Total Resistance to Water Flow in Field Soybeans: II. Limiting Soil Moisture<sup>1</sup>

Zur, B.; Jones, J. W.; Boote, K. J.; Hammond, L. C.

doi:10.2134/agronj1982.00021962007400010026x

Cited by 39 publications

(30 citation statements)

References 9 publications

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“…Alternative explanations for the results of Zur et al 29 are possible. For example, in their experiments root-soil contact may have been poor due to root shrinkage during periods of fast transpiration s .…”

Section: Estimation Of Soil and Root Resistances For Field Cropmentioning

confidence: 92%

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Soil and plant resistances to water uptake byVicia faba L.

Reid

Hutchison

1986

Plant Soil

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Summary The hydraulic resistivity of Vicia faba L. roots grown in soil was estimated from steady state measurements of transpiration rate and leaf and soil water potentials. Root and stem axial resistivities, estimated from xylem vessel radii, were negligible. Root radial resistivity was estimated to be 1.3 • 1012 sm -I This root radial resistivity value was used to estimate root resistance to water uptake for a field crop of Vicia faba. Previously published results were used for root distribution and soil water contents at the drained upper limit (DUL) and the lower limit (LL) of extractable soil water. Soil resistance to water uptake was estimated from single root theory, using the steady rate solution. At the DUL, root resistance was about l0 s times greater than soil resistance. At the LL, soil resistance exceeded root resistance for depths less than 0.3 m, but for depths greater than this soil resistance was smaller than root resistance. Estimates of possible uptake rates at given leaf water potentials indicated that overall soil resistance had a negligible influence upon uptake, even at the LL. The reliability of this result is examined in detail.It is concluded that over the complete range of extractable soil water contents soil resistance per se would not have limited water use by this crop. This conclusion may also be valid for a wide range of soil and crop combinations.

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Section: Estimation Of Soil and Root Resistances For Field Cropmentioning

confidence: 92%

“…Zur et al 29 reported that soil resistances may be 10 6 than suggested from equations such as (7). To account for this they proposed that during uptake a thin annulus of soil around each root remains at the root surface water potential.…”

Section: Estimation Of Soil and Root Resistances For Field Cropmentioning

confidence: 99%

Soil and plant resistances to water uptake byVicia faba L.

Reid

Hutchison

1986

Plant Soil

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“…The influence of such a layer is expected to increase as the bulk soil becomes di ier. At low soil water contents, the water content at the toot sutface is much lower than in the bulk soil (Zur et al, 1982). If there is poor hydraulic continuity between tbe root and the soil, then there will be a large fall in water potential at the interface between thenrr whenever there is a substantial rate of uptake of water by the root (Tinker 1976).…”

Section: Introductionmentioning

confidence: 99%

The gradient between pre‐dawn rhizoplane and bulk soil matric potentials, and its relation to the pre‐dawn root and leaf water potentials of four species

Schmidhalter

1997

Plant Cell & Environment

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Uptake of soil water by plants may result in significant gradients between bulk soil and soil in the vicinity of roots. Few experimental studies of water potential gradients in close proximity to roots, and no studies on the relationship of water potential gradients to the root and leaf water potentials, have been conducted. The occurrence and importance of pre-dawn gradients in the soil and their relation to the pre-dawn root and leaf water potentials were investigated with seedlings of four species. Pre-germinated seeds were grown without watering for 7 and ltd in a silt loam soil with initial soil matric potentials of-0-02, -0-t and -0-22 MPa. Significant gradients, independent of the species, were observed only at pre-dawn soil matric potentials lower than -0-25 MPa; the initial soil matric potentials were > -0-t MPa. At an initial bulk soil matric potential of -0-22 MPa, a steep gradient between bulk and rhizoplane soil was observed after 7 d for maize (Zea mays L. cv. Issa) and sunflower {Heliaiithus annuiis L. cv. Nanus), in contrast to barley {Hordeum vulgare L. cv. Athos) and wheat {Triticum aestivum L. cv. Kolibri). Predawn root water potentials were usually about the same as the bulk soil matric potential and were higher than the rhizoplane soil matric potential. Pre-dawn root and leaf water potentials tended to be much higher than rhizoplane soil matric potentials when the latter were lower than -()-5 MPa. It is concluded that plants tend to become equilibrated overnight with the wetter bulk soil or with wetter zones in the bulk soil. Plants can thus circumvent negative effects of localized steep pre-dawn soil matric potential gradients. This may be of considerable importance for water uptake and growth in drying soil.

