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

Hirasawa, Tadashi; Takahashi, Hideyuki; Suge, Hiroshi; Ishihara, Kuni

doi:10.1046/j.1365-3040.1997.d01-70.x

Cited by 26 publications

(19 citation statements)

References 22 publications

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“…Differential growth is induced by a change in cell wall extensibility and hydraulic conductivity in both gravitropism (Muday, 2001;Miyamoto et al, 2005) and hydrotropism (Hirasawa et al, 1997;Miyamoto et al, 2002). In a root grown under water stress, the rate of cell elongation decreases via a reduction in turgor pressure (Spollen and Sharp, 1991) or in cell wall extensibility (Pritchard et al, 1991;Akmal and Hirasawa, 2004).…”

Section: Discussionmentioning

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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Section: Discussionmentioning

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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“…If a moisture gradient existed between the wet seed holder and the other end of the container, the primary roots would have elongated in an orientation parallel to the direction of the moisture gradient. In this situation, the root cap might be exposed to a symmetrical moisture gradient and might not be stimulated hydrotropically because this is where the sensory apparatus for detecting moisture gradients resides (Jaffe et al 1985, Takahashi and Suge 1991, Takahashi and Scott 1993, Hirasawa et al 1997. On the other hand, lateral roots grew perpendicular to the direction of the moisture gradient because they emerged transversely from the primary roots that grew away from the wet substrate.…”

Section: Introductionmentioning

confidence: 99%

Hydrotropic Response and Expression Pattern of Auxin-Inducible Gene, CS-IAA1, in the Primary Roots of Clinorotated Cucumber Seedlings

Mizuno

Kobayashi

Fujii

et al. 2002

Plant and Cell Physiology

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;Primary roots of cucumber seedlings showed positive hydrotropism when exposed to a moisture gradient and rotated on a two-axis clinostat. To examine the role of auxin in the differential growth of the hydrotropically responding roots, we first examined the expression of auxin-inducible genes, CS-AUX/IAAs, in cucumber roots. After auxin starvation, mRNA levels of CS-IAA1 and CS-IAA3 decreased in the roots. Applying auxin to the auxin-starved roots resulted in accumulation of CS-IAA1 and CS-IAA3 mRNA. The level of expression of these genes increased when the auxin concentration was increased. CS-IAA1 mRNA accumulated in response to 10 -8 M auxin, and the level increased further, depending on the dose. Auxin starvation did not result in a decrease in the level of CS-IAA2 mRNA; however, adding exogenous auxin at concentrations higher than 10 -7 M increased its accumulation. In the primary roots responding hydrotropically or gravitropically, CS-IAA1 expression was greater on the concave side of the curving roots than on the convex side. The difference could be detected 30 min following stimulation by gravity or a moisture gradient, and that difference increased with time. These results support the idea that asymmetry of localization of auxin is associated with differential growth in hydrotropically responding roots.

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“…We could not identify the factors responsible for the difference in hydraulic conductivity within the tissue, but the hydraulic conductivity of the tissues in this study might be affected by the resistance of cell membranes (plasma membrane and tonoplast) and apoplast (outside the cells). In the hydrotropically bending root, both wall extensibility and the hydraulic conductivity of a cell (and, subsequently, the hydraulic conductivity of the tissue) contribute simultaneously to the differential elongation (Hirasawa et al, 1997;Miyamoto et al, 2002). Moreover, water must move Proteins were visualized by staining with Coomassie brilliant blue after SDS-PAGE (A) or with anti-MIP (B) or anti-PIP (C) and alkaline-phosphatase-conjugated second antibody after blotting onto a PVDF membrane.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, a difference in the rate of uptake of solutes by elongating cells or the rate of generation and degradation of compounds within the cells might be essential in maintaining differences in cell enlargement rates among the cells. The increase in volume caused by hydraulic conductivity, solute accumulation (this study; Miyamoto et al, 2002), and the extensibility of the cell wall (Hirasawa et al, 1997;Hoson et al, 2001) must involve many other processes, such as the synthesis of cell walls and cell components. For a comprehensive understanding of the mechanisms of cell growth, further physiological and molecular biological research is obviously necessary.…”

Section: Pipmentioning

confidence: 99%

“…For measurements of the osmotic potential, pieces from 1 to 6 mm and 8 to 13 mm from the root tip were used as the elongating and mature tissue, respectively. The water potential and osmotic potential were measured with an isopiestic psychrometer (Boyer and Knipling, 1965;Boyer, 1995;Hirasawa et al, 1997). We measured the water status of a group of vertically elongating roots (with no bending) at the same time as a control.…”

Section: Determination Of Water Status and The Hydraulic Conductivitymentioning

confidence: 99%

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Hydraulic Conductivity and Aquaporins of Cortical Cells in Gravitropically Bending Roots of Pisum sativum L.

Miyamoto

Katsuhara

Ookawa

et al. 2005

Plant Production Science

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: We examined the differential elongation of gravitropically bending roots of Pisum sativum L. in terms of cell enlargement and water uptake by cells in the growing tissue. Hydraulic conductivity between the elongating and mature tissues (Lp) was estimated from the equation G = A × Lp × ∆Ψ, where G is the water-uptake rate, A is the surface area of a single cell and ∆Ψ is the driving force. The rate of entry of water into a cell was estimated from the rate of increase in the volumes of cells in the outer cortex, which were calculated from longitudinal sections at given times. Gravitropic bending occurred 1 h after the application of gravi-stimulation and the curvature increased rapidly for the next 3 h. The biggest difference in the partial elongation rate between opposite sides of a root was found in the region 3 to 4 mm from the root tip at the start of stimulation. Cell enlargement rate was 2.8 to 3.8 times greater on the upper side of the root than on the lower side. The water potential and the osmotic potential, in both the elongating and mature tissues, were the same on both sides of the root. Therefore, there was no difference in the driving force for water fl ow. Hydraulic conductivity was 2.3 to 4.2 times greater on the upper side of the root than on the lower side. There was no difference between the upper and lower sides of the root in the amounts of 19-kD and 24-kD proteins in membrane fractions, which we assumed to be aquaporins (putative aquaporins), as estimated with two preparations of polyclonal antibodies. The differential elongation that occurred during root gravitropism was caused by a difference in Lp. However, the difference in Lp did not appear to be regulated by the concentration in cell membranes of the putative aquaporins.

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

Cited by 26 publications

References 22 publications

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

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

Hydrotropic Response and Expression Pattern of Auxin-Inducible Gene, CS-IAA1, in the Primary Roots of Clinorotated Cucumber Seedlings

Hydraulic Conductivity and Aquaporins of Cortical Cells in Gravitropically Bending Roots of Pisum sativum L.

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