Abiotic Stress Alleviation with Brassinosteroids in Plant Roots

This chapter covers the advances in establishment and optimization of brassinosteroids (BRs) in the alleviation of abiotic stresses such as water, salinity, temperature, and heavy metals in plant system, especially roots. Plant roots regulate their developmental and physiological processes in response to various internal and external stimuli. Studies are in progress to improve plant root adaptations to stress factors. BRs are a group of steroidal hormones that play important roles in a wide range of developmental phenomena, and recently they became an alleviation agent for stress tolerance in plants. This review is expected to provide a resource for researchers interested in abiotic stress alleviation with BRs

Bakır stresi altında nohut bitkisinde (cicer arietinum l.) stresle ilişkili gen ekspresyon seviyelerinde meydana gelen değişimlerin belirlenmesi ve hücresel h2o2 ile ilişkisi

The aim of this study is to determine the changes in expression levels of stress genes in chickpea (Cicer arietinum) plant leaves exposed to copper (Cu) at different times and concentrations. Also; the relationship between the changes in gene expression and cellular H2O2 was investigated. In this context, the amount of malondialdehyde (MDA) and reactive oxygen species (ROS) hydrogen peroxide (H2O2) levels were determined. Furthermore, the changes in gene expressions of Metallothionein (MT), Catalase (CAT) and superoxide dismutase (Cu / Zn-SOD) enzymes were determined based on the actin expression level that selected as a housekeeping gene. It was determined that MDA content increased significantly due to time and concentration, In all duration and concentrations, the expression of stress-related genes significantly differed from the control group. Hleowever, a decrease has been determined by all gene expressions after the highest expression. This phenomenon is associated with cellular H2O2, which shows a steady increase in stress. At the end of the study, it was concluded that the elevating duration and concentration of Cu induced oxidative stress and caused the expression of stress-related genes. Furthermore, cellular H2O2 might be acting as a signal molecule that, up-regulate gene expressions until a certain concentration and down-regulate until a certain concentration. Thanks to the results of this study; Plants in agricultural areas can be exposed to a certain concentration of H2O2 to provide an earlier response to oxidative stress against biotic or abiotic stresses. In this way, the use of chemical pesticides can be minimized due to obtaining more durable products.Bu çalışmanın amacı, nohut (Cicer arietinum) bitkisinde farklı zaman ve konsantrasyonlarda bakıra maruz kalmış bitki yapraklarındaki stres genlerinin ekspresyon seviyelerindeki değişimlerin belirlenmesidir. Ayrıca; gen ekspresyonlarındaki değişim ile hücresel H2O2 arasındaki ilişki tespit edilmeye çalışılmıştır. Bu bağlamda hücrede oksidatif stresin göstergesi olan melondialdehit (MDA) miktarı ve reaktif oksijen türlerinden (ROS) H2O2 miktarları tespit edilmiştir. Ayrıca antioksidan savunma elemanlarından Metallothionein (MT), Catalase (CAT) ve superoksit dismutaz (Cu/Zn-SOD) enzimlerinin gen ekspresyonlarındaki değişim house-keeping gen olarak seçilmiş aktinin ekspresyon düzeyi baz alınarak tespit edilmiştir. Çalışma sonucunda MDA içeriğinin süre ve konsantrasyona bağlı olarak belirgin bir şekilde arttığı, stres alakalı gen ekpresyonlarının bütün konsantrasyonlarda kontrolden yüksek düzeyde eksprese edildiği ancak en yüksek ekspresyon gerçekleştikten sonra süre ve konsantrasyondan arttıkca ekpsreyon düzeylerinde bir azalma olduğu belirlenmiştir. Bu durum stres anındaki kararlı bir artış gösteren hücresel H2O2 ile ilişkilendirilmiştir. Çalışma sonucunda Cu maruziyetinin oskidatif strese neden olarak stres alakalı genlerin ekpresyonlarını indüklediği tespit edilmiştir. Ayırca hücresel H2O2’nin belirli konsantrasyona kadar gen ekpresyonunu up-regule ederken belirli konsantrasyondan sonra down regule etmiş olduğu düşünülmektedir. bu calısmanın sonucları sayesinde; tarım alanlarındaki bitkiler belirli konsantrasyonda H2O2 ye maruz bırakılarak biyotik ve ya abiyotik streslere karsı oksidadatif stres cevabını daha erken evrede vermesi sağlanabilir. Bu sayede, daha dayanıklı ürünler elde edilmesine bağlı olarak kimyasal zirai ilac kullanımı asgari düzeye indirilebilir

