Allelopathic Effects of Eucalyptus globulus, Eucalyptus viminalis, and Juglans californica on Triticum aestivum (Wheat)

Abstract:

Allelopathy is the process by which biochemicals from a plant inhibit the growth or development of nearby plants. The purpose of this experiment was to investigate and compare the allelopathic effects of solutions made from the extracts of leaves of Eucalyptus globulus (Blue Gum), Eucalyptus viminalis (Manna Gum), and Juglans californica (California Black Walnut) trees on the growth of Triticum aestivum (Wheat) seedlings. Six solutions were created from soaking leaves from the three tree species in two solvents, distilled water and ethyl alcohol. Distilled water with wheat seedlings served as the control group. It was hypothesized that if both distilled water and ethyl alcohol are used to obtain extracts from the leaves of the tree species mentioned above, extracts obtained using ethyl alcohol will inhibit the growth of the wheat seedlings more than extracts produced with a distilled water solvent; the extracts produced from the Juglans californica leaves will inhibit the growth of the wheat seedlings more than the other tree species.

Exactly 140 wheat seeds were sterilized in a dilute bleach solution prior to testing and germinated with distilled water for three days, so that only seeds which germinated were used for further experimentation. Wheat seedlings of equivalent growth were distributed among seven petri dishes (one for the control group plus six for the experimental groups). Root lengths of the seedlings were measured and recorded on a daily basis for three days.

The results show that the control group had the greatest seedling growth and the Eucalyptus globulus alcohol group exhibited the least seedling growth. The extracts made with the ethyl alcohol solvent promoted a greater allelopathic effect on the growth of the wheat seedlings in comparison to the extracts made with the distilled water solvent. Examination under a microscope revealed that the root tips of the control group displayed far more actively growing cells than any of the test groups.