Salt Tolerance of Sego SupremeTM Plants

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  • 1 Department of Plants, Soils, and Climate, Utah State University, 4820 Old Main Hill, Logan, UT 84322
  • | 2 Western Arid Region Grassland Resources & Ecology Key Lab, Xinjiang Agricultural University, No. 311 East Nongda Road, Urumqi, Xinjiang 830052, China
  • | 3 Utah State University Botanical Center, 725 Sego Lily Drive, Kaysville, UT 84037

Sego SupremeTM is a designated plant breeding and introduction program at the Utah State University Botanical Center and the Center for Water Efficient Landscaping. This plant selection program introduces native and adapted plants to the arid West for aesthetic landscaping and water conservation. The plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salt tolerance has not been considered during the evaluation processes. Four Sego SupremeTM plants [Aquilegia barnebyi (oil shale columbine), Clematis fruticosa (Mongolian gold clematis), Epilobium septentrionale (northern willowherb), and Tetraneuris acaulis var. arizonica (Arizona four-nerve daisy)] were evaluated for salt tolerance in a greenhouse. Uniform plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. After 8 weeks of irrigation, A. barnebyi irrigated with saline solution at an EC of 5.0 dS·m−1 had slight foliar salt damage with an average visual score of 3.7 (0 = dead; 5 = excellent), and more than 50% of the plants were dead when irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1. However, C. fruticosa, E. septentrionale, and T. acaulis had no or minimal foliar salt damage with visual scores of 4.2, 4.1, and 4.3, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. As the salinity levels of treatment solutions increased, plant height, leaf area, and shoot dry weight of C. fruticosa and T. acaulis decreased linearly; plant height of A. barnebyi and E. septentrionale also declined linearly, but their leaf area and shoot dry weight decreased quadratically. Compared with the control, the shoot dry weights of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Aquilegia barnebyi and C. fruticosa did not bloom during the experiment at all treatments. Elevated salinity reduced the number of flowers in E. septentrionale and T. acaulis. Elevated salinity also reduced the number of shoots in all four species. Among the four species, sodium (Na+) and chloride (Cl) concentration increased the most in A. barnebyi by 53 and 48 times, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In this study, C. fruticosa and T. acaulis had minimal foliar salt damage and less reduction in shoot dry weight, indicating that they are more tolerant to salinity. Epilobium septentrionale was moderately tolerant to saline solution irrigation with less foliar damage, although it had more reduction in shoot dry weight. On the other hand, A. barnebyi was the least tolerant with severe foliar damage, more reduction in shoot dry weight, and a greater concentration of Na+ and Cl.

Abstract

Sego SupremeTM is a designated plant breeding and introduction program at the Utah State University Botanical Center and the Center for Water Efficient Landscaping. This plant selection program introduces native and adapted plants to the arid West for aesthetic landscaping and water conservation. The plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salt tolerance has not been considered during the evaluation processes. Four Sego SupremeTM plants [Aquilegia barnebyi (oil shale columbine), Clematis fruticosa (Mongolian gold clematis), Epilobium septentrionale (northern willowherb), and Tetraneuris acaulis var. arizonica (Arizona four-nerve daisy)] were evaluated for salt tolerance in a greenhouse. Uniform plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. After 8 weeks of irrigation, A. barnebyi irrigated with saline solution at an EC of 5.0 dS·m−1 had slight foliar salt damage with an average visual score of 3.7 (0 = dead; 5 = excellent), and more than 50% of the plants were dead when irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1. However, C. fruticosa, E. septentrionale, and T. acaulis had no or minimal foliar salt damage with visual scores of 4.2, 4.1, and 4.3, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. As the salinity levels of treatment solutions increased, plant height, leaf area, and shoot dry weight of C. fruticosa and T. acaulis decreased linearly; plant height of A. barnebyi and E. septentrionale also declined linearly, but their leaf area and shoot dry weight decreased quadratically. Compared with the control, the shoot dry weights of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Aquilegia barnebyi and C. fruticosa did not bloom during the experiment at all treatments. Elevated salinity reduced the number of flowers in E. septentrionale and T. acaulis. Elevated salinity also reduced the number of shoots in all four species. Among the four species, sodium (Na+) and chloride (Cl) concentration increased the most in A. barnebyi by 53 and 48 times, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In this study, C. fruticosa and T. acaulis had minimal foliar salt damage and less reduction in shoot dry weight, indicating that they are more tolerant to salinity. Epilobium septentrionale was moderately tolerant to saline solution irrigation with less foliar damage, although it had more reduction in shoot dry weight. On the other hand, A. barnebyi was the least tolerant with severe foliar damage, more reduction in shoot dry weight, and a greater concentration of Na+ and Cl.

Field trials are used to successfully identify suitable plants with outstanding landscape performance for various plant selection and evaluation programs. Superior plants are selected mostly on the basis of their appearance, environmental adaptability, drought tolerance, and disease/pest tolerance. For example, Earth-Kind® is one of the special plant selection programs of the Texas A&M Agrilife Extension Service (Aggie Horticulture, 2019). A total of 21 garden roses (Rosa ×hybrida) with superior stress tolerance and outstanding landscape performance were categorized as Earth-Kind® Roses. Similarly, Texas Superstar® program promotes superior plants that can grow well at various locations in Texas with minimal soil preparation and irrigation and no pesticides (Mackay et al., 2001). Sixteen perennial ornamental plants have been designated as Texas Superstar® perennials. Colorado State University has collaborated with the Denver Botanic Gardens to establish the Plant Select® program to promote plants annually which are water-wise and adapted to the Rocky Mountains (Colorado Gardening, 2019). Native plants from arid and semiarid environments, introduced by Plant Select® program, are excellent candidates for water-efficient landscaping. Sales of native plants have grown from $1.46 million in 2007 to $1.68 million in 2012 through Plant Select® program (National Information Management and Support System, 2019). However, these programs have overlooked the salinity tolerance of the plants during the selection and evaluation processes.

Sego SupremeTM is a plant breeding and introduction program developed by Utah State University (USU) Botanical Center and the USU Center for Water-Efficient Landscaping with the intention of introducing native and adaptable plants into arid west landscapes to conserve water without compromising the aesthetic value of the landscapes (Anderson et al., 2014). Sego SupremeTM plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salinity tolerance has not been considered during the evaluation processes.

