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Two cultivars of Matthiola incana (L.) R. Br. (`Cheerful White' and `Frolic Carmine') were grown in greenhouse sand cultures to determine the effect of salt stress on growth, ion relations, and flower quality. Two types of irrigation waters, differing in ion composition, were prepared to simulate saline wastewaters commonly present in two inland valley locations in California. Solution ICV was typical of saline tailwaters frequently found in the Imperial and Coachella Valleys and contained Cl^–, Na⁺, SO₄ ^2–, Mg²⁺, Ca²⁺, predominating in that order. Solution SJV was dominated by Na⁺ and SO₄ ^2– and simulated saline drainage effluents often present in the San Joaquin Valley. Five treatments of each salinity type were imposed; each was replicated three times. Electrical conductivities of the irrigation waters (EC_i) were 2.5, 5, 8, 11, and 14 dS·m^–1. Plant heights were determined weekly. Seedlings were sampled for ion analysis 9 weeks after planting. Flowering stems were harvested when about 50% of the florets in the inflorescence were open. Total stem length, weight and diameter, numbers of florets and buds, and inflorescence length were measured at final harvest. All plants remained healthy throughout the experimental period with no visible signs of ion toxicity or deficiency. Although length of the flowering stems decreased with increasing salinity, stems were of marketable quality even at the highest salinity level. Mineral ion composition of the vegetative tissues generally reflected ion concentrations in the irrigation waters. Shoot Mg²⁺ and Cl^– were higher and shoot Na⁺ lower in seedlings irrigated with ICV waters than with SJV waters. Shoot P was reduced over control levels once salinity exceeded 11 dS·m^–1. Both cultivars were highly selective for K⁺ over Na ⁺ and selectivity coefficients (S_{K, Na}) increase about 60% as salinity increased from 2.5 to 14 dS·m^–1. This study illustrates that commercially acceptable cut flowers of stock may be produced under irrigation with moderately saline wastewaters.

Abstract

The salt tolerance of cultivars of muskmelon (Cucumis melo, L.) was established under 2 levels of radiation in a glasshouse experiment. ‘Galia’ and ‘Top Mark’ muskmelon differed very little in salt tolerance at either radiation level. The maximum electrical conductivity of a saturated soil extract without yield reduction, the salt tolerance threshold, was 2.0 dS m⁻¹. Beyond the threshold, yield was reduced at a rate of 14.3% per unit increase in soil salinity. Both cultivars were more salt-tolerant at the higher level of solar radiation.

The capture and reuse of nutrient-rich greenhouse effluents may be an environmentally sound option for floriculture production, which would conserve fresh water resources and reduce off-site pollution of surface and groundwaters. This study was initiated in 24 outdoor lysimeters to determine effects of salinity and varying concentrations of nitrogen on the growth, yield, and ion relations of stock [Matthiola incana (L.) R. Br.] cultivar Cheerful White. The experiment was a 4 × 4 factorial, partially replicated design with four irrigation water salinities (2, 5, 8, and 11 dS·m⁻¹) and four nitrate concentrations (2.5, 3.6, 5.4, and 7.1 mmol·L⁻¹; N = 35, 50, 75, and 100 ppm). Ammonium nitrogen was included in the nutrient solutions. Stem lengths were measured three times weekly. Measurements at final harvest were stem and inflorescence lengths, stem and floret diameters, number of axillary buds and florets, and shoot and root fresh weights. Time course of stem elongation was quantified as a function of thermal time with a phasic growth model. Salinity significantly delayed initiation of the exponential growth phase, shortened its duration, and reduced the rate of plant development. The overall effect was to delay time to harvest of marketable stems. Although length of the flowering stems decreased with increasing salinity, marketable stems (≈60 cm) were produced in all treatments. Mineral ion relations in the plant tissues were influenced significantly, but independently, by both salinity and nitrogen. Leaf sodium, magnesium, and chlorine concentrations increased with increasing salinity; calcium and potassium decreased. In response to increasing external nitrogen, both potassium and chlorine decreased; sodium increased, whereas calcium and magnesium were unaffected. We conclude that in closed-loop irrigation systems, the nitrogen requirements for stock are low and that growers could minimize costs and limit off-site pollution by reducing nitrogen inputs.

Common stock flower production can be achieved under moderate levels of salinity and relatively low levels of nitrogen with no significant decrease in quality in a closed-recirculating irrigation system. A 4 × 4 factorial design with partial replication was used to assess the effects of salinity and nitrogen on the production of Matthiolaincana (L.). Seeds were sown in outdoor volumetric lysimeters at the George E. Brown, Jr., Salinity Laboratory in Riverside, Calif., with target electrical conductivity (EC) levels of 2, 5, 8, and 11 dS·m^–1 combined with four nitrogen treatments of 35, 50, 75, and 100 ppm N. An empirical model was implemented to evaluate the growth response of each combination of salinity and nitrogen treatments over the course of plant development. The three-phase model is represented by an initial size parameter (alpha), an estimation of the intrinsic growth rate of the exponential phase (beta), a transitional phase between the first two phases (tl), the length of the linear phase (epsilon), and the final intrinsic saturation rate (gamma), The model successfully fitted the plant height data over time for all 16 nitrogen and salinity treatment combinations. Effects of salinity on epsilon and t2 (epsilon + t1) were nonsignificant. Nitrogen treatments had no significant effect on any of the model parameters and the effect of salinity was greatest when irrigation water EC was 11 dS·m^–1. The length of the flower-bearing stems exceeded the standards recommended for commercial acceptability in all treatments (>41 cm). If 60 cm is the minimum length acceptable, then 50 ppm N or more where the EC was 8 dS·m^–1 or less is required. Nitrogen uptake per unit evapotranspiration increased with salinity and nitrogen.

