With the global climate anomalies and the destruction of ecological balance, the water shortage has become a serious ecological problem facing all mankind, and drought has become a key factor ...restricting the development of agricultural production. Therefore, it is essential to study the drought tolerance of crops. Based on previous studies, we reviewed the effects of drought stress on plant morphology and physiology, including the changes of external morphology and internal structure of root, stem, and leaf, the effects of drought stress on osmotic regulation substances, drought-induced proteins, and active oxygen metabolism of plants. In this paper, the main drought stress signals and signal transduction pathways in plants are described, and the functional genes and regulatory genes related to drought stress are listed, respectively. We summarize the above aspects to provide valuable background knowledge and theoretical basis for future agriculture, forestry breeding, and cultivation.
Salinity is a major problem affecting crop production all over the world: 20% of cultivated land in the world, and 33% of irrigated land, are salt-affected and degraded. This process can be ...accentuated by climate change, excessive use of groundwater (mainly if close to the sea), increasing use of low-quality water in irrigation, and massive introduction of irrigation associated with intensive farming. Excessive soil salinity reduces the productivity of many agricultural crops, including most vegetables, which are particularly sensitive throughout the ontogeny of the plant. The salinity threshold (ECt) of the majority of vegetable crops is low (ranging from 1 to 2.5 dS m−1 in saturated soil extracts) and vegetable salt tolerance decreases when saline water is used for irrigation. The objective of this review is to discuss the effects of salinity on vegetable growth and how management practices (irrigation, drainage, and fertilization) can prevent soil and water salinization and mitigate the adverse effects of salinity.
Nowadays, crop insufficiency resulting from soil salinization is threatening the world. On the basis that soil salinization has become a worldwide problem, studying the mechanisms of plant salt ...tolerance is of great theoretical and practical significance to improve crop yield, to cultivate new salt-tolerant varieties, and to make full use of saline land. Based on previous studies, this paper reviews the damage of salt stress to plants, including suppression of photosynthesis, disturbance of ion homeostasis, and membrane peroxidation. We have also summarized the physiological mechanisms of salt tolerance, including reactive oxygen species (ROS) scavenging and osmotic adjustment. Four main stress-related signaling pathways, salt overly sensitive (SOS) pathway, calcium-dependent protein kinase (CDPK) pathway, mitogen-activated protein kinase (MAPKs) pathway, and abscisic acid (ABA) pathway, are included. We have also enumerated some salt stress-responsive genes that correspond to physiological mechanisms. In the end, we have outlined the present approaches and techniques to improve salt tolerance of plants. All in all, we reviewed those aspects above, in the hope of providing valuable background knowledge for the future cultivation of agricultural and forestry plants.
Water management is rapidly becoming one of the most pressing issues facing all countries in semi-arid and arid parts of the world. Global water consumption is predicted to increase by 50% in 2030, ...resulting in an acute water shortage. Presently, the agricultural sector consumes more than 70% of freshwater in most regions of the world, putting more pressure on water scarcity. Hydrogels are superabsorbent polymers that can hold plant nutrients and water when the soil around plant roots starts to dry out. Research evidence has revealed that water stored by hydrogel slowly returns to the soil, thereby increasing the volumetric water content of the soil. Hydrogel increases water use efficiency and irrigation intervals, decreases irrigation costs, and provides plants with the required nutrients and moisture. Numerous properties of hydrogels, including moderate water retention and high swelling, make them ideal as a safe delivery mechanism in agriculture for soil conditioners and agents for the controlled release of fertilizers. Numerous research publications on hydrogel polymer synthesis and its characteristics have been published. However, the current review emphasizes the critical role of superabsorbent hydrogels in an integrated approach for the balanced protection of seeds, plants, and soil to conserve the ecosystem.
Biostimulants are agronomic tools that have been gaining importance in the reduction of fertilizer applications. They can improve the yield of cropping systems or preventing crop yield losses under ...abiotic stresses. Biostimulants can be composed of organic and inorganic materials and most of the components are still unknown. The characterization of the molecular mechanism of action of biostimulants can be obtained using the omics approach, which includes the determination of transcriptomic, proteomic, and metabolomic changes in treated plants. This review reports an overview of the biostimulants, taking stock on the recent molecular studies that are contributing to clarify their action mechanisms. The omics studies can provide an overall evaluation of a crop’s response, connecting the molecular changes with the physiological pathways activated and the performance with or without stress conditions. The multiple responses of plants treated with biostimulants must be correlated with the phenotype changes. In this context, it is also crucial to design an adequate experimental plan and statistical data analysis, in order to find robust correlations between biostimulant treatments and crop performance.
