Regulation of lettuce hypocotyl elongation by gibberellic acid. Correlation between cell elongation, stress-relaxation properties of the cell wall and wall polysaccharide content

Kawamura, Hideto; Kamisaka, Seiichiro; Masuda, Yoshio

doi:10.1093/oxfordjournals.pcp.a075262

Cited by 37 publications

(20 citation statements)

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“…The control of such wall expansion can be thought of as falling somewhere between two extremes, with pure physical extension (viscoelasticity) at one extreme and biochemical reaction-dependent extension (chemorheology) at the other extreme. When viscoelastic processes limit growth, the wall yield threshold (Y) and yield coefficient (X) should correlate with mechanical measures of the wall, as provided by Instron analysis (3,4), physical stress relaxation analysis (4,18) and other stress/strain techniques. When growth is more tightly dependent on biochemical processes, it takes on the character of a chemorheological process (21) and mechanical properties of the wall may not correlate with growth behavior.…”

Section: Discussionmentioning

confidence: 99%

“…Confficting evidence came from Yoda and Ashida (28) who used a similar method, but found that GA stiffened the wall in pea stems. This bending technique is subject to various criticisms; nevertheless, other mechanical techniques have provided additional evidence that GA makes the wall more extensible in oat internodes (1), lettuce hypocotyls (16,18,27), and pea apical hooks (22). However, the biochemical basis for the altered wall remains uncertain; it might result from enhanced wall loosening, reduced wall cross-linking, or altered wall composition (14,15).…”

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confidence: 99%

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Mechanism of Gibberellin-Dependent Stem Elongation in Peas

Cosgrove¹,

Sovonick-Dunford²

1989

Plant Physiol.

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Stem elongatfon in peas (Pisum sativum L.) is under partial control by gibberellins, yet the mechanism of such control is uncertain. In this study, we examined the cellular and physical properties that govem stem elongation, to determine how gibberellins influence pea stem growth. Stem elongation of etiolated seedlings was retarded with uniconozol, a gibberellin synthesis inhibitor, and the growth retardation was reversed by exogenous gibberellin. Using the pressure probe and vapor pressure osmometry, we found little effect of uniconozol and gibberellin on cell turgor pressure or osmotic pressure. In contrast, these treatments had major effects on in vivo stress relaxation, measured by turgor relaxation and pressure-block techniques. Uniconozoltreated plants exhibited reduced wall relaxation (both initial rate and total amount). The results show that growth retardation is effected via a reduction in the wall yield coefficient and an increase in the yield threshold. These effects were largely reversed by exogenous gibberellin. When we measured the mechanical characteristics of the wall by stress/strain (Instron) analysis, we found only minor effects of uniconozol and gibberellin on the plastic compliance. This observation indicates that these agents did not alter wall expansion through effects on the mechanical (viscoelastic) properties of the wall. Our results suggest that wall expansion in peas is better viewed as a chemorheological, rather than a viscoelasfic, process.Gibberellins were discovered because of their marked stimulation of shoot elongation. In recent years notable progress has been made in the genetics of gibberellin synthesis and its control of shoot elongation, particularly in pea and maize plants (see Ref. 20 for review). However, the mechanism of action of GA on shoot growth in these species is not fully understood. Two general, and complementary, approaches have been taken to examine GA action. The first views the stem as composed of cell files, and asks how GA affects the number and final size ofthe cells making up the stem. Various studies (e.g. 24, 26) have shown that GA may affect both cell division and final cell size. However, final cell size is a complex function of the patterns of cell expansion and cell division, which are themselves likely to be interdependent, so the causal mechanism of GA action is not clear from these studies. The second approach considers that stem elongation '

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Mechanism of Gibberellin-Dependent Stem Elongation in Peas

Cosgrove¹,

Sovonick-Dunford²

1989

Plant Physiol.

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“…The root cell wall fraction was extracted according to a modification of the method of Kawamura et al (1976). Excised roots were homogenized with distilled water and centrifuged at 10,000•…”

Section: Methodsmentioning

confidence: 99%

Copper binding by the root cell walls of Italian ryegrass and red clover

Iwasaki

Sakurai

Takáhashi

1990

Soil Science and Plant Nutrition

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“…Furthermore, in cucumber, the fast regulation of wall yielding by BL occurred without detectable changes in the viscoelastic properties of the cell walls (10). On the other hand, in several studies a correlation has been found between elongation rate and mechanical cell-wall properties as measured in vitro by Instron analysis (5), stress-relaxation (17,30), or in vivo by extensibility measurements ( 19,20). It is noteworthy that the changes in viscoelastic properties of the wall usually lag behind the changes in elongation rate and/or are of a smaller magnitude (3).…”

Section: Stress Strain Analysismentioning

confidence: 99%

Photoinhibition of Stem Elongation by Blue and Red Light

Kigel¹,

Cosgrove²

1991

Plant Physiol.

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The underlying mechanism of photoinhibition of stem elongation by blue (BL) and red light (RL) was studied in etiolated seedlings of pea (Pisum sativum L. cv Alaska). Brief and r = L(Ar -P)in which 0 is the cell wall yield coefficient, Y is the yield threshold (the turgor pressure that must be exceeded for wall yielding to occur), P is turgor pressure, Air is the difference in osmotic pressure, and L is the cell hydraulic conductance (8,21,23

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Regulation of lettuce hypocotyl elongation by gibberellic acid. Correlation between cell elongation, stress-relaxation properties of the cell wall and wall polysaccharide content

Cited by 37 publications

References 0 publications

Mechanism of Gibberellin-Dependent Stem Elongation in Peas

Mechanism of Gibberellin-Dependent Stem Elongation in Peas

Copper binding by the root cell walls of Italian ryegrass and red clover

Photoinhibition of Stem Elongation by Blue and Red Light

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