Indian Ricegrass Research Articles

Germination of Prechilled Mechanically Scarified and Unscarified Indian Ricegrass Seed

Seed dormancy typically limits stand establishment of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker]. The mechanical and physiological mechanisms that contribute to dormancy must both be overcome before germination. Our objective was to study potential interactions between the breaking of mechanical dormancy and breaking of physiological dormancy. Germination of 13 seedlots of 'Nezpar', 'Paloma', and PI 478833, ranging in age from 4 to 19 years and in viability from 67 to 96%, was tested. Seed was scarified with an air-gun scarifier to reduce mechanical dormancy approximately 2 1/2 years before testing, or left unscarified. Over 77% of seeds remained intact following scarification. Seed was moved from 5 degrees C to room temperature 1 year before testing to reduce physiological dormancy, or left refrigerated. Seed was also prechilled for 3 weeks at 5 degrees C to reduce physiological dormancy, or left nonprechilled. Germination was determined after 2-week and 3-week 15 degrees C germination periods for prechilled and nonprechilled treatments, respectively. Scarification improved germination of undamaged seed in 12 of the 13 seedlots from 9.5 to 29.7%. Prechilling improved germination of 10 of the 13 seedlots from 8.0 to 22.8%. Room-temperature storage improved germination of 5 seedlots from 4.9 to 12.8%. In 9 seedlots prechilling improved germination of scarified seed 13.1% less than unscarified seed. In 4 seedlots room-temperature storage improved germination of scarified seed 6.5% less than unscarified seed. Depending on the vigor of the seedlot, such effects may be related to a greater reduction of either physiological dormancy or viability in scarified seed than in unscarified seed.

High Seed Retention of Indian Ricegrass PI 478833

Reduction of Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] seed shattering losses is of interest because it would result in more economical seed harvest. PI 478833, a genotype with glumes closely surrounding the seed, was compared with 'Paloma' for glume pair angle and seed retention parameters. Our objective was to determine its suitability as a source of seed shattering resistance for genetic transfer to an Indian ricegrass variety. Regrowth from a 19 June 1989 clipping of 'Paloma' and PI 478833 with and without supplemental irrigation was evaluated in late July. Irrigation did not affect glume pair angle or percentage intact seed (number of seeds/number of mature florets). Though Paloma and PI 478833 glume pair angles averaged 66% and 44%, respectively, percentage intact seed was 13% higher for Paloma than PI 478833 because Paloma's more indeterminate flowering pattern allowed it to replace its shattered florets more quickly than PI 478833. In a second experiment we observed individual florets of Paloma and PI 478833 for 7 weeks starting 5 September 1989. Floret opening occurred mostly during daylight hours and on warm days. Shattering events occurred when a storm followed a period of floret opening. Duration of seed retention from glume opening to shattering averaged 91% longer for PI 478833 than Paloma. After 7 weeks 83 and 35% of Paloma and PI 478833 florets had shattered, respectively. In a third experiment seed retention index (seed yield/forage dry weight) on 15 September 1989 was 0.45, 0.19, and 0.11 for PI 478833, 'Nezpar', and Paloma, respectively. PI 478833's acute glume pair angle and resultant increased seed retention make it a valuable source of shattering resistance for introduction into bred Indian ricegrass varieties.

Variation in N 2 Fixation (C 2 H 2 Reduction) Associated with Rhizosheaths of Indian Ricegrass (Stipa hymenoides)

-Relatively low but significant rates of N2 fixation (C2H2 reduction) associated with rhizosheaths of Indian ricegrass Stipa hymenoides varied inversely with percent 02 in test atmospheres, and directly with percent water-holding capacity of sand substrate. Nitrogen fixation was not observed for plants tested in late summer or for nonrhizosheath plants inhabiting nonsandy soil. Delayed linear rates of C2H2 reduction preceded by ca. 2448 h lag periods were observed.

A Viewpoint on Indian Ricegrass Research: Its Present Status and Future Prospects

Indian ricegrass (Oryzopsis hymenoides (Roem. & Schult.) Ricker) is adapted to sandy arid areas of much of the western USA and is a highly desirable species on winter range sites. Seed is typically highly dormant. Mechanical dormancy has been reduced by mechanical and sulfuric acid scarification, and physiological dormancy has been reduced with stratification, giberellic acid, and kinetin. A better understanding of the relationship between mechanical and physiological dormancy may lead to a practical procedure for breaking dormancy in harvested seed. Alternatively, a better understanding of environmental factors on seed production may lead to production of already low dormancy seed. Establishment success will also depend on development of appropriate seedbed management practices for various soils. Reduction of the currently large shattering losses would have a favorable impact on the economics of Indian ricegrass seed production. An interdisciplinary approach including seed physiology, seedbed ecology, seed technology, and plant breeding can potentially solve these problems. The potential of seeding Indian ricegrass for improving rangelands can only be realized after low dormancy seed becomes available, appropriate seedbed management practices are developed, and seed shattering losses are reduced.

