Gradients in maize roots: local elongation and pH

Versel, Jean-Marc; Mayor, Guy

doi:10.1007/bf00391031

Cited by 26 publications

(18 citation statements)

References 23 publications

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“…Growth measurements were made using photocopied films and a digitizing pad (Hi Pad, Houston Instruments Austin, TX) interfaced with a microcomputer (ABC 80, Luxor, Motala, Sweden) (23). After photographing at both zero time and 8 h later, the elongation zone of each root, located 2.5 to 5.0 mm from the tip (32), was excised and stored (-80°C). The segments of the selected growth classes mentioned above were pooled.…”

Section: Methodsmentioning

confidence: 99%

Effect on Root Growth of Endogenous and Applied IAA and ABA

Pilet¹,

Saugy²

1987

Plant Physiol.

152

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Applications of indole-3yl-acetic acid (IAA) and abscisic acid (ABA) were done on two-day-old intact maize (cv LG 11) roots. The effect of the treatment on the root growth depends on their initial elongation rate. The slow growing roots were all inhibited by exogenous IAA and ABA at any concentrations used whereas for the fast growing roots their elongation was promoted by these two hormones at low concentrations. Quantitative analyses of endogenous IAA and ABA were performed using the gas chromatography-mass spectrometry technique. Detection and quantification of endogenous IAA and ABA were done on the zone of the root implicated in elongation. These techniques were achieved by electron impact on the IAA-Me-heptafluorobutyryl derivative and by negative ion chemical ionization with NH3 on the ABA-Me ester derivative. A negative correlation between the growth and the endogenous content of these two hormones was obtained. ABA presented a larger range of endogenous level than IAA on the whole population of roots tested. When using applied IAA and ABA at different concentrations the same differentiating effect on the growth was observed. This allowed us to conclude that for identical concentrations, IAA has a more powerful effect on root elongation than ABA. Present results are discussed in relation to previous data related to the role of IAA and ABA in the growth and gravireaction of maize roots.Root elongation is controlled by several endogenous regulators (2,3,24) whose interaction appears essential (19). Many published results indicate that, at least in the elongating part of the root, some growth inhibitors produced in the cap move from the tip to the base (8,15,16). The preferential movement of ABA is basipetal (6,10,17) while that of IAA is acropetal (2, 9, 14). Exogenous IAA usually inhibits root growth (19, 22,30) as does applied ABA (18,20). But in some cases IAA (13, 22) gravitropism (4, 29). The same technique has also indicated similar relations with ABA content in roots (21,28).The aim of the present work was to analyze the level of endogenous IAA and ABA in maize roots to understand better some controversial data obtained on the growth effect of these hormones when applied. It was necessary to correlate for identical material which means growth in the same conditions, information about the endogenous hormone content and the concentration effect of applied hormone on root growth. The reason that we insisted on identical material was that, unfortunately, many reports have used different material for testing both elongation and for analyzing hormone content. Furthermore, in the roots which we have used, it is the zone 2.5 to 5.00 mm behind the tip which is most relevant to total axial growth. It is in this zone that the hormone status of the root has been analyzed. which humid atmosphere (90 ± 5%) was maintained. After 4 h, the elongation that had occurred in that period was measured and two groups of roots were selected: roots having a low (about 0.37 mm-h-') or a high (about 0.81 mm-h-') gro...

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Section: Methodsmentioning

confidence: 99%

Effect on Root Growth of Endogenous and Applied IAA and ABA

Pilet¹,

Saugy²

1987

Plant Physiol.

152

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“…The zone chosen was 2.5 to 5 mm from the root tip; (25) for all roots data were expressed on a fresh weight basis, since this gives the best estimate of concentration (Table III).…”

Section: Resultsmentioning

confidence: 99%

“…First, they were collected for length, fresh weight, and (after freezedrying) dry weight measurements. Selected roots (as described above) were harvested for the determination of endogenous IAA in the whole root or in the elongation zone (2.5-5.0 mm; 18,25).…”

Section: Materuils and Methodsmentioning

confidence: 99%

Changes in the Level of Free and Ester Indol-3yl-Acetic Acid in Growing Maize Roots

Saugy¹,

Pilet²

1987

Plant Physiol.