The use of synthetic fungicides to control fungal diseases has growing limitations due to eco-toxicological risks. Therefore, it is necessary to replace or integrate high risk chemicals with safer ...tools for human health and environment. Consequently, research on the selection, evaluation, characterization, and use of biocontrol agents (BCAs) has consistently increased in the last decades. BCA formulates, particularly in some countries, are still scarce in coping with the growing demand for their use in sustainable agricultural management. To foster development and utilization of new effective bioformulates, there is a need to optimize BCA activity, to share knowledge on their formulation processes and to simplify the registration procedures. Studies based on new molecular tools can significantly contribute to achieve such objectives. The present review provides the state of the art on biocontrol of fungal plant diseases with special emphasis on (i) features of the most studied BCAs; (ii) key strategies to optimize selection and use of BCAs (iii); mechanisms of action of the main BCAs; (iv) molecular tools and metagenomic studies in the selection and use of BCAs; (v) main issues and constraints in the registration and commercialization of BCAs, and (vi) perspectives in the biocontrol of fungal plant diseases.
The yield and quality of horticultural crops mainly depend on genotype, environmental conditions, and cultivation management. Abiotic stresses, such as adverse environmental conditions, can strongly ...reduce crop performance, with crop yield losses ranging from 50% to 70%. The most common abiotic stresses are represented by cold, heat, drought, flooding, salinity, nutrient deficiency, and high and low light intensities, including ultraviolet radiation. These abiotic stresses affect multiple physiological and biochemical processes in plants. The ability of plants to face these stresses depends on their adaptation aptitude, and tolerant plants may express different strategies to adapt to or avoid the negative effects of abiotic stresses. At the physiological level, photosynthetic activity and light-use efficiency of plants may be modulated to enhance tolerance against the stress. At the biochemical level, several antioxidant systems can be activated, and many enzymes may produce stress-related metabolites to help avoid cellular damage, including such compounds as proline, glycine betaine, amino acids, etc. This special issue gathers eight papers; three are reviews and five are research papers. Two reviews are focused on the application of appropriate agronomic strategies for counteracting the negative effects of abiotic stresses. The third review is based on ornamental plant production under drought stress conditions and the effect on their ornamental quality. The research papers report the effect of climate change on crop development, yield, and quality. Abiotic stresses have been proven to reduce crop performance and yield. Research studies are essential for understanding the key adaptation strategies of plants that can be exploited for improving the crop stress tolerance.
This study monitored changes in chlorophyll fluorescence (CF), growth parameters, soil moisture content, phytochemical content (proline, ascorbic acid, chlorophyll, total phenol content (TPC), and ...total flavonoid content (TFC)), and antioxidant activities in 12-day-old lettuce (Lactuca sativa L.) seedlings grown under drought stress (no irrigation) and control (well irrigated) treatments in controlled conditions for eight days. Measurements occurred at two-day intervals. Among ten CF parameters studied, effective quantum yield of photochemical energy conversion in PSII (Y(PSII)), coefficient of photochemical quenching (qP), and coefficient of photochemical quenching of variable fluorescence based on the lake model of PSII (qL) significantly decreased in drought-stressed seedlings from day 6 of treatment compared to control. In contrast, maximum quantum yield (Fv/Fm), ratio of fluorescence (Rfd), and quantum yield of non-regulated energy dissipation in PSII (Y(NO)) were significantly affected only at the end. All growth parameters decreased in drought-stressed seedlings compared to control. Proline started increasing from day 4 and showed ~660-fold elevation on day 8 compared to control. Chlorophyll, ascorbic acid, TPC, TFC, and antioxidant activities decreased in drought-stressed seedlings. Results showed major changes in all parameters in seedlings under prolonged drought stress. These findings clarify effects of drought stress in lettuce seedlings during progressive drought exposure and will be useful in the seedling industry.
Ornamental plants use unique adaptive mechanisms to overcome the negative effects of drought stress. A large number of species grown in the Mediterranean area offer the opportunity to select some for ...ornamental purposes with the ability to adapt to drought conditions. The plants tolerant to drought stress show different adaptation mechanisms to overcome drought stress, including morphological, physiological, and biochemical modifications. These responses include increasing root/shoot ratio, growth reduction, leaf anatomy change, and reduction of leaf size and total leaf area to limit water loss and guarantee photosynthesis. In this review, the effect of drought stress on photosynthesis and chlorophyll a fluorescence is discussed. Recent information on the mechanisms of signal transduction and the development of drought tolerance in ornamental plants is provided. Finally, drought-induced oxidative stress is analyzed and discussed. The purpose of this review is to deepen our knowledge of how drought may modify the morphological and physiological characteristics of plants and reduce their aesthetic value—that is, the key parameter of assessment of ornamental plants.
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