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See detailChanges in polyamines, auxins and peroxidase activity during in vitro rooting of Fraxinus angustifolia shoots: an auxin-independent rooting model
Tonon, Giustino; Kevers, Claire ULiege; Gaspar, Thomas ULiege

in Tree Physiology (2001), 21(10), 655-663

Among shoots of Fraxinus angustifolia Vahl raised in vitro, 76% rooted after culture on root induction medium for 5 days in darkness followed by culture on root expression medium for 15 days in light. The ... [more ▼]

Among shoots of Fraxinus angustifolia Vahl raised in vitro, 76% rooted after culture on root induction medium for 5 days in darkness followed by culture on root expression medium for 15 days in light. The addition of 20.7 muM indole-butyric acid (IBA) to the root induction medium did not significantly increase the rooting percentage (88%). Putrescine, spermidine, cyclohexylamine (CHA) and aminoguanidine (AG) enhanced rooting up to 100% (98.66% for AG), when applied during root induction in the absence of IBA, otherwise these compounds inhibited rooting, as did spermine and difluoromethylornithine (DFMO) + difluoromethylarginine (DFMA). The root induction phase was characterized by a temporary increase in endogenous free indole-acetic acid (IAA) and putrescine concentrations during root induction, whereas the root expression phase was characterized by increased peroxidase activity and low concentrations of polyamines. These changes were specifically associated with the rooting process and did not depend on the presence of exogenous IBA, because application of exogenous IBA enhanced the amount of IAA in the cuttings but did not affect rooting or the pattern of changes in polyamines and peroxidase. The effects of CHA, AG and DFMO + DFMA on endogenous concentrations of auxins and polyamines highlight the close relationship between the effects of IAA and putrescine in root induction and suggest that polyamine catabolism has an important role in root formation and elongation. [less ▲]

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See detailAssessing forest soil CO(2) efflux: an in situ comparison of four techniques.
Janssens, Ivan A.; Kowalski, Andrew S.; Longdoz, Bernard ULiege et al

in Tree Physiology (2000), 20(1), 23-32

A dynamic, closed-chamber infrared gas analysis (IRGA) system (DC-1: CIRAS-1, PP-Systems, Hitchin, U.K.) was compared with three other systems for measuring soil CO(2) efflux: the soda lime technique (SL ... [more ▼]

A dynamic, closed-chamber infrared gas analysis (IRGA) system (DC-1: CIRAS-1, PP-Systems, Hitchin, U.K.) was compared with three other systems for measuring soil CO(2) efflux: the soda lime technique (SL), the eddy correlation technique (EC), and another dynamic, closed-chamber IRGA system (DC-2: LI-6250, Li-Cor, Inc., Lincoln, NE). Among the four systems, the DC-1 systematically gave the highest flux rates. Relative to DC-1, SL, EC and DC-2 underestimated fluxes by 10, 36 and 46%, respectively. These large and systematic differences highlight uncertainties in comparing fluxes from different sites obtained with different techniques. Although the three chamber methods gave different results, the results were well correlated. The SL technique underestimated soil CO(2) fluxes compared with the DC-1 system, but both methods agreed well when the SL data were corrected for the underestimation at higher fluxes, indicating that inter-site comparisons are possible if techniques are properly crosscalibrated. The EC was the only system that was not well correlated with DC-1. Under low light conditions, EC values were similar to DC-1 estimates, but under high light conditions the EC system seriously underestimated soil fluxes. This was probably because of interference by the photosynthetic activity of a moss layer. Although below-canopy EC fluxes are not necessarily well suited for measuring soil CO(2) efflux in natural forest ecosystems, they provide valuable information about understory gas exchange when used in tandem with soil chambers. [less ▲]

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See detailChanges in the Concentrations of Auxins and Polyamines During Rooting of in-Vitro-Propagated Walnut Shoots
Heloir, Marie-Claire; Kevers, Claire ULiege; Hausman, Jean-François et al

in Tree Physiology (1996), 16(5), 515-9

Rooting was induced in in-vitro-propagated walnut (Juglans regia L.) shoots by subculturing the shoots on rooting medium containing agar and 3 mg l(-1) indole-3-butyric acid (IBA) for 7 days in darkness ... [more ▼]

Rooting was induced in in-vitro-propagated walnut (Juglans regia L.) shoots by subculturing the shoots on rooting medium containing agar and 3 mg l(-1) indole-3-butyric acid (IBA) for 7 days in darkness. Changes in the concentrations of endogenous free indole-3-acetic acid (IAA), indole-3-acetylaspartic acid (IAAsp) and free polyamines were determined during culture on root-inducing medium. In extracts of whole shoots, the concentration of free IAA showed a transient peak at 60 h (around 48 h in extracts from basal shoot portions) and then remained at a relatively low concentration for the remainder of the 7-day culture period. The concentration of IAAsp in extracts of whole shoots peaked at about the same time as the concentration of free IAA, whereas the IAAsp concentration in extracts from basal shoot portions peaked earlier, at around 12 h. The concentrations of free polyamines in extracts of whole shoots increased soon after the shoots were transferred to root-inducing medium. The concentrations of IAA and IAAsp remained stable when the rooted shoots were transferred to a vermiculite/gelrite mixture (without auxin) and grown in light. [less ▲]

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