PLANT BIOLOGY WITH RESPECT TO ABIOTIC STRESSES TO ENVIRONMENT [pic] Plant biology with respect to Abiotic stresses to environment Biology assignment:- Given by MAM MARYIM To Group # 4 Group members:- UMMA-E-FARWA (34) ADEEB DANISH (20) MUHAMAD SHEHZAD (33) Content • Abiotic stress • Abiotic stress conditions • Drought • Salinity • High temperature • Chilling • Flooding • Troposphere ozone • Oxidative damage Defense mechanism Plant biology with respect to Abiotic stresses to environment ABIOTIC STRESS:- Abiotic stress is defines as the negative impact of non-living factors on the living organisms in a specific environment Plants being sessile organisms are exposed to external factors that can be stressful in such a way that development, growth and reproduction or the yield of crops becomes compromised. Expanding extensive physiological studies, the last decades has seen a focus on genes and biochemical pathway that determine whether plants are sensitive or tolerant to the many different stress factors: heat, cold & freezing, drought salinity, flooding or oxidizing agents. Abiotic stress conditions The most commonly encountered stress factor are drought flooding or submergence, temperature extremes such as heat stress, cold spells and freezing and soil ion content. With the latter typically in the form of increased salinity. Stress may also occur in the form of natural or man-made excess of heavy metal ion content. In addition, defrost of inorganic and nitrogen, to name only the ions important for plant growth, may restrict plant development.
Furthermore, residual of chemicals used in normal crops may generate stress; because such compounds may reach the underlying aquifer or persist in the soil finally the continued modification of the atmosphere by human activities is of some concern. One example in this respect is the acidification of soils and waterways based on acid rain. Also an increase in the concentration of ozone in the ground, deserves attention, because ozone that is generated from nitric oxides by ultraviolet (UV) light can generate oxidative stress conditions, which leads to the destruction of portions & cells, premature aging and ultimately to deteriorating ecosystems & reduced yield in crops. A final paint to make is the consideration of compound damaging effect by multiple stress factors that act simultaneously. The lack of water in soil with naturally high ion content exemplifies a stress, which is both osmotic &ionic, but other conditions are more sublet. One example may suffice.
High light whit low temperature, conditions that may coincide during early spring at high latitudes; constitute a composite stress because the energy captured by photosynthesis, a physical process, can not be converted into carbon biosynthesis, a biochemical process, which is slower at low temperature. Low temperature restricts biochemical reactions that accomplish biosynthesis and reduce the transport that accomplish biosynthesis and reduce the transport of nutrients and water form the soil to the photosymtheticaly active tissue Abiotic external the factors are exacerbated by biotic interactions exerted by viral, bacterial or fungal pathogens or for example insect predation. Once plants have been weakened by Abiotic challenges typically increase and tend to reduce growth and reproductive success even further. The overlap of Abiotic and biotic stress conditions can be seen in typically increase and tend to reduce plant stress responses: many genes & proteins, whose actions protect plants, are induced in the following will be on this Abiotic on these Abiotic stresses that relate to temperature extremes & the availability of water. Plant life depends on sufficient water supply for at least part of the life cycle.
Water is FIRST essential as a transport medium for inorganic nutrients from the soil into aerial parts of plants. This flux is dependent on the regulated opening & closing of stomata in the leaf epidermis each stomata apparatus consisting of a pair of guard cells. Open stomata lead to the evaporation of water that may also be used to cool the leaves. SECOND water is essential for the initial, physical phase of photosynthesis, the light-driven separation of electrons & protons from water molecules resulting in oxygen production THIRD; open stomata are required for the entry of carbon dioxide into leaves to be converted into fixed carbon compounds. hus, if water is scarce or cannot be transported the rapidly induced closure of stomata will conserve water but will at the same time reduce or abolish carbon fixation, while photosynthetic light reaction continue.
This will lead to an increase of energetically charged molecules, which may be visualized by the picture of a reservoir with a finite capacity. Once full the overflow appears in the form of oxygen radicals that act destructively on the cells and tissue of the leaves. The problem plants face is available in biomass& harvestable yield, fruits or seeds and what to do developmentally or metabolically when water become scarce. The symptoms elicited by Abiotic stress are drought, salinity , high temperature , chilling & freezing stresses , flooding & submergence , troposphere ozone oxidative damage . Drought Drought is difine as ” A PERIOD OF ABNORMALY DRY WEATER SUFFICIENTLY PROLONGED FOR THE LACK OF WATER TO CAUSE SERIOUS HYDROLAGIC IMBALANCE IN HT EAFFECTED AREA” ( GLOSSARY OF METEOROLOGY 1959) DROUGHT EFFECTS ON PLANTS:-How does drought affect plants DRYING SOIL LEAD: DECREASED PLANT WATER UP TAKE PLANT TISSUE DEHYDRATION REDUCED FOOD PRODUCTION (PHOTOSYNTHESISI) & STROAGE SHOOT AND ROOT GROWTH MEMBRANE INTEGRITY SELF DEFENCE ABILITY SURVIVAL [pic] Salinity:- Salt stress is partially related to water availability as well. Increase in cat ions and their salt, NaCl in particular, in the soil generate osmotic potential that can prevent or reduce the influx of water into the root.
