[en] Highlights: • AUX1 acts upstream of PIN2 in the control of root gravitropism by regulating the asymmetric auxin distribution. AUX1 and PIN2 auxin transporter are required for the asymmetric distribution of auxin for root gravitropic response. However, the relationship between AUX1 and PIN2 in root gravitropism is unclear. Here, we report that aux1-T mutant show stronger defects in root gravitropism than pin2-T, and aux1-T pin2-T double mutants display similar agravitropic phenotype to aux1-T. The gravity-induced asymmetric distribution of auxin responses could not be established in pin2-T, aux1-T and aux1-T pin2-T mutants; whereas aux1-T pin2-T double mutants showed similar auxin responses to aux1-T mutant. These findings support AUX1 plays a role in root gravitropism upstream of PIN2.

[en] Melia volkensii is one of the most popular fast growing agro-forestry tree species in East Africa's arid and semi arid lands. It is valued for for production of termite resistant timber. Kenya Forestry Research Institute is carrying out studies on management, improvement and domestication of species with a major focus on improving low germination mortality and other propagation methods. Vegetative propagation was investigated in order to supplement more seedlings for increased demand of the species. The objective of this study was to determine and predict the effect of varying levels of auxin concentrations on rooting of melia volkensii shoot cuttings under different provenances. The experiment was set in a split plot design and conducted in a non-mist propagator. The number of roots was recorded for every cutting in the experiment. Mean cumulative cutting percentage were analysed using ANOVA procedures by first checking homogeneity of variance; Pearson correlation were carried out to check the interrelation of the factors with rooting and Logistic ability of the cuttings. The results showed that cuttings inoculated with 0.3 mgl-1^significantly (p<0.01) rooted better than all other auxin concentration levels. Cuttings collected from Taveta, significantly (p<0.01) rooted better than those from Meru and Kitui. Overall, there was negative significant (p<0.01) correlation between rooting and concentrations with 7 mgl-1ⁿot showing any rooting from three provenances. In conclusion 0.03 mgl-1^should be used for further vegetative propagation of M. vokensii. Cutting from Taveta inoculated with 0.3 mgl-1^would significantly increase the number of seedlings for planting

[en] Intracellular polarisation of auxin efflux carriers is crucial for understanding how auxin gradients form in plants. The polarisation dynamics of auxin efflux carriers PIN-FORMED (PIN) depends on both biomechanical forces as well as chemical, molecular and genetic factors. Biomechanical forces have shown to affect the localisation of PIN transporters to the plasma membrane. We propose a physico-genetic module of PIN polarisation that integrates biomechanical, molecular, and cellular processes as well as their non-linear interactions. The module was implemented as a discrete Boolean model and then approximated to a continuous dynamic system, in order to explore the relative contribution of the factors mediating PIN polarisation at the scale of single cell. Our models recovered qualitative behaviours that have been experimentally observed and enable us to predict that, in the context of PIN polarisation, the effects of the mechanical forces can predominate over the activity of molecular factors such as the GTPase ROP6 and the ROP-INTERACTIVE CRIB MOTIF-CONTAINING PROTEIN RIC1. (paper)

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[en] To induce in vitro callus induction, leaf and nodal stem explants of Achyranthes aspera were compared for their callusing response on MS (Murashige and Skoog, 1962) medium supplemented with NAA, IAA, IBA and 2,4-D at various concentrations. Best callus was derived from adaxial surface of leaf explants. MS medium supplemented with 2.0 mg/l 2,4-D was found suitable for callus induction. After subculture the colour of callus turned brown and the quantity of callus declined. Influence of charcoal was tested to stop browning of the callus. Influence of sucrose percentage on callus fresh weight and growth regulators combined with coconut milk was also tested. (author)

[en] The synthesis of six useful auxins labelled with tritium is described. The following compounds were prepared: 3-indoleacetic acid-5-³H (28.9 Ci-1.07 TBq/mmol), 3-indolebutyric acid-5-³H (7.3 Ci-270 GBq/mmol), 1-naphthylacetic acid-4-³H (27.6 Ci-1.02 TBq/mmol), 2,4-dichloropheno-xyacetic acid-5-³H (18.5 Ci-685 GBq/mmol), 2(2,4-dichlorophenoxy-5-³H) -propionic acid (20.7 Ci-766 GBq/mmol), 2(2,4-dichlorophenoxy)-propionic acid-3-³H (0.39 Ci-14.4 GMq/mmol), and 4-chlorophenoxyacetic acid-2-³H (13.3 Ci-492 GBq/mmol). (author)

[en] Justicia gendarussa or known as gandarusa, a member of the Acanthaceae family, is recognised for its medicinal properties. To date, the optimisation of total phenolic and total flavonoid contents in adventitious root biomass of J. gendarussa has not been reported. Therefore, in this study, the effects of auxins and methyl jasmonate (MeJa) on adventitious root biomass, total phenolic content (TPC), and total flavonoid content (TFC) of J. gendarussa were investigated. Adventitious root induction from leaf explant was studied when treated with different concentrations of indole butyric acid (IBA), indole acetic acid (IAA), and naphthalene acetic acid (NAA). The total phenolic content (TPC) and total flavonoid content (TFC) were recorded after 7 weeks of cultures. Results demonstrated that the maximum root biomass was obtained when treated with 2 mg/L IAA (1591.40 ± 14.14 mg). Analysis of TPC and TFC revealed that the combination of 2 mg/L IAA + 0.5 mg/L NAA had an optimum value of 0.30 ± 0.02 mg gallic acid equivalent/g dry roots and 0.24 ± 0.01 mg of (+) catechin equivalent/g dry roots, respectively. However, the addition of MeJa had reduced the root biomass, TPC, and TFC. In conclusion, a combination of IAA and NAA had a positive effect on root biomass, TPC, and TFC values. (author)

[en] A study was undertaken to identify by a direct method the cells involved in auxin transport through maize mesocotyl tissue. The auxin photoaffinity labeling agent, 7-[³H], 5-azidoindole 3-acetic acid (N₃IAA), was loaded into excised stem tissue from a cut end. Polar transport of this analog was demonstrated over 4 hours by comparing uptake into tissue loaded with N₃IAA from the apical vs. the basal end. Triiodobenzoic acid, an auxin transport inhibitor, inhibited N₃IAA uptake into tissue. Tissue which had taken up the photoaffinity labeling agent was photolyzed to covalently fix the radioisotope within cells. This tissue was sectioned and subjected to in situ autoradiography. The outermost cell of epidermal tissue and certain files of cells in vascular tissue were densely labeled indicating that on a per cell basis these two cell types are most actively transporting auxin

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