Ecophysiology

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Ecophysiology (from Greek οἶκος, oikos, "house(hold)"; φύσις, physis, "nature, origin"; and -λογία, -logia) or environmental physiology is a biological discipline which studies the adaptation of organism's physiology to environmental conditions. It is closely related to comparative physiology and evolutionary physiology.

Contents 1 Ecophysiology of plants 1.1 Temperature 1.2 Wind 1.3 Water 1.4 CO2 concentration 2 Ecophysiology of animals: Important Scientists 3 Further reading 4 See also 5 References

[edit] Ecophysiology of plants

This section requires expansion.

Plant ecophysiology is an experimental science that seeks to describe the physiological mechanisms underlying ecological observations. In other words, ecophysiologists, or physiological ecologists, address ecological questions about the controls over the growth, reproduction, survival, abundance, and geographical distribution of plants, as these processes are affected by interactions between plants with their physical, chemical, and biotic environment. These ecophysiological patterns and mechanisms can help us understand the functional significance of specific plant traits and their evolutionary heritage. The questions addressed by ecophysiologists are derived from a higher level of integration, i.e. from “ecology” in its broadest sense, including questions originating from agriculture, horticulture, forestry, and environmental sciences. However, ecophysiological explanations often require mechanistic understanding at a lower level of integration (physiology, biochemistry, biophysics, molecular biology). It is therefore essential for an ecophysiologist to have an appreciation of both ecological questions and biophysical, biochemical, and molecular methods and processes. In addition, many societal issues, often pertaining to agriculture, environmental change or nature conservation, benefit from an ecophysiological perspective. A modern ecophysiologist thus requires a good understanding of both the molecular aspects of plant processes and the functioning of the intact plant in its environmental context.

In many cases, animals are able to escape unfavourable and changing environmental factors such as heat, cold, drought or floods, while plants are unable to move away and therefore must endure the adverse conditions or perish (animals go places, plants grow places). Plants are therefore phenotypically plastic and have an impressive array of genes which aid in adapting to changing conditions. It is hypothesized that this large number of genes can be partly explained by plant species' need to adapt to a wider range of conditions.

[edit] Temperature

In response to extremes of temperature plants can produce various proteins that protect them from the damaging effects of ice formation and falling rates of enzyme catalysis at low temperatures and enzyme denaturation and increased photorespiration at high temperatures. As temperatures fall production of antifreeze proteins and dehydrins rise. As temperatures rise production of heat shock proteins fall. Plants can also adapt their morphology (change their shape) to adapt to longer term temperature changes. For example to protect against frost cell walls can be made thicker and stronger (through more lignification) so that water freezes in between cells (in the apoplast) and not in the cells (in the cytoplasm). Cell membranes are also affected by changes in temperature and can cause the membrane to lose its fluid properties and become a gel in cold conditions or become leaky in hot conditions. This can affect the movement of compounds across the membrane. To prevent these changes plants can change the composition of their membranes. In cold conditions more unsaturated fatty acids are placed in the membrane and in hot conditions more saturated fatty acids are inserted.

See also: Plant adaptations to wildfires

[edit] Wind

Strong winds can affect plants by uprooting them or damaging their leaves. Whereas responses to temperature changes are often acclimatory there is not enough time for this to occur to wind and so plants must be permanently adapted to survive potentially damaging winds. Examples of adaptations to prevent damage include having leaves with thick cuticles, and large root systems. One reason that deciduous trees shed their leaves in the autumn is to reduce their surface area and make it less likely that they will be blown over.

[edit] Water

Too much or too little water can damage plants. If there is too little water then tissues will dehydrate and the plant may die. If the soil becomes waterlogged then the soil will become anoxic (low in oxygen) which could kill the roots. If tissues become dehydrated they lose turgor which in turn causes abscisic acid, a plant hormone, to be produced. This travels throughout the plant and has a number of effects. It increases the number of closed stomata, reducing water loss and also stimulates growth of the roots in an attempt to increase the supply of water. Some plants, for example maize and rice are able to produce aerenchyma in their roots if the soil they are growing in becomes waterlogged. These are hollow vessels that allow the diffusion on oxygen into the roots.