The resulting water deficit is similar to drought conditions & addionally compounded by the presence of sodium ions. Plant metabolism depends on the presence & accumulation of potassium to high concentration in cells. K* provides osmotic pressure, associates with proteins and is also used for PH regulation in cellular compartments plant cell establish a membrane potential, a gradient of proteins, [H*] across membranes by the action of several energy-consuming proton transporters The exchange across membranes of k* & H* located on different sides of biological membrane, provide a signaling pathway between cells, and modulating the steepness of the proton gradient. The presence of sodium in high concentrations interferes with this orderly functioning ion membrane traffic. while both Na+ &K+ carry the same charge, the size of the two ions & their charge density are different, so that Na+ cannot function exactly by the action of several K+ transport proteins in membranes, some of which may transport Na+ when present as well.
This generates another problem-keeping one ion outside while taking in an essential ion. This is only incompletely accomplished &different transport proteins must be engaged to partition Na that inevitably arrives in the cytoplasm. Plant evolution provides different solutions. one of these is export through Na+ specific transport protein to the outside medium or soil which simultaneously accumulating K, or other somatically activemetaboilites, sugars, sugar alcohols & amino acids , inside cells to allow for water to enter the cells. A variant of this strategy is to accumulate Ma &Cl2 inside the central vacuole of plant cells [pic] High temperature:-Developing in a daily fashion or as a sudden increase in temperature (heat shock), the condition is stressful because it leads to the more rapid turn over of enzymes and unfading of proteins and it may rapid turn the capacity of cellular machineries that repair protein & membranes in ATP-consuming reactions. High temperature may also lead to water deficit as the plants evaporate more water to cool their above ground tissues.
A common response to elevated temperatures is the biosynthesis of specific heat shock proteins (HSPs) and this increase in expression is regulated transcription-ally by the appearance of new mRNAs. The dramatic uperqulation of the HSPs depends on the presence heat shock factors, transcription factors that induce the subset of genes that are then translated into HSPs. Several types of HSPs exist with a verity of functions in facility repair of damaged of cellular structure during high temperature stress, HSP expression can also be triggered by exposure to different binds of stress such as infection, or the exposure of cells to toxins, heavy metals, UV light , and in plants response to nutrient deficits, hypoxia and water deficit. It appears that the presence & accumulation of damage membranes and proteins provides a signal for the rapid induction of the heat shock response. [pic] Chilling & freezing stresses Chilling stress identifies a temperature that is too low for normal growth to continue buy not low enough for ice crystals to form, which is the case under freezing stress. Low temperature slows biochemical reaction such as enzyme &membrane transport activities.
Membranes become leaky because the lipid bilayr interspersed with proteins that constitutes the membrane system of cells becomes disorganized . hus, a transfer of warm temperature to a lower temperature will lead to freezing stress inevitably leads to ice formation and the growth of ice crystals can then led o disruption of cell membrane system. In fact the loss of ions and proteins from frozen and then thawed plants provides a measure of damage. Several strategies have evolved for protection. A different strategy allows for water to exist cells and form ice crystals in intracellular space. The process is prevalent in trees that grow in high latitudes and depends on chilling tromp during a time in fall long enough to induce the synthesis &accumulation of metabolites &proteins .
he result will be dehydrated, super cooled cytoplasm that can remain viable t temp lower than -35 C* Flooding & submergence :- Both conditions can not be tolerated by most plants for periods of time longer than a few days. These stresses lead to anoxic conditions in the root system. At a critical oxygen pressure, mitochondrial respiration that provides the energy for growth in photosynthically inactive roots will decrease then cease & the cells will die. Adapted species that grow permanently in for example swamps. Typically also, flod-tolerant species exhibit a developmental programmed that leads to elongation growth of theirs stems as water level rise Troposphere ozone:- Combustion of fossil & volcanoes put sulfur, nitric oxide & UV light generates ozone. Ozone have been shown to significantly reduce in no of crops The entry of O3 through stomata is inevitable & leads to an increase of reaction oxygen specus molecules of super oxide hydrogen peroxide & hydroxyl radicals that interfere with normal ROS production used by plants for signaling purpose.
While the partial closure of stomata can reduce this stress, the inevitable compounds the effect of ROS & growth may be compromised. Oxidative damage ROS are generated in all organisms accompanying biochemical reaction, for example in mitochondria, paroxysms or vacuoles. They include the super oxide anion, hydrogen per oxide & the extremely short lived OH. If these compounds are not detoxified, severe damage not only to DAN, RNA & potions but also to lipid membranes can occur. In plants, chloroplast that capture light energy constitute on additional strong source of ROS organism include detoxification mechanism that deal with the appearance of ROS during normal mechanism Super oxide & Hydrogen peroxide or in all organisms-also used as signaling molecules. In plants, they report the status of mitochondrial respiration capacity & chloroplast photosynthetic activity.
