A new plant growth stimulant
FORWARD
The purpose of writing on this topic is twofold. First of all, it aims to draw the attention of the scientific community to the very real possibility of the stimulating effect of stearic acid on plants.
Second, publication of these results should make them available for further evaluation of the potential benefit of using this material in stimulating plant growth.
INTRODUCTION
Stearic acid is one of a group of long-chain fatty acids found in plant and animal cells. It occurs very widely in nature, most often being incorporated into triglycerides.
It is a solid, a white amorphous powder. Other physical properties include a molecular weight of 248.47; density 0.747 gms./ml.; melting point 393 degrees centigrade and solubility 0.034 gms. in 100ml. of water.
It is known to have surface-active properties, being only slightly soluble in polar and non-polar solvents. Due to its surface-active properties, it has been widely used in the manufacture of soaps and detergents. It is also known to promote the growth of some soil organisms, such as bacteria.
EXPERIMENTAL
This report describes the results obtained on five different varieties of vegetable plants and one flowering plant, to illustrate the possible overall effectiveness of plant growth stimulation.
Other types of affected plants have also been observed to grow at a faster rate after treatment with stearic acid.
These affected plants include the following: A Pereskia (“lemon vine”) cactus had been growing very slowly for three months. After treatment, it grew to over fifteen feet long, over a period of five months. A two-year-old Swedish ivy plant had leaves on new growth twice as large as the older leaves, beginning two months after treatment began.
Finally, six months after treatment, a hibiscus plant, which was a cutting from another plant, had outgrown its untreated parent.
Tomatoes and other vegetables (radish, broccoli, cabbage) and cactus plants were also observed to be stimulated to a higher rate of growth by using stearic acid alone, leading to this claim that it is a general stimulating agent. of plants.
Test results on beans, squash, carrots, red beets, corn, and marigolds are reported here. Only stearic acid powder was used to treat the plants. Control plants were not treated. No additional irrigation was used in an outdoor garden. Only the normal amount of rain reached the plants.
The method used was to place about two grams of stearic acid powder under the soil, close to the plant, when the plants were two to three weeks old and had developed true leaves. This has been found to be a necessary procedure, because when the seeds were planted in soil that had already been treated with Stearic Acid, a reduction in the number of seeds germinating was observed.
In a separate experiment, when pea seeds were placed in water containing some stearic acid, the seeds swelled and burst within three to four days; resulting in a white, gelatinous mass. Seed treatment with stearic acid appears to negatively affect the speed of seed germination.
The somewhat reduced amount of germination that has been observed, plus the definitely slower growth rate of most of the treated seedlings, confirm the need to add stearic acid after the plants have advanced beyond the seedling stage, to obtain the maximum benefit from this method of treatment.
SUMMARY OF RESULTS
The yield of bean plants treated with stearic acid was almost double in terms of number and weight of pods per plant, compared to untreated plants. Fifteen plants were tested both control and treated. The mean number of pods/plant was 14 for control plants and 25 pods/plant for treated plants.
In carrot, an increase of 30% in the average root weight was obtained; which was the smallest yield increase obtained in this test. Twenty plants, both control and treated plants, were tested. The average weight of the controls was 31 grams, and for the treated plants an average weight of 40 grams was obtained.
Red beet showed 60% more weight for treated plants, compared to controls. Eleven control plants and eleven treated plants were tested. The mean weight of the control plants was 168 grams, while the mean weight of the treated plants was 385 grams.
Pumpkin plants were stimulated to produce fruit that was twice as large for treated plants compared to controls. Twelve plants, both control and treated plants, were tested. The average weight of the control plants was 1.5 pounds, while the fruit weight of the treated plants was 3.0 pounds.
Treated Marigold plants were twice as large and had twice as many flowers, compared to control plants. The average height of twelve controls was 6 inches. The height of the treated plants was 12 inches.
Control plants had an average of 10 flowers, while treated plants had an average of 20 flowers.
Corn gave very different results, producing even less average weight per ear for treated plants, compared to controls. Since only 2 or 3 ears per plant were obtained, the largest ear from each plant was weighed. Twelve plants were measured. The mean weight of ears from the controls was 162 grams, while the mean weight of ears from the treated plants was 144 grams. The conclusion reached was that no effect of Stearic Acid was observed on corn.
