Soil Chemical Analysis

Stressful environments such as salinity, drought, and high temperature (heat) cause alterations in a wide range of physiological, biochemical, and molecular processes in plants. Photosynthesis, the most fundamental and intricate physiological process in all green plants, is also severely affected in all its phases by such stresses. Since the mechanism of photosynthesis involves various components, including photosynthetic pigments and photosystems, the electron transport system, and CO2 reduction pathways, any damage at any level caused by a stress may reduce the overall photosynthetic capacity of a green plant. Details of the stress-induced damage and adverse effects on different types of pigments, photosystems, components of electron transport system, alterations in the activities of enzymes involved in the mechanism of photosynthesis, and changes in various gas exchange characteristics, particularly of agricultural plants, are considered in this review. In addition, we discussed also progress made during the last two decades in producing transgenic lines of different C3 crops with enhanced photosynthetic performance, which was reached by either the overexpression of C3 enzymes or transcription factors or the incorporation of genes encoding C4 enzymes into C3 plants. We also discussed critically a current, worldwide effort to identify signaling components, such as transcription factors and protein kinases, particularly mitogen-activated protein kinases (MAPKs) involved in stress adaptation in agricultural plants.

Photosynthesis under stressful environments: An overview

Protein hydrolysates as biostimulants in horticulture

Cereals are grown in almost every region of the world and are exposed to a variety of environmental stresses that severely affect their growth and grain yield. Of various abiotic stresses, salinity is one of the more significant threats to cereal crops. To ensure food security, there is a need to adopt strategies to overcome this specific threat. Undoubtedly, plant scientists have been exploiting a variety of approaches to achieve enhanced crop productivity on salt affected soils. Of the various biotic approaches, conventional breeding, marker-assisted selection and genetic engineering to develop salt-tolerant lines/cultivars of cereals all seem plausible. Some success stories have been reported for improvement in salt tolerance of wheat and rice, but are scarce for other cereals. A number of barriers to the development of salt-tolerant cultivars/lines have been identified and include a lack of knowledge about the genetics of crops, their physiological and biochemical behavior, wide variation in environme...

Improving Salinity Tolerance in Cereals

Soil salinization is one of the major environmental stressors hampering the growth and yield of crops all over the world. A wide spectrum of physiological and biochemical alterations of plants are induced by salinity, which causes lowered water potential in the soil solution, ionic disequilibrium, specific ion effects, and a higher accumulation of reactive oxygen species (ROS). For many years, numerous investigations have been made into salinity stresses and attempts to minimize the losses of plant productivity, including the effects of phytohormones, osmoprotectants, antioxidants, polyamines, and trace elements. One of the protectants, selenium (Se), has been found to be effective in improving growth and inducing tolerance against excessive soil salinity. However, the in-depth mechanisms of Se-induced salinity tolerance are still unclear. This review refines the knowledge involved in Se-mediated improvements of plant growth when subjected to salinity and suggests future perspectives as well as several research limitations in this field.

https://www.mdpi.com/1422-0067/21/1/148/pdf

An Overview of Hazardous Impacts of Soil Salinity in Crops, Tolerance Mechanisms, and Amelioration through Selenium Supplementation.

Seed priming with silicon (Si) is an efficient and easy method to regulate plant tolerance against different abiotic stresses. A pot experiment was conducted to examine the Si-mediated changes in oxidative defense and some vital physio-biochemical parameters of maize under a limited water supply. For this purpose, two maize varieties (Pearl and Malka) with different Si priming treatments (0, 4 mM, 6 mM) were grown under a control and 60% field capacity for three weeks. At 60% field capacity, significant reductions in plant growth attributes and chlorophyll contents were recorded compared with the control. The negative effects of drought stress were more severe for Malka compared with Pearl. Drought stress increased the malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, altered the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), and triggered the accumulation of soluble sugars, glycine betaine, proline, and phenolics contents. Nevertheless, seed priming with silicon at 4 or 6 mM was effective in alleviating the detrimental effects of drought stress in both cultivars. Si priming particularly at 6 mM significantly enhanced the shoot and root lengths as well as their biomass and improved the levels of photosynthetic pigments. Moreover, Si treatments enhanced the activities of antioxidant enzymes (SOD, POD, and CAT) while it reduced the MDA and H2O2 contents in both cultivars under stress conditions. In crux, the present investigation suggests that Si priming mitigates the harmful effects of drought stress and contributes to the recovery of maize growth.

Silicon Priming Regulates Morpho-Physiological Growth and Oxidative Metabolism in Maize under Drought Stress

To assess the effect of exogenous application of triacontanol (TRIA) as a presowing seed treatment on wheat under saline conditions, a greenhouse experiment was performed. Seeds of two wheat cultivars, MH-97 (moderately salt sensitive) and S-24 (salt tolerant) were primed with TRIA for 12 h. Plants raised from TRIA-treated seeds were grown in full strength Hoagland’s nutrient solution for 24 days under non-saline conditions, after which time, they were subjected to 0 (control) or 150 mM NaCl. After 21 days of salt application, data for different growth, plant pigments and gas exchange characteristics were recorded. Salt stress of the root growing medium markedly decreased shoot and root fresh biomass, net CO2 assimilation rate (A), stomatal conductance, and transpiration rate (E), while no significant effect of salinity was observed on chlorophyll pigments (a, b and a/b ratio), quantum yield of PSII, substomatal CO2 concentration and water use efficiency (A/E). Exogenous application of TRIA as seed priming did not ameliorate the inauspicious effects of salt stress effectively, although it slightly increased photosynthetic rate in both wheat cultivars, transpiration rate in MH-97 and water use efficiency in S-24 under saline conditions.

