Influence of solar radiation on the production of secondary metabolites in three rice (Oryza sativa) cultivars

Rice (Oryza sativa L.) is one of the most produced and consumed cereals worldwide and has its importance highlighted mainly in developing countries, where it plays a strategic economic and social role. Due to the importance of rice in the diet, its composition and nutritional characteristics are directly related to the health of the population. In the rice production systems, some climatic factors are determinants for the good performance of the crop, inducing the biosynthesis of primary and secondary metabolites. The present study determined the metabolic profiles through UV-visible spectrophotometry of leaf samples of three rice cultivars (Marques -- white, \\^Onix -- black, and Rubi -- red pericarp) throughout the rice's vegetative stages in two experimental times, from September to December 2015 and from January to April 2016. Solar radiation was recorded along the experimental period. To the organosolvent extracts of leaf samples, UV-vis spectrophotometric techniques were applied and the quantitative results of certain metabolites, e.g., chlorophylls, carotenoids, phenolics, flavonoids, and sugars, as well the antioxidant activity, which were analyzed by chemometrics tools. The results showed that biochemical parameters carotenoids, chlorophylls and sugars are more affected by the intensity of the radiation do que as vari\\'\a\veis phenolics, flavonoids and these alterations may be detected through statistical analysis of biochemical concentrations and UV-vis spectra.CAPES -Coordenação de Aperfeiçoamento de Pessoal de Nível Superior(407323/2013-9)info:eu-repo/semantics/publishedVersio

UV-B exposure, ROS, and stress: inseparable companions or loosely linked associates?

Ultraviolet-B (UV-B) radiation has long been perceived as a stressor. However, a conceptual U-turn has taken place, and UV-B damage is now considered rare. We question whether UV-stress and UV-B-induced reactive oxygen species (ROS) are still relevant concepts, and if ROS-mediated signaling contributes to UV-B acclimation. Measurements of antioxidants and of antioxidant genes show that both low and high UV-B doses alter ROS metabolism. Yet, there is no evidence that ROS control gene expression under low UV-B. Instead, expression of antioxidant genes is linked to the UV RESISTANCE LOCUS 8 pathway. We hypothesize that low UVB doses cause ‘eustress’ (good stress) and that stimulispecific signaling pathways pre-dispose plants to a state of low alert that includes activation of antioxidant defenses.Funding agencies are:COST Action  FA0906UV4Growth  Faculty of Business, Science, and Technology at Örebro University  Science Foundation Ireland (SFI)  11/RFP.1/EOB/3303 Hungarian Scientific Research Fund  OTKA NN-85349 UV-B-fotobiologi: mekanismer för perception och cellulära response

Flavonoid Accumulation Behavior in Response to the Abiotic Stress: Can a Uniform Mechanism Be Illustrated for All Plants?

This review concentrates on two aspects of how total flavonoid content and individual flavonoid compounds change with the perception of environmental stress and the subsequent changes in those metabolites after post-harvest conditions are of the main points of the study. Hereby, along with this study, the flavonoid synthesis or their accumulation with their importance in plants and then in humans is briefly described. According to the literature cited herein, it seems that a universal mechanism concerned with flavonoid accumulation in response to the abiotic stress factors cannot be illustrated. Flavonoid accumulation exhibits different reactions to the different stressors. Flavonoid accumulation behavior not only varies depending on the developmental stage, species and even cultivars of the same species but also post-harvest processes

Plants and Environment

Changing environmental condition and global population demands understanding the plant responses to hostile environment. Significant progress has been made over the past few decades through amalgamation of molecular breeding with non-conventional breeding. Understanding the cellular and molecular mechanisms to stress tolerance has received considerable scientific scrutiny because of the uniqueness of such processes to plant biology, and also its importance in the campaign "Freedom From Hunger". The main intention of this publication is to provide a state-of-the-art and up-to-date knowledge of recent developments in understanding of plant responses to major abiotic stresses, limitations and the current status of crop improvement. A better insight will help in taking a multidisciplinary approach to address the issues affecting plant development and performance under adverse conditions. I trust this book will act as a platform to excel in the field of stress biology

Relationship between growth traits and yield formation in Indica-type rice crop

Introduction. Climatic variation is one of the causes for the decrease in yield and its variability in Indica-type rice (Oryza sativa L.). This evidences the necessity of the study of the interaction of meteorological variables with the behavior of rice cultivars, to establish the base of management of the harvest and increase of the yield. Objective. The objective of the present study was to relate the yield of rice with variables of plant growth. Materials and methods. Four rice cultivars were planted in the “dry” season of December 2004, February 2005 and January 2006, and in the rainy season of March 2006, April 2008 and 2009, in Los Palacios, Pinar del Río province, Cuba. The yield and its components, the dynamics of plant growth (LAI and dry matter), the variation of the dry matter of the internodes, peduncle, flag leaf, leaf and leaf sheath during the grain filling phase were evaluated the panicle growth in addition to the meteorological data. A multivariate analysis was used to relate the performance to the characteristics of the plants evaluated. Results. The yield was higher in the “dry” season and to obtain higher yields, the growth dynamics of the plant and the variation of the dry matter of the third internode during the grain filling were important. In both seasons, different source-sink relationships were established and these situations depended mainly on the temperature regime at which the plants were subjected. Conclusion. Breeders, in order to increase potencial yields, may fows their atttention in grow traits during vegetative stages