Further, ROs are signaling intermediates affecting the opening. & closing of stomata, in reporting pathogen attack, in the recognition of hormones such as Abscises acid (ABA) they r also components of mechanisms that let plants recognize & respond to touch signals & in the perception of light Abiotic stress Defiance Mechanism Defense mechanisms of Abiotic stress is have to look in different pathways or plants First we know, how the cells are damage by the Abiotic stresses on cells and its metabolic, transport or signal and hormonal First we want to bi know that how and what kind of stress is effected on plant then we want to able to control the environments effect on plant. Metabolic:- All the chemical reaction taking place with in the body is called metabolism We know that all chemical reaction take place in metabolism, if the freezing point is disrobed and cooling in environment is produced then the soot able conditions not give them to the react ions and the growing pride of metabolism is taken by long time, which is not soot able to plants and is growth, metabolism take a main role to adjustment of photosynthesis. If photosynthesis is disrobed then the growth rate of plant is slow down and food is not properly transport to all parts of the plant. We control the environment effect on plant by change the genes or plant and to control the emission of toxic gases.
Transport of signal:-Weather is very affected on the plants and most comment and most important part of the plant is to damage by the environment is a transport of signals through out the plant body, if the weather is too cooled then the transport of signal is not properly by the plant because at freezing point the water is freeze in the plant and plant not doing work which is necessary for plant growth and in flowering and period of flowering is slow down and if flower is full flowered in a 10 days, and by acting of environment the flower is flowering at may be a 15 to 20 days. We control by the increased export of proteins and different compounds which is essential for proper growth (carbons compound and nitrogen, hydrogen, calcium and magnesium compounds) Hormonal signaling in plant:-Hormonal is a response of plant against the unhealthy activity o other plants and other living organism plant not move one place to other place by weathering conditions so it may be a destroyed and fully damage by the weather , salinity , heating, cooling and in oxidative damage It is very damage and most important of disorder of plant by environment We may speedily the hormonal signaling in the plant by change the genes and turnover of enzymes and make sure the interaction of transport pathways in the plantsEnvironment effect on shoot:- If the environment is not favorable for the plant it is most dangerous for plant and specially is shoot/leaf because the leaf is most important part in the plants because leaf is making a food for all plants and distributive is in all part of the plant leaf make a food by photosynthesis process in a photosynthesis process the sun light is necessary to plant and its proper growth of plant all the environmental factor is take a main role to reduced the photosynthesis and its growth. If photosynthesis is not doing then is very damage to plant and its mountainous of the plant and food making and collecting of water and important minerals which is present in the earth is collected by the root, the ABA (abscises acid play a role in closing of stomata) and acid rain is effected or minerals and destroyed the leaf and in appearance and minerals solubility All stresses lead to reduced photosynthesis, altered stomata conductance (the aperture of stomata), and changes in biochemical pathways. The latter show stress specificity. The hormone ABA occupies a central role in altering growth as an antagonist of processes initiated by growth-promoting axons. Meristems:- Protective measures to assure continued cell divisions in the root and shoot apical moistens (a tissue that produces new cells) include molecular and metabolic adjustment.
The term ‘ stem cells’ that is used in analogy to animal stem cells is misleading because all plant cells can theoretically (through hormone treatments) be converted into stem cells. Flowering:- Abiotic stresses delay flowering. They may act on the development or maturation of the flower organs or on fertilization per se, on embryo formation and growth, or on the maturation of fruits and seeds. The integration of stress sensing in different cells or tissues, reporting the altered physiological status through signals is crucial on the whole plant level. Transported in the xylem/phloem continuum of the veins and vascular tissues are signaling molecules, such as peptides, hormones and ions, but several signaling molecules are volatile, such as ethylene and methyljasmonate.
Changes in the water flux rate and changes in the osmotic potential of the cell wall space, i. . outside the plasma membrane that surrounds the cytoplasm, are perceived and signaled to the nucleus where altered transcription of genesmay be initiated. The example chosen is largely based on water deficit conditions, an osmotic stress that accompanies many other stress conditions, in particular high and low temperature stresses and high salinity. However, all stresses include a sensing and signaling compound that must eventually be decoded by cells such that a stress-specific defense or at least damage control can be initiated.
OUR SUGESSION TO REDUCE TO ABIOTIC STRESSESIncreased salinity in irrigated agriculture, as well as projected changes in precipitation and increases in severe weather conditions require that we learn to understand how plants may be protected against abiotic stresses . the understand that has been achieved is being applied in a number of national and international dreading programs and biotechnological approaches are progressing. It well is impossible to generate crops that grow productively in true deserts or full-strengths sea water. However, appropriately Dred or engineered crops with deeper root system, or