Paul-Emile Pilet

Abscisic acid as a root growth inhibitor: Physiological analyses.

SummaryAbscisic acid (ABA) moves basipetally and laterally in maize (Zea mays L.) root segments placed horizontally; its transport properties are thus similar to those of the growth-inhibiting substances produced by the root cap. The two opposite flows af ABA and of indolyl-3-acetic acid (IAA) — substances both present in the cap — may control elongation and georeaction of the root.

Indolyl-3-acetic acid in cap and apex of maize roots: Identification and quantification by mass fragmentography.

SummaryQuantitative analysis of indolyl-3-acetic acid (IAA) in different parts of maize root tips (Zea mays L. cv. Kelvedon 33) were performed by selective ion current monitoring detection (or mass fragmentography). It was found that the cap contained 356.6±16.2 μg of IAA kg-1 fresh weight; the apex had only half this concentration of IAA. Calculations indicated that the 10-mm apical segments of the root contained 109.6 μg kg-1 fresh weight. The possibility that the growth regulator formed in the cap and inhibiting the elongation of the extension zone of the root is IAA is discussed.

Growth distribution and surface pH patterns along maize roots

The distribution of elongation and surface pH patterns along the primary roots of maize (cv. LG 11), maintained vertically in humid air (darkness, 22°C), have been analysed quantitatively. A new technique employing Sephadex G 25 beads containing a pH indicator dye (bromocresol purple), was used for measuring both the growth gradient of the roots (Sephadex beads as markers) and at the same time, the surface pH changes (referring to a standard scale). The optimal axial growth was located between 2 and 4 mm from the tip. This coincides with the optimal decrease in surface pH.

Root Cap and Root Growth

SummaryThe caps of the roots of Zea mays (var. Kelvedon 33) are the source of a growth inhibitor system which also acts on the root elongation of Lens culinaris.

Effect of abscisic acid on maize root growth. A critical examination

Abstract The effect of abscisic acid (ABA) on the growth of maize roots maintained in the dark is investigated in relation to the root varieties and the root age, the mode of application, the concentration used and the duration of both the treatment and the culture. In all the assays, when ABA produces a significant change in root elongation, it shows an inhibitory effect which is enhanced with increasing ABA concentration. The data strongly support the hypothesis that ABA could be one of the growth inhibitors which are formed in or released from the root cap.

Growth inhibitor from the root cap of Zea mays

SummaryThe downward lateral transport of at least one inhibitor produced in or released by the cap of a maize root partly explains differences in growth of the upper and lower sides of roots placed in the horizontal position.The relative activity or level of such a regulator increases with the increase in root length.

Effect of applied and endogenous indol-3-yl-acetic acid on maize root growth

The level of endogenous Indol-3-yl-acetic acid (IAA) measured by gas chromatography-mass spectrometry in the elongating zone of intact primary roots of Zea mays showed a good linear correlation with the growth rate of these roots. When they were treated with IAA, their relative elongation decreased; this indicates a supraoptimal content of endogenous IAA. However, the growth of some of the relatively rapidly extending roots was enhanced by such treatment. Interactions between endogenous and applied IAA in the control of root growth are discussed.

Kinetics of the light-induced georeactivity of maize roots

Apical root segments of Zea mays L. cv. Orla 264 undergo some geotropic curvature in complete darkness but the curvature increases considerably if prior to geostimulation the segments are given a light pretreatment. If the light treatment is follwed by a dark treatment before the root is geostimulated the light-induced response is not changed by dark periods up to 2 h but declines with longer ones, and disappears completely after 5 h of darkness.

Root cell georeaction and growth inhibition

Abstract The asymmetrical increase of length for the cortical cells from the extending zone of vertical maize roots—which causes georeaction—was due to a growth inhibitor formed in the cap. Results obtained when removing the cap during geocurvature and decapitating the vertical roots, with the tip asymmetrically replaced, were discussed.

Level changes of jasmonic, abscisic, and indole-3yl-acetic acids in maize under desiccation stress

Summary Desiccation-stress conditions were applied to the roots of etiolated Zea mays L. (cv. Zhengsan 3) plantlets using polyethylene glycol (PEG) solutions. Levels of JA, ABA and IAA in the roots and shoots were quantitatively determined by ELISAs at 0, 1, 3, 5, 7 and 13 h. The enhancement in JA and ABA levels in both roots and shoots during desiccation stress was observed. The largest increases in the root and shoot contents of ABA were found at 5 h (about 3.2-fold) and 7 h (about 6.3-fold), respectively. The IAA root level increased strongly after 1 h of immersion, and reached its highest value at 3 h (about 5.2-fold), then decreased. However, the level of IAA in the shoots decreased rapidly, and reached its lowest value at 7 h (about one-fourth).