James W. O'Leary

Salicornia bigelovii Torr.: An Oilseed Halophyte for Seawater Irrigation

The terrestrial halophyte, Salicornia bigelovii Torr., was evaluated as an oilseed crop for direct seawater irrigation during 6 years of field trials in an extreme coastal desert environment. Yields of seed and biomass equated or exceeded freshwater oilseed crops such as soybean and sunflower. The seed contained 26 to 33 percent oil, 31 percent protein, and was low in fiber and ash (5 to 7 percent). The oil and meal were extracted by normal milling equipment, and the oil was high in linoleic acid (73 to 75 percent) and could replace soybean oil in chicken diets. The meal had antigrowth factors, attributed to saponins, but could replace soybean meal in chicken diets amended with the saponin antagonist, cholesterol. Salicornia bigelovii appears to be a potentially valuable new oilseed crop for subtropical coastal deserts.

Effects of salinity on growth and cation accumulation of Sporobolus virginicus (Poaceae)

Optimal growth of euhalophytes requires moderate concentrations of salt and, in dicotyledons, is associated with succulence and accumulation of Na(+) in plant tissues. However, reports of salt-stimulated growth in monocotyledons are rare. Relative growth rate (RGR), biomass accumulation, and water content were studied in Sporobolus virginicus (Poaceae), a C(4) chloridoid grass, grown hydroponically with different concentrations of NaCl. Cation concentrations were determined by atomic absorption spectrophotometry. Optimal growth occurred at 100-150 mmol/L NaCl and was not dependent on nitrogen levels or accompanied by accumulation of Na(+) in leaves. Biomass accumulation and RGR in plants grown at 450 mmol/L NaCl were greater than in plants grown at 5 mmol/L. The Na : K ratios were lower in leaves than in roots, indicating discrimination in Na(+) and K(+) transport. Secretion of Na(+) increased from 166.5 to 336.7 mmol · g(-1) dry biomass · d(-1) as the NaCl concentration of the nutrient solution increased from 125 mmol/L to 450 mmol/L. Water concentrations of leaves and shoots were significantly greater in plants grown at optimal levels of salinity than in plants grown at lower or higher salinities. These results demonstrate salt-stimulated growth in a monocotyledon.

Agricultural production of halophytes irrigated with seawater

Growing agricultural crops with direct seawater irrigation has progressed within the past few years from the conceptual to the experimental phase. This has been accomplished by selecting halophytes with inherently high salinity tolerance for use as crop plants rather than by increasing the ability of traditional crop plants to tolerate seawater. Some of the halophytes being investigated for use as crops in seawater irrigation scenarios have high nutritional value as forage or fodder crops. Most of them also have high digestibility. The limiting factor in such use is their high salt content, but this limitation can be moderated. However, since seeds of halophytes do not accumulate salt any more than do those of glycophytes, the greatest promise for seawater-irrigated halophytes probably will be as seed crops. The seeds of many halophytes have high protein and oil contents and compare favorably with traditional oilseed crops. Sustained high yields of seed and biomass already have been obtained from some halophytes irrigated with seawater, and within the next few years seawater agriculture should proceed from the experimental to the operational phase.

Performance of Atriplex species in the San Joaquin Valley, California, under irrigation and with mechanical harvests

Abstract Field studies were conducted in the San Joaquin Valley, California to evaluate perennial Atriplex species as multi-clipped forage crops under irrigated field conditions. Plants were first established using fresh water irrigations and then irrigated with saline drainage water (electrical conductivity, 18 dS m−1). Plant stands were cut and baled four times during the first 27 months of growth using conventional farm equipment. Analyses of ash, crude protein and fat, acid detergent fiber, neutral detergent fiber, lignin and macromineral contents were performed on bale samples collected from each species harvest. Estimated regrowth yields ranged from 2.2 to 5.3 t ha−1 year−1 for the species planted on areas larger than 0.25 ha. Those species, such as Atriplex deserticola Phil. and Atriplex undulata (Moq.) D. Dietr., which displayed relatively woody basal stems and were capable of producing adventitious roots appear to be more tolerant of multiple harvests, low cut heights and harvest traffic operations than those species not having the combination of these characteristics. Atriplex canescens (Pursh.) Nutt. regrowth forage provided the best combinations of low ash and sodium levels and low Na/K ratios.

Effect of salinity and K/Na ratio of irrigation water on growth and solute content of Atriplex amnicola and Sorghum bicolor

Total salinity and K/Na ratios in the irrigation water were varied for two different types of plants; sorghum, a moderately salt tolerant crop plant whose growth is inhibited by high NaCl levels, and Atriplex, an extreme halophyte whose growth is stimulated by high NaCl levels. Sorghum growth was significantly reduced at all salinity levels from 50 to 150mM, but Atriplex growth was not reduced until salinity exceeded 100 mM. In both species, growth reductions were increased by increasing the ratio of K to Na from 1/100 to 1/1 in the irrigation water. The amount of K and Na accumulated in the leaves of Atriplex reflected the relative amounts in the irrigation water, but in sorghum most of the increase in the concentration of K + Na was due to the increase in K regardless of the ratio of K/Na in the irrigation water. Nitrate levels in leaves of sorghum were little affected by salinity but were decreased in Atriplex by the combination of high salinity and K/Na ratio. The lower amount of salt accumulation in sorghum was compensated for by greater accumulation of soluble organic compounds, such as proline and soluble carbohydrates, that presumably were osmotically active and could contribute to osmotic adjustment. All of the results supported the general conclusion that, despite differences between glycophytes, such as sorghum, and halophytes, such as Atriplex, in sensitivity to the total soluble salt concentration in irrigation water, in both species growth was reduced more by K/Na ratios of 1/1 and 1/10 than by a ratio of 1/100 at those salinity levels that significantly reduced growth in each species.

