Water-use efficiency

Rosenberg, N. J. (1981). The increasing CO2 concentration in the atmosphere and its implications on agricultural productivity. I. Effects on photosynthesis, transpiration and water use efficiency. Climat. Change 3,265-279. 

The integral of this over the life of the plant, the water-use efficiency W is... 

Isotope discrimination and water-use efficiency If we rearrange Equation 6 and substitute for pjp. in Equation 4, we obtain a negative dependence of IV on A ... 

Fig. 5. Water-use efficiency (carbon basis) v. average carbon isotope discrimination in the whole plant, r= -0.88. Open symbols represent well-watered plants and closed symbols represent plants that were droughted. Tifton 8 A, Florunner A, VB187 and +, Chico are cultivars of peanut (Arachis hypogaea). (From Flubick etal., 1986).

Environmental effects on discrimination and water-use efficiency Any environmental stress that affects leaf conductance and assimilation rate differently, so that the changes in one are not proportional to the changes in the other, will affect pjp and therefore A. If the changes do not affect the terms in the denominator of Equation 8 independently of pjpa, then W will also be affected. 

Farquhar, G.D., Hubick, K.T., Condon, A.G. Richards, R.A. (1988). Carbon isotope fractionation and plant water-use efficiency. In Applications of Stable Isotope Ratios to Ecological Research, ed. P.W. Rundel, J.R. Ehleringer K.A. Nagy, pp.21 0. New York Springer-Verlag. 

Farquhar, G.D. Richards, R.A. (1984). Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Australian Journal of Plant Physiology, 11, 539-52. 

Hubick, K.T. Farquhar, G.D. (1987). Carbon isotope discrimination - selecting for water use efficiency. Australian Cotton Grower 8, 66-8. 

Hubick, K.T., Farquhar, G.D. Shorter,R. (1986). Correlation between water-use efficiency and carbon isotope discrimination in diverse peanut (Arachis) germplasm. Australian Journal of Plant Physiology, 13, 803-16. 

Martin, B.J. Thorstenson, Y.R. (1988). Stable carbon isotope composition (6 C), water use efficiency and biomass productivity of Lycopersicon esculen-tum, Lycopersicon pennellii and the Fi hybrid. Plant Physiology 88, 218-23. 

Masle, J. Farquhar, G.D. (1988). Effects of soil strength on the relation of water use efficiency and growth to carbon isotope discrimination in wheat seedlings. Plant Physiology, 6,147-55. 

Drought is perhaps one of the most complex examples to choose but it illustrates well the possibilities of, and pitfalls to, progress. Drought affects almost every facet of plant function and we are faced with the paradox that yield and evapotranspiration are intimately linked. In general, increases in yield when water supply is limiting are likely to result from characteristics which increase the available water supply, increase water use efficiency or increase biomass allocation to the economically useful plant parts (Pass-ioura, 1986). Additionally, features which maintain cell viability and protect metabolism in water-stressed tissue and allow rapid recovery after dry periods will contribute yield under some circumstances. 

Abscisic acid accumulation during drought Water-use efficiency -1- Innes et al., 1984... 

Owonubi, J.J. Kanemasu, E.T. (1982). Water-use efficiency of three height isolines of sorghum. Canadian Journal of Plant Science, 62, 35-41. 

Vaadia, Y. (1987). Salt and drought tolerance in plants regulation of water use efficiency in sensitive and tolerant species. In NATO Conference on Biochemical and Physiological Mechanisms Associated with Environmental Stress Tolerance in Plants, University of East Anglia, Norwich, 2-7 August 1987. 

Flowers, T.J., Salama, F.M. Yeo, A.R. (1988). Water use efficiency in rice Oryza sativa L.) in relation to resistance to salinity. Plant, Cell and Environment 11, 453-9. 

Metabolic features which increase water use efficiency (a) CAM metabolism (b) C4 metabolism and (c) other CO2 concentrating mechanisms. 

Cooper, P.J.M., Gregory, P.J., Tully, D. Harris, H.C. (1987). Improving water use efficiency of annual crops in the rainfed farming systems of West Asia and North Africa. Experimental Agriculture, 23,113-58. 

A. H. C. M. Schapendonk, P. Dijkstra, J. Groenwold, C. S. Pot, and S. C. Van De Geijn, Carbon balance and water use efficiency of frequently cut Loliuni perenne L. swards at elevated carbon dioxide. Global Change Biol. 5 207 (1997). 

The assessment of the sustainability of the cultivation of energy crops includes the input and recycling of nutrients, the application of pesticides, the water-use efficiency, the consumption of fossil fuels and the balance of soil carbon. The aim is to recycle the nutrients, which is simple in the case of anaerobic digestion by applying the digestate to the field. If crops are combusted many of the minerals can be returned via the ash. In the case of liquid biofuels, exported nutrients are lost and have to be replaced. The application of pesticides, mainly herbicides, can often be reduced in comparison to food production, but the energy yield per hectare might be reduced if the share of weeds exceeds certain thresholds. Water use efficiency,... 

Carbon 13c/12c 12C = 98.89 13C= 1.11 Organic matter, carbonates, biomineralized tissue, soil, C02 Diet, plant water-use efficiency, climate and habitat, provenance (ivory, marble)... 

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