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Bedding plants are extensively used in urban landscapes. As high-quality water supply becomes limited in many parts of the world, the use of recycled water with high salt levels for landscape irrigation is being encouraged. Therefore, information on salt tolerance of bedding plants is of increasing importance. Two experiments were conducted, one in a 25% light exclusion shadehouse in summer (Expt. 1) and the other in a greenhouse in winter (Expt. 2). Plants were irrigated with saline solution at electrical conductivities of 0.8, 2.8, 4.0, 5.1, or 7.4 dS·m-1 created by adding NaCI, MgSO4, and CaCI2 to tap water to simulate the composition of local reclaimed water. In Expt. 1, shoot dry weight (DW) at the end of the experiments was reduced in all species at 7.4 dS·m-1 compared with the control (0.8 dS·m-1). The magnitude of reduction varied with species and cultivars. The salinity thresholds of irrigation water in which growth reduction occurred were 4.0 dS·m-1 for angelonia (Angelonia angustifolia) cultivars and ornamental pepper (Capsicum annuum) 'Calico' and 4.0 to 5.1 dS·m-1 for helenium (Helenium amarum), licorice plant (Helichrysum petiolatum), and plumbago (Plumbago auriculata). Shoot DW and growth index of ornamental pepper 'Black Pearl' and vinea (Catharanthus roseus) 'Rose' decreased linearly as salinity increased. All plants survived in Expt. 1 regardless of treatment, except for ornamental pepper 'Purple Flash'. No visual injuries were observed in Expt. 1 regardless of treatment. Leaf sodium (Na) and chlorine (CI) concentrations varied with species and treatments. Ornamental pepper 'Black Pearl' had the highest leaf CI concentrations at higher salinities compared with other species and cultivars. Leaf Na concentrations in licorice plant and plumbago were in the range of 10 to 30 g·kg-1 DW, higher than those in other species. In Expt. 2, shout DW was reduced by salinity, treatments in ornamental pepper 'Black Pearl', plumbago, and angelonia but not in other species. The three ornamental peppers, 'Black Pearl', 'Calico', and 'Purple Flash', exhibited slight follar injuries on some plants in Expt. 2 as a result of high salinity in the root zone in the highest salinity treatment. Ornamental pepper 'Black Pearl' was most sensitive to salinity, stress. In general, the bedding plants tested in this study are moderately tolerant to salt stress and may be irrigated with saline water up to 4.0 dS·m-1 with little reduction in aesthetical appearance. [ABSTRACT FROM AUTHOR]

The effect of drought on the growth and gas exchange of six bedding plant species--agastache [Agastache urticifolia (Benth.) O. Kuntze 'Honeybee Blue'], dusty miller (Cineraria maritima L. 'Silverdusty'), petunia (Petunia xhybrida 'Wave Purple'), plumbago (Plumbago auriculata Lam. 'Escapade'), ornamental pepper (Capsicum annuum L. 'Black Pearl'), and vinca [Catharanthus roseus (L.) G. Don 'Titan'l--was quantified under greenhouse conditions. Seeds were sown in January and seedlings were grown in the greenhouse until 18 Apr., when two irrigation treatments--drought (D, ≈18% volumetric moisture content at reirrigation) and control (C, ≈25% volumetric moisture content at reirrigation)--were initiated. Leaf net photosynthetic rate (P.), stomatal conductance (gs), and transpiration (E) were determined in response to a range of substrate moisture content (from ≈5% to 30% by volume) and temperature (from 20 °C to 40 °C). Dry weight of agastache, ornamental pepper, and vinca was unaffected by drought, whereas that of other species was reduced. Leaf area of plumbago and height of plumbago and vinca were reduced by drought. As substrate moisture content decreased from 25% to 10%, Pn, E, and gs decreased linearly in all species except petunia and plumbago. Leaf net photosynthetic rate of all species declined as leaf temperature increased from 20 °C to 40 °C. In contrast, E of all species, except petunia, increased as temperature increased. Transpiration rate of petunia increased as temperature increased from 20 °C to 30 °C, and then decreased between 30 °C and 40 °C. Although petunia had the highest Pn among the tested species, its Pn and gs declined more rapidly compared with the other species as temperature increased from 20 °C to 40 °C or as substrate moisture content decreased, indicating that petunia was most sensitive to high temperature and drought. [ABSTRACT FROM AUTHOR]

Use of recycled water to irrigate urban landscapes and nursery plants may be inevitable as fresh water supplies diminish and populations continue to grow in the arid and semiarid southwestern United States. Lupinus havardii Wars. (Big Bend bluebonnet) has potential as a cut flower and Lupinus texensis Hook. (Texas bluebonnet) as a bedding plant, but little information is available on salt tolerance of these species. A greenhouse study was conducted to characterize the growth in response to various salinity levels. Plants were grown in 10-L containers and drip-irrigated with synthesized saline solutions at electrical conductivity levels of 1.6, 3.7, 5.7, 7.6, or 9.4 dS⋅m-1. Although shoot growth of L. texensis was reduced as salinity levels increased, it was visually acceptable (without any visual injury) when irrigated with salinity levels of less than 7.6 dS⋅m-1. All plants survived at 7.6 dS⋅m-1, whereas only 15% did at 9.4 dS⋅m-1. In contrast, L. havardii had leaf injury at 5.7 dS⋅m-1. No plants survived at 9.4 dS⋅m-1, and only 7% plants survived at 7.6 dS⋅m-1. In addition, growth of L. havardii was significantly reduced and plants were shorter at elevated salinity levels. Cut raceme yield of L. havardii decreased at salinity levels greater than 3.7 dS⋅m-1. However, no difference in cut raceme yield was observed between the control and 3.7 dS⋅m-1, although shoot growth was reduced. Overall, L. texensis was more salt-tolerant than L. havardii. [ABSTRACT FROM AUTHOR]

As high-quality water supply becomes limited in many regions of the world, alternative water sources are being used for irrigating urban landscapes. Therefore, salt-tolerant landscape plants are needed. Two greenhouse experiments were conducted to screen the salt tolerance of Zinnia marylandica ('Zahara Coral Rose', 'Zahara Fire', 'Zahara Scarlet', 'Zahara Starlight', 'Zahara White', and 'Zahara Yellow') and Z. maritima 'Solcito'. In Expt. 1, plants were subirrigated with nutrient or saline solutions at electrical conductivity (EC) at 1.4 (base nutrient solution, control), 3.0, 4.2, 6.0, or 8.2 dS·m-1 for 4 weeks, whereas in Expt. 2, plants were surface-irrigated with the same nutrient or saline solutions for 4 weeks. In Expt. 1, all plants, regardless of cultivar, died by the end of the treatment at EC 6.0 and EC 8.2 as a result of high salinity in the root zone. Plants became shorter and more compact as EC of irrigation water increased. Shoot dry weight of all cultivars in EC 4.2 was reduced by 50% to 56% compared with that of the control. Shoot Na+ and Cl- accumulated excessively as salinity increased in the irrigation water, whereas Ca2+, Mg2+, and K+ did not change substantially. In Expt. 2, mortality varied with cultivar and treatment. Similar to Expt. 1, growth reduction resulting from elevated salinity across cultivars was found. Therefore, it is concluded that zinnia cultivars used in this study are sensitive to salinity and should not be planted in areas with high soil salinity or when alternative waters with high salinity may be used for irrigation. [ABSTRACT FROM AUTHOR]