| Several roles have been described for NO in animals, where it takes part in neurotransmission, vasorelaxation, smooth muscle relaxation, and immunoregulation of pathophysiological processes. Even though NO research in plants is not as advanced as in animals, in the last decade No was proved to participate in many key plant physiological process such as growth, development, pathogen defense reaction, programmed cell death, and stress tolerance. Though NO mediation of the adventitious rooting process induced by auxins had been demonstrated, the time and space changes of NO and the source of NO accompanied adventitious root generation and development are unknown. In this study, mung bean hypocotyls were used as materials, and the role and the source of NO of the cuttings treated by H2^O, IBA or NAA during the adventitious root formation were studied from several aspects. The results were as follows:1. The cuttings were treated with NO-associated reagent. The results showed that NO donor-SNP significantly enhance the adventitious rooting. 300μmol/L SNP proved an optimal concentration for the initiation of organogenesis. The treatment time of SNP, the ages and the position of the cuttings also influenced the rooting. The hypocotyls of 5 days old seedlings was excised 6 cm below the cotyledonary node and then treated with 300μmol/L SNP by 24h had the optimal rooting effect. SNP obviously enhanced the effects of IBA or NAA in stimulating rooting. C-PTIO, NO specific scavenger, or NOS inhibitor L-NAME treted alone or plus IBA or NAA resulted in an inhibitory effect. It's indicated that endogenous NO appears to play a key role in the generation and development of adventitious roots, and the production of NO in this process maybe catalyzed by NOS.2. The temporal and spatial change of NO of the cuttings treated by H2O, IBA or NAA during the generation and the development of adventitious roots of mung bean hypocotyl cuttings were detected by NO-sensitive fluorescence probe DAF-2DA. Theresults indicated that, with the development of root primordium, the fluorescence of NO appeared and increased gradually in 2mm region of hypocotyl basal part in all treatments. The green fluorescence of NO was detected in the region between the vascular tissues of the hypocotyls at 36h after cutting. The cytosol of DAF-2DA-positive cells stained uniformly for NO. With the development and elongation of root primordium, the number of DAF-2DA-positive cells increased gradually, and the root apical meristem cells show intense fluorescence. No NO was observed in non-rooting areas. In 2mm-5mm region of hypocotyl basal part, the generation and distribution of NO of the cuttings treated by IB A or NAA were different with that of treated by H2O. No NO was detected in control. The generation, distribution and change of NO of cuttings treated by IBA or NAA in this region were in accordance with that of in 2mm region of hypocotyl basal part. C-PTIO, the specific NO scavenger, suppressed the fluorescence and inhibited the formation of root primordial clearly. The results strongly argue that that endogenous NO appears to play a key role in the adventitious rooting process. It also suggested that NO could also mediate the IBA and NAA response during the rooting process in mung bean.3. NOS-like enzyme activity was detected during adventitious root formation by NADPH-diaphorase histochemical method. With the origination and development of adventitious roots, not in control but in the cuttings treated by IBA or NAA, the activity of NADPH-diaphorase and the number of cell expressing NADPH-diaphorase-positive increased rapidly in the forming root in 2mm region of hypocotyl basal part. The non-rooting areas haven't positive cells. In accordance with the distribution of NO, intense staining mainly distributed in root meristem. The NADPH-diaphorase activity of the cuttings treated by IBA or NAA were more intense than the control in the same time. In 2mm-5mm region of hypocotyl basal part, the distribution of NADPH-diaphorase of the cuttings treated by IBA or...
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