Distribution of cations in leaves of salt‐tolerant and salt‐sensitive lines of sunflower under saline conditions

Abstract Two lines of sunflower (Helianthrus annuus L.), a salt‐tolerant Euroflor and a salt‐sensitive SMH‐24, were grown for three weeks in sand culture containing 0 or 150 mol/m3 NaCl in full strength Hoagland nutrient solution. Distribution of cations in the leaves of varying ages was determined. The older leaves of SMH‐24 contained more sodium (Na) in the laminae than the younger leaves at the salt treatment, whereas laminae of leaves of varying ages of Euroflor maintained Na concentration almost uniform. Distribution of potassium (K), calcium (Ca), and magnesium (Mg) in the laminae was strongly age‐dependent in both lines, i.e., the older leaves contained greater concentrations of these cations than did the younger leaves. The lines did not differ in concentrations of the three cations. The older leaves of SMH‐24 had significantly lower K/Na ratios than those of Euroflor, but the lines did not differ in lamina Ca/Na ratios. It is concluded that distribution of K, Ca, and Mg in the leaf laminae is age...

The effects of humidity and cytokinin on growth and water relations of salt-stressed bean plants

SummarySalinity inhibited growth of plants in both low and high humidities when compared to control plants grown under the same conditions. However, salttreated plants grew better under high humidity when compared to saltstressed plants grown under low humidity. Benzyl adenine (B.A.) sprays did not have any effect on growth of salt-treated plants grown in low humidity. However, when plants were grown in high humidity, B.A. either had no effect or inhibited the growth of the plants. Salinity increased leaf resistance to water vapor loss (Rl) in both low and high humidity, and B.A. decreased Rlof salt-treated plants in both humidities. The effects of salinity on decreasing root permeability were the same in both humidities studied, and they were not reversed by B.A. applications. The results do not support the idea that growth inhibition due to salinity is simply the result of impaired cytokinin metabolism and/or transport. Rather, the growth inhibition probably is due to the effect of salinity on the balance of hormones and could be acting at several different steps. re]19720725

Elevated CO2 Concentration Increases Stomate Numbers in Phaseolus vulgaris Leaves

Beans were grown under a constant CO2 concentration of either 400 or 1,200 μl liter-1. There was no significant difference in stomate density on the adaxial surface, but there was a significantly lower stomate density on the abaxial surface of leaves in the higher CO2 concentration. The leaf area was significantly greater at the higher CO2 concentration, and total number of stomates per leaf, calculated from the density and leaf area, was significantly greater for both surfaces of the leaf. We conclude that the observed CO2 effect on stomatal density is the result of the large change in leaf area.

Trace element composition of Atriplex grown with saline drainage water

Abstract In the western San Joaquin Valley, California, there has recently been emphasis on identifying suitable halophytes for irrigation with agricultural effluent and grown as crops using standard farming practices. Five perennial halophyte species belonging to the genus Atriplex (common name, saltbush) were established with fresh water, irrigated with saline drainage water, and mechanically harvested four times during the first 27 months of growth. Bale samples collected from three regrowth harvests were analysed for Selenium (Se), Boron (B), Sulfur (S), Iron (Fe), Zinc (Zn), Manganese (Mn) and Copper (Cu). The mean tissue concentrations for all species over regrowth harvests were 129 mg kg−1 dry weight for B and 0.6 mg kg−1 dry weight for Se. Tissue levels of B and S were above, and the remaining trace elements were below the maximum tolerable levels recommended for ruminants. All species showed trends of increased tissue B concentrations with cumulative age of plants. Over all the species the highest Se concentrations were measured in forage harvested 27 months after planting. The trace element composition of the harvested forage from this site does not appear to be a limiting factor when considering the use of Atriplex bales as a blend in animal feed rations.

Responses of a salt‐tolerant and a salt‐sensitive line of sunflower to varying sodium/calcium ratios in saline sand culture

Abstract The effects on two‐week‐old plants of a salt‐tolerant line (Euroflor) and a salt‐sensitive (SMH‐24) line of sunflower, of varying sodium/calcium (Na/ Ca) ratios in a saline growth medium were assessed after three weeks growth in sand culture under greenhouse conditions. The different Na/Ca ratios of the salt treatment were 36.5, 74.0, and 149, at a constant concentration of 150 mol m‐3 NaCl. Euroflor was superior to SMH‐24 in fresh and dry matters of shoots and roots at varying external Na/Ca ratios. The leaf Na+ concentration in SMH‐24 increased consistently with increase in external Na/Ca ratio, whereas that in Euroflor remained almost unaffected. Although leaf chlorine (Cl‐) was significantly greater in SMH‐24 than Euroflor, there was no effect of decreasing Ca2+ concentration of the saline growth medium on the leaf Cl‐ concentrations of both lines. The lines did not differ in K+, Ca2+ or Mg2+ concentrations of both shoots and roots. The leaf K/Na and Ca/ Na ratios, K versus Na selectivity wer...