Soil salinity is one of the major obstacles for horticultural production all over the world. Soil is defined as a saline soil when the salinity level in a plant root zone exceeds 4 dS·m−1, which affects plant growth and may not be suitable to grow plants (Chinnusamy et al., 2005). In many parts of the world, poor-quality water (such as reclaimed water that contains high concentrations of soluble ions) is used to irrigate ornamental plants to conserve potable water (Cassaniti et al., 2013; Niu and Cabrera, 2010). Both saline soil and irrigation water can have adverse effects on plant performance by affecting nutrient availability and competitive uptake, transport, and partitioning within the plant (Grattan and Grieve, 1999). Plant species or cultivars have different responses to salinity (Munns and Tester, 2008; Niu and Cabrera, 2010). Therefore, selection and identification of salt-tolerant ornamental plants are crucial for nursery production and landscape use.

Plants selected from the Earth-Kind® and Texas Superstar® programs have been studied for salinity tolerance by independent researchers. The salt tolerance of 18 Earth-Kind® Rose cultivars was investigated, and it was concluded that ‘Belinda’s Dream’, ‘Climbing Pinkie’, ‘Mrs. Dudley Cross’, ‘Reve d’Or’, and ‘Sea Foam’ roses were salt-tolerant when irrigated with saline water at an EC of 10.0 dS·m−1 (Cai et al., 2014). Sun et al. (2015) reported that Texas Superstar® perennials such as Malvaviscus arboreus var. drummondii (Turk’s cap), Ruellia brittoniana ‘Katie Blue’ (‘Katie Blue’ ruellia), Salvia farinacea ‘Henry Duelberg’ (‘Henry Duelberg’ salvia), and Verbena ×hybrida ‘Blue princess’ (‘Blue Princess’ verbena) were tolerant to salinity levels at ECs of 5.0 and 10.0 dS·m−1, whereas Phlox paniculata ‘John Fanick’ (‘John Fanick’ phlox), Phlox paniculata ‘Texas Pink’ (‘Texas Pink’ phlox), and Salvia leucantha (Mexican bush sage) were sensitive to salinity levels at ECs of 5.0 and 10.0 dS·m−1.

Aquilegia barnebyi, Clematis fruticosa, Epilobium septentrionale, and Tetraneuris acaulis var. arizonica are categorized as Sego SupremeTM selections. Aquilegia barnebyi is a perennial plant that usually occurs on oil shale substrates and is native to northeastern Utah and adjacent parts of Colorado (U.S. Department of Agriculture, 2019). It is a drought-tolerant species and suitable for xeriscaping (Dave’s Garden, 2019). Clematis fruticosa is an erect, woody shrub with insect and disease tolerance (Missouri Botanical Garden, 2019). It grows in medium moisture, well-drained soil and has some drought tolerance. Epilobium septentrionale, a drought-tolerant perennial plant native to California, can grow in thin patches of soil between rocks (California Flora Nursery, 2019). Tetraneuris acaulis var. arizonica is a perennial plant that can tolerate many soil types and does not need much water once established in the landscape (Moosa Creek Nursery, 2019). It is native to western United States from Idaho to New Mexico (U.S. Department of Agriculture, 2019). These plants have potential for adoption by the landscape industry, but their salinity tolerance is unclear. In this study, the four Sego SupremeTM plant species were irrigated with saline solution at different salinity levels in a greenhouse to determine their salinity tolerance through measuring their growth responses and mineral nutrient status.

Materials and Methods

Plant materials and culture.

The study was conducted in a research greenhouse at USU in Logan, UT (lat. 41°45′28″N, long. 111°48′48″W, elevation 1409 m). On 24 Aug. 2018, 1-year-old Sego SupremeTM plants produced from cuttings were received in a square pot (10.5 × 10.5 × 12.3 cm) from the USU Botanical Center (Kaysville, UT). On 27 Aug. 2018, plants were transplanted into 3.8-L injection-molded, polypropylene container (PC1D-4; Nursery Supplies, Orange, CA) filled with a soilless growing substrate consisting of 75% peatmoss (Canadian sphagnum peatmoss; SunGro Horticulture, Agawam, MA), 25% vermiculite (Therm-O-Rock West, Chandler, AZ), and 24.3 g·ft−3 white athletic field marking gypsum (92% calcium sulfate dihydrate, 21% calcium, 17% sulfur; Western Mining and Minerals, Bakersfield, CA). All plants were watered with tap water (EC = 0.344 dS·m−1; pH = 7.65). During the experiment, aphids (Aphidoidea) and whiteflies (Aleyrodidae) were observed on C. fruticosa. To control aphids and whiteflies, all plants were sprayed with abamectin (Avid® 0.15 EC; Syngenta Crop Protection, Greensboro, NC) at a rate of 0.1 mL per gallon as needed. During the experimental period, the average air temperature in the greenhouse was 24.9 ± 1.2 °C during the day and 22.0 ± 2.4 °C at night. The average daily light integral in the greenhouse was 24.8 ± 12.5 mol·m−2·d−1. Supplemental light at 160.4 µmol·m−2·s−1 was provided using 1000-W high-pressure sodium lamps (Hydrofarm, Petaluma, CA) from 600 to 2200 HR when light intensity inside the greenhouse was less than 544 µmol·m−2·d−1 from 10 Oct. to 14 Dec. 2018. Supplemental light was measured using a full-spectrum quantum meter (MQ-500; Apogee Instrument, Logan, UT).

Treatments.

Plants were pruned to uniform height (≈13 cm), and flowers were removed before the experiment was initiated. From 15 Oct. to 3 Dec. 2018, treatment solutions were applied on a weekly basis up to 8 weeks. Plants were irrigated with 1 L of nutrient solution (control) at an EC of 1.25 dS·m−1 or saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 (Table 1) with a leaching fraction of 15.1% ± 6.4%. In addition, plants were watered with 500 mL of nutrient solution whenever the substrate surface became dry. The nutrient solution was prepared in a 100-L tank by adding 0.8 g·L−1 of 15N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special; ICL Specialty Fertilizers, Dublin, OH) to tap water and used as a control. The saline solution was prepared with an addition of sodium chloride (NaCl; Fisher Chemical, Logan, UT) and calcium chloride (CaCl2; Fisher Chemical, Logan, UT) at a molar ratio of 2:1 in the nutrient solution. The ECs of the solutions, measured using an EC meter (LAQUA Twin; Horiba, Kyoto, Japan), were 1.2 ± 0.1 (control, nutrient solution), 2.5 ± 0.2 (EC 2.5), 4.7 ± 0.1 (EC 5), 7.5 ± 0.2 (EC 7.5), and 9.8 ± 0.2 dS·m−1 (EC 10) (mean ± sd) during the experiment. The pH of the solutions was adjusted to 6.7 ± 0.4 using 1 m nitric acid.

