DEVELOPMENTAL STUDIES OF ELODEA CANADENSIS MICHX: II. EXPERIMENTAL STUDIES ON MORPHOLOGICAL EFFECTS OF DARKNESS

Author:
  • HDHugh M. Dale
    Hugh M. Dale
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Abstract
A description of the morphological characteristics of sprigs grown in the dark is given. Among the factors that may be responsible for the pattern of growth there is the absence of direct light stimulus, the effect of the sugar solution, the lack of auxins, and the oxygen factor. Experimental evidence suggests that the lack of light per se has little effect upon the form of Elodea. Indole-3-acetic acid in the concentrations used indicate only a stimulation of root production. The effect of the sugar solution appears quite noticeable. Gaseous exchange in cotton-plugged flasks is of significance particularly in dim light. Also, in plants grown with and without added oxygen, in darkness and light, it has been established that the relative amount of oxygen is a major factor influencing not only the size of cells in the leaves and internodes but also the type of air space produced. Finally, changes of gas pressure within the intercellular spaces do enlarge these spaces so that lacunae can be made to occur even in the apical cone.