Fluorescence-based systems for detection of abiotic stresses on horticultural crops

The main objective of this thesis was to assess the impact of economically important abiotic stresses on the plant physiology using non-destructive fluorescence indices, and to evaluate the potential use of the sensor techniques as supporting tool for plant phenotyping in horticulture. The early detection of water deficiency and salinity was studied at leaf level in tomato (Solanum lycopersicum L.) plants by means of non-destructive fluorescence techniques. Evaluations comprised multiparametric fluorescence indices and pulse-amplitude modulated (PAM) chlorophyll fluorescence parameters for an effective and rapid sensing of water deficiency stress and stress recovery in three tomato genotypes. In addition, the impact of salinity on tomato genotypes was also studied using both methods. In the next step, the response of tomato genotypes exposed to simultaneous occurrence of salinity and water deficiency was examined by multiparametric fluorescence indices. An additional objective of the work was to investigate the suitability of chemically induced osmotic stress by polyethylene glycol (PEG) for drought stress experiments based on key physiological parameters of apple (Malus domestica Borkh.) leaves.Fluoreszenzbasierende Systeme zur Erkennung von abiotischem Stress in gartenbaulichen Kulturen Ziel dieser Arbeit war es, das Potential ausgewählter fluoreszenzbasierter Indizes für die Erfassung der Pflanzenreaktion auf ökonomisch bedeutende abiotische Stressfaktoren zu ermitteln. Zudem sollte evaluiert werden, inwiefern sich diese Technologie für die Pflanzenphänotypisierung im Gartenbau eignet. Dazu wurden nicht-destruktive Fluoreszenztechniken zur Früherkennung von Wassermangel und Salinität bei Tomatenpflanzen (Solanum lycopersicum L.) auf Blattebene getestet. Die Evaluierung umfasste multiparametrische Fluoreszenzindizes und Puls-Amplituden-modulierte (PAM) Chlorophyllfluoreszenzparameter, untersucht sowohl in der Wassermangelphase als auch in der darauf folgenden Erholungsphase an drei Tomatengenotypen. Diese Methoden wurden ebenfalls für die Untersuchung der Tomatengenotypen auf deren Salztoleranz verwendet. Darüber hinaus wurde ermittelt, wie sich das zeitgleiche Auftreten der Stressfaktoren Salinität und Wassermangel auf die Fluoreszenzindizes auswirkt. Als ein weiterer Aspekt der Studie wurde die Eignung von Polyethylenglycol (PEG) als osmotisch aktive Substanz zur Induktion von Trockenstress an Apfelblättern (Malus domestica Borkh.) evaluiert

Approaches in Enhancing Antioxidant Defense in Plants

This Special Issue, “Approaches in Enhancing Antioxidant Defense in Plants” published 13 original research works and a couple of review articles that discuss the various aspects of plant oxidative stress biology and ROS metabolism, as well as the physiological mechanisms and approaches to enhancing antioxidant defense and mitigating oxidative stress. These papers will serve as a foundation for plant oxidative stress tolerance and, in the long term, provide further research directions in the development of crop plants’ tolerance to abiotic stress in the era of climate change