DISCUSSION
As stated above, subsequent tests confirmed that the most suitable time for application was about a week after germination; for bean plants past the seedling stage.
During the course of other tests, some of the same plant varieties that were stimulated were found to have inhibited growth if an excessive amount of stearic acid was used (radish, red beet, and cabbage). This effect occurred when an excessive amount of powdered material was placed on the ground around potted plants in a greenhouse.
Consequently, this treatment method is not recommended for houseplants or other potted plants. Watering with a saturated solution of stearic acid may be more beneficial in this case.
Similarly, it is speculated that a buildup of this material could occur in outdoor areas used for commercial growing after years of use, resulting in poor seed germination and loss of plant vigor. Therefore, an evaluation of a fumigation program during the growing season might give better results; in addition to requiring less material and, as a result, less expense.
This procedure is also suggested due to the possibility of formation of metallic salts of this compound by chemical fertilizers or enriched soils. This occurrence could then interfere with the expected beneficial effects of free stearic acid.
A PROPOSED MECHANISM OF ACTION OF STEARIC ACID IN PLANTS
Since the plant only absorbs the amount of stearic acid dissolved in water, the amount used by plants must be very small. The solubility of Stearic Acid in water (0.034 grams/100 ml. of water), indicates that only a small amount would be added to the plant to exert a stimulating effect.
This suggests that it is possible that this material is a plant hormone. Since hormones are known to stimulate enzymes, it would be desirable to determine which enzyme system might be affected.
The plants shown stimulated in this report (beans, red beets, for example), are known as type C-3 plants; while corn, which was not stimulated in these tests, is known as a type C-4 plant. The mechanism of action of Stearic Acid, then, could be in its effect on one of the different metabolic pathways that distinguish these two types of plants.
Type C-3 plants are those that operate by the Calvin Cycle of photosynthetic reactions, while type C-4 plants are those that have different intermediates in the cycle of photosynthetic reactions. C-3 plants use 3-phosphoglyceric acid as a product of carbon dioxide fixation.
C-4 plants use malic, aspartic, and oxaloacetic acid as products of carbon dioxide fixation. These two systems also use different enzymes to produce these acids.
Thus, it is proposed that the mechanism of stimulation in an enzyme system by stearic acid is in the Calvin cycle of photosynthetic reactions. Specifically, the rate-limiting step of carbon dioxide fixation, in which ribulose 1,5-diphosphate is converted to 3-phosphoglyceric acid; It is proposed that the affected system is a reaction catalyzed by reibulose 3,5 bisphosphate carboxylase.
An additional consideration might be to try to determine why so much of this enzyme is present in the leaf tissue (40% dry weight). Enzymes are generally present only in small amounts, and their activity is limited by the amount of available substrate.
The amount of carbon dioxide in the substrate appears to be an important limiting factor in the activity of this enzyme. This might suggest a reason for the large amount of enzyme present: to ensure that all available carbon dioxide is readily used by the plant. Another possibility may be that early in the evolutionary history of plants, there was probably a quite different atmosphere, with an abundance of carbon dioxide, which would have been more readily utilized by plants with an abundance of the enzyme.
Therefore, it would seem that to more effectively increase the growth rate of plants, carbon dioxide and stearic acid, used together, would be an even more advantageous method of treatment. Of course, the enclosed area of a greenhouse would probably be necessary to retain the excess carbon dioxide released into the atmosphere.
CONCLUSION
A summary of the observed effects of stearic acid on plants shows that it stimulated C-3 type plants; it is more effective at lower concentrations than a saturated water solution and can even inhibit plant growth when a large excess of the acid is used.
In addition to the experimental results recorded here, all other observations were made by visually comparing the size of the treated plants with the controls.
Therefore, it is proposed that the observed stimulant effect of stearic acid is due to its hormone-like effects in plants.
It is possible that the many variables that are obtained in the environment can affect the result of any test program.
But it remains the assertion of this author that the observed results were obtained and are sufficient to validate the claim made here about the stimulating effect of stearic acid on plants.