Agroforestry plantations offer environmentally acceptable strategies for the reuse of saline drainage waters. Tree species suitable for use in such systems must be selected for survival and sustained growth under highly saline conditions. In this screening trial, four clones of Eucalyptus camaldulensis Dehn. (4543, 4544, 4573, and 4590) and one clone of E. rudis Endl. (4501) were grown in greenhouse sand cultures irrigated with sodium sulfate–dominated waters. Solution compositions were prepared to simulate saline drainage waters typically found in the San Joaquin Valley of California. Electrical conductivities of the solutions ranged from 2 to 28 dS·m^–1. Treatments were replicated three times. All plants survived and were harvested after 7 weeks under saline treatment. Plant height was measured weekly and shoot biomass was determined at final harvest. The salinity levels that resulted in a 50% reduction in biomass production (C₅₀) were 16.4 (4573), 17.1 (4543), 17.7 (4544), 29.0 (4590), and 30.0 dS·m^–1 (4501). Over the range of salinities from 4 to 20 dS·m^–1, clones 4501, 4590, and 4573 generally maintained higher relative growth rates (RGR) than did clones 4544 and 4543. However, at the highest salinity, RGRs of clones 4501, 4544, and 4573 were significantly greater than those of clones 4543 and 4590. Assessed on the basis of biomass production, clones 4501 (E. rudis) and 4590 (E. camaldulensis) showed exceptional potential for use in agroforestry systems where the saline drainage waters are sodium sulfate–dominated.

To explore the possibility that saline wastewaters may be used to grow commercially acceptable floriculture crops, a study was initiated to determine the effects of salinity on two statice cultivars. Limonium perezii (Stapf) F. T. Hubb. `Blue Seas' and L. sinuatum (L.) Mill `American Beauty' were grown in greenhouse sand cultures irrigated with waters prepared to simulate saline drainage waters typically present in the western San Joaquin Valley (SJV) of California. Seven salinity treatments were imposed on 3-week-old seedlings. Electrical conductivities of the irrigation waters (EC) were 2.5 (control), 7, 11, 15, 20, 25, and 30 dS·m^–1. Vegetative shoots were sampled for biomass production and ion analysis ten weeks after application of stress. Flower stem numbers, length, and weight were determined at harvest. Stem length of L. perezii was significantly reduced when irrigation water salinity exceeded a threshold of 2.5 dS·m^–1. Salt tolerance threshold based on stem length for L. sinuatum was 7 dS m^-1. The species exhibited significant differences in shoot-ion relations which appear to be related to differences in salt tolerance. Sodium, K⁺, Mg²⁺, and total-P were more strongly accumulated in the leaves of L. sinuatum than L. perezii. Both species accumulated K⁺ in preference to Na⁺, but selectivity for K⁺ over Na⁺ was significantly higher in L. sinuatum than in the more salt-sensitive L. perezii. Chloride concentration in L. sinuatum leaves increased significantly as salinity increased, whereas the 20-fold increase in substrate-Cl had no effect on leaf-Cl in L. perezii. Both Limonium species completed their life cycles at salt concentrations exceeding 30 dS·m^–1, a character associated with halophytic plants. Maximum growth of each species, however, occurred under relatively low salt stress, and steadily declined as external salinity increased. Based on this crop productivity response, L. perezii should be rated as sensitive and L sinuatum as moderately tolerant.

Performance of `Kerman' pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart and `UCB-1', a P. atlantica × P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO₄ ^2- and Cl^- salinity and boron (B) stress for 6 months. Four salinity treatments were imposed by irrigating the plants with water at electrical conductivity (EC_iw) of 3.5, 8.7,12, or 16 dS·m^-1 each containing B at 10 mg·L^-1. Growth of `Kerman' was evaluated based on increase in total leaf area, increase in trunk diameter, and total above-ground biomass production. All growth parameters decreased as salinity increased, but were not significant until EC<sub>iw</sub> exceeded 12 dS·m<sup>-1</sup>. However, growth of `Kerman' on P. atlantica and `UCB-1' was considerably better than on P. integerrima at 16 dS·m^-1. The onset and severity of foliar injury differed among scions and treatments and was attributed primarily to B toxicity, rather than the effects of salinity. Concentrations of B in injured leaf tissue ranged from 1000 to 2500 mg·kg^-1. Leaf injury decreased with increasing salinity, although leaf B was not significantly reduced suggesting an internal synergistic interaction between B and other mineral nutrients. However for P. vera on P. integerrima, the highest level of salinity produced the greatest injury, possibly as a combination of B plus Cl^- and/or Na⁺ toxicity. Leaf transpiration, stomatal conductance, and chlorophyll concentration of P. vera, determined by steady-state porometry, were also reduced to a greater degree by combined salinity and B when budded on P. integerrima than on the other two rootstocks.