Hydrotropism in roots: sensing of a gradient in water potential by the root cap

Takano, Masaharu; Takahashi, Hideyuki; Hirasawa, Tadashi; Suge, Hiroshi

doi:10.1007/bf00202664

Cited by 57 publications

(46 citation statements)

References 13 publications

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“…When a sorbitolcontaining agar block was applied unilaterally to the root cap, the root under saturating humidity bent towards the agar block on the opposite side which did not contain sorbitol. However, no such bending of roots occurred when the sorbitol-containing agar block was applied to the elongation region (Takano et al 1995). These results indicated that hydrotropism in roots might occur after perception of a difference in water potential by the root cap, with subsequent changes in the extensibility of cell wall and the hydraulic conductance of the elongating tissues.…”

Section: Discussionmentioning

confidence: 85%

See 1 more Smart Citation

Water potential, turgor and cell wall properties in elongating tissues of the hydrotropically bending roots of pea (Pisum sativum L.)

Hirasawa

Takahashi

Suge

et al. 1997

Plant Cell & Environment

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The hydrotropic bending of roots of an ageotropic pea mutant, ageotropum, was studied in humid air in a chamber with a steady humidity gradient. We examined the effects of atmospheric humidity around the root on the water status of root tissues, as well as the wall growth and the hydraulic properties of the elongating tissues. Atmospheric humidity at the surface of the root was clearly lower on the side orientated towards the air with lower humidity than on the side orientated towards the air with higher humidity. However, there were no differences in water potential and osmotic potential between the tissues that faced air with higher and lower humidities in the elongating and mature regions. Plastic extensibility was higher in the tissues that faced the air with lower humidity than in the tissues that faced the air with higher humidity. No differences in turgor pressure and yield threshold were observed between the tissues that faced air with higher and lower humidities. Therefore, the extensibility of the cell wall appeared to be responsible for the different growth rates of tissues in root hydrotropism. A further probable cause of the hydrotropical bending of roots is changes in the hydraulic conductance in the elongating tissues. Since the hydrotropic bending of roots occurred only when a root tip was exposed to a humidity gradient, hydrotropism might occur after perception of a difference in humidity by the root tip, with accompanying changes in cell wall extensibility and hydraulic conductance.

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Section: Discussionmentioning

confidence: 85%

“…Such difference in humidity is equivalent to a water potential of 0-6-0-7 MPa. When a root tip was exposed unilaterally to a sorbitol-containing agar block with a water potential of -0-5 MPa, hydrotropic bending of the root occurred (Takano et al 1995). This earlier experiment was conducted in a moisture-saturated chamber.…”

Section: Discussionmentioning

confidence: 99%

Water potential, turgor and cell wall properties in elongating tissues of the hydrotropically bending roots of pea (Pisum sativum L.)

Hirasawa

Takahashi

Suge

et al. 1997

Plant Cell & Environment

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“…A pair of agar blocks (1 3 1 3 1 mm 3 ) with known water potential was applied bilaterally and directly to the surface of individual roots (Takano et al, 1995;Miyamoto et al, 2002). Agar for plant culture (Wako Chemicals) at a concentration of 1% (w/v) was prepared in 2 mM MES buffer.…”

Section: Hydrostimulation Of Rootsmentioning

confidence: 99%

“…Research on root hydrotropism by Takano et al (1995) demonstrated that hydrotropism can be induced by applying small agar blocks with and without sorbitol unilaterally to the tip of a root. In this study, we employed this system to impose water stress on a specific region of a root by bilaterally applying two small agar blocks with decreased water potential to the primary roots of maize seedlings.…”

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confidence: 99%

The Root Tip and Accelerating Region Suppress Elongation of the Decelerating Region without any Effects on Cell Turgor in Primary Roots of Maize under Water Stress

2005

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To identify the region in which a root perceives a decrease in the ambient water potential and changes its elongation rate, we applied two agar blocks (1 3 1 3 1 mm 3 ) with low water potential bilaterally to primary roots of maize (Zea mays) at various positions along the root. When agar blocks with a water potential of 21.60 MPa (21.60-MPa blocks) or lower were attached to a root tip, the rate of elongation decreased. This decrease did not result from any changes in the water status of elongating cells and was not reversed when the 21.60-MPa blocks were replaced by 20.03-MPa blocks. The rate decreased slightly and was unaffected, respectively, when 21.60-MPa blocks were applied to the so-called decelerating region of the elongating zone and the mature region. However, the rate decreased markedly and did not recover for several hours at least when such blocks were attached to the accelerating region. In this case, the turgor pressure of the elongating cells decreased immediately after the application of the blocks and recovered thereafter. The decrease in elongation rate caused by 21.60-MPa blocks applied to the root tip was unaffected by additional 20.03-MPa blocks applied to the accelerating region and vice versa. We concluded that a significant reduction in root growth could be induced by water stress at the root tip, as well as in the accelerating region of the elongating zone, and that transmission of some signal from these regions to the decelerating region might contribute to the suppression of cell elongation in the elongation region.

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“…In recent years, however, a positive hydrotropic response of the root was confi rmed in a study that used a mutant pea plant that did not exhibit gravitropism (Takahashi, 1997). Just as with the root gravitropism, the region of the root that responds to hydrotropic stimulation is the RC (Takano et al, 1995).…”

Section: Root Tropism and The Rcmentioning

confidence: 99%