This article is about water use in plant physiology. For water use efficiency by humans, see Water efficiency.
Water-use efficiency (WUE) refers to the ratioofplantbiomass to water lost by transpiration, can be defined either at the leaf, at the whole plant or a population/stand/field level:
plant level : water-use efficiency of productivity (also called integrated water-use efficiency or transpiration efficiency,TE), which is typically defined as the ratio of dry biomass produced to the rate of transpiration.[3]
field level : based on measurements of CO2 and water fluxes over a field of a crop or a forest, using the eddy covariance technique[4]
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
low WUE plants could either correspond to a drought tolerance strategy, for example by anatomical adaptations reducing vulnerability to xylem cavitation, or to a drought avoidance/water spender strategy through a wide soil exploration by roots or a drought escape strategy due to early flowering
whereas high WUE plants could correspond to a drought avoidance/water saving strategy, through drought-sensitive, early closing stomata.
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]orforest trees,[13] and is still used today, for example related to a drought-induced limitation of tree growth[14]
^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.
^ abMaximov, N. A. (1929). The plant in relation to water. George Allen & Unwin LTD London.
^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. doi:10.1016/j.agrformet.2012.07.008.
^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.
^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. doi:10.1007/BF00320986. ISSN0029-8549.
^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. doi:10.1111/ele.12575. ISSN1461-023X.
^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. ISSN0022-0957.
^Bacon, M. Water Use Efficiency in Plant Biology. Oxford: Blackwell Publishing Ltd., 2004. ISBN1-4051-1434-7. Print.
^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. doi:10.1016/j.fcr.2009.03.009.
^Iljin, V. (1916). "Relation of transpiration to assimilation in steppe plants". Journal of Ecology. 4 (2): 65–82. doi:10.2307/2255326. JSTOR2255326.
^Bates, C.G. (1923). "Physiological requirements of Rocky Mountain trees". Journal of Agricultural Research. 24: 97–164.[1]
^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. doi:10.1111/j.1365-2486.2011.02566.x.
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. ISSN1460-2431.
Tambussi, E. A.; Bort, J.; Araus, J. L. (2007). "Water use efficiency in C3 cereals under Mediterranean conditions: a review of physiological aspects". Annals of Applied Biology. 150 (3): 307–321. doi:10.1111/j.1744-7348.2007.00143.x.
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. ISSN0022-0957.
Cregg, B. M. (2004). "Improving Drought Tolerance of Trees: Theoretical and practical considerations". Acta Horticulturae. 630 (630): 147–158. doi:10.17660/ActaHortic.2004.630.18. ISSN0567-7572.