Oxidative Stress in Plants

Plants are continuously exposed to different environmental stress conditions that have a huge impact on agriculture worldwide, consequently leading to massive economic losses. These adverse conditions alter the metabolism of reactive oxygen and nitrogen species (ROS and RNS). High concentrations of these reactive species—that exceed the capacity of antioxidant defense enzymes—disturb redox homeostasis, which can trigger damage to such macromolecules as membrane lipids, proteins, and nucleic acids, ultimately resulting in nitro-oxidative stress and plant cell death. Significant progress has been made to understand how plants persist in these stressful environments which could be vital to improving plant crop yield. This Special Issue “Oxidative Stress in Plants” includes both original research articles and detailed reviews that aim to better understand the nitro-oxidative stress networks in higher plants, and the addressed topics provide updated and new knowledge about ROS and RNS metabolism in plant responses to abiotic stress as well as the modulation of antioxidant systems in the control of ROS production and accumulation

Physiological and Molecular Characterization of Crop Resistance to Abiotic Stresses

Abiotic stress represents the main constraint for agriculture, affecting plant growth and productivity worldwide. Yield losses in agriculture will be potentiated in the future by global warming, increasing contamination, and reduced availability of fertile land. The challenge for agriculture of the present and future is that of increasing the food supply for a continuously growing human population under environmental conditions that are deteriorating in many areas of the world. Minimizing the effects of diverse types of abiotic stresses represents a matter of general concern. Research on all topics related to abiotic stress tolerance, from understanding the stress response mechanisms of plants to developing cultivars and crops tolerant to stress, is a priority. This Special Issue is focused on the physiological and molecular characterization of crop resistance to abiotic stresses, including novel research, reviews, and opinion articles covering all aspects of the responses and mechanisms of plant tolerance to abiotic. Contributions on physiological, biochemical, and molecular studies of crop responses to abiotic stresses; the description and role of stress-responsive genes; marker-assisted screening of stress-tolerant genotypes; genetic engineering; and other biotechnological approaches to improve crop tolerance were considered

Bacterial ACC deaminase: Insights into enzymology, biochemistry, genetics, and potential role in amelioration of environmental stress in crop plants

Growth and productivity of crop plants worldwide are often adversely affected by anthropogenic and natural stresses. Both biotic and abiotic stresses may impact future food security and sustainability; global climate change will only exacerbate the threat. Nearly all stresses induce ethylene production in plants, which is detrimental to their growth and survival when present at higher concentrations. Consequently, management of ethylene production in plants is becoming an attractive option for countering the stress hormone and its effect on crop yield and productivity. In plants, ACC (1-aminocyclopropane-1-carboxylate) serves as a precursor for ethylene production. Soil microorganisms and root-associated plant growth promoting rhizobacteria (PGPR) that possess ACC deaminase activity regulate growth and development of plants under harsh environmental conditions by limiting ethylene levels in plants; this enzyme is, therefore, often designated as a “stress modulator.” TheACC deaminase enzyme, encoded by the AcdS gene, is tightly controlled and regulated depending upon environmental conditions. Gene regulatory components of AcdS are made up of the LRP protein-coding regulatory gene and other regulatory components that are activated via distinct mechanisms under aerobic and anaerobic conditions. ACC deaminase-positive PGPR strains can intensively promote growth and development of crops being cultivated under abiotic stresses including salt stress, water deficit, waterlogging, temperature extremes, and presence of heavy metals, pesticides and other organic contaminants. Strategies for combating environmental stresses in plants, and improving growth by introducing the acdS gene into crop plants via bacteria, have been investigated. In the recent past, some rapid methods and cutting-edge technologies based on molecular biotechnology and omics approaches involving proteomics, transcriptomics, metagenomics, and next generation sequencing (NGS) have been proposed to reveal the variety and potential of ACC deaminase-producing PGPR that thrive under external stresses. Multiple stress-tolerant ACC deaminase-producing PGPR strains have demonstrated great promise in providing plant resistance/tolerance to various stressors and, therefore, it could be advantageous over other soil/plant microbiome that can flourish under stressed environments

