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Grieve, C.M., M.C. Shannon, and D.A. Dierig. 1999. Salinity effects on growth, shoot-ion relations, and seed production of Lesquerella fendleri. p. 239–243. In: J. Janick (ed.), Perspectives on new crops and new uses. ASHS Press, Alexandria, VA.

Salinity Effects on Growth, Shoot-ion Relations, and Seed Production of Lesquerella fendleri

Catherine M. Grieve, Michael C. Shannon, and David A. Dierig*

    1. Plant Growth
    2. Ion Relations

Lesquerella fendleri (Gray) S. Wats., a native of the arid and semiarid regions of southwestern US, has been proposed as an important industrial seed oil crop (Thompson and Dierig 1988). Intensive breeding and agronomic research efforts at the US Water Conservation Laboratory have been directed towards domesticating and commercializing the crop (Dierig et al. 1993; Coates 1994; Brahim et al. 1996; Dierig et al. 1996; Nelson et al. 1996).

Information on the management of lesquerella under saline conditions is limited to a two-season (1993–4 and 1994–5) field trial conducted by Leland E. Francois at the Irrigated Desert Research Station located at Brawley, CA (Grieve et al. 1997). Six salinity treatments were imposed by adding NaCl and CaCl2 (2:1 molar ratio) to Colorado River water. Electrical conductivities of the irrigation waters (ECi) ranged from 1.4 to 10.0 dS m-1. Both biomass production and seed yield were significantly reduced by salinity, although salt stress had no effect on either the content or the composition of the oil. Based on the combined seed yield data for both years, the salt tolerance threshold (the maximum allowable ECe without a yield decline) was 6.1 dS m-1 and the C50 (ECe value that would result in a 50% yield reduction) was 9 dS m-1. [As an approximation: ECe = 1.5 ECi]. Each unit increase in salinity above the threshold resulted in a 19% decrease in yield.

Under nonsaline control conditions in the Brawley plots (ECi = 1.4 dS m-1), lesquerella was a strong calcium accumulator, and as external calcium increased in concert with salinity, leaf-Ca2+ significantly increased. In response to Cl- salinity, leaf-Cl- increased three-fold as ECi increased from 1.4 to 10 dS m-1. Large increases in external Na+ had no effect on leaf-Na+. Sodium levels in lesquerella leaves were at least an order of magnitude lower than leaves of other crucifers grown at the same location with the same compositions of Cl--dominated salinity (Francois and Kleiman 1990; Francois 1994). Lesquerella apparently possesses an unique and effective exclusion mechanism that limits the accumulation of potentially toxic levels of Na+ in the leaves.

One objective of the current study was to determine the response of lesquerella to sodium sulfate-dominated irrigation waters that are typical of the saline drainage waters commonly encountered in the San Joaquin Valley of California. Lesquerella was evaluated as a crop that could fill a niche in the drainage water reuse system where only moderate tolerance is required. A second objective was to identify and isolate individuals that exhibited salt tolerance and use this germplasm for establishing a base population for breeding more salt tolerant lesquerella.


On 1 Oct 1997, lesquerella seeds, collected from 1993–1994 seed-increase plot located at the US Water Conservation Laboratory, were planted in a greenhouse in Speedling1 trays containing a peat-sand-perlite mix. Two months after planting, the seedlings were transferred to the US Salinity Laboratory and transplanted to 24 outdoor sand tanks. Each tank contained 12 rows with six seedlings per row. The tanks (1.5 × 3.0 × 2.0 m deep) contained washed sand having an average bulk density of 1.2 Mg m-3. At saturation, the sand had an average volumetric water content of 0.34 m3 m-3. Plants were irrigated once daily with a nutrient solution consisting of (in mol m-3): 3.5 Ca2+, 2.5 Mg2+, 21.5 Na+, 6.0 K+, 10.9 SO42-, 7.0 Cl-, 5.0 NO3-, 0.17 KH2PO4, 0.050 Fe (as sodium ferric diethyleneamine pentaacetate), 0.023 H3BO3, 0.005 MnSO4, 0.0004 ZnSO4, 0.002 CuSO4, and 0.0001 H2MoO4 made up with city of Riverside municipal water. This solution, with an electrical conductivity (ECi) of 3 dS m-1, served as the control treatment. Each sand tank was irrigated from a 3700-L reservoir. Irrigations were of 15 min duration, which allowed the sand to become completely saturated, after which the solution drained to the reservoir for reuse in the next irrigation. Water lost by evapotranspiration was replenished automatically to maintain constant electrical conductivites in the solutions.

