Grass Root System Research Articles

678 Turfgrass Response to Phosphorus Applications

Phosphorus (P) applications to turfgrasses vary with the development stage of the plant. At establishment, it is common to use “starter fertilizers,” such as 12N–25P–10K, that are high in P and relatively low in nitrogen (N). Mature grass plants, however, are very efficient users of P. As the root system develops, the amount of P added as fertilizer decreases, unless the soil is very deficient in P. A common analysis for mature turf would be a 20N–2P–15K. The reason for this change is the relative immobility of P in the soil. At the time of establishment, the limited root system is unable to obtain sufficient P to meet the plant's needs for this element. The P does not readily move in the soil solution to the vicinity of the plant and it must be placed on the surface in close proximity to the developing root. At maturity, the fibrous, multibranched root systems of grasses make them some of the most efficient species at removing P from the soil. A major concern over the use of P fertilizers on turf in recent years has been the possibility of movement of this element into surface waters. Excess P in surface water may result in algal blooms and other environmental problems. While there is some reason for concern where fertilizers are applied on sidewalks and streets in urban areas, P movement from most turf areas is very limited and properly applied fertilizer results in little damage to the environment.

Interspecific variation in plant responses to mycorrhizal colonization in tallgrass prairie

Symbiotic associations between plants and arbuscular mycorrhizal fungi are ubiquitous and ecologically important in many grasslands. Differences in species responses to mycorrhizal colonization can have a significant influence on plant community structure. The growth responses of 36 species of warm- and cool-season tallgrass prairie grasses and 59 tallgrass prairie forbs to arbuscular mycorrhizal (AM) fungal colonization were assessed in greenhouse studies to examine the extent of interspecific variation in host-plant benefit from the symbiosis and patterns of mycorrhizal dependence among host plant life history (e.g., annual, perennial) and taxonomic (e.g., grass, forb, legume, nonlegume) groups and phenological guilds. There was a strong and significant relationship between phenology of prairie grasses and mycorrhizal responsiveness, however this relationship was less apparent in forbs. Perennial warm-season C(4) grasses and forbs generally benefited significantly from the mycorrhizal symbiosis, whereas biomass production of the cool-season C(3) grasses was not affected. The root systems of the cool-season grasses were also less highly colonized by the AM fungi, as compared to the warm-season grasses or forbs. Unlike the native perennials, annuals were generally not responsive to mycorrhizal colonization and were lower in percentage root colonization than the perennial species. Plant growth responsiveness and AM root colonization were positively correlated for the nonleguminous species, with this relationship being strongest for the cool-season grasses. In contrast, root colonization of prairie legumes showed a significant, but negative, relationship to mycorrhizal growth responsiveness.

Spatial Distributions of Grass and Shrub Root Systems in the Shortgrass Steppe

In water-limited ecosystems such as the shortgrass steppe of North America, the ability of plants to absorb sufficient water for growth and reproduction is dependent upon the characteristics of their root systems. Our objective was to evaluate the spatial dis- tributions of roots of three plant life forms: a grass (Bouteloua gracilis) (H.B.K.) Lag., a dwarf shrub (Gutierrezia sarothrae (Pursh.) Britt. & Rusby) and a shrub (Atriplex canescens (Pursh.) Nutt.). Our interests were in a qualitative evaluation of evidence that different life forms obtained water from different soil layers. Root systems were excavated and evaluated in terms of horizontal and vertical extension, and proportion of total root length in each 10-cm layer of the soil profile. Bouteloua gracilis had over 80% of its roots in the top 50 cm of the soil, whereas the depth at which Atriplex canescens had over 80% of its roots was 100 cm. The corresponding depth for Gutierrezia sarothrae was 80 cm. Both of the woody plants had deeper and more widely spreading root systems than the grass. The environment of the shortgrass steppe is characterized by low and variable water avail- ability. These conditions lead to a distribution of available water that is biased toward the upper soil layers. The greater concentration of roots of Bouteloua gracilis in the soil layers near the surface compared to the two woody species provides a potential explanation for its dominance in the shortgrass steppe.

