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Stress is an external factor affecting the growth of plants. There are types of stress. Biotic stress, abiotic stress. Bacteria, fungus, insects, weeds, Nematodes, and arachrids from biotic stress. Salinity, drought, cold, high temperature from Abiotic stress. We will talk about the drought in Egypt as an example of stress. So from reasons of the drought of Egypt is the problem of water in Egypt. Also, the stress effect on the productivity of plants in addition to the development of plants.
Assuming continued population growth and taking into account the land reclamation projects in the desert and the fact that more than 50% of the cereals consumed are already imported, Egypt cannot meet its food demand by relying on Nile water for irrigation. In other words, Egypt is already utilizing most of the Nile’s flow, and it plans to use even more. According to the Ministry of Water Resources and Irrigation, there is a deficit in the national water budget. So Egypt faces a big problem in drought which effects plants. So there are responses from the plants to face the drought. The plant has biochemical, molecular, physiological, and morphological responses. Morphological responses like small plant size, and leaf area. Physiological response like the closure of stomata, decrease in the activity of photosynthesis. Biochemical responses like a reduction in efficiency of photochemical, reduced in antioxidative enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) which are a very important enzyme. molecular responses, some genes effects about drought stress so produce different types of proteins related to drought stress late embryo abundance (LEB) proteins, the expression of ABA genes production of RAB proteins.
Stress exerts negative impacts on many crops during germination. So biochemical responses are to make some chemicals or proteins have a role of defense against drought stress or even some proteins. From this defense increase in antioxidative. Which their role is too protective enzyme-catalyzed to clean up system in plants from toxicity. Like antioxidative glutathione ascorbate carotenoids superoxide known as SOD, it was known that transpiration of genes decreased significantly under drought stress; then heat can slowly be lost from leaves and leaf temperature can be increased. The growth of plants is negatively affected by molecular alterations under stress. Drought stress induces the transcript of the number of genes s however gene transcript in response to both stresses are quite different. Transcript of dreb1 also called CBFSOR the c-box binding factors and DREB2 families were affected in defense to chilling and drought stresses. So that how the plant defense in drought stress.
Water scarcity is problematic in Egypt. the presence of water per person rate is already the lowest in the world. this is suggested for further declines. a major challenge is to close the rapidly the high ratio gap between the limited water and the escalating require from various economic sectors. The Nile is the main source of water in Egypt with a share of more than 95%. the storage reservoir of Nasser lake provides 56 billion m3 hereinafter referred to bcm per annum. the issue of Egypt’s share of Nile waters is under difficult negotiations. in April 2011 Ethiopia has launched the construction of the Grand Ethiopian refuse to model water quality 4 dam GERD. with a water storage capacity of 63 bcm and an energy generation capacity of 6 000 MW, the GERD is anticipated to be the biggest hydroelectric power plant and one of the water reservoirs in the continent. Egyptian experts give indications of 20- 34% water reduction when the filling period overcuts the drought period. this will be 11-19 bcm on average over the dams filling period.
Scientists in Egypt warn of increased water poverty in Egypt as a result of the Ethiopian renaissance dam which is about to become operational. Egypt is reducing the cultivation of water-consuming crops like rice. By refusing the growing of some crops we are risking the big loss of large farmland this will affects very bad at the salinity of the soil in some farmland which will be disastrous to the agriculture sector.
Analysis of variance showed significant and highly significant effects for irrigation treatments on grain yield in the 1st and 2nd season, respectively. As shown in the grain yield significantly decreased from 5.88 to 3.73 tons/ha, averaged over both seasons, with decreasing the number of irrigation from seven to two irrigations/season. These results could be attributed predominantly with decreasing in spikes per unit area and grains per spike which was also attributed to a reduction in the number of effective tillers. Our results are in agreement with those Soil properties.
Rice is a very important food crop and it needs a large amount of water to grow. Rice plays a fundamental role as a basic food that has nutrition to more than three billion people. Rice has an important role in Egypt. Identifying rice genotypes and breeding lines with high levels of tolerance to drought to use as patrons inbreeding and gene discovery are challenges for rice research. Drought is the most important stresses that affect the growth of the plants. And it is also a challenge to agricultural researchers and plant breeders. Water stress causes many threats in rice and it affects morphological physiological biochemical and molecular characteristics of rice crops along with its productivity.
