《植物逆境生理.ppt》由会员分享，可在线阅读，更多相关《植物逆境生理.ppt（52页珍藏版）》请在三一文库上搜索。
1、Plant Environmental Stress Physiology,Fan Hai,What is Plant Stress,Plant stress is the adverse reaction of plants to environmental conditions that are unfavorable to growth, such as lack of sufficient nutrients, inadequate watering, flooding, high or low temp., disease or insect infestation.,Stress,
2、Biotic stress,pathogen microbes insects allelopathy,Abiotic stress,water,Temp.,light,drought flooding,High temp. Low temp.：chilling , freezing,photoinhibition UV damage,chemicals,Salinity Alkalinity Insecticide, herbicide Air pollution,Plant stresses greatly diminish crop yields,Biotic and abiotic s
3、tresses can reduce average productivity by 65%87%,Table: Average yields and record yields of 8 major crops,What is Strain,Strain is the biologic changes of plants under the influence of plant stress. Strain can be elastic or plastic depending on the degree and lasting time of stress. Elastic strain:
4、 recoverable, temporary Plastic strain: non-recoverable, permanent,I. Damages of stress to the plant,stress,Primary damage,Secondary damage,Primary direct- damage,Primary indirect damage,（injury to the plasma lemma）,（dysfunction of metabolism）,（e.g. water stress in salt stress）,I. Damages of stress
5、to the plant,Bio-membrane Change in membrane phase Change in membrane constituents Change in membrane permeability,Photosynthesis Decrease in Pn Decrease in stomatal aperture Decrease in Fv/Fm Decrease in quantum yield,Respiration Change in respiration path E.g. Turn EMP-TCA pathway to PPP under dro
6、ugh, pathogen and wounding stress. Decrease in respiration rate under freezing, hot and flooding stress Increase in respiration rate under wounding and pathogen stress Under chilling and drought stress, the respiration rate increase first and then decrease,Changes of phytohormone level Decrease in I
7、AA, CTK, GB Significant increase in ABA Increase of Eth under flooding,Oxidative stress induced by reactive oxygen species (ROS) Reactive oxygen species are highly reactive molecules containing atom oxygen. It mainly include 4 species: O2.-, OH, H2O2 and 1O2 ROS can attack chloroplast, mitochondria
8、and other organelles. ROS can also attack membrane by causing membrane peroxidation.,II. Plants Respond to Stress in Several Different Ways,Environmental Stress,Stress response,Tolerance,Avoidance,Escape,Stress Escape: Plant avoid the injury of stress by regulating its life cycle to avoid meeting wi
9、th stress. E.g. some short-lived, desert ephemeral plants germinate, grow and flower very quickly following seasonal rains. They thus complete their life cycle during a period of adequate moisture and form dormant seeds before the onset of dry season.,Stress avoidance: plants avoid the injury of str
10、ess by building up a barrier to prevent stress factors entering the plant. E.g. alfafa survive dry habitats by sending down deep root systems that penetrate the water table. Salt-secretion halophytes secrete the salts out from the leaf thus reduce salt content in the leaf.,Stress tolerance: Plants a
11、dapt to the stress environment by regulating their metabolism and repair the damage caused by stress. E.g. Highly salt tolerant halophytes such as suaeda salsa survive salty habitat by many strategies such as high ROS scavenging ability, high osmotic adjustment ability, high ion compartmentalization
12、 ability and so on.,Adaptation vs. Acclimation,Adaptation and acclimation both are means of achieving tolerance to a particular stress. Adaptation refers to heritable modifications in structure or function that increase the fitness of the organism in the stressful environment. e.g. CAM plants to des
13、ert. Acclimation refers to nonheritable physiological modifications that occur over the life of an individual. These modifications are induced by gradual exposure to the stress. E.g. slow drying increases the drought resistance of plants. The process of acclimation is known as hardening.,How plants
14、get adapted to stress?,Osmotic adjustment Stress proteins Scavenge ROS Synthesis ABA Cross-adaptation,1. Osmotic adjustment,Water deficit can be induced by many environmental conditions Drought Salinity Cold temperature Osmotic adjustment is a biochemical mechanism that helps plants to acclimate to
15、drought, salinity etc. Osmotic adjustment is an active process of increasing the number of solute particles in the plant that resulting in a reduced osmotic and water potential and enables the plant to absorb water in drought and saline habitat.,Compatible solutes share specific biochemical attribut
16、es Highly soluble Low molecular weight Do not interfere with cellular metabolism Neutrally charged at physiological pH Mainly distributed in the cytosol, not vacuoles,Most compatible osmolytes are AA, QACS or poly alcohols,Some compatible solutes may serve other protective functions in addition to o
