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How Cress Seedlings Respond to Light and "Feeding"

by Simon Martin, 140 Addison Road,
Guildord, Surrey, England GU1 3QF

ABSTRACT: Cress seedlings grown in daylight leant towards the source of the light. Seedlings grown in the dark grew longer on average, and did not lean in any particular direction. Seedlings grown in the dark and watered with extremely diluted commercial plant good grew longer still, while cress seedlings placed in material plant food failed to germinate.

Objective: To find out whether light is essential for the growth of plants, by

1. Comparing the growth of cress seedlings kept in the dark against those in the light;
2. Seeing whether seedlings "follow" light; and
3. Comparing the growth of cress seedlings kept in the dark and given two different versions of natural-source plant food composed of a balance of nitrogen, phosphorus and potassium.

Procedure: As outlined in the instructions, but with the addition to two more saucers to test the outcome of adding plant food.

The food used was "Back to Nature" commercial food produced by Pan Britannica Industries Limited. It is a mixture of entirely organic and natural ingredients, including manure, bone meal, bone flour and seaweeds. The mixture contains nitrogen (N), phosphorus pentoxide (P2O2) and potassium oxide (K2O) in a balanced ratio of 7.3:5.0:5.2.

In one saucer, one dessertspoonful of this food was taken straight from the packet and sprinkled on two thicknesses of paper towel. This was then folded over to make a "sandwich" of plant food with two thicknesses of paper on each side. The cress seeds were sprinkled on top and watered like the others.

Another saucer of cress seeds was prepared according to the instructions, but instead of being watered with ordinary tap water (as the rest of the seeds were), in this saucer they were watered with "homeopathic" * plant food in a "5x" dilution.

This was prepared by taking one dessertspoonful of the plant food and mixing it with one pint of water. Nine-tenths of this liquid was discarded, and the remainder was topped up to one pint and vigorously shaken. This procedure was repeated another four times.

The resulting liquid was used to water one saucer of seedlings.

* Homeopathy is a system of medicine developed by the German physician and chemist Dr. Samuel Hahnemann (1755-1843) and still in use today. One of its main principles is the use of remedies of vegetable, mineral, animal or human origin that are extremely diluted with water and alcohol.

Many of the most effective remedies today used by homeopathic practitioners are diluted beyond the limit at which it is accepted that a single molecule of the original substance can remain (Avogadro's Limit).

Homeopathy maintains that the vigorous shaking, or "succussion" applied in the preparation of these substances "potentises" the material in some way as yet unknown.

One explanation, proposed by Drs. Robin and Sheila Gibson of the Glasgow Homeopathic Hospital, is that the energy of succussion imposes a pattern on the otherwise seemingly random arrangement of molecules of water (H₂O) (1).

Trevor James Constable has suggested that plants are better able to take up nutrients if they are supplied in "homeopathic" form, because they are less dense and heavy and do not need any further breaking down, or "digesting" before becoming available for the plant to take up (2). Constable proposed testing this hypothesis with germinating seeds.

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Results:

The seedlings were examined after 14 days.

1) Seedlings grown in light.

These were the healthiest looking of all, with dark green petals and greenish-white stems that were whitest at the tissue paper. This crop showed a marked leaning towards the light, ranging from 10o to 50o. The angle of lean was greater the nearer the seedlings were to the light. Length of seedlings varied from 2.5cm to 6.5cm, averaging 5.1cm. 8 "roots" had penetrated through all four layers of tissue paper to the saucer beneath. One of them was 4cm long.

2) Seedlings kept in the dark.

These had yellow petals and white stems. There was no discernable leaning in any particular direction. Length of the seedlings varied from 3cm to 6cm, with an average of 4.7cm. No "roots" appeared to have penetrated the tissue paper.

3) Seedlings exposed to light from one direction.