PRELIMINARY STUDY ON MECHANISM OF PLANT ROOTS TO INCREASE SOIL ANTISCOURIBILITY ON THE LOESS PLATEAU

The effects of the root system of trees, shrubs and grasses on the hydraulic and physical properties of soil and their interrelation with increasing soil anti--scouribility by roots are quantitatively demonstrated in this paper for the first time. Based on the analysis of the leading factors of roots to increase the soil anti--scouribility, a mathematical model on increasing soil anti-scouribility by roots is established. The value in application of the model is to explain the mechanism of roots to increase the soil anti-scouribility and to evaluate the increasing effects of soil anti-scouribility by roots in different layers of soil The calculated results of the values in soil anti--scouribility intensified by roots at various intensities of rainfall and slopes of the model have higher precision, all of the mean maximum deviations between the estimated and observed values being less than 1.417 s/g.

Persistence of Maternal Nutrient Effects in Plantago Major: The Third Generation

Plants of Plantago major were grown for two generations in different environments. Seed germination of the second generation was examined for the effects of maternal environments, as well as subsequent plant growth and reproduction in the presence of inter— and intraspecific competitors. Maternal treatments were (1) plants that had received nutrient pulses in both the first and second generations (PP plants), (2) plants that had received a nutrient pulse only in the first generation (PC plants), (3) plants that had received a nutrient pulse only in the second generation (CP plants), and (4) plants that did not receive a nutrient pulse in either generation (CC plants). Under favorable conditions (with out interaction with a leaf canopy and root system of grasses), seeds of CC plants generally germinated earlier and had a higher final germination percentage. In contrast, under a Poa canopy, seeds of PP plants germinated earlier and had a higher final germination percentage. For adult plants, there were significant interactions between maternal environment and neighbor density. The effects of maternal environments on leaf area generally were evident before flowering but disappeared after flowering. The greatest difference in leaf area occurred between CC and PP plants, and these were often different from CP and PC plants. There was a significant three—way interaction among the type of competition, maternal treatment, and neighbor density of biomass characters. In intraspecific competition with one neighbor, the spike biomass was highest in PP plants followed by CP plants, PC plants, and CC plants, with the last significantly lower than the first two. In general, the juvenile maternal effect did not necessarily result in an adult reproductive advantage. The influence of the maternal environment differed among plant characters. These results demonstrate that maternal environmental factors can affect plant phenotypic characters for at least three generations. The expression and the extent of these maternal effects varied with the resource condition experienced by the progeny, the intensity of competitive interactions, and life history stage.

Size and morphology of root systems of perennial grasses from contrasting habitats as affected by nitrogen supply

This paper discusses interspecific differences and phenotypic responses to nitrogen supply in various root parameters of five perennial grasses from contrasting habitats. The following root parameters were studied: root:shoot ratio, specific root length, specific root area, mean root diameter, frequency of fine roots, and the length and density of root hairs. Significant between-species variation was found in all of these features. Species from fertile sites had higher root:shoot ratios at high nitrogen supply than species from infertile habitats. All species growing at low nitrogen supply showed a significant increase in root:shoot ratio. Specific root length, specific root area, mean root diameter and frequency of fine roots were not affected significantly by nitrogen supply. Species from infertile sites responded to low nitrogen supply by a significant increase in root hair length and root hair density.

The influence of grass root systems on growth and form of Trifolium repens

Pure swards of the grasses Dactylis glomerata, Holcus lanatus, and Lolium perenne were allowed to grow in boxes in a standard growth medium; one additional set of boxes with no grasses was used as a control. After 43 weeks, all aboveground parts of the grasses were removed by harvesting at 2 cm below ground level. Next, clones of Trifolium repens collected from patches in a pasture dominated by these three grasses were introduced into each of the grass boxes, in all combinations of grass treatment and T. repens origin, and allowed to grow for 16 weeks. Both the site of origin of the T. repens clones and the treatment imposed by the grasses had significant influences on the growth and form of T. repens. Treatment effects were consistent for most characters, and on average, depression of growth was in the following order: Dactylis > Lolium > Holcus > control. This ranking differs from that reported by many other studies where either whole plants or shoot systems alone were used as the treatment effects on T. repens. Key words: interference, growth, morphogenesis, roots, Trifolium repens.