Table 1.

The chemical compositions of tap water, nutrient solution (control), and saline solutions used in the experiment.z

Table 1.

Data collection.

Leachate solution was collected during each application of treatment solutions. The EC of the leachate solution was determined on one plant per species per treatment using the pour-through method described by Cavins et al. (2008). Plant heights, the length of the longest shoot, were measured at the start and end of the experiment. A visual score of 0 to 5 was assigned to each plant where 0 = dead, 1 = severe foliar damage (>90% leaves with burn, necrosis, and discoloration), 2 = moderate foliar damage (90% to 50%), 3 = slight foliar damage (50% to 10%), 4 = minimal foliar damage (<10%), and 5 = excellent without foliar damage (Sun et al., 2015). Plant size was not considered while assigning the visual score. Leaf greenness of each plant was measured 4 d before harvest using a handheld chlorophyll meter [soil-plant analysis development (SPAD) 502 Plus; Minolta Camera Co., Osaka, Japan]. Four fully expanded leaves from each plant were chosen for the measurements. The number of flowers of E. septentrionale and T. acaulis were counted, whereas A. barnebyi and C. fruticosa did not flower during the experimental period. The number of shoots were counted, and leaf area was measured using an area meter (LI-3100; LI-COR® Biosciences, Lincoln, NE). In addition, shoot dry weight was taken after plants were dried in an oven at 70 °C for 3 d.

Mineral analyses.

Three Sego SupremeTM plants per species per treatment were selected randomly and ground with a stainless Wiley mill (Thomas Scientific, Swedesboro, NJ) and allowed to pass through a 1-mm mesh screen. Powder samples were sent to the USU Analytical Laboratories for mineral analyses. In brief, the powder samples were extracted using 2% acetic acid (Fisher Scientific, Fair Lawn, NJ) following the protocol described in Miller et al. (2013). The Cl concentration was determined using a flow injection analysis and ion chromatography system (QuikChem 8000; Lachat Instrument, Loveland, CO) and reported on a dry plant basis (mg·g−1). For Na+, calcium (Ca2+), and potassium (K+), 0.5 g of powder samples and 8 mL of nitric acid (HNO3) were added into a digestion tube that was then placed in a digestion block (Environmental Express, Charleston, SC) at 95 °C for 1 h and subsequently cooled for 15 to 20 min. A total of 4 mL of 30% hydrogen peroxide (H2O2) was added into the digestion tube that was placed again in the digestion block at 95 °C for 30 min. The H2O2 addition was repeated two more times, and the tube was cooled for 15 to 20 min between H2O2 additions. Then the digestion tube was cooled at a room temperature, and deionized water was added to bring the final volume up to 25 mL. The digest was analyzed using an inductively coupled plasma-optical emission spectrometry (iCAP 6300 ICP-AES; Thermo Scientific, Waltham, MA) and reported on a dry plant basis (mg·g−1).

Experimental design and data analyses.

The experiment was conducted using a randomized complete block design with six blocks. Each block consisted of 20 plants (four species and five treatments). A two-way analysis of variance was conducted to test the effects of salinity and species on plant growth and mineral nutrient data. Linear and quadratic trend analysis was performed for all data. Correlation analysis was also carried out between mineral concentration and visual quality. All statistical analyses were performed using a generalized linear model in JMP (Version 13.2; SAS Institute, Cary, NC).

Results and Discussion

Leachate and substrate EC.

As Sego SupremeTM plants were irrigated with saline solution, the salinity levels of leachate solution gradually increased (Fig. 1). When irrigated with saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1, the ECs of the leachate solutions increased from 2.3 to 5.5 dS·m−1, 3.6 to 12.4 dS·m−1, 4.9 to 16.5 dS·m−1, and 6.4 to 18.8 dS·m−1, respectively. These values were greater than the EC of the leachate solution (1.7 ± 0.2 dS·m−1) when the nutrient solution was used. Leachate solution EC increased over time with increasing salinity of irrigation water, which verifies that salts accumulate in plant rhizosphere (Wu et al., 2016a).

Fig. 1.
Fig. 1.

Electrical conductivity (EC) of leachate solution collected after irrigating the Sego SupremeTM plants with a nutrient solution at an EC of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15 N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. Vertical bars represent standard errors of four measurements, one plant per treatment per species.

Citation: HortScience horts 54, 11; 10.21273/HORTSCI14342-19

Visual quality.

Saline solution had different effects on the visual quality of the four Sego SupremeTM plant species (Fig. 2A). The visual score of A. barnebyi and E. septentrionale decreased linearly [r2 = 0.95 (P < 0.0001) and r2 = 0.94 (P < 0.0001), respectively] with increasing EC levels in the treatment solution. However, the visual score of C. fruticosa and T. acaulis decreased quadratically [R2 = 0.998 (P = 0.008) and R2 = 0.995 (P = 0.0002), respectively] as EC levels increased. Aquilegia barnebyi showed slight foliar salt damage when irrigated with saline solution at an EC of 5.0 dS·m−1 with an average visual score of 3.7, but more than 50% of plants died when irrigated with saline solution at an EC of 7.5 or 10.0 dS·m−1. Similarly, Aquilegia canadensis (eastern red columbine) plants had moderate foliar salt damage when irrigated weekly with saline solution at an EC of 5.0 dS·m−1 for 8 weeks, and all plants died at an EC of 10.0 dS·m−1 (Wu et al., 2016a). Gerber et al. (2011) also reported that Aquilegia × cultorum ‘Crimson Star’ plants started to show foliar damage (marginal necrosis, chlorosis, and purpling) at the second weeks when they were watered with 0.05, 0.15, and 0.25 m NaCl solution (corresponding to about EC of 4.6, 11.0, and 18.3 dS·m−1, respectively). Clematis fruticosa, E. septentrionale, and T. acaulis irrigated with saline solution at an EC of 10.0 dS·m−1 had no or minimal foliar salt damage with averaged visual score of 4.2, 4.1, and 4.3, respectively. These results demonstrated that C. fruticosa, E. septentrionale, and T. acaulis had a strong tolerance to the salinity levels tested in this study. Likewise, in a 3-year field study, it is reported that all Clematis ispahanica plants survived without any foliar damage and their visual quality was still acceptable up to an EC of 16.3 dS·m−1 in the treatment solution (Razmjoo and Aslani, 2018). Conversely, Wu et al. (2016b) reported that Tetraneuris scaposa (four-nerve daisy) showed moderate to severe foliar salt damage when irrigated with saline solution at an EC of 5.0 dS·m−1 for 5 weeks and were almost all dead at an EC of 10.0 dS·m−1.

