When I was an undergraduate, our plant propagation course experiment on
rooting of mung bean cuttings failed and was blamed on bacterial
contamination of the distilled water supply.
Did you root the mung bean cuttings in plain distilled water?
Researchers using the mung bean hypocotyl cutting rooting system
sometimes use a complete nutrient solution (Dhindsa et al. 1987)
because roots require boron and calcium in the external solution for
normal functioning. Epstein (1972) noted that
"for many years it was not realized that even brief exposure of plant
tissue to solutions lacking calcium will cause injury..."
Bohnsack (1991) has a nice teaching lab that shows retardation of
squash root elongation three hours after being placed in minus boron
solutions.
Houseplant cuttings might be a more practical choice to show that auxin
promotes adventitious root formation. Mung bean seedlings are not
rooted commercially but coleus, chrysanthemum, poinsettia and many
houseplant cuttings are routinely treated with auxin to promote
rooting. An advantage of using an ornamental plant is that students can
take the plants home after the experiment. Ross Koning (1994) has a
student lab using houseplant cuttings and three commercial rooting
powders.
References
Bohnsack, Charles W. 1991. Investigating the boron requirement of
plants. American Biology Teacher 53: 486-488.
Dhindsa, Rajinder S., Dong, Guangyuan and Lalonde, Louis. 1987. Altered
gene expression during auxin-induced root development from excised mung
bean seedlings.
Plant Physiology 84(4): 1148-1153.
http://www.pubmedcentral.nih.gov/pagerender.fcgi?artid=1056743&pageindex=1
Epstein, E. 1972. Mineral nutrition of plants: Principles and
perspectives. New York: Wiley.
Koning, Ross E. 1994. Vegetative Propagation. Plant Physiology
Information Website.
http://plantphys.info/Plants_Human/labpdf/vegprop.pdf
Plieth, Christoph. 2005. Calcium: Just another regulator in the
machinery of life? Annals of Botany 96 :1-8.
http://aob.oxfordjournals.org/cgi/content/full/96/1/1
White, Philip J. and Broadly, Martin R. 2003. Calcium in plants. Annals
of Botany 92: 487-511
http://aob.oxfordjournals.org/cgi/content/full/92/4/487
