Gas chromatography-mass spectrometric determinations of abscisic acid levels in the cap and the apex of maize roots

150

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...

mentioning

confidence: 99%

Effect on Root Growth of Endogenous and Applied IAA and ABA

Pilet¹,

Saugy²

1987

150

“…ABA is present in roots of several species (5,7). It is in root caps (4, 21) and in root tips of several maize varieties (18,23). White light seems to increase the ABA level (17,23,25,26) while it inhibits root elongation (3).…”

Section: Mean Growth Rate and Light Treatmentmentioning

confidence: 99%

“…Briefly, 20 ng of hexadeuterated-(+)ABA (21) were added at the beginning of the extraction to the collected segments as an internal standard. Three mL sodium acetate/acetic acid buffer (1/15 M, pH = 4.0) were added to the plant material at 4°C, and the samples were allowed to equilibrate for 5 min.…”

Section: Growth Measurementsmentioning

confidence: 99%

Endogenous ABA in Growing Maize Roots: Light Effects

Saugy

Mayor²,

Pilet³

1989

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.

“…Ultrapure He was used as a carrier gas at a flow rate of 1 ml/min. Me-ABA was quantitatively estimated with a Hewlett-Packard 5880 GC equipped with a 63Ni EC detector (7,11,17) and a fused silica capillary column (methyl silicone fluid, 12.5 m x 0.2 mm). The GC-MS qualitative validation was performed on the same sample which was used for ELISA, lettuce seed bioassay, and GC-EC.…”

mentioning

confidence: 99%

Effect of Paclobutrazol on Water Stress-Induced Abscisic Acid in Apple Seedling Leaves

Wang¹,

Sun²,

Ji³

et al. 1987

Abscisic acid (ABA) was quantitated by enzyme-linked immunosorbent assay (ELISA) in water-stressed leaves from control apple seedlings, and also from apple seedlings treated for 28 days with paclobutrazol (12RS, 3RSI-144-chlorophenyll-4,4-dimethyl-2-11,2,4-triazol-1-ylI pentan-3-ol).The ELISA quantitative estimates were also validated by gas chromatography-electron capture detector and lettuce seed germination inhibition bioassay. Paclobutrazol treatment reduced endogenous ABA levels by about one-third, and prevented the marked accumulation of water-stressinduced ABA that occurred in untreated seedlings. The presence of ABA in the apple leaf extracts was confirmed by gas chromatography-mass spectrometry.The accumulation ofABA in the leaves ofwater-stressed plants has been shown by numerous investigators (12,18,22,23). Our previous reports showed that the accumulation of water stressinduced 1 -aminocyclopropane-1 -carboxylic acid, 1 -(malonylamino)cyclopropane-l-carboxylic acid, ethylene production, and polyamines also occurred in water-stressed apple leaves, but these increases were prevented by the treatment with the plant bioregulant ([2RS,