Regulation in gas exchange and quantum yield of photosystem ii (psii) in salt-stressed and non-stressed wheat plants raised from seed treated with triacontanol

Before sowing, the seeds of two wheat cultivars, S-24 and MH-97, were treated with three levels [(0 (water), 10 and 20 µM)] of triacontanol (TRIA) for 12 h. TRIA-treated seeds were grown in full strength nutrient solution for 24 days in a greenhouse, after which time, they were supplied with two salt treatments (0 and 150 mM NaCl ). After 21 days of salt application, changes in the malondialdehyde (MDA), hydrogen peroxide (H2O2) and total soluble proteins contents as well as activities of some key antioxidant enzymes (CAT, POD and SOD) were measured. Salinity stress of 150 mM NaCl significantly decreased the activity of SOD, while increased that of CAT, and enhanced the levels of MDA and H2O2 contents in both cultivars under salt stress conditions. The outcome of salt stress was non-significant on soluble proteins and activity of POD. The effect of pre-sowing application of TRIA was non-significant on all measured attributes except that it significantly increased the activity of POD under non-saline conditions. The cultivar difference with respect to the different attributes measured in the present investigation was non-significant.

Modulation in activities of antioxidant enzymes in salt stressed and non-stressed wheat (triticum aestivum l.) plants raised from seed trearted with triacontanol

An experiment was conducted to assess the effect of pre-sowing seed treatment with triacontanol (TRIA) in canola (Brassica napus L.) cultivar (RBN-3060) under saline stress. Canola seeds were soaked in three levels of TRIA (0, 0.5, and 1 mg L−1) for 12 hours. Three levels of salt stress (0, 100, and 150 mM NaCl) in full strength Hoagland's nutrient solution were applied to 56-days-old plants. Salt stress caused a significant reduction in growth, gas exchange, photochemical quenching (qP), and shoot and root K+ contents, while increased leaf glycine betaine, free proline, and shoot Na+ contents. Pre-sowing seed treatment with TRIA increased shoot fresh weight, number of seeds per plant, photosynthetic rate, transpiration rate, ratio of chlorophyll a/b, qP, electron transport rate, shoot and root K+ contents, and free proline and glycine betaine contents of canola plants at various TRIA levels under nonsaline or saline conditions.

https://www.tandfonline.com/doi/pdf/10.1080/17429145.2013.764469

Triacontanol modulates photosynthesis and osmoprotectants in canola (Brassica napus L.) under saline stress

The role of pre-sowing treatment with triacontanol (TRIA) on two cultivars [MH-97 (moderately salt sensitive) and S24 (salt tolerant)] of wheat (Triticum aestivum L.) was assessed under saline and non-saline conditions. Twenty four day old plants raised from seed pretreated with TRIA for 24 h were subjected to 0 (control) or 150 mM NaCl. After 21 days of salt application, changes in shoot and root mineral nutrient concentrations, nutrient uptake and use efficiency, and shoot and root K + /Na + ratios were measured. Salt stress (150 mM NaCl) significantly increased the shoot and root Na + and Cl contents, while decreased that of K + , and K + /Na + ratios in shoot and root of both cultivars under saline conditions. The uptake of shoot Na + increased significantly, while that of the remaining nutrients decreased under saline conditions. Shoot and root nutrient (Na + , K + , Ca 2+ , Cl ) use efficiency (NUE) decreased significantly in both cultivars under saline conditions. The exogenous application of TRIA as pre-sowing seed treatment significantly increased the shoot Na + and K + contents, shoot K + uptake and shoot Cl use efficiency, while its effect was non-significant on the remaining attributes in both cultivars under nonsaline or saline conditions. Overall, the performance of S-24 was better than MH-97 in shoot and root K + and Ca 2+ contents and the uptake of these nutrients under both saline and non-saline conditions.

Changes in mineral composition, uptake and use efficiency of salt stressed wheat (triticum aestivum l.) plants raised from seed treated with triacontanol

Shagufta Perveen

Papers

Silicon Priming Regulates Morpho-Physiological Growth and Oxidative Metabolism in Maize under Drought Stress

Regulation in gas exchange and quantum yield of photosystem ii (psii) in salt-stressed and non-stressed wheat plants raised from seed treated with triacontanol

Modulation in activities of antioxidant enzymes in salt stressed and non-stressed wheat (triticum aestivum l.) plants raised from seed trearted with triacontanol

Triacontanol modulates photosynthesis and osmoprotectants in canola (Brassica napus L.) under saline stress

Changes in mineral composition, uptake and use efficiency of salt stressed wheat (triticum aestivum l.) plants raised from seed treated with triacontanol