Effects of Herbicides on Raphanus sativus Plant Growth Allison Paige Provey Undergraduate Student (Biology, Pre-Pharmacy) Department of Biology Tennessee Tech University Cookeville, TN 38505

Introduction Herbicides are defined as any chemical substance that is used to destroy or inhibit the growth of plants, mostly weeds.Herbicides are defined as any chemical substance that is used to destroy or inhibit the growth of plants, mostly weeds. They can be divided into two different categories; selective and non-selective herbicides (McCourt 2005).They can be divided into two different categories; selective and non-selective herbicides (McCourt 2005). 2,4 dichlorophenoxyacetic acid or 2,4-D is a common selective herbicide that is toxic to plants, but less harmless to grasses (Winder 2006).2,4 dichlorophenoxyacetic acid or 2,4-D is a common selective herbicide that is toxic to plants, but less harmless to grasses (Winder 2006).

Introduction  The reason some plants are able to overcome elimination by inheriting herbicide tolerance or resistance, which is the ability of a species to survive following a herbicide treatment (Ward 2006).  The wild radish population is phenoxy herbicide resistant (Pryor 2002). Meaning, it can survive the toxins of the herbicide 2,4-D.

Objective/ Hypothesis My objective was to see how plants will react once specific herbicides are added during germination.My objective was to see how plants will react once specific herbicides are added during germination. My hypothesis is that at least one of the radish plant groups will have a hormetic effect.My hypothesis is that at least one of the radish plant groups will have a hormetic effect. My null hypothesis is that none of the groups will have a beneficial effect.My null hypothesis is that none of the groups will have a beneficial effect.

Methods and Materials Eleven cups prepared for planting; each cup had the same amount of potting soil and radish seeds added to it.Eleven cups prepared for planting; each cup had the same amount of potting soil and radish seeds added to it. According to Manuja (2005), packing the soil down onto the seed could cause problems in the sprouting processAccording to Manuja (2005), packing the soil down onto the seed could cause problems in the sprouting process Plants were watered consistently, until germination occurred.Plants were watered consistently, until germination occurred.

Methods and Materials  2,4-D herbicide concentrations were prepared with appropriate mix of clean, diluted water and the herbicide.  The mixtures were then applied to the specific plant groups (Exp: herbicide mixture 1 only for plant cup #1)  Plant cup #11 was the control group, and it was given no herbicidal concentrations.

Methods and Materials Table ,4-D Herbicide Solution Mixtures Solution #110%= 1.6 ppm 2,4-D Solution #220%= 3.1 ppm 2,4-D Solution #330%= 4.7 ppm 2,4-D Solution #440%= 6.2 ppm 2,4-D Solution #550%= 7.8 ppm 2,4-D Solution #660%= 9.4 ppm 2,4-D Solution #770%= 10.9 ppm 2,4-D Solution #880%= 12.5 ppm 2,4-D Solution #990%= 14.0 ppm 2,4-D Solution #10100%= 15.6 ppm 2,4-D Solution #11No herbicide added

Methods and Materials  Over the next six weeks, the plants were watered and observed.  After the growth had occurred in all the plants, the height and weight was measured for each plant.  The recovered data from this experiment was then recorded, and determined that the hypothesis was accepted.

Methods and Materials Plant Group #2- 3.1ppm Controlled Plant Group- No herbicide

Results As I had expected some of the plants did show some beneficial effects with the addition of 2,4-D herbicide.As I had expected some of the plants did show some beneficial effects with the addition of 2,4-D herbicide. Group #2 (3.1 ppm herbicide) grew to average height of 4.18cm, while the controlled group only grew to 3.75cm.Group #2 (3.1 ppm herbicide) grew to average height of 4.18cm, while the controlled group only grew to 3.75cm. Group #3 (4.7 ppm herbicide) weighed in at 1.9 grams and the controlled group weighed only 1.6 grams.Group #3 (4.7 ppm herbicide) weighed in at 1.9 grams and the controlled group weighed only 1.6 grams.

Tables and Graphs

Discussion  After performing this experiment, I confirmed Winder’s statement that the herbicide 2,4-D is indeed a selective herbicide.  Raddish plants must inherit some herbicide tolerance and resistance, because the harmful effects were limited in this case.  The remark from Pryor supported my hypothesis, that at least one of the radish plant groups would have a beneficial effect from the herbicides.

Conclusions  I concluded that with the addition of certain herbicide concentrations, radish plants can have a hormetic or beneficial growth effect.  The results indicated that the plants in Group #2 (3.1ppm) and Group #3 (4.7 ppm) had significantly more growth over the controlled group in height and weight.  Therefore, the hypothesis that at least one group would have a hormetic effect, was proven true and the experiment rejected the null.