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Effect of Herbicides on lawn weeds Investigatory Project


Investigatory Project on Effect of Herbicides on lawn weeds


STUDY OF THE EFFECT OF A HERBICIDE ON LAWN WEEDS (To compare the effect of a herbicide on monocotyledonous and dicotyledonous plants)




Weeds are unwanted plants which grow in cultivated fields and compete with the useful plants for the resources. They compete for the light, space, nutrients, water and reduce the crop yield. Weeds acts as alternate host for certain diseases and these help in spreading the diseases. Many weeds cause allergy and other skin diseases in human beings. Weeds can be removed from the fields, play grounds and lawns either by mechanical or chemical method. In chemical method, certain chemicals are used to kill the weeds. These chemicals are called weedicide. The synthetic auxins like 2, 4-D (2, 4 Dichlorophenoxy acetic acid) interferes with the translocation of carbohydrate and thus kills the plants. Dicot and monocot plants respond differently to different concentrations of 2, 4-D. Specific concentrations of 2, 4 - D can destroy dicot plants, while monocot plants remain unaffected. Therefore, 2, 4 - D is commonly used as selective herbicide.

Materials and Methods


2, 4 - D, sprayer, beakers, measuring cylinder, cord, nails etc were collected. Then prepared ten gram 2, 4-D was dissolved in 3 ml of ethanol. This solution was mixed with 100 ml of distilled water. A weed growing lawn was selected for the study. A square area was masked out by using nails and cord. 2, 4 - D solution was spread over the selected area once in a week.


Observation and Results


After a few days the marked and treated area was observed. The broad leaved dicot plants showed wilting after a day or two and gradually died. But the monocot plant such as grass remain unaffected.


Discussions and Conclusions


2, 4 - D had killing effect on broad leaved dicot plants and not on monocot plants.


Model Viva Questions and Answers


1. What are weeds?

Weeds are unwanted plants which compete with economically useful plants for the resources and reduce the yield.


2. Name a few common weeds.

Amaranthus, Alternanthera, Convolvulus, crotton sps. etc.


3. What are herbicides?

Herbicides are chemical substances which are used to kill herbs.


4. Why 2, 4 - D is used as a common herbicides for lawns?

Because 2, 4 - D kills broad leaved dicot plants without affecting narrow leaved monocot plant or the grass of the lawn.


5. Name a few commonly used herbicides.

2, 4 - D, Atrazine, Simazine etc.



1. G. Ray Noggle and George J. Fritz. Introductory Plant Physiology. Prentice, Hall of India Pt. Limited. New Delhi.

2. William. G. Hopkins, Introduction to Plant Physiology. John Wiley and Sons Inc. NewYork.

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