Spatial Heterogeneity of the Root System of Grasses in the Patagonian Arid Steppe

SORIANO, A., R. A. GOLLUSCIO AND E. SATORRE (Depto. Ecol., Facultad Agron., Univ. Buenos Aires, Av. San Martin 4453, 1417-Buenos Aires, Argentina). Spatial heterogeneity of the root system of grasses in the Patagonian arid steppe. Bull. Torrey Bot. Club 114:103-108. 1987.Root biomass distribution and root growth into traps buried in the soil have been studied in the three dominant grasses (Stipa speciosa Trin. et Rupr., S. humilis Vahl and Poa ligularis Nees ap. Steud.) of extensive plant communities of the Patagonian arid steppe. Root biomass decreases sharply from center to the periphery of young and old plants of the three species. As a result of this attenuation, low root density pockets, corresponding to bare soil patches between tussocks, are found in the upper soil layer. At these pockets, water from small rains would be underutilized. Comparison of root biomass and spring root growth into traps supports the conclusion that, in a growing season, the three grasses were able to rebuild the roots only to the size previous to ablation provoked by trap installation. It is, therefore, postulated that lack of full colonization of low density root pockets by established root systems is determined by morphological constraints that limit their size and geometry. Potentiality seems to exist for the establishment of new individuals that would contribute to the formation of a continuous layer of uniform root density in the upper soil. Better use would thus be made of small rains, amounting to 57% of total rainfall events.

A laboratory experiment on the role of grass for infiltration and runoff processes

Two lysimeters with the same dimensions were provided, and filled with the same loam clay. On the soil surface of one lysimeter, grass was planted to compare the hydrologic response of the grassed lysimeter with that of the other bare soil lysimeter. About half of the runoff from the bare soil lysimeter occurred as overland flow, the rest being groundwater flow. Overland flow scarcely occurred from the grassed lysimeter. Grass roots that developed deep into the soil layer play an important role in increasing the infiltration rate as well as in drying the soil uniformly throughout the soil layer by evapotranspiration, preparing for high infiltration and large rainwater storage for the subsequent rainfall event. Accordingly, the total loss by evapotranspiration from the grassed soil amounts to almost twice that from the bare soil. For an evaporation- and evapotranspiration-prohibited experiment, the recession characteristics from a saturation state showed similar features for the bare and grassed soils, indicating the same microstructure of high moisture reservability for both soils. The well-developed grass root system reformed the soil structure considerably to produce the seemingly contradicting characteristics of high moisture conductivity and high moisture reservability; i.e. a high infiltration rate and prolonged groundwater discharge. Finally, the importance of the initial soil moisture in the rainfall-runoff process, rainfall loss and runoff ratio is stressed.

A Practical Guide to Political Effectiveness

The future viability of nursing research depends on federal funding decisions, which in turn depend upon national and local action by researchers and other advocates of nursing research. Since successful action is facilitated by familiarity with national policy-making, the legislative process is reviewed and a plan for action at the state and local level is offered. Basic actions are suggested to organize, arouse public support, build coalitions, and gain access to legislators. All these must follow a developed work plan. Ideas for specific implementing steps are provided, but each local area requires specially designed activities appropriate for their own needs and resources. The goal is to build a grass roots system to support national lobbying to stabilize and increase federal funding for nursing research.

Ecology of Nitrogen Fixation in Soils and Rhizospheres V. Oxygen Limited Growth and N-Metabolism in Wheat Roots

Summary The effects of reduced oxygen concentration on root growth and activities of enzymes of N-metabolism of wheat ( Triticum aestivum var. Kolibri) have been studied, for low O 2 tensions are required for N 2 fixation by microaerophilic bacteria (e.g. Azospirillum ) associated with root systems of grasses. In hydrocultures with oxygen concentrations in the range of 0.2 to 1 mg O 2 · 1 −1 compared to aerated cultures (8-9 mg O 2 · 1 −1 ) root growth was reduced from 10 mg fresh weight · day −1 · plant −1 to one tenth 15 to 30 d after sowing. Specific activity of NADH and NADPH dependent glutamate dehydrogenase (E.C. 1.4.1.2 and 1.4.1.4) is reduced by 50 % in the cultures with low oxygen concentrations 20 to 30 days after sowing, whereas specific activity of aspartate aminotransferase (E.C. 2.6.1.1) and alanine amino transferase (E.C. 2.6.1.2) is enhanced by a factor of two to three. Specific activity of glutamine synthetase is almost unaffected. Specific activity of glutamate dehydrogenase is lowest in the root tips, medium in young root hair zone and highest in the old root hair zone, glutamine synthetase activity is reverse in the three zones with differences by a factor of 3-5; aspartate aminotransferase is similarly active in the three zones. Nitrate concentration used (100 μM) for cultivation of the wheat plants was tested with Azospirillum brasilense in pure culture on agar surfaces exposed to air at the same pH (5.8), used for cultivation of the wheat plants. Activity over a 14 day period (peak activity 70 nmol C 2 H 4 · mg protein −1 · h−1) was not affected, however 1 mM and 5 mM nitrate added reduced the total activity to 50 % and 10 % respectively.