Fig. 2.
Fig. 2.

Visual score (A), height (B), leaf area (C), and number of shoots (D) of Sego SupremeTM plants after irrigating a nutrient solution at an EC of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. Visual score reference scale: 0 = dead; 1 = severe foliar damage (>90% leaves with burn, necrosis, and discoloration); 2 = moderate foliar damage (50% to 90%); 3 = slight foliar damage (50% to 10%); 4 = good quality with minimal foliar damage (<10%); 5 = excellent without foliar damage. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15 N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. Vertical bars represent standard errors of six measurements.

Citation: HortScience horts 54, 11; 10.21273/HORTSCI14342-19

Plant height.

Height of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased linearly [r2 = 0.96 (P < 0.0001), r2 = 0.94 (P = 0.0001), r2 = 0.98 (P < 0.0001), and r2 = 0.98 (P < 0.0001), respectively] as EC levels increased (Fig. 2B). Height of the four Sego SupremeTM plants irrigated with saline solution at an EC of 2.5 dS·m−1 were similar to that of the control. Saline solution at an EC of 5.0 dS·m−1 also did not affect the growth of C. fruticosa, but plants irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1 were 13.4% and 19.6% shorter than the control, respectively. When plants were irrigated with saline solutions at an EC of 5.0, 7.5, and 10.0 dS·m−1, plants were 36.7% to 63.7% shorter for A. barnebyi, 12.6% to 35.4% shorter for E. septentrionale, and 18.0% to 33.6% shorter for T. acaulis, respectively, compared with the respective control. Similarly, Wu et al. (2016a) observed a 75% reduction in a growth index (average of height and two perpendicular crown diameter) of A. canadensis when they were irrigated weekly with saline solution at an EC of 10.0 dS·m−1 for 8 weeks. Razmjoo and Aslani (2018) also found a 15% reduction in height of C. ispahanica when irrigated with saline solution at an EC of 16.3 dS·m−1. In a 4-week study by Hadi et al. (2014), there was a significant reduction in growth of Epilobium laxum (lax willowherb) at 6000 ppm NaCl solution (EC of ≈7.5 dS·m−1). Tetraneuris scaposa also had a 37.2% reduction in plant height when they were irrigated weekly with saline solution at an EC of 10.0 dS·m−1 for 5 weeks (Wu et al., 2016b).

Leaf area.

Leaf area decreased linearly for C. fruticosa and T. acaulis [r2 = 0.98 (P < 0.0001), and r2 = 0.91 (P < 0.0001), respectively], but quadratically for A. barnebyi and E. septentrionale [R2 = 0.98 (P = 0.0005) and R2 = 0.98 (P = 0.0004), respectively] with increasing EC levels (Fig. 2C). Compared with the control, the leaf area of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 82.5%, 56.2%, 82.5%, and 65.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Even at an EC of 5.0 dS·m−1, A. barnebyi and E. septentrionale had a high reduction in leaf area of 71.2% and 55.7%, respectively. Similar results regarding the reduction of leaf area with increasing concentration of saline solution were observed in previous studies on A. canadensis and Tagetes sp. (marigold) (Sun et al., 2018; Wu et al., 2016a).

Number of shoots and flowers.

Saline solution irrigation affected the number of shoots, but there were no interactive effects between salt treatment and Sego SupremeTM plant species. With increasing EC levels, the number of shoots of C. fruticosa and T. acaulis decreased linearly [r2 = 0.88 (P = 0.0003) and r2 = 0.84 (P = 0.004), respectively], but the number of shoots of E. septentrionale decreased quadratically [R2 = 0.98 (P = 0.0007)] (Fig. 2D). Similarly, Sun et al. (2015) reported that the number of shoots of M. arboreus, S. leucantha, and V. ×hybrida decreased significantly when irrigated with saline solution at an EC of 10.0 dS·m−1 for 8 weeks, whereas the number of shoots of S. farinacea was not reduced. Although the number of shoots of T. scaposa tended to decrease with saline solution irrigation at an EC of 10.0 dS·m−1 for 5 weeks but still was not significant (Wu et al., 2016b). In addition, A. barnebyi had no significant reduction in the number of shoots in this study.

In the same way, increasing salt levels of the irrigation water reduced the number of flowers linearly in E. septentrionale and T. acaulis [r2 = 0.74 (P = 0.0001) and r2 = 0.97 (P = 0.001), respectively] (Fig. 3A). Compared with the control, the number of flowers of E. septentrionale and T. acaulis decreased by 46.5% and 50.3%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. According to the study by Wu et al. (2016b), T. scaposa had a 50% reduction in the number of flowers when irrigated weekly with saline solution at an EC of 5.0 dS·m−1 for 5 weeks. High salinity levels can affect the development of flower buds, which fail to open or grow in flowering woody shrubs or trees (Azza-Mazher et al., 2007). Aquilegia barnebyi and C. fruticosa did not produce any flowers during the experimental period. However, lower numbers of shoots may help to predict a reduction in the number of flowers with increasing salt concentrations in the irrigation water. Razmjoo and Aslani (2018) actually observed a 20% reduction in the number of flowers of C. ispahanica when irrigated with saline solution at an EC of 16.3 dS·m−1.

Fig. 3.
Fig. 3.

Number of flowers (A), shoot dry weight (B), and relative chlorophyll content [soil-plant analysis development (SPAD)] (C) of Sego SupremeTM plants after irrigating with a nutrient solution at an electrical conductivity of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. No flowers were observed in A. barnebyi and C. fruticosa during the experimental period. Clematis fruticosa and E. septentrionale had no significant reduction in SPAD readings with increasing EC levels. Vertical bars represent standard errors of six measurements.

Citation: HortScience horts 54, 11; 10.21273/HORTSCI14342-19

Shoot dry weight.

