Ethylene and rooting of mung bean cuttings. The role of auxin induced ethylene synthesis and phase-dependent effects

We have re-examined the role of ethylene during rooting of mung bean cuttings. Cuttings were treated for 5 days with a low or a high concentration of NAA (naphthaleneacetic acid). During this 5 days period, we also applied STS (silverthiosulfate, an inhibitor of ethylene action) or ACC (1-aminocyclo-propane-l-carboxylic acid, a direct precursor of ethylene). At high NAA concentration, STS promoted and ACC inhibited rooting, respectively. At low NAA concentration, the effects were opposite, STS being inhibitory and ACC promotive. AVG (aminoethoxyvinylglycine, an inhibitor of ethylene synthesis) gave similar results as STS. Together, these data suggest supraoptimal and suboptimal ethylene levels in the tissue at high and low NAA concentration, respectively. We also examined whether the effect of ethylene varied during the successive phases of the rooting process. Thus, we gave 24 h pulses with either STS or ACC during the rooting treatment. During the first two days (0-48 h), ACC-pulses were promotive and STS-pulses inhibitory. Later on (48-168 h), the ACC-pulses were inhibitory and the STS-pulses promotive. Whether this effect was observed or not was dependent on the NAA concentration. These data indicate that ethylene promotes or inhibits rooting depending on the stage in the rooting process. When ACC was added only during the initial period, rooting was increased at all NAA concentrations in a NAA dose-response curve and the optimal NAA concentration remained the same. This suggests that ethylene renders more cells responsive to NAA

Effect of medium-pH and MES on adventitious root formation from stem disks of apple

We have examined the effect of medium-pH on rooting using 1-mm slices cut from stems of apple microshoots. Before autoclaving, the pH of the rooting medium was set at various pH values between 4.5 and 8.0. During autoclaving, the pH drifted in particular in the alkaline region. Additional changes occurred during culture and the range set at 4.5-8.0 had shifted to 5.2-6.0 after autoclaving and 3 weeks of culture. When 10 mM 2-(N-morpholino)ethanesulfonic acid (MES) had been added as buffering agent, the pH was stable when set at 5.0-6.5. Highest rooting was achieved at pH similar to 5.3 with and without MES (pH measured after autoclaving). This maximum did not correlate with highest auxin uptake. MES inhibited adventitious root formation during the initial phase of root formation when the meristemoids are being formed (ca. 30% reduction at 10 mM) but was promotive during outgrowth of the meristemoids to roots (30% increase at 10 mM). Inhibition and promotion by MES were not related to its buffering action as they were observed at all pHs

Time series outlier detection using the trajectory matrix in singular spectrum analysis with outlier maps

Singular spectrum analysis is a powerful non-parametric time series method that appliessingular value decomposition to a Hankel structured matrix. The method can handle complex time series structures that include combinations of polynomials, sinusoids and exponentials. Outlier maps combined with robust principal component analysis is considered and shown to compare very favourably with existing time series methods to identify an additive time series outlier. The wellknown airline time series as well as a South African tourism time series are used to illustrate the usefulness of the methodology

Die wetenskap 'in u lig' – wat sê dit vir die PUK self?

Science 'in Thy light' – what does it say to the PUK itself? At the moment of the name change of the Potchefstroom University for Christian Higher Education (PU for CHE) it may be opportune to take not only an outward look but also an inward look at the implications of this step, and to ask ourselves what these issues look like to the inside. With reference to the past it is important to ask to what extent the PU for CHE, i.e. its body of staff, wants to live and work according to its motto. This contribution attempts to investigate this matter by subjecting to scrutiny a variety of issues – in particular on the academic terrain

Die roeping van die staat t.o.v. die onderwys en kultuur in die Republiek van Suid-Afrika

My toespraak verplaas my na die dae van my minislerskap van Nasionale Opvoeding, waarby Kultuur en Onderwys inbegrepe is. Wat ek nou daarvan sal sê bly my oortuiging, net soos dit enkele maande gelede in my vorige hoedanigheid was