The biochemical traits that effects by drought stress in rice. Is the increasing and decreasing in some chemicals and some enzyme we will talk about it? Enzyme that has antioxidant features observed that is in high concentration in drought stress to overcome the toxicity caused by this stress. A decrease caused by drought relative water content in the leaves changing in the plant that observed synthesis of chlorophyll but not very much reduced as a result of drought stress. Membrane stability index that is tolerance genotype to drought. The percentage of proline increase in leaf more than an amino acid due to the decrease of water which is acts as osmolyte during lack of water also metal chelator an antioxidative defense molecule. Proline can be used as a marker for screening to make sure that rice is tolerant. Peroxidase activity is also an increase in the absence of water catalase activity has a remarkable increase during the lace of water. So plants with a major level of antioxidant system and substrate have the tolerance to drought stress.
Plants sometimes have to exposure to drought stress due to the lack of water and plants must have a response to this stress to maintain plants to be alive or tolerant of this situation. From these responses, the molecular response in the next few lines will talk about genes expressed in the presence of a lack of water stress. SNAC1, PoPW gene that enhances the overexpression of this gene enhanced the relative transcript level of genes that responsible for droughts like NtAPX, NtCAT1, NtGST, and Ntcuzn-SOD. LEA gene also has a role in the plant which increases water-deficit stress tolerance through a decrease of photosynthetic activity and increases activation of the antioxidant system.
Environmental diversity and drought are a major threat to the largest of the crops. Drought stress is one of the outcomes of environmental diversity that harms crop growth and yield. Extremely important to improve essential crops to meet the challenges of drought stress which defines crop fertility and production. Wheat is one of the several popular and universally used crops due to its economic and social advantages. Many nations depend on wheat this crop for food and feed, this crop is unprotected to drought stress. Improving drought stress tolerance is an extremely challenging task for wheat. Wheat genotype has a high degree of drought tolerance and choosing with their descendants. Also, distinguishing genes participating in drought tolerance is very valuable. Drought stress can be simply described as a lack of water that induces tense, biochemical, and molecular changes. All of these differences decrease plant growth and crop product. Wheat Is an important cereal crop and large parts of human populations in many parts of the world take it as a source of food and animal? Wheat is very important crop.
From the biochemical rejoinder to drought stress some chemicals or enzymes including and we will talk about it in the next few lines.
Reactive oxygen species (ROS) can be singlet oxygen, superoxide radicals (O2), (H2O2), and (OH) resulted in oxidative damages to plants. The presence of ROS causes alteration of the cellular water. ROS production is linear with the severity of water stress that triggered the peroxidation of membranes as a defense against stress.
Generation of antioxidant enzymes as a defense facing drought stress such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR) and glutathione reductase and glutathione peroxidase (GPX) in response to water stress is a well-known adaptive mechanism in wheat. Acclimatization of plants to water-deficit classified into three classes: drought escape, dehydration avoidance, dehydration tolerance, or its combination.
Osmolyte accumulation is one of the drought tolerance mechanisms which allows cells to control their dehydration and membrane structural integrity during drought stress to give tolerance against drought and cellular dehydration. Osmotic organization in plants shown to drought may match the storage of low-molecular-weight organic solutes. The wheat plant reserves several inorganic and organic solutes in its cytosol to decrease its osmotic potential for the maintenance of cell turgor.
From these hormones is Abscisic acid (ABA) generation can affect drought acclimatization through both dehydration avoidance and dehydration tolerance as protection upon drought stress. Abscisic acid (ABA) is the most important hormone required in controlling tolerance to abiotic stresses such as drought, salinity, cold, heat, and wounding. (ABA) has long been recognized as a major chemical root-to-shoot stress sign inducing inhibition of leaf increase and short-term responses like stomatal closure. ABA is included in the control of systemic responses to abiotic stress before there are any detectable changes in leaf water.
