Browsing by Author "Ilan Chet"

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    Aerotaxis and Chemotaxis of Azospirillum brasilense: A Note
    (1980) Yaacov Okon; Lutfu Cakmakci; Israel Nu; Ilan Chet
    Azospiritlum brasilense was attracted to capillaries containing either phosphate buffer, distilled water, or saline. The number of bacteria in these capillaries was 3-4 X 10^4, after 1 h of incubation, [n the presence of phosphate buffer + attractants, the number of cells accumulated in the capillary increased only to5x 10^4-I.I x 10^5 cells. It was not possible, therefore, to measure chemotaxis in A. brasilense as distinct from aerotaxis by the capillary method. Chemotaxis was observed in semi-solid agar plates and was determined by a growth band oriented towards the attractant. Positive chemotactic response was obtained with peptone, tryptone, yeast extract, amino acids, organic acids, arabinosc and galactose
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    Hormone concentrations in tobacco roots change during arbuscular mycorrhizal colonization with Glomus intraradices
    (2002) Orna Shaul-Keinan; Vijay Gadkar; Idit Ginzberg; Jose M. Grunzweig; Ilan Chet; Yigal Elad; Smadar Wininger; Edi Belausov; Yuval Eshed; Nir Atzmon; Yossi Ben-Tal; Yoram Kapulnik
    Phytohormones are known to play a pivotal role In various developmental processes In plants and in arbuscular-mycorrhizal (AM) fungal-host symbiosis. This study focuses on characterizing the changes In the concentrations of auxins, cytokinlns and gibberellins in tobacco (Nicotiana tabacum) during the early stages of colonization by Clomus intraradices, using advanced analytical detection techniques. • High-pressure liquid chromatography analysis followed by radioimmunoassay detection revealed that AM colonization induced the accumulation of specific zeatin riboside-like and isopentenyl adenosine-like compounds in both roots and shoots. • Use of the gas chromatography-mass spectrometry technique on the same developmental stage revealed that gibberellins (GA) of the earl-13-hydroxylation bio-synthetic pathway (GA,,, GAg, GA19 and GA20) were significantly more abundant in roots, but not shoots, of AM inoculated plants than in those of nonmycorrhlzal plants. Indoleacetic acid concentrations (total and free) remained unaltered by AM colonization. • This study demonstrates that hormonal changes do occur during AM symbiosis with tobacco, before the fungal benefits manifest.