Shoot dry weight decreased quadratically for A. barnebyi and E. septentrionale [R2 = 0.95 (P = 0.001) and R2 = 0.99 (P = 0.002), respectively] with increasing EC levels, but decreased linearly for C. fruticosa and T. acaulis [r2 = 0.92 (P < 0.0001) and r2 = 0.88 (P = 0.0017), respectively] (Fig. 3B). Compared with controls, the shoot dry weight of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis irrigated with saline solution at an EC of 10.0 dS·m−1 decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively. Elevated salinity has been reported to reduce plant shoot dry weight in various ornamental plants such as A. canadensis, aster perennials, E. laxum, and rose rootstocks (Hadi et al., 2014; Niu et al., 2008; Wu et al., 2016a, 2016b). This is a consequence of salinity-induced water deficit, resulting in stunted growth and reduced leaf size described earlier.

Relative chlorophyll content (SPAD).

Elevated salinity affected the SPAD readings of the four Sego SupremeTM plants with varying responses among species. Clematis fruticosa and T. acaulis had similar SPAD readings among different EC levels, which indicated that increased salinity level did not affect their relative chlorophyll content, but the SPAD readings decreased linearly [r2 = 0.42 (P = 0.05)] for A. barnebyi and quadratically [R2 = 0.75 (P = 0.02)] for E. septentrionale (Fig. 3C). Saline solution at an EC of 10.0 dS·m−1 decreased the SPAD readings of A. barnebyi and E. septentrionale by 17.7% and 6.2%, respectively. Similarly, Sun et al. (2015) documented that the SPAD readings of M. arboreus, R. brittoniana, and V. ×hybrida did not change, but S. farinacea and S. leucantha decreased significantly when irrigated weekly with saline solution at an EC of 10.0 dS·m−1 for 8 weeks. In a study of rose rootstocks by Niu et al. (2008), Rosa ×fortuniana had greater SPAD readings compared with R. ×multiflora and R. ×odorata when irrigated with saline solution at an EC of 6.0 dS·m−1 for 15 weeks. These results consistently indicated that salinity stress negatively affected the chlorophyll content and the effect is dependent on plant species.

Mineral analyses.

Sodium and Cl concentrations in the leaf tissue of Sego SupremeTM plants were significantly affected by both elevated salinity and plant species (Table 2). Sodium concentration of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis increased linearly [all r2 values ≥0.93 (all P values < 0.0001)] with increasing salt levels in the irrigation water. Compared with the respective control, A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis had 4 to 7 times increased Na+ concentration when irrigated with saline solution at an EC of 2.5 dS·m−1. Similarly, the Na+ concentrations were further increased by 17, 37, and 53 times for A. barnebyi; 13, 25, and 33 times for C. fruticosa; 9, 26, and 38 times for E. septentrionale; and 8, 18, and 35 times for T. acaulis when plants irrigated with saline solutions at ECs of 5.0, 7.5, and 10.0 dS·m−1, respectively. Chloride concentration of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis increased linearly [all r2 values ≥0.93 (all P values < 0.0001)] with increasing amount of salts in the irrigation water (Table 2). Compared with the respective control, the Cl concentration increased by 7, 24, 41, and 48 times for A. barnebyi, 6, 10, 13, and 16 times for C. fruticosa, 2, 6, 15, and 17 times for E. septentrionale, and 4, 5, 14, and 17 times for T. acaulis when plants were irrigated with saline solutions at ECs of 2.5, 5.0, 7.5, and 10.0 dS·m−1, respectively. Wu et al. (2016b) observed that T. scaposa irrigated weekly with saline solutions at an EC of 5.0 and 10.0 dS·m−1 for 5 weeks had 29 and 58 times more Na+ concentration and 9 and 21 times more Cl concentration in leaves than the control. These results indicate that T. scaposa accumulated much more Na+ concentration in the leaves than T. acaulis in the study, but similar Cl concentrations are observed in the leaves of both species. In another similar study, A. canadensis also accumulated a significant amount of Na+ and Cl ions in the leaves (Wu et al., 2016a), which were 6 and 35 times more for saline irrigation water at an EC of 5.0 dS·m−1, respectively, and 70 and 62 times more at an EC of 10.0 dS·m−1, respectively, compared with their respective control.

Table 2.

Leaf ion concentrations of Sego SupremeTM plants irrigated with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks.z

Table 2.

Sodium and Cl are common ions present in reclaimed water and cause leaf injury to plants (Wahome et al., 2001). Generally, salt-tolerant ornamental plants accumulate less Na+ and Cl ions in their leaves when compared with salt-sensitive plants (Wu et al., 2016a). In this study, Na+ and Cl concentrations significantly increased in A. barnebyi compared with the other three species, which is in line with the lower visual quality of A. barnebyi with increasing salt levels in the irrigation water. There was a significant correlation of visual score to Na+ [r = –0.94 (P < 0.0001)] and Cl [r = –0.96 (P < 0.0001)] concentration. These results point out that, like A. canadensis, A. barnebyi has low tolerance of Na+ and Cl accumulation and poor potential to exclude these ions from plant tissue. On the other hand, some plants can tolerate accumulated Na+ and Cl in shoot tissue (Munns and Tester, 2008). In this study, T. acaulis and C. fruticosa accumulated high levels of Na+ and Cl- ions in the leaves and still had good visual quality. These results indicate that T. acaulis and C. fruticosa can tolerate high accumulation of Na+ and Cl ions in the tissue. Krupenikov (1946) also reported that Clematis orientalis (chinese clematis) was tolerant over 2.0% of total salts, which is calculated on the basis of solid residue. Similarly, Wu et al. (2016a) indicated that Scabiosa columbaria (butterfly blue), Lobelia cardinalis (cardinal flower), A. canadensis, and Cuphea hyssopifolia (mexican false heather) plants had severe foliar salt damage with increasing Na+ and Cl concentration in shoots, whereas Dicliptera suberecta (Mexican hummingbird bush) and Cestrum diurnum × C. nocturnum ‘Orange Peel’ (orange peel jessamine) plants had the ability to tolerate high Na+ and Cl accumulation without a reduction in visual quality.