Effects of Melatonin on Morus nigra cv. 'Eksi Kara' Exposed to Drought Stress

Today, drought stress threatens the world seriously. Determining the effects of some exogenous stimulators in acquiring resistance against stress will contribute to agriculture under drought stress. In this regard, we investigated the effects of melatonin (MEL) on Morus nigra cv. 'Eksi Kara' (black mulberry) in challenging drought. To reach this object, we reproduced 'Eksi Kara', which is registered in Turkey and has economic importance, in tissue culture by using the meristem culture method. Plants were then transferred in a medium containing polyethylene glycol (PEG) 8000, which causes -1.5 MPa drought stress, and 20 μl MEL has applied. Leaf samples were taken on the 5th, 10th, and 15th days after treatments in groups of plants grown in a different medium (Control, Control+MEL, PEG and PEG+MEL). The changes in the pigment system, relative water content (RWC) and antioxidant system were evaluated comparatively between the groups to assess plants' growth and determine their roles in coping with stress. Our findings showed that RWC decreased in leaves under drought. Exogenous MEL added in MS medium had a mitigation effect on stress. The reduction was detected in the chlorophyll and carotenoid content of leaves. Moreover, MEL+PEG combination improved the chlorophyll level. It was seen that exogenous MEL application promoted the plant defence mechanism of M. nigra plants, which exposed to drought stress, by increasing the accumulation of non-enzymatic antioxidants; total glutathione (GSH), total phenolic, proline) and activities of antioxidant enzymes; catalase (CAT), superoxide dismutase (SOD), Glutathione-S-transferase (GST), glutathione reductase (GR), peroxidase (POD), ascorbate peroxidase (APX). This study also indicates that the application of MEL+PEG composition partially prevented membrane lipid peroxidation by decreasing (malondialdehyde) MDA content

Improvement of Abiotic Stress Tolerance in Plants with the Application of Nanoparticles

Plants are under the threat of climatic changes and there is a reduction in productivity and deterioration in quality. The application of nanoparticles is one of the recent approaches to improve plant yield and quality traits. A number of nanoparticles, such as zinc nanoparticles (ZnO NPs), iron nanoparticles (Fe2O3 NPs), silicon nanoparticles (SiO2 NPs), cerium nanoparticles (CeO2 NPs), silver nanoparticles (Ag NPs), titanium dioxide nanoparticles (TiO2 NPs), and carbon nanoparticles (C NPs), have been reported in different plant species to play a role to improve the plant physiology and metabolic pathways under environmental stresses. Crop plants readily absorb the nanoparticles through the cellular machinery of different tissues and organs to take part in metabolic and growth processes. Nanoparticles promote the activity of a range of antioxidant enzymes, including catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), in plant species, which in turn improve the growth and development under stressful conditions. The present review focuses on the mode of action and signaling of nanoparticles to the plant systems and their positive impact on growth, development, and ROS scavenging potential. The appropriate elucidation on mechanisms of nanoparticles in plants leads to better growth and yields under stress conditions, which will ultimately lead to increased agricultural production

Meta-analysis of the effect of expression of MYB transcription factor genes on abiotic stress

Background MYB proteins are a large group of transcription factors. The overexpression of MYB genes has been reported to improve abiotic stress tolerance in plant. However, due to the variety of plant species studied and the types of gene donors/recipients, along with different experimental conditions, it is difficult to interpret the roles of MYB in abiotic stress tolerance from published data. Methods Using meta-analysis approach, we investigated the plant characteristics involved in cold, drought, and salt stress in MYB-overexpressing plants and analyzed the degrees of influence on plant performance by experimental variables. Results The results show that two of the four measured plant parameters in cold-stressed plants, two of the six in drought-stressed, and four of the 13 in salt-stressed were significantly impacted by MYB overexpression by 22% or more, and the treatment medium, donor/recipient species, and donor type significantly influence the effects of MYB-overexpression on drought stress tolerance. Also, the donor/recipient species, donor type, and stress duration all significantly affected the extent of MYB-mediated salt stress tolerance. In summary, this study compiles and analyzes the data across studies to help us understand the complex interactions that dictate the efficacy of heterologous MYB expression designed for improved abiotic stress tolerance in plants