17、smotic adjustment Minimizing the perturbing impact of ions Protecting enzymes (pro,glycine betain) Scavenging ROS (pro, mannitol, sorbitol),2. Stress proteins,HSPs(Heat shock proteins) CRP(Cold regulated proteins) anaerobic peptides LEAs(late embryogenensis abundant proteins) Osmotin Pathogenesis-re
18、lated proteins,3. Scavenging ROS,Enzymes： SOD（superocide dismutase) CAT (Catalase) POD (Ascorbic acid Peroxidase) Oxidants： carotene Vit E DMSO Vit C GSH,4. ABA-stress hormone,Keep membrane stability Promote synthesis of osmolytes Reduce water loss Increase water conductivity,Cross-adaptation,Cross-
19、adaptation mains exposure of an organism to a given adverse environment modifies its response to other adverse factors. E.g. exposure of plants to various stresses such as chilling temperature, heat, drought, and radiation conferred resistance to other stresses.,Causes of cross-adaptation,ABA is ind
20、uced under many stresses. Stress induces many stress proteins, and stress protein functions in many stresses. Osmolytes are induced by many stresses Membrane change. ROS scavenging system is activated.,III. Freezing Stress,Freezing injury is caused by low temp.0 Supercooling,Intercellular crystalliz
21、ation Ice crystals form between cells. Intracellular crystallization Ice crystals form in the cell.,Freezing Injury: Direct injury: injury by crystal formation Indirect injury: dehydration, suffocating Injury mechanism: Membrane injury Mechanical injury -SH theory,Strategies of increasing plant free
22、zing tolerance: Lower water content Reduce photosynthesis Increase ABA/GB Dormant Increase osmolytes All the above can be attained by cold hardening,IV. Chilling Stress,Caused by low temp. 0 Damage Membrane phase Root water absorption ability Dysfunction of respiration, accumulation of ethanol. Dysf
23、unction of metabolism,Mechanism of chilling injury: membrane phase transition: LC phaseGel phase,Liquid crystalline phase. The typical phase in biological membranes. The lipids have both lateral and kinetic motion and contain membrane proteins,Gel phase. The membrane lipids have less kinetic energy
24、and lateral motion than in the liquid crystalline phase resulting in a regular spacing between the acyl tails,Strategies of improving plant chilling tolerance: Increase IUFA (index of unsaturated fatty acid), which leads to the decrease of phase transition temp. Synthesis of chilling-tolerant isoenz
25、ymes.,V. Drought Stress,Drought stress includes: Soil drought, no rain for long time and no-available water in the soil. Air drought, RHwater absorption. If longer, soil drought occurs.,Symptoms in plant facing to drought： stun, red color in base，small cell and leaf area，leaf yellowish and abscissio
26、n. Young leaves or/and reproductive organs wilt to death.,Mechanisms of drought stress: Membrane damage Metabolic disorder: Water redistribution in the organ Photosynthesis reduction Respiration rises then drops Decrease in nuclear acids and proteins Accumulation of proline ABA accumulation Mechanic
27、al damage Formation of S-S,Strategies of increasing drought resistance Stress avoidance: absorption of water, declination of transpiration and increase in water transportation. Developed root system and higher ratio of root to shoot Thick leaf , smaller leaf area and thick cuticle Accumulation of AB
28、A and stomatal control Stress tolerance Osmotic adjustment Change of photosynthetic pathway,VI. Flood stress,Injury of flood:(Secondary injury) Anaerobic stress: anaerobic respiration ethanol Ethylene evolving,(1) Injury in morphology and anatomy by O2 deficiency：growth，leaf yellowish (nutrition def
29、iciency），epinasty（Eth), stem hollow (tissue degradation caused by Eth ）. (2) Injury in metabolism by O2 deficiency，photosynthesis stomatal block, inhibition of CO2 entrance . Anaerobic respiration，toxicants: alcohol ，acetaldehyde，NH3，lactate , H2S,(3) Nutrition disorder： absorption ，soil N、P、K、Ca lo
30、ss but H2S、Fe、Mn ，microelements poison。 (4) Changes in plant hormones：IAA and CTK 。ACC synthesis in root and release of Eth in shoot.,Mechanism of flood resistance Well-developed aerenchyma More lenticles More adventitiouse root,白骨壤的气生根,红海榄的支柱根(prop roots)，支柱根具有支撑和呼吸的功能，根中的通气组织相当发达，下陷的气孔、皮孔等都有助于体内外气
31、体交换。,VII. Salt stress,Salt stress includes 3 aspects: Ionic stress: Na+ Cl- Drought stress Metabolic disorder: Ch1 and Rubisco，protein degradation,Pro，NH4+ poison,Mechanism of salt resistance: Salt avoidance: Salt secretion Salt dilution Salt reclusion Salt tolerance: Osmotic adjustment ROS scavengi
32、ng,VIII. Pathogen stress,Pathogen stress to plants: Water balance disorder Respiration (PPP) Photosynthesis Abnormal growth,Plant resistance to pathogen stress: Local resistance system: supersensitlve reaction phytoalexin chintinase pathogenesis related protein accumulation of lignin and callus oxidative burst System acquired resistance Send the signal to other parts of plant, and thus the plant is immune or alerted to the stress.,