Carnegie Institution of Washington Publication Volume 314

Carnegie Institution of Washington Publication Volume 314

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1921 edition. Excerpt: ...plants had stomata half open, while those brought in were but 10 per cent. The next hour the greenhouse plants showed stomata at maximum, and the out-door plants 35 per cent opening. At 9 a. m. both groups of plants had wide-open stomata. It is evident that the stomata of wheat plants accustomed to strong light do not open as readily in difiuse light as those of plants adjusted to such light conditions. To find the effect of night illumination upon alfalfa plants growing in the field, a series was made on August 13, 1919, from midnight to 2 a. m. A 250-watt mazda light was suspended 1 meter above a plot of alfalfa and a similar one above a plot of cow-beet. The night was clear and moonlight, the average temperature during the experiment being 60F. No difference in stomatal movement could be detected between the lighted and unlighted plots, the stomata of alfalfa being 40 per cent open throughout the experiment and those of cow-beet remaining 75 per cent open during the 2 hours. Hence, it seems that the additional light was not sufficient to cause further opening in either plant, and that the amount of opening found was caused by moonlight alone. Another series was made August 23, 1919, to find the effect of such illumination on a dark night. A plot of alfalfa and one of cowbeet were illuminated from 10 p. m. to midnight and strips collected every 30 minutes. The stomata of alfalfa were closed at the start and remained closed until 11" 30'" p. m. in the dark plot. In the illuminated plot the upper stomata showed slight opening at 11 p. m. and by 12 had opened to 25 per cent. Night opening also occurred in the dark plot, but was only 5 per cent at midnight. No opening occurred in the lower stomata of either plot. In the cow-beet, more

Product details

  • Paperback | 42 pages
  • 189 x 246 x 2mm | 95g
  • United States
  • English
  • black & white illustrations
  • 1236884566
  • 9781236884565