Project Abstract

    The word allelopathic means the effect of one plant species from nature on another, be it in a harmful or in a beneficial way. There is evidence that the ground below pine trees contains a high level of acid, which inhibits the growth of grass and other vegetation. The high level of acidity is likely related to some of the chemical compounds that can be found in pine needles. 

    This indicates that the chemical compounds could theoretically be extracted from the pine needles and used on unwanted grass and weeds as a natural herbicide. In order to do this, pine needle composition was researched, and it was discovered that pine needles contain polyphenols and monoterpenes, both of which have been connected with the inhibition of the growth of some plants. Fresh pine needles were then broken down and the compounds extracted with either ethyl acetate or water, and tested on dandelions and grass. Isopropanol was added to the ethyl acetate extracts, as they were not of appropriate consistency to spray on plants. Several different concentrations of each extract, a 5:1 water to isopropanol blank solution as well as a synthetic herbicide were tested for comparison. Grass and dandelion seeds were tested with the same concentrations and conditions to see if these compounds would inhibit germination. 

    The lower concentration of the ethyl acetate extracts killed several of the dandelions and some of the grass it was tested on. All of the concentrations inhibited the germination of grass and dandelion seeds, however the ethyl acetate extract suspended in isopropanol/water yielded ambiguous results; the isopropanol/water test inhibited germination itself. 

    From this data, it was concluded that there are many other tests and proceedings that might aid this experiment, and that this theory is still plausible. The monoterpenes and polyphnols may be masked by other compounds in the extraction process, or the concentrations of the liquids may not have been strong enough to cause much harm. Although this experiment did not produce a concrete herbicide, a potential natural herbicide can be produced from pine needles. 

  By: Ashlea Wilmott