On 15 Dec. 1997, two weeks after the seedlings were transplanted, eight salinity treatments were imposed with irrigation waters designed to simulate saline drainage waters commonly present in the San Joaquin Valley of California, and compositions of increased salinity which would result from further concentration of these drainage waters (Table 1). Electrical conductivities of the saline treatments were increased to the desired levels by incremental additions of the salts over a 9-day period to avoid osmotic shock to the seedlings. Targeted ECi values of the solutions were 3 (nutrient solution only), 6, 9, 12, 15, 18, 21, and 24 dS m-1. The experiment was a randomized complete block with 8 salinity treatments and three replications. The pH was uncontrolled and varied between 7.5 and 8.5. Initially the tanks were irrigated on a daily basis, and later in the season, on alternate days.

Table 1.Composition of salinizing salts in irrigation waters used for determining salt tolerance of lesquerella in sand cultures.

(dS m-1)

Composition (mol m-3)































































Irrigation waters were analyzed at weekly intervals for Ca2+, Mg2+, Na+, K+, and total-S by inductively coupled plasma optical emission spectroscopy (ICPOES), and for Cl- by coulometric-amperometric titration. Nutrients and salinizing salts were replenished as required.

Plant survival and time of flowering were recorded on a regular basis. On 20 Feb., 15 Mar. and 15 Apr. 1998, plants were sampled and the following measurements were recorded: fresh weight, height of the main axis, number of secondary branches. Leaves and stems were separated. Leaf area was measured. Shoot tissues were washed with deionized water, dried at 70°C, reweighed, and ground in a Wiley mill. Total-S, -P, Ca2+, Mg2+, Na+, and K+ were determined on nitric-perchloric acid digests of the plant material by ICPOES. Chloride was determined on nitric-acetic acid extracts by titration. Irrigation was discontinued and plants were sprayed with a desiccant 1 wk before final harvest on 9 Jun. 1998. Individual shoots were weighed, and seeds of each plant were separated and weighed.

Statistical analyses of the ion data were performed using SAS release version 6.12 (SAS Institute Inc. 1997). The effects of salinity on shoot biomass and seed yields were determined by the procedure described by van Genuchten and Hoffman (1984).

Figure 1

Fig. 1. Survival of lesquerella plants (%) recorded on three dates as a function of increasing irrigation water salinity.

Figure 2

Fig. 2. Lesquerella shoot biomass production as a function of increasing irrigation water salinity.

Figure 3

Fig. 3. Mean seed weight of lesquerella as a function of irrigation water salinity.


Plant Growth

Within two weeks after imposition of full treatments, transplant survival in the sand cultures was reduced in treatments in which salinity exceeded 15 dS m-1 (Fig. 1). Survival continued to decrease with salt treatment over time. In contrast, salinity had no effect on plant survival in the Brawley field plots. The difference in response may be due to plant age at initiation of salinization, e.g. 12 weeks in the field compared with 10 weeks in sand cultures. In addition, root growth of the transplants may not have been well established in the sand tanks prior to salt treatment.

On 10 Apr. l998, survival was so poor at 24 dS m-1 that this treatment was discontinued; the few survivors were rescued and grown in crossing blocks under nonsaline conditions. During the last month of crop growth, stem cracking and stem rot became evident in all treatments. Plants grown at the lower salinity levels were particularly susceptible. Sclerotinia sclerotinia, which was isolated from affected stems, appeared to be the causal agent. Because of this infection, survival of plants grown at 3 dS m-1 was reduced to about 40% at final harvest. Regardless of salinity level, root morphology, as observed at final harvest, was invariably distorted and taproots were either atypical or absent.

Biomass production, measured at final harvest, decreased significantly in response to salinity (Fig. 2). The salinity level that resulted in a 50% reduction in final shoot weight was 14.9 dS m-1. Average seed yield per plant was about 2 g in the 3, 6, 9, and 18 dS m-1 treatments and 3 g at 12 and 15 dS m-1 (Fig. 3). Leaf area, determined at a midseason harvest (15 Apr. l998), decreased consistently and significantly from a mean of 950 to 65 cm2 per plant as salinity increased from 3 to 21 dS m-1.

Ion Relations

The divalent cations, Ca2+ and Mg2+, were strongly accumulated by lesquerella shoots and both cations were preferentially accumulated in the leaves rather than the stems (Figs. 4A and 4B). Leaf-Ca2+ was reduced by salinity when ECi exceeded 15 dS m-1, although over this salinity range, Ca2+ concentration in the irrigation waters increased nearly four-fold. At higher salinities, leaf-Ca2+ decreased significantly as Ca2+ in the substrate continued to increase. The Ca2+ status of salt-stressed plants is strongly influence by the ionic composition of the external medium. The presence of salinizing ions such as Na+ or Mg2+ in the substrate may reduce Ca2+ activity and limit the availability of Ca2+ to the plant. High Na+/Ca2+ may affect vital physiological and nutritional processes. External Mg2+/Ca2+ ratios greater than 1 are known to reduce growth and yield of several crop species (Grattan and Grieve 1994). In the present experiment, external Mg2+/Ca2+ increased from 1.1 in the 15 dS m-1 treatment to 2 at 18 and 21 dS m-1, and at the same time, Na+/Ca2+ increased from 9 to 14 and 17 as salinity increased from 15 to 18 to 21 dS m-1, respectively (Table 1). These imbalances, as well as ion interactions that occurred within the plant, may have contributed to reduced Ca2+ in lesquerella leaves and stems.