Calcium concentration in the leaf tissue was affected by both salt treatment and plant species interactively (Table 2). The Ca2+ concentration in the leaves of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis increased linearly [r2 = 0.96 (P < 0.0001), r2 = 0.83 (P = 0.008), r2 = 0.91 (P < 0.0001), and r2 = 0.91 (P = 0.0004), respectively] with elevated salt levels in the irrigation water. There was only a slight increase in the Ca2+ concentration compared with the increment in Na+ and Cl concentration, although CaCl2 was used to prepare the saline solution. Compared with the control, leaf Ca2+ concentration of A. barnebyi irrigated with saline solution at an EC of 10.0 dS·m−1 increased by 175.3%, which was the greatest increment observed among all tested plants in all treatments. In addition, there was a significant correlation of visual score and Ca2+ concentration of A. barnebyi [r = –0.89 (P < 0.0001)]. Nazrul-Islam (1986) reported that Epilobium hirsutum (great willowherb) grows well in calcareous soil and is susceptible to lower calcium level. Similarly, in the present study calcium level may not be sufficient for E. septentrionale at higher EC levels and they showed more reduction in shoot dry weight when compared with C. fruticosa and T. acaulis. Moreover, plant requirements for Ca2+ ions increase with increasing concentration of salts in the root zone. However, Ca2+ transport and mobility to growing parts of plant is reduced by Na+ dominated salinity stress (Grattan and Grieve, 1999).

Increasing salt concentration in the irrigation water linearly decreased the amount of K+ ions in the leaves of C. fruticosa, E. septentrionale, and T. acaulis (Table 2). However, elevated salinity did not affect the K+ concentration of A. barnebyi. Compared with the control, the leaf K+ concentration of C. fruticosa, E. septentrionale, and T. acaulis irrigated with saline solution at an EC of 10.0 dS·m−1 declined by 25.1%, 32.7%, and 43.8%, respectively. When plants are exposed to salinity stress induced by high NaCl levels, Na+ accumulation increases and causes a reduction in K+ concentration (Hasegawa et al., 2000). Similar observations are made on Chrysactinia mexicana (damianita), T. scaposa, Santolina chamaecyparissus (lavender cotton), Leucanthemum ×superbum (Shasta daisy), and Viguiera stenoloba (skeletonleaf goldeneye) (Wu et al., 2016b), S. columbaria and C. diurnum × C. nocturnum ‘Orange Peel’, but not for A. Canadensis (Wu et al., 2016a).

In summary, Sego SupremeTM plants had different responses to saline water irrigation. Clematis fruticosa and T. acaulis were the most tolerant perennials with the least reduction in visual score and growth when irrigated with saline solution. Epilobium septentrionale was moderately tolerant, and A. barnebyi was the least tolerant perennial to saline solution irrigation with the most reduced visual quality and growth while showing the greatest increase in leaf Na+ and Cl concentrations. These results are helpful for selecting salt tolerant Sego SupremeTM plant species for use in the landscape where reclaimed water is used for irrigation.

Literature Cited

  • Aggie Horticulture 2019 Texas AgriLife Extension Service. Earth-Kind® roses, College Station, TX. 2 Apr. 2019. <https://aggie-horticulture.tamu.edu/earthkindroses/>.

  • Anderson, R., Goodspeed, J.L., Gunnell, J. & Rupp, L. 2014 Going native in the landscape. Sego SupremeTM plants. Kaysville, UT. 2 Apr. 2019. <https://slco.org/uploadedFiles/depot/publicWorks/fwatershed/symposium2014/GoingNativeInTheLand.pdfs>.

  • Azza-Mazher, A.M., Fatma EI-Quesni, E.M. & Farahat, M.M. 2007 Responses of ornamental plants and woody trees to salinity World J. Agr. Sci. 3 386 395

  • Cai, X., Sun, Y., Starman, T., Hall, C. & Niu, G. 2014 Response of 18 Earth-Kind® rose cultivars to salt stress HortScience 49 544 549

  • California Flora Nursery 2019 Epilobium septentrionale. Fulton, CA. 2 Apr. 2019. <https://www.calfloranursery.com/plants/epilobium-select-mattole>.

  • Cassaniti, C., Romano, D.I., Hop, M.E.C.M. & Flowers, T.J. 2013 Growing floricultural crops with brackish water Environ. Expt. Bot. 92 165 175

  • Cavins, T.O., Whipker, B.E. & Fonteno, W.C. 2008 Pourthru: A method for monitoring nutrition in the greenhouse Acta Hort. 779 289 297

  • Chinnusamy, V., Jagendorf, A. & Zhu, J.K. 2005 Understanding and improving salt tolerance in plants Crop Sci. 45 437 448

  • Colorado Gardening 2019 Resources. Plant Select®. Fort Collins, Colorado. 2 Apr. 2019. <http://www.coloradogardening.com/resources-plantselect.htm>.

  • Dave’s Garden 2019 Aquilegia barnebyi. El Segundo, CA. 2 Apr. 2019. <https://davesgarden.com/guides/pf/go/73538/>.

  • Gerber, C., Deeter, L., Hylton, K. & Stilwill, B. 2011 Preliminary study of sodium chloride tolerance of Rudbeckia fulgida var. speciosa ‘Goldsturm’, Heuchera americana ‘Dale’s Variety’ and Aquilegia × cultorum ‘Crimson Star’ grown in greenhouse conditions J. Environ. Hort. 29 4 2056 2062

    • Search Google Scholar
    • Export Citation
  • Grattan, S.R. & Grieve, C.M. 1999 Salinity–mineral nutrient relations in horticultural crops Scientia Hort. 78 127 157

  • Hadi, F., Ahmad, A. & Ali, N. 2014 Cadmium (Cd) removal from saline water by Veronica anagallis and Epilobium laxum plants in hydroponic system Agr. Sci. 5 935 944

    • Search Google Scholar
    • Export Citation
  • Hasegawa, P.M., Bressan, R.A., Zhu, J.K. & Bohnert, H.J. 2000 Plant cellular and molecular responses to high salinity Annu. Rev. Plant Physiol. Plant Mol. Biol. 51 463 499

    • Search Google Scholar
    • Export Citation
  • Krupenikov, I.A. 1946 On the salt resistance of Clematis orientalis L. under natural conditions Acad. Sci. U. R. S. S., Compt. Rend. 53 271 272

    • Search Google Scholar
    • Export Citation
  • Mackay, W., George, S.W., Davis, T.D., Arnold, M.A., Lineberger, R.D., Parsons, J.M., Stein, L.A. & Grant, G.G. 2001 Texas Superstar® and the coordinated educational and marketing assistance program (CEMAP): How we operate HortTechnology 11 389 391

    • Search Google Scholar
    • Export Citation
  • Miller, R.O., Gavlak, R.G. & Horneck, D.A. 2013 Soil, plant, and water reference methods for the western region. Western Regional Extension Publication (WREP) 125

  • Missouri Botanical Garden 2019 Plant finder. Clematis fruticosa ‘Mongolian Gold’. St. Louis, MO. 2 Apr. 2019. <http://www.missouribotanicalgarden.org/PlantFinder>.