Colouring was similar to group 1, but less distinct. The green of the petals was slightly lighter, and the stems were only tinged with green near the petals, becoming white approximately O.5 cm (on average) away from the petals. When uncovered they were not leaning towards the light, except for a small cluster of seedlings at the very mouth of the slit. These were leaning towards the light at angles between 10o and 40o, which was less pronounced than the leaning of the seedlings grown in full light.

These seedlings ranged in length from 3cm to 5.5cm, with an average of 5cm. This is almost the same average length as the seedlings grown in full light, but with noticeably less range of growth.

Five "roots", one of the 3cm long, had penetrated the tissue paper to the saucer.

4) Seedlings kept in the dark and watered with "homeopathic" plant food.

Bright yellow coloured petals with white stems, these were not only noticeably longer than the other seedlings, but also had grown more uniformly straight. Length ranged from 2.5cm to 8cm, with an average of 6.1cm.

Six "roots" had penetrated through all four layers of tissue to the saucer beneath.

5) Seedlings kept in the dark and grown with plant food contained in the tissue paper.

These seeds failed to germinate. They were still brown in colour and were soft. Some of them had mould on them. The fertiliser underneath was completely covered with grey-blue hairy mould and there were mould spots showing through the upper layer of tissue behind the seeds.

Summary table:

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Discussion/Conclusions: Plants, or at least seedlings, do not need light to grow.

The experiment surprised me on three main counts. I thought the seedlings grown in the dark would turn out to be much longer than those grown in light. I expected the seedlings exposed to light from one direction to lean towards it much more obviously; in fact the seedlings grown in full light showed more lean. Thirdly, I did not expect the seedlings grown with plant food to fail so spectacularly.

Some of these effects may have been caused by the density of the seeds. I should have used exactly the same amount for each saucer, instead of approximating, and I should have arranged them on the tissues in a pattern that allowed adequate space and stopped "clumping".

Why did the seedlings placed on a "sandwich" of plant food fail to germinate? By the end of the experiment mould was growing on the plant food. Perhaps the moulds released substances that poisoned the seeds. It seems that the mixture contained in the tissues held too much moisture. This was worsened by this particular saucer being farthest from the radiator and also suffering by a huge pile of books and papers which progressively grew during the experiment, ultimately blocking the other source of heat -- the modest amount of winter sunlight that was falling on the other saucers.

While the "homeopathic" sample grew the tallest, the healthiest looking plants were the ones grown with access to light. And of these two samples, the greenest were the ones given full access to light. Is this because the seedlings were able to produce chlorophyll?

These seedlings were also the most vigorous, judging by the number of "roots" penetrating through the four layers of paper towel. However the resistance of the towel is not constant, varying with the amount of water used, for one thing.

Although it seems that all the nutrients required for growth are contained in the seeds, I can't help wondering how the "greenness" of the seedlings relates to the relative amounts of nutrients available to promote human growth. For instance, I would like to be able to check the nutrient contents of the homeopathic seedlings and the green ones (for vitamin C, for example).

I was surprised that the seedlings exposed to light from one direction showed less "lean". I made the slit a full centimetre (1cm) wide rather than the suggested 3mm-5mm wide, but I would have expected this to improve the chances of the lean showing up, since a smaller slit would be likely to become blocked by the seedlings growing closest to it. This could easily be checked by repeating the experiment with smaller and larger slits in the containers.

The seedlings grown in full "light" were actually given a mixture of light from moderately dirty glass windows and/or from electric light bulbs received through a clear plastic cover which itself had a slightly blue tinge to it. In no sense could any of this light be described as full-spectrum, and it would be interesting to grow seedlings in a variety of lighting conditions, ranging from daylight with no glass or other material in the way, and (say) red light, blue light and "electric" light.

References

1. Gibson, Sheila, and Robin Gibson. Homoeopathy for Everyone. Penguin, 1987. Print. <http://amzn.to/1F60YxW> [Re-ed., 1991: <http://amzn.to/1zK4jTk>]
2. Constable, Trevor J., "Fine Forces and the Plant". Journal of Borderland Research 43:2. Print. <Index>