Antioxidant potential of Indian medicinal plant in Phyllanthus amarus L. under supplementary UV-B radiation

The stratospheric ozone depletion and enhanced solar ultraviolet-B (UV-B) irradiance may have adverse impact on living organism. The impact of UV-B radiation (UV-B, 280~320nm) on growth, biochemical and antioxidant enzymes activity was studied in Phyllanthus amarus (L.) seedling, commonly used as a green manure. The supplementary UV-B radiation significantly decreased the growth, development and changes in UV-B absorbing compounds such as anthocyanin and flavonoids. The antioxidant enzymes were unaffected and showed an enhanced activities in peroxidase, superoxide dismutase, Polyphenoloxidase and phenylalanine ammonia- lyase except catalase in UV-B irradiated seedling. Phyllanthus amarus seedling tries to counteract high level of reactive oxygen species produce under UV-B stress through the increased activities of antioxidant enzyme. We suggest that Phyllanthus amarus is resistant against UV-B radiation damage and the possible negative effect of additional UV-B radiation on the growth of seedling may have been effectively balanced by the UV-B radiation stress through increase in UV absorbing compound and antioxidant enzymes

Decrypting the multi-functional biological activators and inducers of defense responses against biotic stresses in plants

Plant diseases are still the main problem for the reduction in crop yield and a threat to global food security. Additionally, excessive usage of chemical inputs such as pesticides and fungicides to control plant diseases have created another serious problem for human and environmental health. In view of this, the application of plant growth-promoting rhizobacteria (PGPR) for controlling plant disease incidences has been identified as an eco-friendly approach for coping with the food security issue. In this review, we have identified different ways by which PGPRs are capable of reducing phytopathogenic infestations and enhancing crop yield. PGPR suppresses plant diseases, both directly and indirectly, mediated by microbial metabolites and signaling components. Microbial synthesized anti-pathogenic metabolites such as siderophores, antibiotics, lytic enzymes, hydrogen cyanide, and several others act directly on phytopathogens. The indirect mechanisms of reducing plant disease infestation are caused by the stimulation of plant immune responses known as initiation of systemic resistance (ISR) which is mediated by triggering plant immune responses elicited through pathogen-associated molecular patterns (PAMPs). The ISR triggered in the infected region of the plant leads to the development of systemic acquired resistance (SAR) throughout the plant making the plant resistant to a wide range of pathogens. A number of PGPRs including Pseudomonas and Bacillus genera have proven their ability to stimulate ISR. However, there are still some challenges in the large-scale application and acceptance of PGPR for pest and disease management. Further, we discuss the newly formulated PGPR inoculants possessing both plant growth-promoting activities and plant disease suppression ability for a holistic approach to sustaining plant health and enhancing crop productivity

Do changes in Lactuca sativa metabolic performance, induced by mycorrhizal symbionts and leaf UV-B irradiation, play a role towards tolerance to a polyphagous insect pest?

: The increased ultraviolet radiation (UV) due to the altered stratospheric ozone leads to multiple plant physiological and biochemical adaptations, likely affecting their interaction with other organisms, such as pests and pathogens. Arbuscular mycorrhizal fungi (AMF) and UV-B treatment can be used as eco-friendly techniques to protect crops from pests by activating plant mechanisms of resistance. In this study, we investigated plant (Lactuca sativa) response to UV-B exposure and Funneliformis mosseae (IMA1) inoculation as well as the role of a major insect pest, Spodoptera littoralis. Lettuce plants exposed to UV-B were heavier and taller than non-irradiated ones. A considerable enrichment in phenolic, flavonoid, anthocyanin, and carotenoid contents and antioxidant capacity, along with redder and more homogenous leaf color, were also observed in UV-B-treated but not in AMF-inoculated plants. Biometric and biochemical data did not differ between AMF and non-AMF plants. AMF-inoculated plants showed hyphae, arbuscules, vesicles, and spores in their roots. AMF colonization levels were not affected by UV-B irradiation. No changes in S. littoralis-feeding behavior towards treated and untreated plants were observed, suggesting the ability of this generalist herbivore to overcome the plant chemical defenses boosted by UV-B exposure. The results of this multi-factorial study shed light on how polyphagous insect pests can cope with multiple plant physiological and biochemical adaptations following biotic and abiotic preconditioning

Plant Stress Physiology

This book includes ten chapters addressing various aspects of plant stress physiology, including plant responses and tolerance to abiotic and biotic stress. These chapters summarize recent findings on the physiological and molecular mechanisms of stress tolerance. They also discuss approaches to enhancing plant productivity via stress tolerance mechanisms. This book is useful for undergraduate and graduate students, teachers, and researchers in the field of plant physiology and crop science