| Abstract: | The earlier literature on thermonasty is summarized, and itis confirmed that these movements are due to different growth-rateson the two sides of the perianth members. The underlying mesophyll cells are chiefly concerned; thoseof the outer surface have a temperature optimum for growth about10° C. lower than the corresponding cells of the inner surface. The percentage elongation of complete tepals is shown to begreater than that of separate tissue strips, and this differenceis shown to result from the change in internal CO2 concentration. Increasing the CO2 concentration causes a marked cell extensionand a lowering of the temperature optimum for growth. This effectappears to be closely related to respiration. |
