Willow tree experiment

This view is illustrated by Helmonts famous willow tree experiment. A small willow tree weighing five pounds was planted in a tub of earth weighing 200 pounds. For five years nothing was added to the soil but water. At the end of that time, the tree had grown to weigh more than 150... 

It is possible to identify several apparently disconnected themes which led ultimately to the analysis of the chemistry of living cells. Perhaps the first biochemical experiment in Europe may have been that of van Helmont (1579-1644), a physician with a profound interest in chemistry. He grew a willow tree in a weighed amount of earth, watered it for five years and then weighed the earth and the tree again. The... 

At a time when measurement and experiment were just beginning to define science, Van Helmont performed his famous tree experiment. He believed that there were only two true fundamental elements, water and air, and that trees were composed of the element water. To test this hypothesis, he weighed 200 pounds of dried earth, moistened it with distilled water and added the stem of a willow tree weighing 5 pounds. After five years of judicious watering he determined that the tree weighed 169 pounds, the soil, when separated and dried, still weighed 200 pounds and, thus, the extra 164 pounds could only come from addition of the element water. ... 

Indeed, the work shows that Boyle was enthralled with many Helmontian experiments, particularly that of the willow tree, which was supposed to show that all vegetables mm into water. His alter-ego Cameades carried out similar experiments that confirmed Van Hehnont s observations. He also paid close attention to Van Helmont s account of a wondrous solvent, the Alkahest, which was supposed to dissolve all bodies into water. Although Cameades admitted that he had not made the Alkahest, his interest in the subject suggests that he was inclined to believe in it [34]. As pointed out above, the acceptance of the Helmontian view that there is a universal solvent that could transform everything into elementary water implied an automatic rejection of the tria prima. 

Due to the very poor performance of the Insects in the field, as had been noted in the alder experiment above, the test trees were reloaded with an average of 8.0 1 1.0 (S.E.) additional colonies of tent caterpillars, obtained from alder, since none were available from willow, on May 22. These additional colonies were mainly in the 4th and early 5th Instar, whereas the original larvae hatched on the trees were still mainly in the third Instar. Thus, at the time of reload, the trees experienced a large... 

It is possible that the rapid drop in biomass of the assay Insects feeding on leaves from attacked and control trees coincided with reload of the test trees by chance, possibly due to the rapid spread of a pathogen through the laboratory Insect population (11). On the other hand, the possibility that reload of the test trees caused the biomass drop in both test and control assay Insects cannot be discounted. Both attacked and nearby unattacked control willows may have rapidly decreased the food quality of their leaves in response to a sudden Increase In biomass of Insects on the attacked trees. If so, this suggests that unattacked willows are sensitive to signals from the Insects or nearby attacked willows. This possibility was investigated in the following experiment. 

Leaf quality of the four groups of trees before and after load was compared by measuring the relative growth rates of web-worm larvae (14-20 larvae per replicate, one replicate per tree) fed leaves from the assay branches over a one to three day period In the laboratory (Figure 3). These assay larvae were collected from alder and fed willow for two days prior to the feeding experiments. Since mass changes of starved Insects were not measured. 

Higher growth rates of the larvae fed leaves from willows at the airport site than those fed leaves from willows at the Kent site, throughout the experiment, show that significant and fairly constant differences in leaf quality can exist between trees at different sites. Normalized relative growth rates of webworms fed detached leaves in the laboratory were similar to those obtained by growing webworms on the trees. 

On the other hand, no differences were found in growth or mortality of tent caterpillars fed leaves from unattacked willows compared to those fed leaves from willows attacked by tent caterpillars (Figure IB). Reload of the attacked trees with additional tent caterpillars coincided with a rapid decrease in biomass and an increased mortality of Insects fed leaves from both attacked and unattacked control trees. This could have been by chance, but it suggested the possibility that both attacked and control trees exhibited a rapid decrease in food quality in response to the addition of more insects to the attacked trees. If so, this suggested that unattacked willows were sensitive to signals from nearby attacked willows or the attacking Insects. An experiment to test this hypothesis produced positive results (Figure 2). 

As regards tannin, the parts of the cortex, or true bark, in which it is mostly contained, are the exterior layers of the portion known as the liber, and the interior of the cortical tissue—the inside portions of the former, and the most exterior of the latter, yielding very little of this principlo. The same observation is true of other matters, such as quinine and the like. The various dyCB are seated frequently in the exterior portion of the cortical tissue. The sap always ascends through the cellulose of the real hark and as this fluid is the source from which tannin is socreted, it is evident that thcrO will be more of it in the bark, when the flow is greater than at other periods. Experiments have proved this to bo the caso as regards oak, and the same observation applies to the barks of other trees, such as the willow, elm, pine, birch, bcecli, et cetera, with equal force.. ... 

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