PLANT PHYSIOLOGY
Az Agrármérnöki MSc szak tananyagfejlesztése TÁMOP-4.1.2-08/1/A-2009-0010
Plant stress physiology
Overview
1. The basic concepts of plant stress, acclimation, and adaptation
2. The light-dependent inhibition of photosynthesis
3. Temperature stress
4. Imbalances in soil minerals
5. Developmental and physiological mechanisms
against environmental stress
1. The basic concepts of plant stress, acclimation, and adaptation
1.1. The maintenance of a steady-state phase of plant's life in a meta-stable condition called homeostasis
1.2. Environmental modulation of homeostasis defined as biological stress
1.3. Plant stress implies some adverse effect on the physiology of a plant
1.4. Plants respond to stress in several dfferent ways
The effect of environmental stress on plant survival
Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 225.
1. The basic concepts of plant stress, acclimation, and adaptation
1.5. Many plants have the capacity to tolerate a particular stress and hence are considered to be stress resistant 1.6. Stress resistance requires that the organism exhibit the capacity to adjust or to acclimate to the stress
1.7. Adaptations to environmental conditions involve genetic changes
1.8. Individual plants may also show phenotypic plasticity that allows them to respond to environmental fluctuations 1.9. Imbalances of abiotic factors have primary and
secondary effects on plants
A schematic relationship between stress and acclimation
Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 242.
2. The light-dependent inhibition of photosynthesis
2.1. Above the light saturation point for photosynthesis, light causes photoinhibition by disrupting the
photosystems
2.2. Photoinhibition by high light leads to the production of destructive forms of oxygen
2.3. Excess electrons produced under high light generate excess reactive oxygen species (ROS), damaging
proteins, lipids, RNA, and DNA
A schematic representation of the response of photosynthesis to increasing irradiance
Source: Hopkins W.G., Hüner N.P.A. (2009): Introduction to Plant Physiology. p. 226.
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 252.
At higher irradiances there is a large difference between the fraction of light used by photosynthesis versus that which must be dissipated (excess light
energy)
Source: Taiz L., Zeiger E. (2002): Plant Physiology. p. 182.
Changes in the light–response curves of photosynthesis caused by photoinhibition
3. Temperature stress
3.1. High temperatures are most damaging to growing, hydrated tissues
3.2. Temperature stress can result in damaged membranes and enzymes
3.3. Temperature stress can inhibit photosynthesis
3.4. Freezing temperatures cause ice crystal formation and dehydration
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 762.
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 763.
Effect of frosted orache (Atriplex sabulosa) and Arizona honeysweet (Tidestromia oblongifolia) to heat stress: membrane permeability
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 763.
Effect of frosted orache (Atriplex sabulosa) and Arizona honeysweet (Tidestromia oblongifolia) to heat stress: photosynthesis, respiration
4. Imbalances in soil minerals
4.1. Soil mineral content can result in plant stress in various ways
4.2. Soil salinity occurs naturally and as the result of improper water management practices
4.3. High cytosolic Na+ and Cl- denature proteins and destabilize membranes
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 761.
The growth of different species subjected to salinity relative to that of unsalinized controls
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 774.
The role of primary and secondary active membrane transports during an extreme environmental condition
5. Developmental and physiological mechanisms against environmental stress
5.1. Plants can modifiy their life cycles to avoid abiotic stress
5.2. Phenotypic changes in leaf structure and behavior are important stress responses
5.3. Plants can regulate stomatal aperture in response to dehydration stress
5.4. Plants adjust osmotically to drying soil by accumulating solutes
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 766.
Altered leaf shape can occur in response to environmental changes:
leaf from outside (left) and inside (right) of a tree canopy
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 768.
Leaf movement in soybean in response to osmotic stress
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 770.
Osmotic adjustment is the capacity of plant cells to accumulate solutes and use them to lower water potential during osmotic stress
5. Developmental and physiological mechanisms against environmental stress
5.5. Phytochelatins chelate certain ions, reducing their reactiviy and toxicity
5.6. Many plants have the capacity to acclimate to cold temperature
5.7. Plants survive freezing temperatures by limiting ice formation
5.8. Cold-resistant plants tend to have membranes with more unsaturated fatty acids
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 773.
Molecular structure of the metal chelate phytochelatin
Temperature of parenchyma cells in cucumber (Cucumis sativus) fruit during freezing
Source: Taiz L., Zeiger E. (2010): Plant Physiology. Web material, http://5e.plantphys.net
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 775.
5. Developmental and physiological mechanisms against environmental stress
5.9. A large variety of heat schock proteins can be induced by different environmental conditions
5.10. During mild or short-term water shortage, photosynthesis is strongly inhibited, but phloem
translocation is unaffected until the shortage becomes severe
Source: Taiz L., Zeiger E. (2010): Plant Physiology. p. 778.
Effects of water stress on photosynthesis and translocation of sunflower (Helianthus annuus)
