicity response may differ. There can be various crop management practices such as exogenous application of nutrients, hormones, antioxidants, osmolytes, signaling molecules, different chelating agents, microbial inoculants, organic amendments etc. can be effective against As toxicity in plants. There is information gap in understanding the mechanism of As-induced response (damage or tolerance response) in plants. This review presents the mechanism of As uptake and accumulation in plants, physiological responses under As stress, As-induced ROS generation and antioxidant defense system response, various approaches for enhancing As tolerance in plants from the available literatures which will make understanding the to date knowledge, knowledge gap and future guideline to be worked out for the development of As tolerant plant cultivars. Full article

Salinity and drought stress are significant environmental threats, alone or in combination. The current study was conducted to investigate the morpho-physiology, osmotic adjustment, oxidative stress, antioxidant defense and methylglyoxal detoxification of three rice genotypes from the indica (cv. BRRI dhan29 and BRRI dhan48) and japonica (cv. Koshihikari) groups. Eighteen-day-old seedlings of these genotypes were exposed to either in alone salinity (150 mM NaCl) and drought (15% PEG 6000) or in the combination of salinity and drought (150 mM NaCl + 15% PEG 6000) stress in vitro for 72 h. Compared with the control, the water status, biomass and photosynthetic pigments were decreased, where a significant increase was seen in the mortality rate, hydrogen peroxide content, electrolyte leakage, lipoxygenase activity, level of malondialdehyde and methylglyoxal, indicating increased lipid peroxidation in rice genotypes in stress conditions. The non-enzymatic and enzymatic components of the ascorbate-glutathione (AsA-GSH) pool in rice genotypes were disrupted under all stress treatments, resulting imbalance in the redox equilibrium. In contrast, compared to other rice genotypes, BRRI dhan48 revealed a lower Na⁺/K⁺ ratio, greater proline (Pro) levels, higher activity of AsA, dehydroascorbate (DHA) and GSH, lower glutathione disulfide (GSSG) and a higher ratio of AsA/DHA and GSH/GSSG, whereas enzymatic components increased monodehydroascorbate reductase, dehydroascorbate reductase, glutathione peroxidase and glyoxalase enzymes. The results showed that a stronger tolerate ability for BRRI dhan48 against stress has been connected to a lower Na⁺/K⁺ ratio, an increase in Pro content and an improved performance of the glyoxalase system and antioxidant protection for scavenging of reactive oxygen species. These data can give insight into probable responses to single or combination salinity and drought stress in rice genotypes. Full article