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Florida Department of Agriculture and Consumer Services
Adam H. Putnam, Commissioner

Experiments with germination inhibitors

Various substances produced by plants prevent the germination of seeds until conditions are favorable for this development. These substances help to insure the survival of different plant species by limiting the density of plant populations and by giving the plants that do grow from seeds a better start in life.

Various substances produced by plants prevent the germination of seeds until conditions are favorable for this development. These substances help to insure the survival of different plant species by limiting the density of plant populations and by giving the plants that do grow from seeds a better start in life. Most fruits contain such growth inhibitors which delay seed germination until the fleshy part of the fruit has decayed and the inhibitor substance has leached away into the soil. Some growth inhibitors act on the seeds of other species, thus limiting their competition for growing space.

It has been found that the seed coats of certain grasses contain germination inhibitors which can be extracted by soaking them in water over night. By pouring off the liquid and keeping it in a refrigerator to prevent spoilage, it can be used to water pots in which seeds have been planted. When these post are compared with controls, the effect of the inhibitor can be measured. Since very little work has been done with such inhibitors, this field offers excellent opportunities for original research.

In order to eliminate the possibility that fungi may affect the results of the experiments, it is suggested that all of the seeds be germinated in sand which has been boiled in water. After the same number of seeds have been planted in each pot, water the experimental pots with inhibitor water and the control plants with tap water.

Several kinds of seeds and several suspected inhibitors should be tested. Some common substances which seem to reduce seed germination are tomato juice, coumarin (an ingredient of synthetic vanilla), lemon peel, onion juice, apple cider, and the water in which carrots or spinach have been cooked. Graph paper is convenient for keeping daily records and for presenting the results in an effective way.

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