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Robert H. Stamps, Seenivasan Natarajan, Lawrence R. Parsons and Jianjun Chen

-based cold protection systems at these locations ( Fig. 1 ) used mist and fog emitters rather than conventional overhead irrigation systems. Water application rates for cold protection based on shadehouse areas and volumes ranged from 6,919 to 160,810 L·ha −1

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Darren J. Hayes and Bryan J. Peterson

that were treated with solutions varying in concentration of K-IBA and inserted into propagation media varying in their proportions of coarse perlite and milled peatmoss. The effects of these treatments were evaluated in both overhead mist and

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Lucas McCartney and Mark Lefsrud

. Critical temperatures that result in freeze damage to crops. Examples of crops are given. Data from Bootsma and Brown (1985) . The application of a thin layer of ice on the fruit by a continuous misting of a fine water film prevents the crop from reaching

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David W. Burger

Comparisons were made between a commercially available, solar-activated mist control device (Weather Watcher®) and time clocks to determine their relative effectiveness, usefulness, and water-use characteristics on a greenhouse mist propagation bench. Coleus cuttings produced more roots per cutting and had greater average root lengths under Weather Watcher-controlled mist than those cuttings on a mist bench controlled by time. Paulownia cuttings produced the same number of roots under solar- or time-activated mist; however, the average root length was greater under Weather Watcher control. Mist benches controlled by the Weather Watcher used only one-third the water used by benches controlled by a time clock.

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R. Romero-Aranda, T. Soria and J. Cuartero

High salinity levels in irrigation water available in Mediterranean coastal areas induce a significant loss of yield in greenhouse tomato crops. This loss increases during the spring-summer growing season when high irradiance, temperature, and low humidity occur within greenhouses. This study determined whether salt-induced yield losses could be alleviated by increasing humidity by misting the greenhouse atmosphere. Plants of `Daniela' tomato (Lycopersicon esculentum Mill.), were irrigated with 0 or 50 mm NaCl added to the nutrient solution and grown under natural greenhouse conditions or under applications of fine mist every 8 min during the day. During midday hours, misting reduced greenhouse air vapor pressure deficit 1.0 to 1.5 kPa and reduced greenhouse air temperature 5 to 7-°C. Mist reduced root water uptake from the medium by 40% in nonsalinized plants and by 15% in saline conditions. Foliar concentration of Na was lower in misted-salinized plants than in nonmisted salinized plants. Less negative leaf water potential and higher leaf turgor were recorded with mist at midday, in both salinized and nonsalinized plants. Midday stomatal conductances and net CO2 assimilation rates of salinized-misted plants were 3 and 4 times higher, respectively, than those recorded in salinized-nonmisted plants. Misted plants increased instantaneous water use efficiency 84% to 100%, as estimated from the ratio of net CO2 assimilation to transpiration. Nonsalinized plants grown with mist increased total leaf area by 38%, dry matter by 10%, and yield by 18% over nonmisted plants. Salinized plants grown with mist increased total plant leaf area by 50%, dry matter by 80%, and yield by 100%. Greenhouse misting resulted in a saving of total water input of 31 L/plant under nonsaline conditions and in greater yields and fruit size regardless of salinity. Results suggest that greenhouse misting, during the Mediterranean spring-summer growing season, improves tomato crop productivity both under nonsaline and saline growth conditions.

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Hongvi Zhang and William R. Graves

Use of subirrigation to root stem cuttings was compared to using mist, and effects of fertilization during subirrigation were determined. All cuttings of Dendranthema ×grandiflorum (Ramat.) Kitamura `Charm' and Coleus ×hybridus Voss. rooted, but misted D. ×grandiflorum `Charm' had a higher mean root mass than subirrigated cuttings. Percentage rooting and mean root mass of subirrigated Acer rubrum L. `Franksred' were 95% and 321 mg, whereas mean root mass of the 21% of cuttings that rooted with mist was 38 mg. Percentage cuttings with callus, mean callus diameter, rooting percentage, and mean root mass of Syringa retuculata (Blume) Hara were 77%, 124 mm, 21%, and 52 mg with subirrigation and 45%, 63 mm, 0%, and 0 mm with mist. Subirrigation with <7 mol N/m3 improved rooting of Impatiens hawkeri Bull. `Celebration Bright Scarlet' and A. rubrum `Franksred'. Subirrigation can replace mist, and effects of fertilizer in subirrigation solution vary among taxa.