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ABSTRACEThe levels of free and ester-linked indole-3-acetic acid (IAA) in different parts of the maize root were measured using gas chromatographymass spectrometry (selected ion monitoring). In roots of 2-day-old plants, the distribution of free and ester IAA differed both along the root and between stele and cortex. The levels of IAA and IAA esters were then measured in whole roots and in the elongation zone using roots ofdifferent ages. The level of ester IAA decreased steadily with time. In contrast, the level of free IAA in the elongation zone was found to increase after a few days of culture at which time the rate of root growth was decreasing.The role of IAA in the regulation of the growth and development of roots has been extensively reviewed (2,24).Several reports have described the identification and quantification of IAA in maize roots using combined GC-MS (7, 21). These studies have shown that most of the IAA was localized in the stele (7,9,23) and that the root cap also contained large amounts of IAA (21).The amount of IAA which was liberated from esters by alkaline hydrolysis has also been determined in maize seedlings (5, 1 1) and recently in maize roots (14). Several roles for esters of IAA have been proposed. They could be a source of IAA for seed and seedling during germination (10) or be concerned in hormonal homeostasis in the shoot (6). Moreover, esterification could play a protective role in preventing peroxidative attack (8).It has recently been shown that when maize roots were sorted into classes according to their growth rate, there was an inverse correlation between the growth rate and the level of IAA in the elongation zone (18). Thus, the aim of the present investigation was, using GC-SIM'-MS, to determine the level of free and esterified IAA, during germination and growth, in whole roots and in the elongation zone. MATERUILS AND METHODSMaize Seedlings. The germination of selected caryopses of Zea mays cv LG 11 (Association Suisse des Selectionneurs, Lausanne) has been previously described (16 first set of experiments, 2-d-old intact seedlings with straight primary roots (16 ± 1 mm in length) were selected and cut into four sections: the cap (0-0.5 mm), the meristem (0.5-1.0 mm), the elongation (1.0-5.0 mm), and the differentiation zone (5-15 mm). For some of the roots, the stele and the cortex were separated after removing the apical 5 mm and cut giving a segment of 9 mm in length.Plant Material for Time-Course Analyses. In these assays, whole roots were harvested after different periods of culture. First, they were collected for length, fresh weight, and (after freezedrying) dry weight measurements. Selected roots (as described above) were harvested for the determination of endogenous IAA in the whole root or in the elongation zone (2.5-5.0 mm; 18, 25).Growth Classes. Two-d-old intact maize seedlings (15 ± 1 mm in root length) were placed vertically for 8 ± 1 h in closed boxes (90 ± 5% RH). Photographs were taken initially and 8 h later (18). Growth analyses were performed using phot...

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“…Two hypotheses could explain such a result. Firstly, mycorrhizal apices have a lower growth rate than non-infected ones (Harley, 1978); and new growing areas such as apices are also areas of maximum proton release (Pilet, Versel & Mayor, 1983;Versel & Mayor, 1985). Secondly, this difference could also arise from modifications in the exchange mechanism between the root and the medium resulting from the typical interfacial apoplasm of mycorrhizas (Smith & Smith, 1990).…”

Section: Functional Heterogeneity Of Mycorrhizal and Nonmycorrhizal Rmentioning

confidence: 99%

Influence of ectomycorrhizal infection on the rhizosphere pH around roots of maritime pine (Pinus pinaster Soland in Ait.)

et al. 1995

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SUMMARYThis study examined the influence of mycorrhizal infection on ionic exchanges by roots, by measuring rhizosphere pH and the quantities of protons released by roots of mycorrhizal and non-mycorrhizal pine (Pimis pinaster x Suillus collinitus). The effect of inoculation was measured around individual roots and compared with the effect on the root system as a whole, with root heterogeneity thus being taken into account in structural terms and in terms of functioning. Inoculation enhanced significantly the capacity of roots to release protons in a medium with a neutral pH, but the strength of reaction varied with the part of the root involved. This enhancement could possibly be used to improve the bioavailability of compounds not readily soluble in particular chemical conditions of the soil.

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Gradients in maize roots: local elongation and pH

Cited by 26 publications

References 23 publications

Effect on Root Growth of Endogenous and Applied IAA and ABA

Effect on Root Growth of Endogenous and Applied IAA and ABA

Changes in the Level of Free and Ester Indol-3yl-Acetic Acid in Growing Maize Roots

Influence of ectomycorrhizal infection on the rhizosphere pH around roots of maritime pine (Pinus pinaster Soland in Ait.)

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