1985. Changes in root morphology of wheat caused by Azospirillum inoculation. Can. J. Microbiol. 31: 881-887.Wheat seeds (Triticum aestivum L.) were inoculated with Azospirillum brasilense Cd, Sp7, the local isolate Cd-1 , and with other types of bacteria. Inoculation with lo5 to lo6 colony-forming units of Azospirillum caused the largest root elongation and total root surface of seedlings whereas 10' to lo9 colony-forming units of Azospirillum caused inhibition of root development. Similar effects were obtained in 10 different cultivars of wheat inoculated with Azospirillum. Scanning electron micrographs of inoculated wheat root segments showed denser and longer root hairs as compared with the control inoculated with dead cells. This effect was less apparent in more mature roots. In inoculated roots bacteria were located mainly on the cell elongation area and on the bases of root hairs, but fewer bacterial cells were present on the root cap or adsorbed to root hairs. Cross sections of Azospirillum-inoculated roots showed prominent alterations of the cell arrangement in the layers of the cortex. The results suggest the existence of critical numbers of sites for Azospirillum colonization on the roots, to such an extent that root growth is affected. KAPULNIK, Y., Y. OKON et Y. HENIS. 1985. Changes in root morphology of wheat caused by Azospirillum inoculation. Can. J. Microbiol. 31: 881 -887. Des grains de blC (Triticum aestivum L.) ont tte inoculCs avec les souches Cd, Sp7 et I'isolat local Cd-1 d'Azospirillumbrasilense, ainsi qu'avec d'autres types de bactCries. Les inoculations avec 105 a lo6 unites formant des colonies d'Azospirillum ont causC la plus forte Clongation des racines et la plus importante surface racinaire totale des plantules, alors que des unit& formant des colonies de 10' a lo9 d'Azospirillum ont inhibC le dtveloppement des racines. Des effets similaires ont Ct C obtenus chez 10 cultivars de blC differents inoculCs avec Azospirillum. Des micrographies en microscopie ti balayage de segments de racines de blC inoculCes ont rCvC1C la prCsence de poils absorbants plus denses et plus longs que chez les tCmoins inocults avec des cellules mortes. Ces effets furent moins Cvidents chez les racines plus avanctes en maturitk. Chez les racines inocul6es, les bactkries furent localis6es principalement sur les rkgions d'tlongation cellulaire et a la base des poils absorbants, alors qu'un nombre moindre de cellules bacttriennes furent prCsentes au niveau de la coiffe ou adsorb& sur les poils absorbants. Des coupes transversales de racines inoculCes avec Azospirillum ont rtvC1C des altkrations importantes dans I'arrangement cellulaire des assises corticales. Les rksultats suggkrent l'existence d'un nombre critique de sites pour la colonisation des racines par Azospirillum a un point tel que la croissance de la racine en est affectke.[Traduit par le journal]

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Sclerotium rolfsii, grown in a shaken submerged culture, developed a potential for the formation of sclerotia. This potential was inhibited by the presence of glucose in the culture medium. The cultures were capable of producing sclerotia, after transfer to stationary incubation, when glucose was exhausted and the biomass reached its maximal level. The level of adenosine 3′,5′-cyclic monophosphate (cAMP) sharply increased upon glucose depletion and decreased upon glucose addition. Sclerotium rolfsii was grown in a chemostat with glucose of limiting concentration at a dilution rate of 0.05/h. Samples from the chemostat possessed the potential to produce initials when poured into empty Petri plates. Addition of glucose to these plates changed the fungal growth pattern from further differentiation to vegetative growth. Glucose supplementation to clearly differentiated initials did not inhibit further development. It was observed that during morphogenetic events endogenous substrates, e.g., cell wall components, were utilized.

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