Nitrogen Fixation Associated with Sand Grain Root Sheaths (Rhizosheaths) of Certain Xeric Grasses

Wullstein, L. H.; Bruening, M. L.; Bollen, W. B.

doi:10.1111/j.1399-3054.1979.tb03176.x

Cited by 71 publications

(38 citation statements)

References 12 publications

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“…Rhyzosheaths improve water status around the roots of S. hymenoides and enhance water uptake from the rhyzosphere (Bristow et al 1985;Wullstein 1991). The presence of symbiotic N fixers in rhyzosheaths, coupled with seasonally higher plant water availability on the dunes, may explain higher leaf N for S. hymenoides on versus off dunes (Wullstein et al 1979).…”

Section: Plant and Habitat Nutrient Differencesmentioning

confidence: 99%

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

Rosenthal

Ludwig

Donovan

2005

International Journal of Plant Sciences

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In arid ecosystems, variation in precipitation causes broad-scale spatial heterogeneity in soil moisture, but differences in soil texture, development, and plant cover can also create substantial local soil moisture heterogeneity. The boundary between inland desert sand dunes and adjacent desert habitats exhibits abrupt changes in soil and vegetation characteristics that may be associated with differences in plant-available water and nutrients. We hypothesized that differences in plant water status between habitats would mirror changes in soil texture and vegetation cover. Because the dunes have higher water availability, we predicted that plants on dunes would have higher plant water potential (C) and be less water use efficient than plants off dunes. We tested these predictions for three species-Psoralidium lanceolatum (a C 3 perennial N-fixing subshrub), Stipa hymenoides (a C 3 perennial bunchgrass), and Salsola iberica (a C 4 annual)-on actively moving desert dunes and adjacent stabilized dunes at Little Sahara Dunes, Utah. Plants on the dunes maintained higher predawn (C pd ) water potentials (>ÿ1.5 MPa) throughout the summer season, whereas off-dune plants were water stressed from July on (C pd < ÿ1:5 MPa). Midday water potential (C md ) generally mirrored C pd . As predicted, off-dune plants were more water use efficient, on the basis of leaf carbon isotope ratios (d 13 C) for the C 3 species. The observed differences in soil particle size, soil water content, and the concomitant effect on soil C likely explain the observed differences in C pd . Soil N was significantly lower on dunes, while soil P was similar across habitats. In contrast, leaf N was similar across habitats, but leaf P was significantly higher on dunes, possibly because of species-specific differences in nutrient relations or differences in habitat nutrient availability. Abrupt changes in water and nutrient availability associated with soil texture are likely to be important selective forces shaping plants' strategies in this and other desert boundary communities.

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Section: Plant and Habitat Nutrient Differencesmentioning

confidence: 99%

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

Rosenthal

Ludwig

Donovan

2005

International Journal of Plant Sciences

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“…Some tropical grasses also form loose associations with N-fixing bacteria (Wullstein et al 1979;Boddey and Döbereiner 1982). The trait to look for is the presence of sheaths of sand grains on the grass roots ('rhizosheaths').…”

Section: Storing Processing and Observations (Categories 1-4)mentioning

confidence: 99%

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

Cornelissen¹,

Lavorel²,

Garnier³

et al. 2003

Aust. J. Bot.

3,390

3,233

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There is growing recognition that classifying terrestrial plant species on the basis of their function (into 'functional types') rather than their higher taxonomic identity, is a promising way forward for tackling important ecological questions at the scale of ecosystems, landscapes or biomes. These questions include those on vegetation responses to and vegetation effects on, environmental changes (e.g. changes in climate, atmospheric chemistry, land use or other disturbances). There is also growing consensus about a shortlist of plant traits that should underlie such functional plant classifications, because they have strong predictive power of important ecosystem responses to environmental change and/or they themselves have strong impacts on ecosystem processes. The most favoured traits are those that are also relatively easy and inexpensive to measure for large numbers of plant species. Large international research efforts, promoted by the IGBP–GCTE Programme, are underway to screen predominant plant species in various ecosystems and biomes worldwide for such traits. This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field. It features a practical handbook with step-by-step recipes, with relatively brief information about the ecological context, for 28 functional traits recognised as critical for tackling large-scale ecological questions.

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“…Soil or sand sheaths encasing roots of grasses have been described as features found in desert and dry environments (13). More recently they have been described on corn (12) and mesophytic grasses in humid environments (3).…”

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confidence: 97%

Development of Water Conducting Capacity in the Root Systems of Young Plants of Corn and Some Other C4 Grasses

Wenzel

McCully²,

Canny³

1989

Plant Physiol.

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Development of the primary and early nodal roots was studied in Zea mays L., Zea mexlcana (Schrad.) Soil or sand sheaths encasing roots of grasses have been described as features found in desert and dry environments (13). More recently they have been described on corn (12) and mesophytic grasses in humid environments (3). Striking illustrations of such sheaths will be found in these three papers. The sheathed regions of corn roots coincide with the regions of immature xylem where LMX2 elements are still alive (1 1). This region stretches much further back (up to 50 cm from the apex) than has been supposed. The present paper extends the association of soil sheaths with the immaturity of the LMX to four other C4 grasses, and explores the likely effect of the nonfunctioning xylem on water supply to the shoot.It is widely believed that the permeability of roots to water is much greater in the axial direction (P,) than in the radial direction (P,). The finding (11) that, in axile roots of field-grown corn, maturation of LMX is long-delayed, raised the question when in the development of the seedling the full axial permeability became operative. Each nodal root goes through a stage when it bears a coherent soil sheath for up to half a meter proximal to the bare elongating tip (2-5 mm), and has inside immature LMX (with cross walls and cytoplasm) which cannot engage in transporting water more efficiently than any other file of living cells (7). The longitudinal water permeability of such roots is thus limited to the outer ring of small (20 ,um diameter) EMX elements, which are open vessels to within 10 cm from the tip (2). When the LMX elements lose their crosswalls and become open, and the soil sheath disperses leaving the root bare, the longitudinal permeability ofthe root will increase by a factor of at least 100 (1 1). If the first formed seedling roots showed a similar slow maturation oftheir LMX there could be a stage when the primary and early nodal roots all had only their EMX vessels open. The time at which one or more of these early roots opened their LMX would herald a dramatic change in the availability ofwater to the developing shoot. The sequence and numbers ofdeveloping roots in corn have been described (4) for the variety Seneca Chief. The primary root is followed closely by a tier of four roots from the coleoptilar node, and a little later by four to five roots from the second node. Roots ofeach tier are even-aged. Roots of successive tiers (usually seven tiers) go through similar stages ofdevelopment to the earlier lower ones, from sheathed to bare. We determined to follow the development of the primary and early tiers of nodal roots, recording the presence and extent of soil sheaths, the presence or absence of crosswalls and cytoplasm in the LMX and the stage oflignification of the vessel sidewalls. These measurements would be related to the number and size of the leaves. Measurements of stomatal resistance on days of high evaporative demand might reveal whether at any stage the young seedl...

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Nitrogen Fixation Associated with Sand Grain Root Sheaths (Rhizosheaths) of Certain Xeric Grasses

Cited by 71 publications

References 12 publications

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

Plant Responses to an Edaphic Gradient across an Active Sand Dune/Desert Boundary in the Great Basin Desert

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

Development of Water Conducting Capacity in the Root Systems of Young Plants of Corn and Some Other C4 Grasses

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