Seed Abscission and Retention in Indian Ricegrass

Seed Abscission and Retention in Indian Ricegrass

Prevalence of Oryzopsis Hymenoides near Harvester Ant Mounds: Indirect Facilitation by Ants

The distribution of plants in relation to harvester ant mounds was investigated at two study areas to examine associations between ants and plants in semiarid, sagebrush steppe vegetation. The bunchgrass Oryzopsis hymenoides usually was the closest plant to the center of Pogonomyrmex owyheei ant mounds and often was the only plant found within the disk-shaped areas around mounds that is cleared of vegetation by the ants. Although absolute numbers of 0. hymenoides seeds were greatest on mounds, proportions of its seeds in the total seedbank were not significantly different among the mound, cleared disk, and the native plant community. Mean size and density of 0. hymenoides plants near mounds were significantly greater than those of plants 15-20 m from mounds at an undisturbed study area. At the other study area, which three years before the study was burned, mean density and size of 0. hymenoides plants were not significantly different among plots located at 0, 1, 2, 3, 7, 15, and 20 m from the center of ant mounds. These measurements of the seedbank and plant density and size were used to differentiate among four mechanisms by which ants may influence plant distribution. The prevalence of 0. hymenoides near ant mounds was most likely an indirect effect of reduced plant competition caused by the severe defoliation of potential competitors by the ants. A second indirect mechanism, the abundance of 0. hymenoides near mounds resulted from reduced insect herbivory on 0. hymenoides because of ant predation on the herbivores, was specious. Two other mechanisms, a direct effect of seed harvesting activity by ants or an indirect effect of microsite modification were at best of minor importance.

The influence of seed apparency, nutrient content and chemical defenses on dietary preference in Dipodomys ordii.

Physical, nutritional and defensive qualities of seeds differ in the extent to which they influence granivore preference. In a study aimed to quantifying those differences, Ord's kangaroo rats (Dipodomys ordii) were found to prefer the seeds of just three of twenty-nine species: Cryptantha crassisepala, Oryzopsis hymenoides and Salsola kali. Oryzopsis hymenoides was most preferred during the early plant growth season (April-July); preference for S. kali peaked during late (August-November) and dormant (December-March) seasons; and greatest preference for C. crassisepala occurred during dormant and early seasons. Regression of forage ratios, averaged across seasons, against seed length, mass, abundance, patchiness, percent nitrogen, energy content, and chemical defenses showed seed length to be the most important predictor of seed preference. Seed length combined with nitrogen (protein) content and levels of two defensive compounds, saponins and non-protein amino acids, to account for 68% of the variation in seed preference. The importance of seed length rather than biomass indicated that there are limits to the ability of D. ordii to detect small seeds and that small size facilitated escape of dispersed seeds. Seasonality in preference suggested, however, that seed escape was encountered by predispersal harvesting of newly maturing seeds still on plants. Maximization of protein intake contradicted previously published observations, but presumably reflected low nitrogen availability. In addition to small size, the presence of saponins or non-protein amino acids in seeds was sufficient to negate the positive influence of higher protein content.

Clipping and Long-Term Grazing Effects on Biomass and Carbohydrate Reserves of Indian Ricegrass

Long-term heavy grazing had little effect on root and crown biomass of Indian ricegrass (Oryzopsis hymenoides [Roem. and Schult.] Ricker), nor did it significantly affect the total nonstructural carbohydrate (TNC) reserve levels or the seasonal cycle of reserves in this grass. Fifty years of protection from livestock use had not resulted in ecotypic differentiation in Indian ricegrass for these variables. Clipping reduced crown biomass more than root biomass and removal of 90% of the aboveground biomass resulted in more than a 50% reduction in crown biomass and reserve carbohydrate pool. Two commercial strains of Indian ricegrass ('Nezpar' and 'Paloma) were compared with native Chaco Canyon strains in a uniform garden study. The Nezpar strain was superior to Paloma and the Chaco Canyon strains in production of crown biomass and TNC reserves at the more mesic garden site. The native strains from the more arid Chaco Canyon site were superior to both cultivated strains in production of roots. The native Chaco Canyon strains were little affected by clipping and have promising genetic potential for tolerance of drought and heavy grazing.

