Mr. Francis Darwin, president of the Biological Section, read a paper by himself and Miss D. F. Pertz on "The Artificial Production of Rhythm in Plants." The paper was illustrated by experiments. The apparatus employed is a new form of klinostat designed by the Cambridge Scientific Company. The plant to be experimented on is fixed to a spindle, which, by means of a clockwork escapement, makes a sudden semi-revolution every half hour. Thus the plant is subjected to a series of alternate and opposite influences from light or gravitation, as the case may be. To take the case of gravitation, the plant will tend to curve upwards during the first half-hour, and during the second interval (when the horizontal spindle has made half a turn) it will tend to curve geotropically in the opposite direction.

Under these conditions it is found that a rhythmic state is induced which closely resembles the periodicity in rate of growth which is set up in plants by the alternation of day and night.

A remarkable result is obtained by stopping the clockwork; that is to say, by substituting a continuous for a changing stimulus. The plant continues to curve with an acquired rhythm just as if the clockwork were still in action; it has, in fact, learned and remembered the half-hourly period. This is precisely similar to certain natural rhythms - for instance, to the "sleep" of flowers, which for a short time continue to open and shut although kept constantly in the dark.

After Darwin's retirement, Pertz was encouraged by Frederick Blackman to undertake research on meristematic tissue, but after a year observing germinating seeds her results were inconclusive. She abandoned research, possibly over disappointment, though Agnes Arber claimed "she came to recognize that the plant physiology of the twentieth century was developing on lines widely divergent from those on which she had been educated and that it demanded a grasp of mathematics, physics, and chemistry, which she did not possess."

Labels: Carver, Smarty-plants

¶ 5:31 AM