Figure 4 Figure 5

Fig. 4. Concentrations of (4A) Ca2+, (4B) Mg2+ and (4C) K+ in leaves and stems of lesquerella grown at seven salinity levels. Values are the means of three replications ± SD.

Fig. 5. Concentrations of (5A) Na+ and (5B) Cl- in leaves and stems of lesquerella grown at seven salinity levels. Values are the means of three replications ± SD.

The L. fendleri ecotype evaluated in this salt tolerance study was found growing on calcareous soils of limestone origin (Dierig et al. 1996). These neutral or alkaline soils contain high amounts of calcium and bicarbonate and are generally warmer, drier, and more permeable to water than, for example, silicaceous soils (Larcher 1972). Species or ecotypes differ in their management of Ca2+. Those plants that are adapted to calcareous soils and preferentially take up large amounts of Ca2+ for storage in the plant sap are termed calcicoles. Many members of the Brassicaceae are considered calcicoles by virtue of their ability to tolerate high concentrations of external Ca2+ and to actively accumulate Ca2+. For example, even under nonsaline conditions, shoot-Ca2+ concentrations in Eruca sativa (Ashraf and Noor 1993), Brassica juncea (Ashraf 1992), as well as L. fendleri (Grieve et al. 1997), range from 1200 to 1500 mmol kg dry wt-1. These levels are twice as high as in the leaves of other crucifers, e.g. Crambe abyssinica, (Francois and Kleiman 1990), B. napus (Francois 1994), and leafy Brassica vegetables (USSL 1997, in preparation).

With increasing salinity, Mg2+ in the irrigation water increased from 2.4 to 26.5 mol m-3 (Table 1). However, this ten-fold increase had little effect on the Mg2+ content of either the leaves or stems over the range of treatments. Regardless of salinity level, both Ca2+ and Mg2+ were higher in the leaves than in the stems.

With few exceptions, both K+ and Na+ were uniformly partitioned between leaf and stem tissues. Potassium in both leaves and stems decreased with salinity (Fig. 4C), while K+ concentration in the irrigation waters remained constant at 6 mol m-3. Numerous studies with a wide variety of plants have shown that K+ concentration in plant tissues declines with increases in Na+/K+ ratio in the root media. Results from the field study differ from those of the present experiment in that leaf-K+ in field-grown lesquerella was about 400 mmol kg dry wt-1 regardless of salinity, whereas in the sand culture study, leaf-K+ was high (700 mmol kg dry wt-1) at the lower salinity levels and did not fall below 400 mmol kg-1 even at the highest salinity. Perhaps the external K+ concentration (6 mol m-3) used for the latter experiment was in the luxury range.

Differences between the Brawley field study and the sand culture experiment were also apparent in leaf-Na+ accumulation. In both cases external-Na+ increased with increasing salinity. In the SO42--system used for the sand cultures, leaf-Na+ rose significantly (Fig 5A), whereas in the field-grown plants, the mean leaf-Na+ concentration across salinity levels was low (< 25 mmol kg dry wt-1) and unaffected by treatment. The absence of what appears to be a very effective Na+ exclusion mechanism in the plants grown in sand cultures may have resulted from factors associated with abnormal root morphology observed in the transplants.

Both leaf- and stem-Cl- increased as Cl- concentration in the irrigation water increased. Leaves were stronger Cl--accumulators than the stems (Fig. 5B). Comparison of leaf-Cl- levels in response to the lowest salinity at the two experimental sites showed that the field-grown leaves accumulated more than twice as much Cl- (690 mmol kg-1) as those in sand cultures (270 mmol kg-1) despite a large difference in Cl- content in the irrigation waters. The control plants in the Brawley plots were irrigated with Colorado River water (average Cl- = 2.8 mol m-3; ECi = 1.4 dS m-1), whereas the control solution in the sand cultures contained 7 mol m-3 Cl- (ECi = 3.0 dS m-1).

This preliminary sand culture experiment serves as a valuable management guide for our continuing studies of the salt tolerance of lesquerella germplasm in outdoor sand cultures. Changes in management practices for the determination of crop response to sodium sulfate-dominated salinity will include: (1) direct seeding to encourage normal root development, (2) altering the irrigation system to permit more rapid delivery to the plants and to prevent excessive flooding, and (3) changing irrigation scheduling to avoid plant injury associated with stem cracking and subsequent pathogen attack. These modifications are currently under evaluation in greenhouse sand culture experiments.


*Mineral ion analyses were performed by Donald A. Layfield. Technical assistance was provided by: Terence Donovan, John Draper, Aaron Kaiser, Greg Leake, and James Poss.
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