Water content, relative water content, succulence index, water loss rate, raised leaf water recognition, and extra of transpiration rate are some essential characteristics that affect plant water relations. Relative water content (RWC) is a type of plant water status, matching the metabolic project in tissues. And used as the common essential index for dehydration tolerance. A reduction in the RWC in response to drought stress has been remarked in a wide diversity of plants.
Water lack is significant environmental stress that makes the production of reactive oxygen species (ROS). The accession in ROS generation causes molecular responses, which are fundamental agents in managing the level of plant tolerance to stresses, including drought. This research directed to define the expression levels of genes encoding MAPKs (MAPK3 and MAPK6), antioxidant enzymes (CAT, APX, and GPX) and enzymes required in proline biosynthesis (P5CS and P5CR) in Triticum aestivum L. seedlings in rejoinder to short-term drought circumstances. A group of wheat intervarietal replacement lines (ISCSLs) obtained by the replacement of single chromosomes from a drought-sensitive cultivar into the genetic background of a drought-tolerant cultivar was applied. This origin element provided the chromosomal localization of the genetic elements included in the response to the analyzed stress agent (drought). The conclusions showed that the original plant response to drought stress happened notably in variations in the expression of MAPK6 and CAT and both the P5CS and P5CR genes. Our results explained that the replacement of chromosomes had the highest influence on the expression level of all experimented genes, which means that they include genetic factors that have an important purpose in managing tolerance to water shortages in the wheat genome.
MAPKs (MAPK3 and MAPK6) genes: Most ISCSLs noted an accession in the transcript level of MAPK6 after 6 hours. Still, complex expression models were recognized through stress medication for different lines. Rapid MAPK6 initiation already occurred after 1 hour in the drought-tolerant cultivar. A vital raise in MAPK6 transcript levels were recognized for those lines after 3 hours of 10% PEG exposure. However the decrease in MAPK3 expression after 1 hour of PEG medicine. The downregulation of MAPK3 was seen at the following time points (after 3 and 6 hours). Meaningful induction of MAPK3 was recognized in the first hours of stress for the drought-tolerant in some cultivar followed by a rapid reduction in transcript levels. For the remaining forms, no MAPK3 induction was noted in the first hours of plant exposure to drought, and then a significant reduction happened.
(P5CS and P5CR): overexpression of the P5CS gene leads to an extension in proline quantity and improved stress tolerance.
TaMAPK3: TaMAPK3 transcript levels significantly reduced after 6 hours of exposure in most of the examined lines.
the P5CS and P5CR genes: The outcomes of the research showed an important accession in the expression of both genes P5CS and P5CR. Still, raised transcript levels of the P5CS gene were seen directly after 1 hour of stress.
Water scarcity is problematic in Egypt. The presence of water per person rate is already the lowest in the world. This is suggested for further declines. A major challenge is to close the rapidly the high ratio gap between the limited water and the escalating require from various economic sectors. The Nile is the main source of water in Egypt with a share of more than 95%. The storage reservoir of Nasser Lake provides 56 billion m3 hereinafter referred to bcm per annum. The issue of Egypt’s share of Nile waters is under difficult negotiations. In April 2011 Ethiopia has launched the construction of the Grand Ethiopian refuse to model water quality 4 dam GERD. So many crops in Egypt will exposure to drought stress.
Drought is from Abiotic stress which is one of the several significant aspects which bound products’ generation and yield. Crops prove different defense in many ways to survive in the stress. Weather variance is a principal threat to the largest of the crops grown. Drought stress is one of the outcomes of weather modification that harms crop growth and yield. Wheat and rice are with several popular and universally used crops due to their commercial and social values. Nations of the world take these two crops as food. Wheat and rice, have to respond to these stress to make plants alive and healthy so it generates many chemicals, and genes have a defense function to overcome the lack of water and maintain the plant is healthy. Drought stress can also affect plants in terms of protein variations, antioxidant production, osmotic regulation, hormone production, root depth, and expansion, opening and closing of stomata, cuticle thickness, inhibition of photosynthesis, the decline in chlorophyll content, reducing in transpiration, and growth inhibition.
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