The Zambezi Goba Ancestral Cult

Opening ParagraphThe Zimbabwe culture of present day Southern Rhodesia and Mozambique, of which the main occupation at the nuclear site of Great Zimbabwe dates from the twelfth to the fifteenth centuries, is best known for its external trade in gold, ivory, and copper and for its monumental stone ruins. But while important in terms of prestige exchanges at the diplomatic level, mining and trade seem to have been seasonal occupations fitted in round the annual cycle of subsistence cultivation dependent upon the rains (Barreto 1667: 489–92; Mudenge 1974; Phimister 1974). Patron–client relations between Shona-speaking groups were expressed by limited, symbolic tribute in agricultural labor, military service, gold, ivory, livestock, wives, slaves, local produce, and other prestige items (Barros 1552:271; Conçeicão 1696: 66; Andrade 1955: 306, 310–11), but until recent times basic control over social and political groupings was probably exercised through belief in various levels of spirit cult, ranging from the grass-roots system of individual guardian spirits (mudzimu, sing.) in the ancestral cult controlled by village elders in the extended family and descent group, through a hierarchy of ritually senior, loosely territorial land spirits (mhondoro) holding sway over the progressively larger land shrine realms (nyika) of neighborhood leaders, petty chieftains, chiefs, and paramounts. Leaders at each level influenced a following of both spirits and living people who were interconnected, and the fluctuating network of alliances that existed between leaders was symbolized and kept going by an intermittent traffic in tribute, diplomatic missions, and religious congregations coming to the shrines and leaders located at the various headquarters (zimbabwes) of the confederacy. When the confederacy was large and free from civil wars and secession, the system sometimes culminated in a unifying central cult devoted to a supreme spirit (such as Mwari Nyadenga, Leza or Mulungu) supporting a Mambo, whom the Portuguese called King or Emperor (Santos 1609: esp. 196–9; Abraham 1966; Bullock 1928; Garbett 1966, 1969; Holleman 1953).

Development of Grass Root Systems as Influenced by Soil Compaction

Development of Grass Root Systems as Influenced by Soil Compaction

Effectiveness of Root System of Grasses Used in Soil Conservation in Paundi Khola Sub Watershed of Lamjung District, Nepal

The study was carried out in Paundi Khola Sub-watershed of Lamjung District, with the objective of evaluating the effectiveness of root system of grasses used in soil conservation. Different root parameters were recorded through direct field measurement. Key informant's survey, semi-structured walk and focus group discussions were also undertaken to acquire relevant information on pattern of retaining grasses, insect/pest condition, local uses of grasses, perceived weeds and perception of farmers on different issues. Stylo and Molasses are most effective in armouring the slope against surface erosion from both runoff and rain splash due to their dense surface cover, low canopy and small leaves. Broom Grass and Napier are most effective in reinforcing the soil by providing a network of strong roots that increases the soil's resistance to shear. Broom Grass can moderately support the soil mass by its strong and long fibrous roots. Broom Grass can bind average 3.8 cu. m. soil, and that for napier, stylo, and molasses are 0.37 cu. m., 0.45 cu. m. and 0.04 cu. m. soil respectively. It was found that farmers plant the improved varieties of grasses primarily for forage due to high foliage content. Soil conservation is second priority. A combination of improved varieties of grasses and natural grasses helps to conserve soil and moisture more effectively than single-use of grass species on marginal land. Key Words: Effectiveness, Improved grass species, Root, Soil conservation, Napier, Molasses, Stylo, Broom grass. DOI: 10.3126/init.v2i1.2533 The Initiation Vol.2(1) 2008 pp121-129

EFFECT OF DIFFERENT CULTURAL TREATMENTS ON ROOT DEVELOPMENT IN A GRASS SWARD GROWING ON DEEP PEAT

Previous work has shown that on deep peat the root systems of sown grasses are shallow. In order to study the effect of cultivation on root development, an experiment was laid down in an area of deep peat where sown grass swards were established on plots which had been subjected to different cultivation treatments. Root development is shown to be affected by depth of cultivation and this is discussed in relation to surface sowing of peatland areas.