Effects of Protection from Grazing on Morphological and Chemical Characteristics of Indian Ricegrass, Oryzopsis hymenoides

This study was designed to compare several characteristics of grazed, isolated, and commercial strains of Indian ricegrass. The two main objectives were: to determine whether morphological characteristics and chemical components of Indian ricegrass were affected by 50 yr of protection from long-term heavy grazing, and to determine whether the responses observed were the result of plastic adaptations or genetic selection

Self-Compatibility in 'Paloma' Indian Ricegrass

Self-Compatibility in 'Paloma' Indian Ricegrass

Indian Ricegrass Seed Damage and Germination Responses to Mechanical Treatments

Indian Ricegrass Seed Damage and Germination Responses to Mechanical Treatments

Dryland Stand Establishment and Seed Production of Revegetation Species1

Seed of species used for reclamation and soil conservation in the arid western USA often is collected from native stands. There is a need to produce more seed of known genetic identity under cultivation to meet this demand. The objectives of this research were to: (i) compare stand establishment of four species on three planting dates under dryland conditions (< 360 mm annual precipitation), and (ii) evaluate stand establishment and seed production at 0.76‐ and 1.52‐ m row spacing for 11 species used for dryland revegetation. Four species were evaluated for stand establishment in southwestern Colorado when planted in April, May, and October in 1982, and April, June, and October in 1983. Eleven species were evaluated for seed production. Rocky Mountain penstemon (Penstemon strictus Benth.) and Lewis flax (Linum lewisii Pursh.) had higher stand establishment ratings when seeded in October than in the spring. Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] established well at all planting dates. Fourwing saltbush [Atriplex canescens (Pursh.) Nutt.] established equally well in all months tested except April. The highest seed yields were obtained from small burnet (Sanguisorba minor Scop.) and tall fescue (Festuca arundinacea Schreb.). Orchardgrass (Dactylis glomerata L.) and Indian ricegrass generally produced more seed than either western wheatgrass [Elymus smithii (Rydb.) Gould] or basin wildrye [Leymus cinereus (Scribn and Merr.) A. Löve]. The latter two species declined in seed production dramatically in the third year. Seed production in 1983 and 1985 was greater in the 0.76‐ than in the 1.52‐m row width.

Effects of CO 2 Enrichment on Four Great Basin Grasses

Plants of four Great Basin grass species were grown from seed in two greenhouses at low (340 Vl 1-1) and high (680 jl 1-1) CO2 concentration. In all four species, high CO2 promoted mean increases in the number of basal stems, leaf area, specific leaf weight and above-ground dry weight. High CO2 resulted in an increase in CO2 assimilation in two C3 grasses but not in a C4 grass, while all three species showed decreases in stomatal conductance. Mean increases of 60% in aboveground dry weight and 80% in water-useefficiency are consistent with previously reported high CO2 effects on grasses. No consistent differential effects of high CO2 were observed when comparing annual vs perennial species. Global CO2 enrichment may alter the competitive balance of Great Basin plant communities, possibly enhancing the dominance of Bromus tectorum L. on degraded rangelands. Key-words: Bromus tectorum, C02 enrichment, Great Basin, growth, Oryzopsis hymenoides, photosynthesis, rangelands, steppe, stomatal conductance, water-useefficiency

Native seed preferences of shrub-steppe rodents, birds and ants: the relationships of seed attributes and seed use.

This study established the preferences of shrubsteppe granivores among seeds of 6 common sagebrushsteppe plants and related the preferences observed to physical and nutritional attributes of the seeds. Seeds of big sagebrush (Artemisia tridentata), cheatgrass (Bromus tectorum), Indian ricegrass (Oryzopsis hymenoides), western wheatgrass (Pascopyrum smithii), bitterbrush (Purshia tridentata) and green needlegrass (Stipa viridula) were placed in groups of petri dishes designed such that seed removal could be ascribed to either diurnal vertebrates, nocturnal vertebrates or ants. Though absolute quantities of seeds removed varied among the 3 granivore classes, calculations of preference based on weights of each seed species removed by each granivore class indicated that all 3 ranked the seeds similarly. Preference hierarchies of the 3 granivore classes were highly positively correlated with both calories per seed and % soluble carbohydrate of the seeds. The first correlation supports a basic prediction of optimal foraging theory -that foragers should maximize energy intake per unit time spent foraging. Both correlations emphasize the role of seed nutritional qualities in granivore seed selectivity in that soluble carbohydrate is a water-efficient energy source and its percentage is a good indicator of the digestible energy available in a food item. A corollary experiment comparing granivore use of an exotic seed (millet [Panicum miliaceum]) and a preferred native seed (Oryzopsis) demonstrated a distinct preference for the exotic. Since millet seeds are particularly high in % soluble carbohydrate, this result reinforced the apparent value of this nutritional attribute as a predictor of granivore seed preference. Among many seed resource characteristics upon which granivore seed selectivity might operate, our results indicate that individual species' nutritional composition may be particularly important. Thus, inferences about seed selectivity and resource partitioning among arid-land granivores should be interpreted with caution, especially those based on experiments using seed introductions, since the influence of seed nutritional attributes has not been widely acknowledged heretofore.

