The Allelopathic Properties of Black Walnut Hulls

Overview

Objectives/Goals Black walnuts (Juglans Nigra) are allelopathic trees that release toxic chemicals to poison neighboring plants. The purpose of my project is to observe the effects of black walnut hulls on seed germination and radicle growth and to find out if different concentrations of black walnut extract will prevent seeds from germinating in my garden. Methods/Materials Ten seeds of seven plant species were placed in petri dishes with 5 ml of the different test solutions (1%, 2.5%, 5%, 10%, 20% concentration of black walnut hull extract) and a control with only distilled water. This dose/response bioassay was replicated 5 times. Seed germination rate, radicle length, germination index, toxic concentration (TC-50), and variance were calculated after seven days. Results Seeds in the control plate germinated faster and grew longer roots. Lettuce, cabbage, tomato, and beet were the most susceptible to juglone, the toxic allelochemical released by black walnuts. Radish and onion were more tolerant to juglone and their germination was not inhibited but may have been delayed (smaller roots and cotyledons), garden bean was the most resistant to black walnut hulls. Conclusions/Discussion The hypothesis that lettuce, radish, garden bean, tomato, cabbage onion, and beet seeds won#t germinate or grow as well when in contact of black walnut hull extract is supported by the data. The general trend showed that toxicity of the test solution increased with higher concentration. However, some plants might be more resistant (garden beans) or tolerant (radish and onion) to black walnut hulls. This experiment is relevant to landscapers and gardeners to assure survival of plantings. A research on the active compounds of black walnuts can help develop natural herbicides for farmers.

Competition history

• CSEF 2013 Pharmacology/ Toxicology · Entry J1708

Resources

• CSEF project summary ↗

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