See also: Osmoregulation in plants

[edit] CO₂ concentration

The concentration of CO₂ in the atmosphere is rising due to deforestation and the combustion of fossil fuels. Plants use CO₂ as a substrate in photosynthesis and it was previously thought that as the concentration of CO₂ rises that the efficiency of photosyntheis would increase leading to increased growth. Studies using Free-air concentration enrichment have however shown that crop yields are only increased by up to 8%.^[1] Studies of specimens in herbariums have shown that the number of stomata on leaves has decreased over the last 150 years as the concentration of CO₂ has risen.^[2] Stomata let CO₂ diffuse into the leaf but let water leave at the same time. Plants are acclimating to increased CO₂ concentrations by having fewer stomata because they allow the same amount of CO₂ into the leaf as before yet they use less water.^[3] It has also been found that the nitrogen level falls when plants are grown at elevated CO₂ due to plants needing less rubisco to fix the same amount of CO₂. The levels of other micronutrients also fall which may have consequences for human nutrition in the future.^[4]

[edit] Ecophysiology of animals: Important Scientists

George A. Bartholomew (1919-2006) was a founder of animal physiological ecology. He served on the faculty at UCLA from 1947 to 1989, and almost 1,200 individuals can trace their academic lineages to him ^[5]. Knut Schmidt-Nielsen (1915-2007) was also an important contributor to this specific scientific field as well as comparative physiology.

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[edit] Further reading

• Bennett, A. F.; C. Lowe (2005). "The academic genealogy of George A. Bartholomew". Integrative and Comparative Biology 45 (2): 231–233. doi:10.1093/icb/45.2.231. ISSN 1540-7063. 
• Bradshaw, Sidney Donald (2003). Vertebrate ecophysiology: an introduction to its principles and applications. Cambridge, U.K.: Cambridge University Press. p. xi + 287 pp. ISBN 0-521-81797-8. 
• Calow, P. (1987). Evolutionary physiological ecology. Cambridge: Cambridge University Press. p. 239 pp. ISBN 0-521-32058-5. 
• Lambers, H. (1998). Plant physiological ecology. New York: Springer-Verlag. ISBN 0-387-98326-0. 
• Larcher, W. (2001). Physiological plant ecology (4th ed.). Springer. ISBN 3-540-43516-6. 
• McNab, B. K. (2002). The physiological ecology of vertebrates: a view from energetics. Ithaca and London: Comstock Publishing Associates. xxvii + 576 pp. ISBN 0-8014-3913-2. 
• Sibly, R. M.; and P. Calow (1986). Physiological ecology of animals: an evolutionary approach. Oxford: Blackwell Scientific Publications. p. 179 pp. ISBN 0-632-01494-6. 
• Spicer, J. I., and K. J. Gaston. 1999. Physiological diversity and its ecological implications. Blackwell Science, Oxford, U.K. x + 241 pp.
• Tracy, C. R.; and J. S. Turner (1982). "What is physiological ecology?". Bulletin of the Ecological Society of America (Bull. Ecol. Soc. Am.) 63: 340–347. ISSN 0012-9623. . Definitions and Opinions by: G. A. Bartholomew, A. F. Bennett, W. D. Billings, B. F. Chabot, D. M. Gates, B. Heinrich, R. B. Huey, D. H. Janzen, J. R. King, P. A. McClure, B. K. McNab, P. C. Miller, P. S. Nobel, B. R. Strain.

[edit] See also

• Comparative physiology
• Evolutionary physiology
• Ecology
• Phylogenetic comparative methods
• Plant physiology
• Raymond B. Huey
• Theodore Garland, Jr.

[edit] References

1. ^ Ainsworth, Elizabeth; Stephen Long (February 2005). "What Have We Learned from 15 Years of Free-Air CO2 Enrichment (FACE)?". New Phythologist 165 (2): 351–371. doi:10.1111/j.1469-8137.2004.01224.x. http://www.jstor.org/stable/1514718?seq=5. Retrieved on 07/05/2009. 
2. ^ http://www.jstor.org/stable/2558897?cookieSet=1 F. Woodward and C. Kelly New Phytologist 1995 Vol 131 pages 311-327 The influence of CO2 concentration on stomatal density
3. ^ http://arjournals.annualreviews.org/doi/full/10.1146/annurev.arplant.48.1.609?amp;searchHistoryKey=%24{searchHistoryKey}Annual Review of Plant Physiology and Plant Molecular Biology Vol. 48: 609-639 June 1997 (doi:10.1146/annurev.arplant.48.1.609) MORE EFFICIENT PLANTS: A Consequence of Rising Atmospheric CO2?
4. ^ Irakli Loladze Trends in Ecology & Evolution Volume 17, Issue 10, 1 October 2002, Pages 457-461 Rising atmospheric CO2 and human nutrition: toward globally imbalanced plant stoichiometry? doi:10.1016/S0169-5347(02)02587-9
5. ^ BartGen Tree