Foliar Salt Damage Research Articles

Variability in Salt Tolerance of Sorghum bicolor L.

Salt tolerance of ten sorghum (Sorghum bicolor L. Moench) varieties (‘1790E’, ‘BTx642’, ‘Desert Maize’, ‘Macia’, ‘RTx430’, ‘Schrock’, ‘Shallu’, ‘Tx2783’, ‘Tx7078’, and ‘Wheatland’) was evaluated in two greenhouse experiments. In the first experiment, sorghum were sown in substrates moistened with either nutrient solution (no addition of salts, control) at electrical conductivity (EC) of 1.2 dS·m-1 or salt solution at EC 5, 10 or 17 dS·m-1. Seedling emergence percentage decreased in all varieties only at EC of 17 dS·m-1 compared to the control. Seedling emergence percentage of sorghum ‘Macia’ and ‘1790E’ irrigated with salt solution at EC of 17 dS·m-1 decreased by 50% and 51%, while that of ‘RTx430’ reduced by 97%, other varieties ranged from 64% to 90%. Both salt solution at EC of 5 and 10 dS·m-1 reduced the dry weight of sorghum seedlings by 29% and 72% on average, respectively, compared to control. In the 2nd experiment, plants were irrigated with nutrient solution or salt solution at EC of 5.0 or 10.0 dS·m-1 for 30 days. Salt solution at EC of 5.0 and 10.0 dS·m-1 had similar influences on dry weight (DW) of all sorghum varieties except ‘Tx2783’. The relative dry weight of ‘Shallu’, ‘Desert Maize’, and ‘1790E’ irrigated with salt solution at EC of 10 dS·m-1 were over 67%, those of ‘Macia’, ‘Schrock’, and ‘RTx430’ ranged from 30% to 33%, and other varieties were 45% to 59%. Foliar salt damage was observed on all salt-treated sorghum varieties except for ‘Shallu’, which had the lowest shoot DW reduction and greatest visual score. Leaf photosynthesis of all sorghum plants irrigated with salt solution at EC of 5 and 10 dS·m-1 was decreased by 6.0% and 10.6%, respectively. Leaf Na+ concentration at EC of 5.0 and 10.0 dS·m-1 increased by 25.6% and 60.7%, respectively, compared to the control; while Cl- concentration increased by 16.4% and 41.2%, and Ca2+ concentration increased by 17.8% and 34.3%. In conclusion, salt tolerance of sorghum varied with plant growing stage and varieties. ‘Shallu’, ‘Desert Maize’, and ‘1790E’ were the most salt tolerant varieties, while ‘Schrock’ and ‘RTx430’ showed the least salt tolerance in both experiments. All varieties had high Na+ exclusion ability.

Seedling Emergence, Growth, and Mineral Nutrition of Ornamental Chile Peppers Irrigated with Saline Water

Ornamental chile peppers are popular bedding plants. As high-quality water supply becomes limited in many parts of the world, alternative waters such as municipal reclaimed water is encouraged to be used for landscape irrigation. The purpose of this study was to assess the relative salt tolerance of 10 cultivars of ornamental chile peppers by irrigating the mature plants with saline solutions and germinating seeds in saline substrate in a greenhouse. In the mature plant salt tolerance experiment, plants were irrigated with nutrient solution (no addition of salts, control) or saline solution at electrical conductance (EC) of 4.1 dS·m−1 or 8.1 dS·m−1 for 8 weeks. Plants in the EC of 4.1 dS·m−1 treatment did not have any foliar salt damage regardless of cultivar. At EC of 8.1 dS·m−1, ‘NuMex Memorial Day’ had the most severe foliar salt damage, whereas ‘NuMex April Fool’s Day’, ‘NuMex Cinco de Mayo’, ‘NuMex Thanksgiving’, and ‘NuMex Twilight’ had little or no foliar damage. Shoot dry weight (DW) reduction at EC of 8.1 dS·m−1 compared with control was smallest in ‘NuMex Thanksgiving’ (15%), whereas ‘NuMex Memorial Day’ had the greatest reduction of 74% followed by ‘NuMex Christmas’ of 61%. The highest shoot DW reduction in ‘NuMex Memorial Day’ coincided with lowest visual score, indicating that this cultivar was the least tolerant to salinity. The leaf Na+ and Cl− concentrations increased dramatically with increasing EC of the irrigation water in all cultivars. The highest Na+ concentration of 10.9 mg·g−1 DW at EC of 8.1 dS·m−1 was observed in ‘NuMex Christmas’. The highest Cl− concentration at EC of 8.1 dS·m−1 was found in ‘NuMex Memorial Day’ with 64.8 mg·g−1 DW, which was four times higher than the control. In the seedling emergence experiment, seeds of the 10 cultivars were germinated in substrate either moistened with reverse osmosis water (EC ≈0) or saline solution at EC of 17.1 dS·m−1. ‘NuMex Christmas’ and ‘NuMex Memorial Day’ had the lowest relative seedling emergence index, indicating that these two cultivars were the least tolerant to salinity during the seedling emergence stage. ‘NuMex Thanksgiving’ and ‘NuMex Cinco de Mayo’ had the highest relative seedling emergence index. Combining the results from both experiments, we concluded that ‘NuMex Cinco de Mayo’ and ‘NuMex Thanksgiving’ were the most tolerant cultivars, whereas ‘NuMex Christmas’ and ‘NuMex Memorial Day’ were the least tolerant ones.

