Xylogenesis and hormones in soybean callus. I: A histological and ultrastructural study

Abstract

Five ultrastructural developmental stages are described for differentiating tracheary elements in callus of Glycine max (L.) Merr. Xylogenesis was induced by exogenous application of indolebutyric acid (IBA) + kinetin, IBA + trans- zeatin, IBA + benzyladenine (BA) and IBA + gibberellic acid (GA 3 ). Initiation of tracheary elements occurred after division of the callus cells and was followed by cell enlargement, secondary wall deposition and lignification, all of which culminated in the final autolysis of the immature tracheary elements. Mature elements included both tracheids with scalariform to reticulate wall sculpturing and pitted vessels with simple perforations. Nodulation was extensive in all the treatments. A lateral pattern in autolysis of tracheary elements is thought to be a reflection of a concomitant migration of the inductive stimulus ultimately resulting in groups of xylem elements. Vyf ultrastrukturele ontwikkelingstadia vir differensiërende trageale elemente in Glycine max (L.) Merr. (soyaboon) kallus word beskryf. Xilogenese is deur die toediening van indoolbottersuur (IBA) + kinetien, IBA + trans- zeatien, IBA + bensieladenien (BA) en IBA + gibberelliensuur (GA 3 ) geïnduseer. Trageale elemente is na seldeling geïnisieer en is gevolg deur selvergroting, sekondêre selwand-deposisie en lignifikasie, wat uiteindelik tot outolise van die ont- wikkelende elemente lei. Volwasse elemente is gekenmerk deur beide trageïede met leervormige tot netvormige selwandstrukture en stippelhoutvate met eenvoudige perforasies. Bondelvorming is volop in al die behandelings. ’n Laterale outolisepatroon in trageale elemente word toegeskryf aan ’n gepaardgaande migrasie van die induktiewe stimulus om uiteindelik in groepies xileemelemente te eindig.