Differential growth of georeacting maize roots

The growth rate of the two sides of 10-mm apical segments prepared from primary roots and of intact primary roots of maize has been analyzed in both vertical and horizontal positions, using a filming method allowing continuous growth recording. The data showed that the georeaction began by a decrease in the overall elongation rate of the roots. This inhibition is effective on the lower side of the bending zone, where the growth is practically stopped during the period of maximum rate of geocurvature. In contrast, the growth is slightly enhanced on the upper part of the elongating zone.     

Extensibility and rheology of collenchyma I. Creep relaxation and viscoelasticity of young and senescent cells

The extensibility of collenchyma cells was methodologicallyanalyzed; extensibility (elasticity and plasticity) and rheologyof this tissue are discussed. Experimental conditions are described.Rheological data for young and senescent cells were obtained;they were found to be not Boltzmannian. The permanent strainis not viscous, and is larger for young cells than older ones. (Received July 28, 1975; )     

The effect of 4-chlororesorcinol on the endogenous levels of IAA,ABA and oxidative enzymes in cuttings

Treatment of bean cuttings with 4-chlororesorcinol (4-CR), known to increase the number of roots and extend their distribution, prevented the accumulation of free indol-3-yl-acetic acid (IAA) in the hypocotyls within 24 h after cutting preparation. In mung bean there was no change in the distribution (upper half vs. 1 ower half of the hypocotyl) of IAA within the hypocotyl as a result of the treatment. In bean cuttings the treatment with 4-CR prevented the accumulation of IAA in the bottom of the cutting. Oxidation of IAA as a measure of IAA oxidase activity in bean was enhanced appreciably by 4-chlororesorcinol. The level of abscisic acid in mung bean, on the other hand, remained 3–4 fold higher than in the control, yet still about 50% lower than the zero time level. In untreated mung bean cuttings the activity of peroxidase increased after cutting preparation. In contrast, the activity of peroxidase in 4-Cr-treated cuttings was consistently lower. In order to relate to the effect of exogenously applied auxin the level of peroxidase was measured also in indol-3-yl-butyric acid-treated cuttings. The overall peroxidase activity in IBA-treated cuttings was not affected. However, when assaying for the different isozymes the drop in peroxidase activity was most evident in the inducible basic isoperoxidases both in 4-CR and IBA treatments. It appears that the exposure to 4-CR exerts an effect that is similar to that of exogenously applied auxin, affecting the activity of basic peroxidases and enhancing the oxidation of endogenous IAA, thus allowing the organization of the primordia.Abbreviations ABA - abscisic acid - 4-CR - 4-chlororesorcinol - IAA - indol-3-yl-acetic acid - IBA - indol-3-yl-butyric acid     

Abscisic acid effect on the DNA microgradients of decapped maize roots

Longitudinal and transversal total DNA gradients were analysedin 42-µm thin sections of maize root tips. The optimumDNA concentration was found in the apex (quiescent centre andmeristem). It significantly increased after removal of the rootcap, which can be considered an essential source of abscisicacid (ABA). When the caps were taken off and agar blocks containingABA were immediately placed on the apical cut sections, thetotal DNA level in the root apex decreased greatly. ABA regulationof cellular and nuclear behaviour is discussed. (Received June 3, 1978; )     

Action de la kinétine sur la croissance et la teneur en chlorophylles des racines

Lens roots form chlorophylls in well-developed chloroplasts when they are cultivated in continuous light. Chlorophyll accumulation was increased when kinetin (10^?4M) was added for a short time (24 h) of treatment. For a long time (72 h), the increase of chlorophyll content was reduced when roots were cultivated in light and with kinetin. When the roots were transferred from light to dark, chlorophyll content was decreased. This reduction was inhibited when roots were treated with kintin. From these present result it was supposed that kinetin acts on the catabolism and the anabolism of chlorophyll. The necessity of kinetin for chloroplast from amyloplast maturation and differentiation was discussed.     

Preferential azido bridging regulating the structural aspects in cobalt(III) and copper(II)-Schiff base complexes: Syntheses, magnetostructural correlations and catalytic studies

A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol = LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co₂(L)₂(μ_1,1-N₃)₂(N₃)₂] (1), [Cu₂(L)₂(μ_1,3-N₃)]·ClO₄ (2) and [(μ_1,1-N₃)₂Cu₅(μ-OL)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂]_n (3). The complexes have been characterized by elemental analysis, FT-IR, UV-Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ_1,3-N₃ bridged Cu^II-Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed.     

Bean pod mottle virus: a new powerful tool for functional genomics studies in Pisum sativum

Pea (Pisum sativum L.) is an important legume worldwide. The importance of pea in arable rotations and nutritional value for both human and animal consumption have fostered sustained production and different studies to improve agronomic traits of interest. Moreover, complete sequencing of the pea genome is currently underway and will lead to the identification of a large number of genes potentially associated with important agronomic traits. Because stable genetic transformation is laborious for pea, virus‐induced gene silencing (VIGS) appears as a powerful alternative technology for determining the function of unknown genes. In this work, we present a rapid and efficient viral inoculation method using DNA infectious plasmids of Bean pod mottle virus (BPMV)‐derived VIGS vector. Six pea genotypes with important genes controlling biotic and/or abiotic stresses were found susceptible to BPMV carrying a GFP reporter gene and showed fluorescence in both shoots and roots. In a second step, we investigated 37 additional pea genotypes and found that 30 were susceptible to BPMV and only 7 were resistant. The capacity of BPMV to induce silencing of endogenes was investigated in the most susceptible genotype using two visual reporter genes: PsPDS and PsKORRIGAN1 (PsKOR1) encoding PHYTOENE DESATURASE and a 1,4‐β‐D‐glucanase, respectively. The features of the ‘one‐step’ BPMV‐derived VIGS vector include (i) the ease of rub‐inoculation, without any need for biolistic or agro‐inoculation procedures, (ii) simple cost‐effective procedure and (iii) noninterference of viral symptoms with silencing. These features make BPMV the most adapted VIGS vector in pea to make low‐ to high‐throughput VIGS studies.     

Light and decapitation effects on in vitro rooting in maize root segments

The effects of white light and decapitation on the initiation and subsequent emergence and elongation of lateral roots of apical maize (Zea mays L. cv LG 11) root segments have been examined. The formation of lateral root primordium was inhibited by the white light. This inhibition did not depend upon the presence of the primary root tip. However, root decapitation induced a shift of the site of appearance of the most apical primordium towards the root apex, and a strong disturbance of the distribution pattern of primordium volumes along the root axis. White light had a significant effect neither on the distribution pattern of primordium volumes, nor on the period of primordium development (time interval required for the smallest detectable primordia to grow out as secondary roots). Thus, considering the rooting initiation and emergence, the light effect was restricted to the initiation phase only. Moreover, white light reduced lateral root elongation as well as primary root growth.