AOH :: MARTIN.TXT|
Borderland: Cress seedlings response to light
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,
1) Comparing the growth of cress seedlings kept in the dark against those in
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
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
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. 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
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
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
Six "roots" had penetrated through all four layers of tissue to the saucer
5) Seedlings kept in the dark and grown with plant food contained in the
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.
How Grown Average length Range Roots Degree
of seedlings (cm) penetrating of lean
In light 5.1 4.0 8 10-50
In dark 4.7 3.0 0 0 With
slit 5.0 2.5 5 10-40
Diluted food 6.1 5.5 6 0
Straight food 0.0 0.0 0 0
Discussion/conclusions: Plants, or at least seedlings, do not need light to
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
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
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. Homeopathy for Everyone by Drs. Sheila and Robin Gibson
(Penguin, 1987) 2. Constable, T.J., "Fine Forces and the Plant", Journal of
Borderland Research, Vol. XLIII, No. 2, March-April 1987.^Z
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