A dicynodont trackway from the Cistecephalus Assemblage Zone in the Karoo, East of Graaff-Reinet, South Africa

This paper reports a partially exposed late Permian palaeosurface with preserved vertebrate tracks at the "Asante Sana" private game reserve in the vicinity of Petersburg, 46km east of Graaff-Reinet. Excavation of the palaeosurface over an area of 34m2 revealed clear footprints and trackways of six large tetrapods that walked in a westerly direction across a semi-consolidated muddy substrate in the distal floodplain area of a large fluvial system. Clear heteropodous impressions of the footpads and individual toes and claws are preserved as concave epirelief moulds. It is concluded that these fossil tracks were made by a group of therapsids, specifically a group of large dicynodonts, possibly Aulacephalodon. The tracks are here assigned to the ichnospecies Dicynodontipus icelsi sp. nov. A continuous trackway and numerous less distinct individual prints and markings made by smaller tetrapods are also preserved on the palaeosurface. It is probable that these tracks were left by Diictodon, a small common dicynodont of the time.Palaeo-Anthropology Scientific Trust; French Embassy in South Africa; Co-operation and Cultural Servic

Seasonal variations of water and sediment quality parameters in endorheic reed pans on the Mpumalanga Highveld

The Mpumalanga Lakes District consists of approximately 320 pans, of which less than 3% are classified as reed pans. There is limited information available on reed pans and as a result they are at risk of various anthropogenic activities, for example mining and agriculture. Four reed pans were selected and assessed to determine seasonal trends of a variety of water and sediment quality parameters. The study took place over one seasonal cycle from 2008–2009; samples were collected seasonally to account for various hydrological extremes. Water samples were collected and their nutrient and chlorophyll a concentrations were determined, while various other water quality parameters were measured in situ. Sediment samples were analysed for physical and chemical properties, namely, grain size and organic carbon content. The seasonal changes in concentrations of As, Cr, Cu, Fe, Pb, Mn, Mo, Ni, Se, Sr, U and Zn were also analysed within the surface water and sediment. Increased nutrient concentrations within the water were evident during spring and summer at some of the sites, which influenced other water quality variables, e.g., dissolved oxygen and pH. Seasonal trends in metal concentrations were influenced by the prevailing environmental conditions (e.g., rainfall) experienced at the selected sites as well as physical and chemical properties (e.g., grain size and organic carbon content). This study showed distinct seasonal variability of water and sediment quality parameters in endorheic reed pans on the Mpumalanga Highveld. There is a need for further studies on all of the different types of pans in terms of their water and sediment quality. This type of information will allow for a sound and defensible scientific basis for the assessment of likely impacts (e.g., eutrophication), the evaluation of the significance of these impacts, and the design of remedial and preventative measures

Die persoonlike geloofsdaad van die Nagmaalsgebruiker

The act of personal faith of the Communicant The aim of this article is to determine the nature of the communicant’s act of faith in the Three Formulae of Unity. The main theses are:Holy communion is only instituted for the reborn to nourish their spiritual and heavenly life.The only food that can strengthen the new life is the exalted, living Christ, also in accordance with his human nature.The most important act which occurs during Holy Communion is Christ’s act of giving Himself. In fact the reborn partakes of the true Christ with the Holy Spirit and is thus nourished.Because Christ is in heaven, the communicant must raise his heart towards heaven to partake of Christ and to make Him his own

“Debiteure” van die bedryfsekonomie*

Business Economics is a relatively young science, yet this fact presents a challenge to those who want to he called “debtors" of Business Economics. For the Christian businessman or the lecturer in Business Economics it means a reformulation of the basic principle of Economics and an acknowledgement of the fact that economic decisions involve more than economic norms only. Accounts receivables represent I.O.U.’s and in order to evaluate credit risk one must consider the five c’s of credit: character, capacity, collateral, capital and condition. If the liabilities, according to the requirements of the five c’s, are met, the “debtors” will appear in their rightful place on the balance sheet, that is under the assets. Then and then only can “debtors" generate a “profit"'