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“…One possible explanation for the observed decline in photosynthetic rate with increasing light intensity and temperature (conditions which should have favored higher CO2 fixation rates) is that root-soil system resistance to water flow may have limited the water supplied to rapidly transpiring leaves on warm, bright afternoons (28).…”

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Soybean Adaptation to Water Stress at Selected Stages of Growth

Huck

Ishihara²,

Peterson³

et al. 1983

Plant Physiol.

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ABSTRACISoybean (Glycine max [L.] Merr. cv Braxton) plants were grown in sandy soil with only natural rainfall (N) or with supplemental irrigation (I). Water-stressed plants grew more extensive root systems, whereas irrigated plants developed larger shoots and smaller root systems. Maximum stomatal apertures were observed at the beginning of each photoperiod. Partial stomatal closure occurred each afternoon, but stomata of I plants remained open longer than those of N plants. Significant reductions in net carbon fixation rate generally accompanied decreases in stomatal aperture, which coincided with periods of high temperature, low relative humidity, maximum solar radiation, and water stress. Leaf water potential decreased from morning to afternoon, with a greater decrease observed for N plants. Midafternoon stomatal closure did not occur in N plants with very large root systems following a heavy rain which saturated the soil profile. With smaller root systems and greater evaporative demand from larger shoots, the I plants continued to show midafternoon stress following the heavy rain. The large root systems of the N plants absorbed sufficient water to meet shoot evaporative demand for several days following the rain. Root soil system resistance apparently contributed to the aftemoon water stress in the I plants.-11 bars may affect photosynthesis through stomatal closure. Thus, leaf water status, particularly turgor, can affect photosynthetic carbon fixation rate.For maximum photosynthetic productivity, leaves must maintain turgor by obtaining sufficient water from the xylem to replace evaporative loss (9). The xylem, in turn, obtains water by root absorption from soil reserves. If the water supply is not adequate, leaves will initiate stomatal closure, thus limiting photosynthesis. Ishihara et al. (14) noted that leaf water stress induced stomatal closure even in rice plants growing in flooded paddies. The time of stomatal closure coincided with periods of high temperature and maximum solar radiation, conditions which would otherwise facilitate maximum photosynthetic rates (13). Because the rice roots grew in standing water, any reduction in leaf water potential under conditions of high evaporative demand implies that water movement from soil to and through roots and the xylem transport system was too slow.Maintenance of an active root system requires continued growth into new regions of soil to replace older roots which become suberized or die. Thus, continued growth of both shoot and root systems must be coordinated and regulated as the plant adapts to its environment during the growing season (22). The regulatory mechanisms are poorly understood at present (5); this study was initiated to determine effects ofdiurnal and long term water stress on soybean shoot and root growth.Inasmuch as photosynthetic rate is a function of temperature and PPFD3, the highest CO2 fixation rates should be measured during midafternoon when light intensity and temperature reach their daily maximum, provided all other factors are...

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Total Resistance to Water Flow in Field Soybeans: II. Limiting Soil Moisture¹

Cited by 39 publications

References 9 publications

Soil and plant resistances to water uptake byVicia faba L.

Soil and plant resistances to water uptake byVicia faba L.

The gradient between pre‐dawn rhizoplane and bulk soil matric potentials, and its relation to the pre‐dawn root and leaf water potentials of four species

Soybean Adaptation to Water Stress at Selected Stages of Growth

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Total Resistance to Water Flow in Field Soybeans: II. Limiting Soil Moisture1

Cited by 39 publications

References 9 publications

Soil and plant resistances to water uptake byVicia faba L.

Soil and plant resistances to water uptake byVicia faba L.

The gradient between pre‐dawn rhizoplane and bulk soil matric potentials, and its relation to the pre‐dawn root and leaf water potentials of four species

Soybean Adaptation to Water Stress at Selected Stages of Growth

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Product

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Total Resistance to Water Flow in Field Soybeans: II. Limiting Soil Moisture¹