Studies on Uptake and Loss of Water by Barley Roots in Relation to Changes in Root Resistance

Shone, M. G. T.; Flood, Ann V.

doi:10.1093/jxb/31.4.1147

Cited by 32 publications

(11 citation statements)

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“…In fact, sheathed com roots have higher water contents than older, bare regions (Wang et al, 1991), and rhizosheaths of Oyzopsis hymenoides have more water than the surrounding soil (Bristow et al, 1985). Increasing experimental evidence with both xerophytic and mesophytic plants indicates that water can move from their roots into the surrounding soil, pulled out, passively, by the lower water potential of the soil (Shone and Flood, 1980;van Bavel and Baker, 1985;Caldwell and Richards, 1989;Blum and Johnson, 1992;Dawson, 1993) or pumped out, actively, by the root (Schwenke and Wagner, 1992). However, the experimental design used here did not allow us to distinguish between these two mechanisms.…”

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confidence: 99%

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

1994

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Field observations have shown that rhizosheaths of grasses formed under dry conditions are larger, more coherent, and more strongly bound to the roots than those formed in wet soils. We have quantified these effects in a model system in which corn (Zea mays 1.) primary roots were grown through a 30-cm-deep prepared soil profile that consisted of a central, horizontal, "dry" (9% water content) or "wet" (20% water content) layer (4 cm thick) sandwiched between damp soil (15-1 7% water cqntent). Rhizosheaths formed in dry layers were 5 times the volume of the subtending root. In wet layers, rhizosheaths were only 1.5 times the root volume. Fractions of the rhizosheath soil were removed from individual roots by three successive treatments; sonication, hot water, and abrasion. Sonication removed 50 and 90% of the soil from rhizosheaths formed in dry and wet soils, respectively. After the heat treatment, 35% of the soil still adhered to those root portions where rhizosheaths had developed in dry soil, compared with 2% where sheaths had formed in wet soil. Root hairs were 4.5 times more abundant and were more distorted on portions of roots from dry layers than from wet layers. Drier soil enhanced adhesiveness of rhizosheath mucilages and stimulated the formation of root hairs; both effects stabilize the rhizosheath. Extensive and stable rhizosheaths may fundion in nutrient acquisition in dry soils.

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confidence: 99%

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

1994

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“…Simulation of this is difficult as we have been unsuccessful in growing A. myosuroides in the system described by Shone & Flood (1980). Simulation of this is difficult as we have been unsuccessful in growing A. myosuroides in the system described by Shone & Flood (1980).…”

Section: Entry Of Isoproturon From the Root System In Nutrient Culturementioning

confidence: 99%

The relationship between the entry of isoproturon into Alopecurus myosuroides and its effect on growth and CO₂ fixation

Blair¹

1987

Annals of Applied Biology

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S U M M A R YAlopecurus myosuroides (blackgrass) was grown in nutrient and with isoproturon added to the solution when plants had three leaves. The transpiration stream coefficient factor was calculated over a period of 96 h after treatment to be approximately 1. On this basis isoproturon entry into A. myosuroides was estimated using data for water loss through plants and there was a linear relationship between herbicide entry and plant weight 14 days after treatment. Treatment for at least 7 days with isoproturon at a dose of 1 pg a.i./15 ml nutrient solution (= 0.32 x 1 0 -6~) before returning plants to fresh nutrient was necessary for damage to be still evident after 14 days. This time period corresponded with the reduction of C 0 2 exchange to zero as measured by infra-red gas analysis. Some recovery occurred from 6 h treatment with 120 pg a.i. isoproturon/l5 ml nutrient solution when assessed after returning plants to untreated nutrient for 14 days. A quicker depletion in C 0 2 uptake by blackgrass occurred when both the primary and secondary roots were treated compared with secondary alone but eventually the levels reached were similar. The 'CALF' model predicted much higher concentrations of isoproturon than appeared necessary to damage A. myosuroides. This suggests a major influence of climate on the plant and this and other interactions are discussed.

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“…The tendency of root L, to change in response to water availability, i.e., for roots to behave as rectifiers, has been investigated with respect to the structural characteristics of hypodermal sleeves in Zea mays (Shone and Clarkson, 1988). Other anatomical studies, though not specifically addressing root rectification, have similarly focused on the role of the hypodermis (exodermis) in regulating radial water flow (Oleson, 1978;Clarkson et al, 1987).…”

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“…Agave deserti, a perennial leaf succulent of the Sonoran Desert, was used because its roots have been shown to act as rectifiers (Nobel and Sanderson, 1984). After plants were subjected to drying and in some cases rewetting in soil, whole roots and root segments were used for concurrent determinations of changes in tissue anatomy and Lp ; Lp was measured by the technique ofvacuuminduced flow (Shone and Clarkson, 1988). Based on morphological criteria (palta and , roots were classified as old or young nodal roots, previously designated "established roots," arising from nodes at the base ofthe stem; or as lateral roots, previously designated "rain roots," arising as branches from nodal roots.…”

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Changes in Hydraulic Conductivity and Anatomy Caused by Drying and Rewetting Roots of Agave deserti (Agavaceae)

North

Nobel

1991

American Journal of Botany

128

124

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Concurrent determinations of changes in hydraulic conductivity and tissue anatomy were made for roots of Agave deserti excised during drying and following rewetting in soil. At 30 d of drought, hydraulic conductivity had declined less than twofold for older nodal roots, tenfold for young nodal roots, and more than 20-fold for lateral roots ("rain roots" occurring as branches on the nodal roots). These decreases were consistent with increases in cortical lacunae caused by cell shrinkage and collapse. Similarly, reduction of lacunae in response to rewetting after 7 d of drought corresponded to levels of recovery in hydraulic conductivity, with young nodal roots showing full recovery, lateral roots returning to only 21% of initial conductivity, and older nodal roots changing only slightly. Increases in suberization in the exodermis, endodermis, and cortex adjacent to the endodermis in response to drying coincided with decreases in hydraulic conductivity. Measurements of axial hydraulic conductance per unit length before and after pressurization indicated that embolism caused reductions in axial conductance of98% for lateral roots, 35% for young nodal roots, and 20% for older nodal roots at 7 d of drought. Embolism, cortical lacunae, and increasing suberization caused hydraulic conductivity to decline during drought in the three root types, thereby helping limit water loss to dry soil; the recovery in hydraulic conductivity for young nodal roots after rewetting would allow them to take up water readily once soil moisture is replenished.

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Studies on Uptake and Loss of Water by Barley Roots in Relation to Changes in Root Resistance

Cited by 32 publications

References 1 publication

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

The relationship between the entry of isoproturon into Alopecurus myosuroides and its effect on growth and CO₂ fixation

Changes in Hydraulic Conductivity and Anatomy Caused by Drying and Rewetting Roots of Agave deserti (Agavaceae)

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Studies on Uptake and Loss of Water by Barley Roots in Relation to Changes in Root Resistance

Cited by 32 publications

References 1 publication

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

Formation and Stabilization of Rhizosheaths of Zea mays L. (Effect of Soil Water Content)

The relationship between the entry of isoproturon into Alopecurus myosuroides and its effect on growth and CO2 fixation

Changes in Hydraulic Conductivity and Anatomy Caused by Drying and Rewetting Roots of Agave deserti (Agavaceae)

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The relationship between the entry of isoproturon into Alopecurus myosuroides and its effect on growth and CO₂ fixation