Use in Plant Ecology of Causation, Physiology and a Definition of Vegetation

Use in Plant Ecology of Causation, Physiology and a Definition of Vegetation

REPRODUCTION IN THE EAST AFRICAN LUNG‐FISH PROTOPTERUS AETHIOPICUS HECKEL

SUMMARY Four occupied nests, which differ in form and environment, of P. aethiopicus are described from Lake Victoria. These constitute the first definite records of the nests of this species. Evidence is adduced which strengthens the possibility that certain structures previously thought by other authors to be nests were in fact those of lung‐fishes. The oxygen content of one nest was determined and found to be low, probably never exceeding 3 p.p.m. During the breeding periods studied, the modal day water temperature was 23oC. and the temperature range 17‐8o to 25‐0oC. The least diurnal temperature variation was 0–5o and the greatest 3–6oC. From one nest over 5,000 larvae were recovered and from another (incompletely sampled) more than 2,000. Some broods showed a distinct fractioning into several ontogenetic stages. It is concluded that fractioning is attributable to slight initial differences in the time of fertilization and reinforced by individual variation in developmental rates. The scanty data available suggest that more than one female spawns in a nest. Larval P. aethiopicus begin air‐breathing when they have reached a length of 23 to 25 mm. It seems probable that whilst the larvae remain in the nest they are not dependent on aerial respiration. In its external features, the embryology of P. aethiopicus closely resembles that of P. annectens. Slight differences in ontogeny are discussed. The ova, embryos and larvae of P. aethiopicus are larger than those of P. annectens, and have a slower‐ developmental rate. Also, the larvae attain a larger size before the yolk is fully resorbed. At ca 23oC. young P. aethiopicus remain in the nest for fifty to fifty‐five days. Pre‐hatching development takes about fifteen days; thereafter the young grow to a length of ca 35 mm. in forty days. Post larval P. aethiopicus live actively in the matted papyrus roots and the root systems of swamp grasses. There is no evidence to support an earlier idea that they pass the first year of life in a quiescent condition. The external gills are ciliated. Data relating to the development and subsequent necrosis of these gills is reviewed and summarized. The breeding cycles of P. aethiopicus in Lake Victoria are imperfectly known. Observations made on ovarian conditions indicate a peak breeding season from November to April. Occupied nests were found in this period, and in September. This latter nest suggests that spawning may also occur during unseasonal. wet periods.

Cationic Activities in Systems of Plant Roots

AbstractThe activities and mean free bonding energies of Na, K, and Ca on alfalfa, soybean, red top, and Reed canary grass roots were determined by the use of the clay membrane electrode technique. Samples of electrodialyzed roots were saturated with each cation by addition as the hydroxide after the exchange capacity of the roots had been previously determined.Examination of the techniques employed showed that reproducible determinations of the activities could be made after a five minute contact of the clay membrane electrode with the root system. Identical readings from both small and large electrodes indicated that there was no problem in obtaining a representative cross section of the root systems for measurement. There was no appreciable liquid junction potential at the point of contact of KCl bridge with the root system. The cations added were found to be practically all recoverable in a 0.1N HCl extraction without serious contamination from ions within the roots.It was possible to determine a value for the cation exchange capacity of the roots by titrating the electrodialyzed roots with base, stirring, and maintaining the system at pH 7 for ten minutes. Bonding energy determinations on these systems indicate that K is bonded stronger than Na on alfalfa roots, but Na is bonded stronger than K on soybean roots. The legume roots held all of the cations with greater energy than did those of the grasses; however, there was a shift in the relative values obtained for the grass root systems when compared to those of the legumes.

The Root System of Grasses in Soils of the Podzol Type

The Root System of Grasses in Soils of the Podzol Type