Response of Selected Wildflower Species to Saline Water Irrigation

Wildflowers are good candidates for water-wise landscapes because many of them are drought-tolerant after establishment. Little information is available regarding whether these herbaceous wildflowers are tolerant to salt stress. Container experiments were carried out in a greenhouse and a shadehouse under semiarid climate conditions to investigate the salt tolerance of six native wildflowers: Salvia farinacea (mealy cup sage), Berlandiera lyrata (chocolate daisy), Ratibida columnaris (Mexican hat), Oenothera elata (Hooker’s evening primrose), Zinnia grandiflora (plains zinnia), and Monarda citriodora (lemon horsemint). In the greenhouse experiment, mealy cup sage, Hooker’s evening primrose, and plains zinnia were irrigated with a saline solution with an electrical conductivity (EC) of 1.5 (control, nutrient solution), 2.8, 4.1, 5.1, or 7.3 dS·m−1 for 45 days. All plants survived except for plains zinnia at EC of 7.3 dS·m−1. Shoot dry weights decreased as EC of irrigation water increased for all three species. In the shadehouse experiment (second year), plants of all species (plains zinnia was not included) were irrigated with saline solutions at EC of 0.8 (control, tap water), 2.8, 3.9, 5.5, or 7.3 dS·m−1 for 35 days. Plants were fertilized with slow-release fertilizer in the shadehouse experiment. After 5 weeks of treatment, all plants of lemon horsemint in the elevated salinity treatments, regardless of EC levels, were dead. The visual foliar salt damage rating was lowest for lemon horsemint. Chocolate daisy had low survival percentages and low foliar ratings at EC of 5.5 dS·m−1 and 7.3 dS·m−1. For the other three species, survival percentages were 80% and 90% at EC of 7.3 dS·m−1. Hooker’s evening primrose and mealy cup sage had similar low foliar visual ratings at EC of 7.3 dS·m−1, whereas Mexican hat plants had high foliar visual ratings regardless of salinity treatment. All species had similar high uptake of Na+ in shoots, whereas Hooker’s evening primrose had slightly higher Cl− concentrations compared with other species. Based on these results, lemon horsemint was most sensitive to salinity stress followed by chocolate daisy. Hooker’s evening primrose and mealy cup sage were moderately tolerant and may be irrigated with low salinity water at EC of less than 3.9 dS·m−1. Mexican hat was the most tolerant among the six species.

Responses ofJatropha curcasto Salt and Drought Stresses

Two greenhouse experiments were conducted to quantify growth responses ofJatropha curcasto a range of salt and drought stresses. Typical symptoms of salinity stress such as leaf edge yellowing were observed in all elevated salinity treatments and the degree of the foliar salt damage increased with the salinity of irrigation water. Total dry weight (DW) of Jatropha plants was reduced by 30%, 30%, and 50%, respectively, when irrigated with saline solutions at electrical conductivity of 3.0, 6.0, and 9.0 dSm−1compared to that in the control. LeafNa+concentration was much higher than that observed in most glycophytes. LeafCl−concentrations were also high. In the drought stress experiment, plants were irrigated daily with nutrient solution at 100%, 70%, 50%, or 30% daily water use (DWU). Deficit irrigation reduced plant growth and leaf development. The DW of leaves, roots, and total were reduced in the 70%, 50%, and 30% DWU compared to the 100% DWU control treatment. In summary, salinity stress and deficit irrigation significantly reduced the growth and leaf development of greenhouse-grown Jatropha plants.

Responses of Growth and Ion Uptake of Four Rose Rootstocks to Chloride- or Sulfate-dominated Salinity

Salt-tolerant garden roses (Rosa L.) are needed for arid and semiarid regions where high-quality water supply is limited and soil salinization often occurs. This greenhouse study evaluated growth, ion uptake characteristics, and the daily evapotranspiration rate (ET) of four rose rootstocks [‘Dr. Huey’ (Rosa ×hybrida L.), R. ×fortuniana Lindl., R. multiflora Thunb., and R. odorata (Andr.) Sweet] irrigated with saline solutions with chloride or sulfate as the dominant salts. After 16 weeks of treatment, the elevated salinities reduced growth of all rootstocks, but the magnitude varied with the rootstock and dominant salt type. At moderate [3.9 dS·m−1 electrical conductivity (EC)] and high salinities (7.9 to 8.2 dS·m−1), chloride-dominated salinity led to a greater growth reduction in R. × fortuniana, followed by R. odorata and R. multiflora. At high salinity dominated by sulfate, R. odorata had a greater growth reduction, followed by R. multiflora, ‘Dr. Huey’, and R. ×fortuniana. For R. multiflora, growth was reduced more in chloride-dominated salinity at high salinity levels, but no differences were found in the growth between the two salt types at moderate salinity. Rosa multiflora accumulated more Na than R. odorata, and R. ×fortuniana accumulated the least. However, R. multiflora retained most the Na in the roots, whereas R. odorata transported 57% of the Na to shoots. All rootstocks had a similar high leaf Cl concentration at high salinity dominated by chloride, while R. ×fortuniana had the most severe foliar salt damage, indicating that R. ×fortuniana had a lower threshold concentration of tissue Cl. At moderate salinity, all rootstocks had acceptable visual quality. At high salinity, the appearance of all rootstocks declined with typical salt damage on lower, older leaves, and the plants had lower visual scores in chloride-dominated salinity, especially in R. ×fortuniana. Salinity treatment did not affect the daily ET per unit leaf area, regardless of rootstock and dominant salt type. Daily ET per pot was the smallest in R. ×fortuniana among the four rootstocks due to its smaller total leaf area. The four rootstocks responded differently to salinity and dominant salt type.