  • Moosa Creek Nursery 2019 Tetraneuris acaulis. Valley Center, CA. 2 Apr. 2019. <http://www.moosacreeknursery.com/Native_Plants/547/Tetraneuris-acaulis>.

  • Munns, R. & Tester, M. 2008 Mechanisms of salinity tolerance Annu. Rev. Plant Biol. 59 651 681

  • National Information Management and Support System 2019 WERA1013: Intermountain regional evaluation and introduction of native plants. U.S. Department of Agriculture, National Institute for Food and Agriculture, Washington, D.C. 2 Apr. 2019. <https://www.nimss.org/projects/view/mrp/outline/15499>.

  • Nazrul-Islam, A.K.M. 1986 Effects of interaction of calcium and manganese on the growth and nutrition of Epilobium hirsutum L Soil Sci. Plant Nutr. 32 2 2056 2062

    • Search Google Scholar
    • Export Citation
  • Niu, G., Rodriguez, D.S. & Aguiniga, L. 2008 Effect of saline water irrigation on growth and physiological responses of three rose root-stocks HortScience 43 1479 1484

    • Search Google Scholar
    • Export Citation
  • Niu, G. & Cabrera, R.I. 2010 Growth and physiological responses of landscape plants to saline water irrigation: A review HortScience 45 1605 1609

  • Razmjoo, J. & Aslani, H. 2018 Clematis ispahanica Boiss. performances under drought and salinity stresses in Isfahan region Acta Hort. 1190 77 82

  • Sun, Y., Niu, G. & Perez, C. 2015 Relative salt tolerance of seven Texas Superstar® perennials HortScience 50 1562 1566

  • Sun, Y., Niu, G., Perez, C., Pemberton, H.B. & Altland, J. 2018 Responses of marigold cultivars to saline water irrigation HortTechnology 28 166 171

  • U.S. Department of Agriculture 2019 Natural Resources Conservation Service, The Plant Database. National Plant Data Team, Greensboro, NC. 2 Apr. 2019. <https://plants.usda.gov/core/profile?>.

  • Wahome, P.K., Jesch, H.H. & Grittner, I. 2001 Mechanisms of salt stress tolerance in two rose rootstocks: Rosa chinensis ‘Major’ and R. rubiginosa Scientia Hort. 87 207 216

    • Search Google Scholar
    • Export Citation
  • Wang, Y., Sun, Y., Niu, G., Deng, C., Wang, Y. & Gardea-Torresdey, J. 2019 Growth, gas exchange, and mineral nutrients of ornamental grasses irrigated with saline water HortScience 54 1840 1846

    • Search Google Scholar
    • Export Citation
  • Wu, S., Sun, Y. & Niu, G. 2016a Morphological and physiological responses of nine ornamental species to saline irrigation water HortScience 51 285 290

    • Search Google Scholar
    • Export Citation
  • Wu, S., Sun, Y., Niu, G., Altland, J. & Cabrera, R. 2016b Response of 10 aster species to saline water irrigation HortScience 51 197 201

Contributor Notes

This research was supported in part by the U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture Hatch project UTA01381, New Faculty Start-Up Funds from the Office of Research and Graduate Studies, the Center for Water-Efficient Landscaping at Utah State University. This research was also supported by the Utah Agricultural Experiment Station, Utah State University, and approved as journal paper no. 9226. We are grateful for valuable comments from Dr. Larry Rupp and other anonymous reviewers. We appreciate the financial support from Grassology Peak Discipline Foundation of Xinjiang Uygur Autonomous Region and National Modern Agricultural Technology & Industry System (CARS-34) of China to Yuxiang Wang as a visiting scholar at Utah State University, Logan, UT.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the funding agencies. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the USDA and the American Society for Horticultural Science and does not imply its approval to the exclusion of other products or vendors that also may be suitable.

Y.S. is the corresponding author. E-mail: youping.sun@usu.edu.

  • View in gallery

    Electrical conductivity (EC) of leachate solution collected after irrigating the Sego SupremeTM plants with a nutrient solution at an EC of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15 N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. Vertical bars represent standard errors of four measurements, one plant per treatment per species.

  • View in gallery

    Visual score (A), height (B), leaf area (C), and number of shoots (D) of Sego SupremeTM plants after irrigating a nutrient solution at an EC of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. Visual score reference scale: 0 = dead; 1 = severe foliar damage (>90% leaves with burn, necrosis, and discoloration); 2 = moderate foliar damage (50% to 90%); 3 = slight foliar damage (50% to 10%); 4 = good quality with minimal foliar damage (<10%); 5 = excellent without foliar damage. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15 N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. Vertical bars represent standard errors of six measurements.

  • View in gallery

    Number of flowers (A), shoot dry weight (B), and relative chlorophyll content [soil-plant analysis development (SPAD)] (C) of Sego SupremeTM plants after irrigating with a nutrient solution at an electrical conductivity of 1.25 dS·m−1 or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1. A nutrient solution at an EC of 1.25 dS·m−1 was prepared by adding 0.8 g·L−1 15N–2.2P–12.5K water-soluble fertilizer (Peters Excel 15–5–15 Cal-Mag Special) to tap water. Sodium chloride (NaCl) and calcium chloride (CaCl2) were added to the nutrient solution to make the saline solutions. No flowers were observed in A. barnebyi and C. fruticosa during the experimental period. Clematis fruticosa and E. septentrionale had no significant reduction in SPAD readings with increasing EC levels. Vertical bars represent standard errors of six measurements.

  • Aggie Horticulture 2019 Texas AgriLife Extension Service. Earth-Kind® roses, College Station, TX. 2 Apr. 2019. <https://aggie-horticulture.tamu.edu/earthkindroses/>.

  • Anderson, R., Goodspeed, J.L., Gunnell, J. & Rupp, L. 2014 Going native in the landscape. Sego SupremeTM plants. Kaysville, UT. 2 Apr. 2019. <https://slco.org/uploadedFiles/depot/publicWorks/fwatershed/symposium2014/GoingNativeInTheLand.pdfs>.

