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Louise Ferguson and Steven R. Grattan

There are two ways salinity can damage citrus: direct injury due to specific ions, and osmotic effects. Specific ion toxicities are due to accumulation of sodium, chloride, and/or boron in the tissue to damaging levels. The damage is visible as foliar chlorosis and necrosis and, if severe enough, will affect orchard productivity. These ion accumulations occur in two ways. The first, more controllable and less frequent method, is direct foliar uptake. Avoiding irrigation methods that wet the foliage can easily eliminate this form of specific ion damage. The second way specific ion toxicity can occur is via root uptake. Certain varieties or rootstocks are better able to exclude the uptake and translocation of these potentially damaging ions to the shoot and are more tolerant of salinity. The effect of specific ions, singly and in combination, on plant nutrient status can also be considered a specific ion effect. The second way salinity damages citrus is osmotic effects. Osmotic effects are caused not by specific ions but by the total concentration of salt in the soil solution produced by the combination of soil salinity, irrigation water quality, and fertilization. Most plants have a threshold concentration value above which yields decline. The arid climates that produce high quality fresh citrus fruit are also the climates that exacerbate the salt concentration in soil solution that produces the osmotic effects. Osmotic effects can be slow, subtle, and often indistinguishable from water stress. With the exception of periodic leaching, it is difficult to control osmotic effects and the cumulative effects on woody plants are not easily mitigated. This review summarizes recent research for both forms of salinity damage: specific ion toxicity and osmotic effects.

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N.C. Yorio, C.L. Mackowiak, R.M. Wheeler, and J.C. Sager

Potato (Solanum tuberosum L. cvs. Norland and Denali) plants were grown under high-pressure sodium (HPS), metal halide (MH), and blue-light-enhanced SON-Agro high-pressure sodium (HPS-S) lamps to study the effects of lamp spectral quality on vegetative growth. All plants were initiated from in vitro nodal cultures and grown hydroponically for 35 days at 300 μmol·m–2·s–1 photosynthetic photon flux (PPF) with a 12-hour light/12-hour dark photoperiod and matching 20C/16C thermoperiod. `Denali' main stems and internodes were significantly longer under HPS compared to MH, while under HPS-S, lengths were intermediate relative to those under other lamp types, but not significantly different. `Norland' plants showed no significant differences in stem and internode length among lamp types. Total dry weight of `Denali' plants was unaffected by lamp type, but `Norland' plants grown with HPS had significantly higher dry weight than those under either HPS-S or MH. Spectroradiometer measurements from the various lamps verified the manufacturer's claims of a 30% increase in ultraviolet-blue (350 to 450 nm) output from the HPS-S relative to standard HPS lamps. However, the data from `Denali' suggest that at 300 μmol·m–2·s–1 total PPF, the increased blue from HPS-S lamps is still insufficient to consistently maintain short stem growth typical of blue-rich irradiance environments.

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C.P. Sharma and Sandhya Singh

Cauliflower [Brassica oleracea (Botrytis Group) cv. Pusi] grown in refined sand with 0.01 normal K supply had lower dry matter and tissue concentration of K than the controls and developed visible symptoms characteristic of K deficiency. Compared with control plants, the laminae of K-deficient plants contained significantly higher concentrations of sugars and nonprotein N and significantly lower concentrations of starch and protein N. However, the midribs of K-deficient leaves contained more protein N than leaves of control plants. Substitution of K by Na resulted in increased Na concentrations in leaves and recovery from the K-deficiency effect on the carbohydrate and N fractions. Maximum response to sodium was found in the intercoastal-lamina of K-deficient plants.

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Theo J. Blom and Brian D. Piott

Four freesia cultivars were exposed to 24 hour·day-1 high-pressure sodium (HPS) lighting during various stages of their development. Upon emergence, freesia plants were exposed to the following four lighting treatments: 1) ambient; 2) ambient until shoot length was 5 to 8 cm followed by HPS lighting until flowering; 3) HPS lighting until shoot length was 5 to 8 cm followed by ambient lighting; and 4) continuous HPS lighting. Supplemental HPS lighting was provided at 37 μmol·m-2·s-1 at plant level in a glasshouse. Continuous lighting or lighting during flower development hastened flowering but reduced the number of flowering stems per corm, as well as stem length and weight. Lighting during the vegetative and flower initiation periods produced minor effects. The main benefit of supplemental lighting was found in total corm weight.

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Derek N. Peacock and Kim E. Hummer

During research to develop a new germination protocol for Rubus being conducted at the National Clonal Germplasm Repository in Corvallis, we observed mixed responses to sodium hypochlorite (NaOCl) as a seed scarifying agent. For R. parviforus Nutt., scarification with NaOCl resulted in 34% germination. Fewer than 1% of the seedlings showed any negative effects after exposure to 2.6% NaOCl for 24 hours. But in R. ursinus Cham. & Schldl., R. multibracteatus A. Leveille & Vaniot, R. swinhoei Hance, and R. setchuenensis Bureau & Franchet, the percentage of injury observed ranged from 40% to 100%. In these cases, although embryonic tissue did not appear necrotic, the radicle and plumule failed to elongate after emergence. The epicotyl or primary leaves did not develop, and the radicle failed to form root hair. The cotyledons, apparently unaffected, opened and were a healthy green. NaOCl did not kill the embryo, but deterred development of the embryonic axis. As a result of the NaOCl scarification the cotyledons expanded yet the seedlings eventually died.

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Jessie M. Godfrey, Louise Ferguson, and Maciej A. Zwieniecki

this time at intervals of ≈4 h in 50-mL Eppendorf tubes. Sodium analysis. The volumes of aqueous samples collected from the cut distal ends of perfused stems were determined by extracting these volumes from outflow containers with a pipette

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Pedro Gonzalez, James P. Syvertsen, and Ed Etxeberria

molecular analyses in Arabidopsis ( Shi et al., 2003 ; Zhu, 2000 ) and on determinations of intracellular Na + distribution with Sodium-Green ( Hamaji et al., 2009 ), we hypothesized a higher Na + sequestration in the root vacuoles of the relatively Na

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Wesley C. Randall and Roberto G. Lopez

overhead SL ( Oh et al., 2010 ; Randall and Lopez, 2014 ; Sherrard, 2003 ). High-intensity discharge lamps, such as HPS and metal halide lamps, have traditionally been used for SL to increase greenhouse DLI. High-pressure sodium lamps have long been the

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Joshua K. Craver, Jennifer K. Boldt, and Roberto G. Lopez

.R. Peters, Inc., Allentown, PA) providing 100 mg·L −1 nitrogen (N). Fig. 1. Spectral quality from 400 to 700 nm delivered from light-emitting diode (LED) fixtures or high-pressure sodium (HPS) lamps providing a photosynthetic photon flux density ( PPFD ) of

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Christopher J. Currey and Roberto G. Lopez

root development of Impatiens , Pelargonium , and Petunia grown under ambient daylight supplemented with ≈70 μmol·m −2 ·s −1 , respectively, delivered from high-pressure sodium (HPS) lamps or light-emitting diodes with varying proportions of red