Outline a Abiotic Stress b Molecular Biological aspect

Outline a. Abiotic Stress b. Molecular Biological aspect of Abiotic Stress c. Physiological aspect of Abiotic Stress d. Agronomic aspect of Abiotic stress e. Conventional Breeding f. In vitro breeding g. Transgenic breeding h. Molecular Breeding

ABIOTIC PLANT STRESS 2

PLANT STRESS 1. Any external factors that negatively influence plant growth, productivity, reproductive capacity or survival 2. Any change in environmental conditions that produce a less than ideal plant response 3. Any change in environmental conditions that Have a potentially adverse effect on a plant’s survival, growth, and reproduction 4. Any change in environmental conditions that have a devastating impact on crop yields in agriculture 3

Abiotic Stresses Environmental, non-biological Stress Water (high/low) Oxygen Nutrients Temperature (high/low) Salt Radiation Pollutants Excess or deficit http: //www. geo. arizona. edu/gallery/US/tuc_2. html

WATER STRESS • Drought leading to water stress is a major problem in reducing agricultural productivity especially in tropical, semi-arid and arid regions of the world • Water deficits result from low and erratic rainfall, pooor soil water storage and when the rate of water transpiration exceeds water uptake • The cellular water deficits resulr in the concentration of solutes, loss of turgor, change in cell volume, disruption of water potential gradients, change in membrane integraty, denaturation of proteins and several physiological and molecular components • The stress effects depend on the degree and duration of stress, developmental stage of plant, genotypic capacity of species and environmental interaction

FLOODING STRESS • Soil water logging and submergence (collectively termed flooding) influence species composition and productivity in numerous plant communities world wide • Hydrological patterns can determine the vegetation in natural and man-made wetlands, since this is dependent on ecophysiological responses of species to flooding • In Rice farming, flooding regimes are manipulated or are accommodated by genotype’s selection to secure much of the world production of this staple crop • For most crops, excess water is a major constraint to productivity , adversely affecting grain yields • A major constraint from excess water, at least for poorly adapted species is an inadequate supply of oxygen to submerged tisuue

SALT STRESS • Salinity affects agricultural production and its quality in arid and semiarid regions, where rainfall is limited and is not sufficient to transport salts from the plant root zone • Salinity arises due to increase in the concentration of salts like sodium chloride, sodium carbonate, sodium sulphate or salts of magnesium. The dominant salts are either sodium chloride or sodium sulphate or mixtures of them. • The effect of salinity of plant is complex and its adverse effects include ion toxicity, water deficits and nutrient imbalance and deficiencies

SALT STRESS • The saline soil management includes crop selection, crop stand establishment, leaching requirement, drainage and other reclamation practices • Salt tolerance mechanisms are highly complex since the effect are diverse and are controlled by a number of genes or group of genes • Salt tolerance is generally associated with regulated ion uptake compartmentation of ion and gene product including stress proteins • Ion homeostasis is important component of salt tolerance

HIGH TEMPERATURE STRESS • The global mean temperature increased by 0. 6 C between 1990 to 2000 and is projected to increase by another 1. 4 to over 5 C by 2100 • Plants suffer the ups and downs of temperature of their environment and estimate decrease in crop yield range up to a 17% for each degree Celcius increase • The effect of temperature to plants is strongly dependent on ambient air temperature and radiant energy fluxes • All organisms when exposed to rapid increase in external temperature generally 5 to 10 C above normal temperature for a period of few minutes to a few hours exhibit synthesis of an elite set of protein called heat shock proteins (HSP) • HSP proteins are involved in cellular repair, rescue, clean up and/or protection during stress and from its recovery

PHOTOOXIDATIVE STRESS • Light stress is one of the important environmental constraint that limit the efficiency of photosynthesis and plant productivity • Plant when absorbed light energy exceeds the capacity for light energy utilization in plant photosynthesis, the photosynthetic efficiency will be reduced due to the formation of AOS which can damage photosynthetic apparratus and chloroplast components • Plants are believed to develop certain strategies of tolerance mechanisms

NUTRIENT STRESS • Plant growth and development and yield are contributed by 17 essential elements • Nutrient stress and associated metabolic disorders decrease plant growth and yield • Plant growth and metabolism is also affected by heavy metal stress • Developing nutrient stress tolerance may help to extend agriculture to unexplored harsh and nutrient poor soil

Nutrient Deficiency A lack of one or more essential elements needed by plants for optimum growth lead to plant stress. Macroelements Element Microelements Symbol Element Symbol Nitrogen N Chlorine Cl Phosphorous P Iron Fe Potassium K Boron B Manganese Mn Calcium Ca Zinc Zn Magnesium Mg Copper Cu Molybdenum Mb Nickel Ni Sulfur S

HEAVY METAL STRESS 1. Supra optimal concentration of heavy metals such as Cd, Pb, Hg, Cu, Zn and Ni affect growth, development and yield of plants, though Cu, ZN, and Ni are essential micronutrients at low concentration 2. Heavy metals affect several physiological and metabolic processes 3. Plants have developed several mechanisms that control and responds to the uptake and accumulation of both essential and non essential heavy metals

HEAVY METAL STRESS 1. Tolerance mechanisms vary from species to species and their genetic background 2. The important heavy metal tolerance mechanism include metal binding to wall, reduced transport across cell membrane, active efflux of metals, compartementation , chelation and sequestration of heavy metal by particular ligands such as phytochelatins and metallothioneins

Stress is the driving force behind the process of adaptation and evolution 15

Plant Stress Response Preferable! Stresses cause responses in metabolism and development Injuries occur in susceptible plants, can lead to impeding flowering, death

Plant Stress Responses 17