Water uptake and storage by rhizosheaths of Oryzopsis hymenoides: a numerical simulation

Rhizosheaths (sheaths of sand grains that form around the roots of some grasses) are common in perennial grasses that colonise sandy substrates. It has been hypothesised that rhizosheaths increase water availability by increasing the efficiency of water absorption. Others have suggested that rhizosheaths act as storage reservoirs for water. In either case rhizosheaths undoubtedly play an important role in the water relations of these grasses.In an attempt to evaluate the main function of rhizosheaths, we developed a finite element cylindrical water flow model which enabled us to simulate water uptake by Oryzopsis hymenoides (Roem, and Shult.) Ricker. This model allowed us to estimate total water uptake by root systems with and without rhizosheaths and to compare these values to the extra water stored within the rhizosheath. The results of this study suggest that the presence of rhizosheaths is more important in reducing the total resistance to water flow within the rhizosphere than in enhancing water storage.

Enhancing Germination of Indian Ricegrass Seeds with Sulfuric Acid1

AbstractIndian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] is the dominant forage species on millions of hectares of rangeland in the western United States. Revegetation of degraded rangeland by seeding Indian ricegrass has been generally unsuccessful because of low seed germination. Our purpose was to evaluate the influence of acid seed scarification on germination of Indian ricegrass seeds. Seeds of ‘Paloma’ and ‘NezPar’ Indian ricegrass were scarified in sulfuric acid (H2SO4) from 0 through 45 min at 5‐min intervals. Without scarification, germination of the seeds of these two cultivars was less than 10%. Seedlots from 1 to 11 years old were treated. Germination data were used to develop regression equations for the relationship between duration of acid seed scarification and germination for each cultivar. Seeds of Paloma Indian ricegrass required 25 to 35 min of scarification, whereas seeds of NezPar required 15 to 25 min scarification. The relative composition and morphological forms of the seed may explain the difference in duration of required scarification. The scarified seeds were incubated at 55 constant and alternating temperatures to obtain data with which to construct quadratic response surfaces for temperature‐germination profiles. Even with scarification, the seeds of the two cultivars produced mean germination for the profiles of only 9 to 31%. The dormancy of Indian ricegrass seeds is controlled by complex interacting factors. Acid scarification is a very imprecise tool for enhancing the germination of dormant seeds of Indian ricegrass.

Nutritional and Physical Attributes of Seeds of Some Common Sagebrush-Steppe Plants: Some Implications for Ecological Theory and Management

A study was conducted to identify seed attributes which might influence granivore preferences. Physical and chemical characteristics were estimated for seeds of 7 common sagebrush-steppe species (A rtemisia tridentata, Bromus tectorum, Oryzopsis hymenoides, Pascopyrum smithii, Purshia tridentata, Stipa comata and Stipa viridula) and 1 sacrifice food species (Panicum miliaceum). Seed weights and caloric contents were determined, as well as % composition contributed by 5 organic, 3 inorganic and 5 synthetically defined fractions (including crude protein, solvent extract, structural and soluble carbohydrates and lignin). Results indicate that % soluble carbohydrate may be a good predictor of granivore seed preference. The generality of this or any other predictor is unknown, since sufficiently detailed seed attribute data are unavailable for most species. For management scenarios involving seeds subject to predation, such data would help effectively translate ecological understanding of granivory into more efficient management practices.

