Growth Inhibitors in Growing and Geostimulated Maize Roots

Pilet, Paul‐Emile

doi:10.1007/978-3-642-66589-9_13

Cited by 96 publications

(46 citation statements)

References 49 publications

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“…Caryopses of Zea mays L. cv LG 11(Ass. Suisse des Selectionneurs, Lausanne) were germinated for 48 h in the dark at 20°C (13), and roots 15 ± 2 mm long were selected. Segments 5 mm long were prepared from the region 2 to 7 mm counting from the tip.…”

Section: Methodsmentioning

confidence: 99%

Effect of pH on IAA Uptake by Maize Root Segments

Martin¹,

Pilet²

1987

Plant Physiol.

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ABSTRACIThe uptake of 15-3Hlindoleacetic acid (IAA) by Zea mays L. root segments involves nonsaturable and saturable processes. The pH optimum of the saturable component was found to be 5.0. The proton ionophore carbonylcyanidep-trifluoromethoxyphenylhydrazone inhibited at 100 micromolar the saturable component of IAA uptake but had no effect on non-saturable uptake. This indicates that the saturable component of IAA uptake is dependent on the proton gradient across the plasmalemma. The high level of proton extrusion in the elongation zone of the root will stimulate nonsaturable and saturable uptake of IAA in that zone.The movement of IAA involves both diffusion and carriermediated transport. It was suggested (18) that the polarity of auxin transport is brought about by the asymmetrical distribution, on the plasmalemma, of a carrier for the efflux of IAA. Jacobs and Gilbert (6) provided evidence that this carrier is located, in pea stems, preferentially at the basal end of certain cells. This would lead to basipetal polarity of IAA transport in the stem, whereas in the root auxin transport is preferentially acropetal (8,12,20 Incubation. The medium contained 2% (w/v) glucose, and IAA*I at 5 nM and was buffered using Na2HPO4/citric acid (sum of concentrations sodium phosphate plus citric acid: 10 mM). Groups of 20 segments were incubated for 4 min at 20.0 ± 0.2°C in tubes containing 1.0 ml of medium and shaken at 150 r.p.m.Use of FCCP. This protonophore was dissolved in ethanol and added to the medium just before use. To test the effect of FCCP on IAA uptake, segments were first pre-treated in medium, buffered at pH 5.0, without IAA, and containing or not (control) FCCP at 100 tM. The final concentration of ethanol in the medium was 0.5% (v/v). Control media were prepared using an equal quantity of ethanol. No difference was observed between controls with and without ethanol (0.5%). Segments were then transferred to uptake medium (also at pH 5.0) containing IAA* at 5 nm with or without nonradioactive IAA at 10 gM. FCCP (100 Mm) was present in the uptake medium (FCCP-treated) or absent (control).Radioactivity Determination. Segments were rapidly rinsed using distilled water, and placed, 4 per vial, with 4 ml scintillation fluid ('Optifluor,' Packard Instruments). Radioactivity was determined by liquid scintillation counting as previously described (10) using a Kontron 'BETAmatic II' liquid scintillation spectrometer.Replication. Experiments were performed twice, and no significant difference between the two experiments was observed, so treatment means and SE were calculated from 10 scintillation vials, each containing 4 segments. Results were expressed as Bq per segment. RESULTS AND DISCUSSIONIt has previously been shown (10) that after 4 min incubation of maize root segments in medium containing IAA*, radioactivity in the tissue was almost exclusively in the IAA molecule (only about 5% had been metabolized). Therefore, under the present experimental conditions, the radioactivity taken up can be used as a measure ...

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Section: Methodsmentioning

confidence: 99%

Effect of pH on IAA Uptake by Maize Root Segments

Martin¹,

Pilet²

1987

Plant Physiol.

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“…These results also agree with the hypothesis that a high energy state in the root tip is a prerequisite for the expression of the reaction of roots to gravity. Now it is obvious that the first few apical millimeters of a root tip is a very complex system including cap, meristems, quiescent center, and the elongating and georeacting zone (19). Consequently, further studies are needed to determine more precisely in which part of the root tip occur the increases of ATP content and energy charge when the root becomes geosensitive under light.…”

Section: Discussionmentioning

confidence: 99%

“…Anjou 210 (Hodee, Beauforten-Vallee, France). The conditions for preparing the maize seedlings have been previously described (19). After 24 hr of soaking in tap water, selected cayopses were grown in the dark between sheets of moist paper towels at 19 or 21 C C according to the variety.…”

Section: Methodsmentioning

confidence: 99%

Effect of the light on adenine nucleotide content of georeacting maize roots

Steck¹,

Pilet²

1979

Plant and Cell Physiology

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Apical segments from maize roots of LG 11 and Orla 264 varieties georeacted, at least for the first few hours, only in light, while those of the Anjou 210 variety were georeactive both in light and darkness. The energy charge in the apical end of the two light geo-sensitive (LG and Orla) maize roots significantly increased in the light. In contrast, in Anjou root tips, the energy charge was already high in the dark and did not change significantly after light exposure. The time course of light-induced changes in adenine nucleotide contents in root tips was compared with varietal differences in georeactivity in light and darkness. The present data corroborate the hypothesis that a high energy state in the root tip is a prerequisite for the expression of the root reaction to gravity.

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“…It is clear that ABA is an important factor in the regulation of root growth (1,2,10,11). When applied to maize roots, ABA usually inhibits elongation (15,23,25).…”

Section: Mean Growth Rate and Light Treatmentmentioning

confidence: 99%

Endogenous ABA in Growing Maize Roots: Light Effects

Saugy

Mayor²,

Pilet³

1989

Plant Physiol.

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The growth of intact maize (Zea mays L.) roots and the abscisic acid (ABA) content (measured by gas chromatography-mass spectrometry of the root tip were analyzed after a white-light treatment. The decrease of the elongation rate due to the illumination corresponded to a concomitant increase in the ABA found in the root. When selecting roots, on the basis of their growth rate, it was possible to show that the relation between growth and ABA content, previously reported in darkness was conserved after light treatments. Therefore, light decreased the root growth rate while it simultaneously increased the ABA content in the roots. This increase was higher than expected, demonstrating the complexity of the involvement of ABA on root growth.

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Growth Inhibitors in Growing and Geostimulated Maize Roots

Cited by 96 publications

References 49 publications

Effect of pH on IAA Uptake by Maize Root Segments

Effect of pH on IAA Uptake by Maize Root Segments

Effect of the light on adenine nucleotide content of georeacting maize roots

Endogenous ABA in Growing Maize Roots: Light Effects

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