  • Azza-Mazher, A.M., Fatma EI-Quesni, E.M. & Farahat, M.M. 2007 Responses of ornamental plants and woody trees to salinity World J. Agr. Sci. 3 386 395

  • Cai, X., Sun, Y., Starman, T., Hall, C. & Niu, G. 2014 Response of 18 Earth-Kind® rose cultivars to salt stress HortScience 49 544 549

  • California Flora Nursery 2019 Epilobium septentrionale. Fulton, CA. 2 Apr. 2019. <https://www.calfloranursery.com/plants/epilobium-select-mattole>.

  • Cassaniti, C., Romano, D.I., Hop, M.E.C.M. & Flowers, T.J. 2013 Growing floricultural crops with brackish water Environ. Expt. Bot. 92 165 175

  • Cavins, T.O., Whipker, B.E. & Fonteno, W.C. 2008 Pourthru: A method for monitoring nutrition in the greenhouse Acta Hort. 779 289 297

  • Chinnusamy, V., Jagendorf, A. & Zhu, J.K. 2005 Understanding and improving salt tolerance in plants Crop Sci. 45 437 448

  • Colorado Gardening 2019 Resources. Plant Select®. Fort Collins, Colorado. 2 Apr. 2019. <http://www.coloradogardening.com/resources-plantselect.htm>.

  • Dave’s Garden 2019 Aquilegia barnebyi. El Segundo, CA. 2 Apr. 2019. <https://davesgarden.com/guides/pf/go/73538/>.

  • Gerber, C., Deeter, L., Hylton, K. & Stilwill, B. 2011 Preliminary study of sodium chloride tolerance of Rudbeckia fulgida var. speciosa ‘Goldsturm’, Heuchera americana ‘Dale’s Variety’ and Aquilegia × cultorum ‘Crimson Star’ grown in greenhouse conditions J. Environ. Hort. 29 4 2056 2062

    • Search Google Scholar
    • Export Citation
  • Grattan, S.R. & Grieve, C.M. 1999 Salinity–mineral nutrient relations in horticultural crops Scientia Hort. 78 127 157

  • Hadi, F., Ahmad, A. & Ali, N. 2014 Cadmium (Cd) removal from saline water by Veronica anagallis and Epilobium laxum plants in hydroponic system Agr. Sci. 5 935 944

    • Search Google Scholar
    • Export Citation
  • Hasegawa, P.M., Bressan, R.A., Zhu, J.K. & Bohnert, H.J. 2000 Plant cellular and molecular responses to high salinity Annu. Rev. Plant Physiol. Plant Mol. Biol. 51 463 499

    • Search Google Scholar
    • Export Citation
  • Krupenikov, I.A. 1946 On the salt resistance of Clematis orientalis L. under natural conditions Acad. Sci. U. R. S. S., Compt. Rend. 53 271 272

    • Search Google Scholar
    • Export Citation
  • Mackay, W., George, S.W., Davis, T.D., Arnold, M.A., Lineberger, R.D., Parsons, J.M., Stein, L.A. & Grant, G.G. 2001 Texas Superstar® and the coordinated educational and marketing assistance program (CEMAP): How we operate HortTechnology 11 389 391

    • Search Google Scholar
    • Export Citation
  • Miller, R.O., Gavlak, R.G. & Horneck, D.A. 2013 Soil, plant, and water reference methods for the western region. Western Regional Extension Publication (WREP) 125

  • Missouri Botanical Garden 2019 Plant finder. Clematis fruticosa ‘Mongolian Gold’. St. Louis, MO. 2 Apr. 2019. <http://www.missouribotanicalgarden.org/PlantFinder>.

  • Moosa Creek Nursery 2019 Tetraneuris acaulis. Valley Center, CA. 2 Apr. 2019. <http://www.moosacreeknursery.com/Native_Plants/547/Tetraneuris-acaulis>.

  • Munns, R. & Tester, M. 2008 Mechanisms of salinity tolerance Annu. Rev. Plant Biol. 59 651 681

  • National Information Management and Support System 2019 WERA1013: Intermountain regional evaluation and introduction of native plants. U.S. Department of Agriculture, National Institute for Food and Agriculture, Washington, D.C. 2 Apr. 2019. <https://www.nimss.org/projects/view/mrp/outline/15499>.

  • Nazrul-Islam, A.K.M. 1986 Effects of interaction of calcium and manganese on the growth and nutrition of Epilobium hirsutum L Soil Sci. Plant Nutr. 32 2 2056 2062

    • Search Google Scholar
    • Export Citation
  • Niu, G., Rodriguez, D.S. & Aguiniga, L. 2008 Effect of saline water irrigation on growth and physiological responses of three rose root-stocks HortScience 43 1479 1484

    • Search Google Scholar
    • Export Citation
  • Niu, G. & Cabrera, R.I. 2010 Growth and physiological responses of landscape plants to saline water irrigation: A review HortScience 45 1605 1609

  • Razmjoo, J. & Aslani, H. 2018 Clematis ispahanica Boiss. performances under drought and salinity stresses in Isfahan region Acta Hort. 1190 77 82

  • Sun, Y., Niu, G. & Perez, C. 2015 Relative salt tolerance of seven Texas Superstar® perennials HortScience 50 1562 1566

  • Sun, Y., Niu, G., Perez, C., Pemberton, H.B. & Altland, J. 2018 Responses of marigold cultivars to saline water irrigation HortTechnology 28 166 171

  • U.S. Department of Agriculture 2019 Natural Resources Conservation Service, The Plant Database. National Plant Data Team, Greensboro, NC. 2 Apr. 2019. <https://plants.usda.gov/core/profile?>.

  • Wahome, P.K., Jesch, H.H. & Grittner, I. 2001 Mechanisms of salt stress tolerance in two rose rootstocks: Rosa chinensis ‘Major’ and R. rubiginosa Scientia Hort. 87 207 216

    • Search Google Scholar
    • Export Citation
  • Wang, Y., Sun, Y., Niu, G., Deng, C., Wang, Y. & Gardea-Torresdey, J. 2019 Growth, gas exchange, and mineral nutrients of ornamental grasses irrigated with saline water HortScience 54 1840 1846

    • Search Google Scholar
    • Export Citation
  • Wu, S., Sun, Y. & Niu, G. 2016a Morphological and physiological responses of nine ornamental species to saline irrigation water HortScience 51 285 290

    • Search Google Scholar
    • Export Citation
  • Wu, S., Sun, Y., Niu, G., Altland, J. & Cabrera, R. 2016b Response of 10 aster species to saline water irrigation HortScience 51 197 201

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