Variation in Lemma Thickness in Indian Ricegrass: Implications for Dormancy, Scarification, and Breeding1

Indian ricegrass [Oryzopsis hymenoides (Roem. & Schult.) Ricker] has been of interest for revegetation of western mine lands, however, high seed dormancy restricts stand establishment. Breeding to improve Indian ricegrass is hampered by this inherent dormancy, often as high as 98%. Scarification to break dormancy using sulfuric acid has been successful but reduction of viability has occurred. This study examined whether the number of seeds damaged by scarification was related to the thickness of the indurate lemma possessed by Indian ricegrass. Twelve strains and cultivars of Indian ricegrass were examined with a range in lemma thickness of 42 to 76 μm. They differed significantly for this trait, which was not affected by environment. Acid scarification treatments of 20, 30, and 40 rain were followed by water rinses. Viability before and after scarification was determined by tetrazolium tests. Lemma thickness had a significant protectiveffect on seed viability after scarification for all three scarification durations. Coefficients of determination (R2) values were 0.56, 0.75, and 0.79 for 20, 30, and 40 min time, respectively. These results indicate that lemma thickness can be utilized to determine proper scarification duration to minimize seed damage while maximizing germination, resulting in uniform stand establishment and evaluation of Indian ricegrass germplasm.

Germination of Seeds of 'Paloma' and 'Nezpar' Indian Ricegrass

Seedlots of the cultivars ‘Paloma’and ‘Nezpar’ Indian ricegrass [Oryzopsis hymenoides (R. & S). Ricker] were classified as to seed type, germination, and germination in response to the additive enhancement treatments of removing the lemma and palea by dissection, enriching the germination substrate with gibberellin (G&), and cool-moist stratification at 2’C for 2 weeks. The seedlots contained different proportions of polymorphic seed size, color, and covering types. Seedlots of ‘Paloma’were dominated by big black seeds while lots of ‘Nezpar’ contained roughly equal propertions of big and small black seeds. The various seed types had different germination characteristics both under control and enhancement treatments. The initial germination of untreated seeds of either cultivar was very low; however, maximum germination with enhancement did not exceed 5%. Indian ricegrass [Oryzopsis hymenoides (R. & S.) Ricker] is the dominant perennial grass species of salt desert ranges occurring at lower elevations within the sagebrush (Artemisiu) vegetation zone of western North America. On sand dunes Indian ricegrass may form relatively pure stands, sometimes several thousand hectares in extent. Being a widely occurring valuable forage species and a monospecific dominant of harsh, arid environments, Indian ricegrass has received considerable attention from agronomists and range managers as a potential revegetation species (Robertson 1976). Recently, interest in this species has increased because of the importance of revegetating sandy-textured spoils from mining operations. Indian ricegrass seeds (caryopses) are highly polymorphic, but all forms are generally dormant (Huntamer 1934). The nature of the dormancy has been attributed to the persistent lemma and palea and pericarp that probably inhibit oxygen transfer to the embryo (Huntamer 1934, Fendal 1964, Clark and Bass 1970, Shaw 1976, McDonald and Kahn 1977, Zemetra 1979). The lemma and palea have to be removed and the pericarp pricked in order for the seeds to germinate. A form of embryo dormancy that gradually breaks down over time, but can be overcome by cool-moist stratification, has also been documented for Indian ricegrass seeds (Tooele 1940, Clark and Bass 1970). The cool-moist stratification requirement of some lots of Indian ricegrass seeds can be partially or totally substituted by adding gibberellic acid to the germination substrate (McDonald and Kahn 1977). Our purposes were to determine whether different seed types could be identified in seedlots of ‘Paloma’ and ‘Nezpar’ Indian ricegrass and whether these seed types have different germination with and without enhancement treatments.

Elemental Contents of Plants Growing on Soil‐Covered Retorted Shale

AbstractThe concentrations of several potentially toxic elements (F, B, Mo, Pb, Ni, Co, Cd, Cr, Hg, Se, and As) were determined in plants growing on various depths of soil covering retorted (Paraho) shale. The plants that were sampled include: Indian ricegrass (Oryzopsis hymenoides), fourwing saltbush (Atriplex canescens), western wheatgrass (Agropyron smithii), Sherman's big bluegrass (Poa ampla), Utah sweetvetch (Hedysarum boreale), and winterfat (Ceratoides lanata). The F levels were elevated in some of the plants growing on 30 cm of soil over shale. The concentrations of Mo and the Cu/Mo ratios in the plants indicate that molybdenosis could be expected with livestock grazing on revegetated plants. Increasing the depth of soil cover reduced the Mo levels, but the second year's data indicate that increasing the soil depth may only temporarily reduce the potential molybdenosis problem. The plant levels of Pb, Co, Cd, and Hg were below analytical detection limits. The plant concentrations of Ni, As, Se, B, and Cd were too low to be of environmental concern.