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Prepenetration and penetration phenomena after inoculation of roots of Pinus sylvestris seedlings grown in vitro with the P-, S- and F-group isolates of Heterobasidion annosum were observed using scanning electron microscop. There were no differences in the behaviour of hyphae and in the appearence of mycelia formed by the three IS-group isolates. Four types of the root penetration by hyphae were observed. In the first, the entrace of hypha into root was achieved throught tiny pore formed in walls of the cortical cells. In the second, swellings resembling appressoria were formed by the hyphal tips at the points of contact with the root surface. In the third, the hyphae penetrated cells through holes in eroded areas of roots, and in the fourth by the natural crevices at points of the cortical cell junctions. It is concluded that the different frequencies of the four types of penetration observed after inoculation with isolates of the three IS group should be carefully explained in term of their different pathogenic and saprobic capabilities on pine.
Application of 1-naphthaleneacetic acid (NAA) or 1-aminocyclopropane-1-carboxilic acid (ACC) to maize roots growing in hydroponic solution inhibited root elongation, and increased radial growth, but the responses to those treatments differed in degree. Auxin was more effective than ACC as an elongation inhibitor and root swelling promoter. Whereas NAA fully inhibited elongation and maintained swelling over 48 h, ACC inhibited elongation partially (50%) and only promoted swelling for 24 h. It is well-known that auxin, like ACC, promotes ethylene production, but similar levels of ethylene production reached by means of NAA or ACC treatments did not elicit the same response, the response being always stronger to NAA than to ACC. These results suggest that the effect of auxin on root growth is not mediated by ethylene. Elongation and swelling of roots appear to be inversely related: usually a reduction in elongation was accompanied by corresponding swelling. However, these two processes showed different sensitivities to growth regulators. After 24 h treatment with 0.5 μM NAA or 5 μM ACC, root elongation was inhibited by 90% and 53% respectively, but the same treatments promoted swelling by 187% and 140% respectively. Furthermore, 1 μM ACC was shown to promote inhibition of root elongation without affecting swelling. The ethylene antagonist STS (silver thiosulfate) did not affect elongation in control or NAAtreated roots, but increased ethylene production and swelling. These results indicate that longitudinal and radial expansion could be independently controlled.
In two-year field investigations (2008 and 2009) the effect of used preparations on heath status of roots and seedling shoots of celery cvs Edward Mentor and Talar was studied. During experiments Biochikol 020 PC (chitosan 20 g/l), Biosept 33 SL (grapefruit extract 33%), Polyversum WP (106 oospores Pythium oligandrum/1 g) and standard fungicide Gwarant 500 SC (chlorothalonil 500 g/l) and Topsin M 500 SC (tiophanate metyl 500 g/dm3) were used for rootdressing. Fungicides Gwarant 500 SC and Topsin M 500 SC, significantly improved the health status of seedling shoots and seed-yield. The efficacy of preparations Biosept 33 SL and Biochikol 020 PC was lower than standard fungicide, but statistically significantly improved health status and yield compared to control. The application of biopreparation Polyversum WP did not influence significantly to the health of seedling shoots of all tested varieties, and did not increase the yield of seeds.
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