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Robert H. Stamps and Heidi M. Savage

Poinsettias are popular for their colorful bracts and long keeping quality under indoor conditions. However, along with the long display life comes the maintenance issue of repeated waterings that can be labor intensive. It would be useful to have a

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Genhua Niu, Denise S. Rodriguez, and Terri Starman

Water shortage and poor water quality are critical issues in the Southwest and many other regions of the world. With a rapidly increasing population and diminishing water supplies, the competition for fresh water among agriculture, industry, urban

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Katherine F. Garland, Stephanie E. Burnett, Michael E. Day, and Marc W. van Iersel

supplemental lighting and efficient irrigation in greenhouses to optimize energy and water use. Understanding the precise light and water requirements of crops is the key to using supplemental lighting and water efficiently. Insufficient light limits growth for

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Dennis R. Pittenger, A. James Downer, Donald R. Hodel, and Maren Mochizuki

Palms are important constituents of many landscapes in arid and semiarid regions where irrigation is deemed necessary for their successful establishment and maintenance. Reducing or limiting water applied to urban landscapes is a primary focus in

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A.G. Taylor

Four topics are presented on the status of water in seeds; 1) methods to express moisture content (MC), 2) methods to determine MC, 3) relationship between relative humidity (RH) and MC, and 4) utility of water activity measurements in seeds. Seed MC is expressed on a fresh-weight basis in commerce and seed technology, while dry weight basis is used in physiological or biophysical literature. Conversion equations are available for the fresh and dry weight measurements. Moisture testing methods are grouped as primary and secondary. Primary methods are direct methods in which the water is removed and determined, while the secondary methods are indirect methods that rely on a chemical or physical characteristic that changes with MC. The oven method is the most common primary technique and the electronic moisture meter is widely used as a nondestructive secondary technique. The relation between RH and MC is known as an isotherm, and three zones of water binding are observed. The RH and the seed composition, in particular the lipid content, determines the MC. Seeds with low lipid content have a greater equilibrium MC than seeds with high lipid content. Water activity, defined as the ratio of water vapor of the seed over the water vapor of pure water at a particular temperature, is related to water potential in a log-linear relationship. Water activity (aw) can be used to define the water status of any species, regardless of composition.

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Terence L. Robinson and Bruce H. Barritt

Abbreviations: ABA, abscisic acid; c, t-ABA, cis, trans-abscisic acid; LPI, leaf plastochron index; PI, plastochron index age; ψ P , leaf turgor pressure; ψ S , leaf osmotic potential; ψ W , leaf water potential; t , t-ABA, trans, trans

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Jesse R. Quarrels and Paul G. Thompson

An experiment was conducted to determine the rate and frequency of irrigation needed for optimum yield in sweetpotato (Ipomoea batatas (L.)Lam). A line source irrigation system was used to provide continuously increasing amounts of water at each irrigation. The physiological responses of sweetpotato to water application were measured. There was an increase in leaf water potential with increasing rates of irrigation. Leaf diffusive resistance decreased as total water rate increased to 76% of pan evaporation (Epan) and then increased with higher rates of irrigation. Marketable yields increased as total water rate increased to 76% of Epan and then decreased rapidly with higher irrigation rates. Water relations measurements indicated that reduction in yield with higher amounts of water application was due to low soil oxygen content.

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James P. Syvertsen, Juan C. Melgar, and Francisco García-Sánchez

levels of Na + or osmotic stress ( Brumós et al., 2009 ). Citrus trees are almost always grafted on rootstocks, which not only affects tree water relations and growth ( Castle et al., 1993 ), but also the amount of Cl − and/or Na + accumulated in

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C.A. Brown, D.A. Devitt, and R.L. Morris

1 Graduate Student. 2 Professor, Soil and Water. 3 Associate Professor. This paper is a portion of a thesis submitted by C.A.B. We wish to thank the U.S. Dept. of Agriculture and the College of Agriculture, Univ. of Nevada-Reno for financial

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Kathryn M. Santos, Paul R. Fisher, and William R. Argo

ornamental, and fruit production. Agriculture accounts for over 80% of freshwater consumption in the United States and an increase in water use regulations necessitates improved irrigation strategies ( Weibe and Gollehon, 2006 ). Greenhouse propagation