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Brent Tisserat, Daniel Jones and Paul D. Galletta

An inexpensive user-constructed ultrasonic misting system to grow plant tissues in vitro is presented. This system is constructed by coupling two commercially available products, a culture chamber and an ultrasonic humidifier. Plant cultures are grown within a culture chamber on a platform and bathed periodically by an ultrasonic nutrient mist. Carrot cultures were found to grow as much as four to 10 times as great as those grown on agar medium.

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R.L. Geneve, S.T. Kester and J.W. Buxton

A capillary mat-mist system was developed to provide near constant media water contents at differing quantities of mist. Media water contents were reduced by increasing the capillary mat height above a constant water table maintained at bench level. Increased tensions from 0 to 10 cm above the water table reduced water content in Oasis, rockwool, and peat-perlite by 35.4%, 27.6%, and 17.4%, respectively. There was no difference in water content for each medium when the mist quantity ranged between 600 and 1800 mL·m-2·h-1, except when the capillary mat was at 9 cm above the water table and mist volume was 300 mL·m-2·h-1. Chrysanthemum cuttings rooted best when water content was highest regardless of media. Using the peat-perlite medium, water content had the greatest impact on rooting when the mist volume was low (600 mL·m-2·h-1). Relative water content of cuttings was lowest during the first 5 days of sticking and both reduced media water content and mist quantity resulted in the lowest internal water status for the cuttings.

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Y. Zhang, J.L. Shipp and T.J. Jewett

Overhead fogging or misting is an essential technique applied in modern greenhouses for cooling and humidifying. This technique can be used to promote yield and quality of greenhouse crops either by providing favorable environment for the plant growth or by increasing the efficiency of greenhouse pest and disease control. In this study, the effect of high-pressure overhead misting on greenhouse climate and leaf surface microclimate conditions for cucumber crops in a glass greenhouse was investigated. It was found that the temperature of the greenhouse air was lowered by 5-6 °C and relative humidity was increased by 20% to 30% during misting. The temperature of sunlit leaves was slightly reduced in the morning (2-3 °C), and leaf wetness duration was significantly extended by misting. Leaf wetness duration under misting was predominately influenced by light intensity at the leaf level and was modelled as a function of misting period and average radiation intensity. Results of this study can be used to improve the predictions of pest and disease breakout and the efficiency of their control measures. The empirical model developed in this study can be integrated with leaf surface microclimate models to correctly predict surface moisture conditions and evaporative cooling from water films at the leaf surface.

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Hongyi Zhang and William R. Graves

A subirrigation method for rooting stem cuttings was compared to intermittent mist. Both methods resulted in 100% rooting of `Charm' chrysanthemum [Dendranthema × grandiflorum (Ramat.) Kitamura] and coleus (Coleus × hybridus Voss.) after 2 weeks. Subirrigated cuttings of `Charm' chrysanthemum had a lower mean root dry mass than misted cuttings, but root dry mass of coleus was not affected. Percentage rooting and mean root dry mass of subirrigated cuttings of `Franksred' red maple (Acer rubrum L.) were 95% and 321 mg, whereas the mean root dry mass of the 33% of cuttings that rooted under mist was 38 mg. For Japanese tree lilac [Syringa reticulata (Blume) Hara], the percentage of cuttings with living callus, mean callus diameter, and percentage rooting were higher for subirrigated cuttings than for misted cuttings. In a second study, cuttings of `Franksred' red maple were subirrigated with a solution containing 0 to 7.2 mol N/m3 and not misted. Cuttings given 3.6 or 7.2 mol N/m3 had > 90% rooting after 2 weeks, whereas only 8% of unfertilized cuttings had rooted, and root mass and chlorophyll content were highest for cuttings given 7.2 mol N/m3. Subirrigation can replace mist during propagation of some florist and nursery crops, and subirrigating with fertilizer solution improves rooting of `Franksred' red maple.