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

Abstract

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.

Ultrastructural characteristics of callus cells of Nicotiana tabacum L. var. BELW3 grown in presence of NaCl

“…Moreover, the synthesis of the above mentioned osmolytes as an energy dependent process which consumes a great quantity of ATP molecule, might affecting the growth (Raven 1985). On the other hand, a strong decline of cell division rate surely occurs in salt treated N. tabacum callus cell as observed in maize (Zidan et al 1990;Shimazaki et al 2005), in A. cepa (Bennici and Tani 2009) and Arabidopsis roots (West et al 2004). In regard to this last phenomenon, chromosomal aberrations (bridges, stickiness, fragmentation, exclusion, laggard and others) can not be excluded (Hossain et al 2004).…”

Interaction of aluminium and drought stress on root growth and crop yield on acid soils

“…Root elongation is also inhibited under water stress, but there are two main differences between Al and drought stress: (i) under drought stress shoot growth is much more affected than root growth (reviewed by , whereas short and medium-term Al excess may strongly reduce root growth without affecting shoot growth (Kochian et al 2004;Yang et al 2009); (ii) Al toxicity reduces cell elongation along the entire elongation zone (Kollmeier et al 2000), whereas under water deficit or osmotic stress cell elongation is inhibited only in the basal and central elongation zones (definition of zones according to Ishikawa and Evans 1993), but maintained toward the root apex (Sharp et al 1988) in the distal and apical elongation zones (Shimazaki et al 2005) (Fig. 1).…”

Modeling the Hydraulics of Root Growth in Three Dimensions with Phloem Water Sources

“…As in the shoot model, growing tissue was seen as a distributed sink for water. However, since the publication of that theory, experimental studies have revealed that the root tip is not in equilibrium with the bathing medium (Pritchard et al, , 2000Gould et al, 2004;Shimazaki et al, 2005). Pressure probes combined with osmotic potential determinations have shown that the C of exterior root cells ranges from 20.17 to 20.6 MPa, depending on environmental conditions.…”