Water-use efficiency

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Water-use efficiency (WUE) refers to the ratio of plant biomass to water lost by transpiration, can be defined either at the leaf, at the whole plant or a population/stand/field level:

Research to improve the water-use efficiecy of crop plants has been ongoing from the early 20th century, however with difficulties to actually achieve crops with increased water-use efficiency. [5]

Intrinsic water-use efficiency Wi usually increases during soil drought, due to stomatal closure and a reduction in transpiration, and is therefore often linked to drought tolerance. Observatios from several authors [3] [6] [7] [8] have however suggested that WUE would rather be linked to different drought response strategies, where

Increases in water-use efficiency are commonly cited as a response mechanism of plants to moderate to severe soil water deficits and have been the focus of many programs that seek to increase crop tolerance to drought. [9] However, there is some question as to the benefit of increased water-use efficiency of plants in agricultural systems, as the processes of increased yield production and decreased water loss due to transpiration (that is, the main driver of increases in water-use efficiency) are fundamentally opposed. [10] [11] If there existed a situation where water deficit induced lower transpirational rates without simultaneously decreasing photosynthetic rates and biomass production, then water-use efficiency would be both greatly improved and the desired trait in crop production.

Water-use efficiency is also a much studied trait in Plant ecology, where it has been used already in the early 20th century to study the ecological requirements of Herbaceous plants [12] or forest trees, [13] and is still used today, for example related to a drought-induced limitation of tree growth [14]

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Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way.

<span class="mw-page-title-main">Stoma</span> In plants, a variable pore between paired guard cells

In botany, a stoma, also called a stomate, is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere. The pore is bordered by a pair of specialized parenchyma cells known as guard cells that regulate the size of the stomatal opening.

C<sub>4</sub> carbon fixation Photosynthetic process in some plants

C4 carbon fixation or the Hatch–Slack pathway is one of three known photosynthetic processes of carbon fixation in plants. It owes the names to the 1960s discovery by Marshall Davidson Hatch and Charles Roger Slack.

C<sub>3</sub> carbon fixation Series of interconnected biochemical reactions

C3 carbon fixation is the most common of three metabolic pathways for carbon fixation in photosynthesis, the other two being C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into two molecules of 3-phosphoglycerate through the following reaction:

Nitrogen assimilation is the formation of organic nitrogen compounds like amino acids from inorganic nitrogen compounds present in the environment. Organisms like plants, fungi and certain bacteria that can fix nitrogen gas (N2) depend on the ability to assimilate nitrate or ammonia for their needs. Other organisms, like animals, depend entirely on organic nitrogen from their food.

Moisture stress is a form of abiotic stress that occurs when the moisture of plant tissues is reduced to suboptimal levels. Water stress occurs in response to atmospheric and soil water availability when the transpiration rate exceeds the rate of water uptake by the roots and cells lose turgor pressure. Moisture stress is described by two main metrics, water potential and water content.

<span class="mw-page-title-main">John Monteith</span>

John Lennox Monteith DSc, FRS was a British scientist who pioneered the application of physics to biology. He was an authority in the related fields of water management for agricultural production, soil physics, micrometeorology, transpiration, and the influence of the natural environment on field crops, horticultural crops, forestry, and animal production.

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<span class="mw-page-title-main">Transpiration</span> Process of water moving through a plant parts

Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. It is a passive process that requires no energy expense by the plant. Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients. When water uptake by the roots is less than the water lost to the atmosphere by evaporation, plants close small pores called stomata to decrease water loss, which slows down nutrient uptake and decreases CO2 absorption from the atmosphere limiting metabolic processes, photosynthesis, and growth.

Hydraulic redistribution is a passive mechanism where water is transported from moist to dry soils via subterranean networks. It occurs in vascular plants that commonly have roots in both wet and dry soils, especially plants with both taproots that grow vertically down to the water table, and lateral roots that sit close to the surface. In the late 1980s, there was a movement to understand the full extent of these subterranean networks. Since then it was found that vascular plants are assisted by fungal networks which grow on the root system to promote water redistribution.

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<span class="mw-page-title-main">Chlorophyll fluorescence</span> Light re-emitted by chlorophyll molecules during return from excited to non-excited states

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<span class="mw-page-title-main">Vegetation index</span>

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References

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  2. Meinzer, F. C., Ingamells, J. L., Crisosto, C. (1991). "Carbon Isotope Discrimination correlates with bean yield of diverse coffee seedling populations". HortScience. 26 (11): 1413–1414. doi:10.21273/HORTSCI.26.11.1413.
  3. 1 2 Maximov, N. A. (1929). The plant in relation to water. George Allen & Unwin LTD London.
  4. Tallec, T.; Béziat, P.; Jarosz, N.; Rivalland, V.; Ceschia, E. (2013). "Crops' water use efficiencies in temperate climate: Comparison of stand, ecosystem and agronomical approaches". Agricultural and Forest Meteorology. 168: 69–81. Bibcode:2013AgFM..168...69T. doi:10.1016/j.agrformet.2012.07.008.
  5. Vadez, V.; Kholova, J.; Medina, S.; Kakkera, A.; Anderberg, H. (2014). "Transpiration efficiency: new insights into an old story". Journal of Experimental Botany. 65 (21): 6141–6153. doi:10.1093/jxb/eru040. PMID   24600020.
  6. Ehleringer, J. R. (1993). "Variation in Leaf Carbon-Isotope Discrimination in Encelia farinosa : Implications for Growth Competition and Drought Survival". Oecologia. 95 (3): 340–346. Bibcode:1993Oecol..95..340E. doi:10.1007/BF00320986. ISSN   0029-8549. PMID   28314008.
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  8. Campitelli, B. E., Des Marais, D. L., Juenger, T. E. (February 2016). "Ecological interactions and the fitness effect of water-use efficiency: Competition and drought alter the impact of natural MPK12 alleles in Arabidopsis". Ecology Letters. 19 (4): 424–434. Bibcode:2016EcolL..19..424C. doi:10.1111/ele.12575. ISSN   1461-023X. PMID   26868103.
  9. Condon, A. G., Richards, R. A., Rebetzke, G. J., Farquhar, G. D. (2004). "Breeding for high water-use efficiency". Journal of Experimental Botany. 55 (407): 2447–2460. doi:10.1093/jxb/erh277. ISSN   0022-0957. PMID   15475373.
  10. Bacon, M. Water Use Efficiency in Plant Biology. Oxford: Blackwell Publishing Ltd., 2004. ISBN   1-4051-1434-7. Print.
  11. Blum, A. (2009). "Effective use of water (EUW) and not water-use efficiency (WUE) is the target of crop yield improvement under drought stress". Field Crops Research. 112 (2–3): 119–123. Bibcode:2009FCrRe.112..119B. doi:10.1016/j.fcr.2009.03.009.
  12. Iljin, V. (1916). "Relation of transpiration to assimilation in steppe plants". Journal of Ecology. 4 (2): 65–82. Bibcode:1916JEcol...4...65I. doi:10.2307/2255326. JSTOR   2255326.
  13. Bates, C.G. (1923). "Physiological requirements of Rocky Mountain trees". Journal of Agricultural Research. 24: 97–164.
  14. Linares, J. C.; Camarero, J.J. (2012). "From pattern to process: linking intrinsic water-use efficiency to drought-induced forest decline". Global Change Biology. 18 (3): 1000–1015. Bibcode:2012GCBio..18.1000L. doi:10.1111/j.1365-2486.2011.02566.x.

Further reading