Lecture18 - MCDB312 Plant Physiology Mar. 22, 2011 Plant...

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Plant Response to Stress environmental stress may be caused by a number of different factors 1) temperature - high or low (takes just a few minutes) 2) water - flooding or drought (takes days/weeks) 3) salinity - high 4) light - high, UV-B 5) pollutants - heavy metals, smog, ozone 6) biotic - pathogens, competition stress reduces productivity Limits distribution of plant species. extreme stress may kill plant or eliminate reproduction It was estimated that the yield of field-grown crops in USA is only 20% of the genetic potential yield MCDB312 Plant Physiology Mar. 22, 2011 Plant Response to Stresses
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Important concepts of stress physiology Important concepts of stress physiology A. Stress – external factor that exerts a disadvantageous influence on the plant; usually measured in plant’s survival ability, crop yield, growth, or primary assimilation processes B. Stress tolerance -plant fitness to cope with an unfavorable environment C. Acclimated (Hardened)- increased stress tolerance as a result of prior exposure to a stress condition ( non-heritable physiological modification) D. Adaptation - refers to a genetically determined level of resistance acquired by a process of selection over many generations E. Cross Resistance- tolerance to a stress based on exposure to a previous stress event of a different nature
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Adaptation and acclimation to environmental stresses result from integrated events occurring at all levels of organizations: A. Anatomical/morphological changes B. Changes in cell cycle/cell division, endomembrane systems, and vacuolization, and cell wall architecture C. Altering metabolic activities such as producing osmoregulatory compounds D. Changes in gene expression
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Different Plant Strategies I) Escape never experiences stress (e.g. Annual plant) completes life cycle in non-stressful environmental conditions e.g. ephemeral plant in desert (life cycle after rain) Desert ephemerals are plants which are adapted to take advantage of the short wet periods in arid climates.
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Avoidance oderates the stress; reduces impact of ress when present xamples desert plant may avoid water stress by extending roots into water table (e.g. mesquite, 200 ft in depth) 2) 2) plant may drop leaves when drought occurs, then produce leaves after rain (drought deciduous, e.g. ocotillo) 3) morphological adaptations e.g. cacti - have succulent photosynthetic stems & leaves reduced to thorns to avoid water stress
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) Tolerance ant actually endures the adverse environment amples resurrection plants - lose almost all of their water, but survive when re-watered creosote - tolerates extreme drought conditions ( < -4 MPa) Ψ
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rought is one of the most serious world-wide problems for agriculture. 0%
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This note was uploaded on 11/30/2011 for the course BIOLOGY 321 taught by Professor Min during the Winter '11 term at University of Michigan.

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Lecture18 - MCDB312 Plant Physiology Mar. 22, 2011 Plant...

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