Abstract
The behavior of stomatal opening in the field-grown tobacco (Bright Yellow variety) was investigated by silicone rubber method. The results obtained are summarised as follows: (1) In the immature leaves with deep green color, the stomatal opening showed a diurnal change with the maximum aperture at 12 a. m.. In the mature leaves with light green color, on the oher hand, the stomata remained closed throughout day and night. In addition, more immature leaves had longer hours of stomatal opening in a day. (2) The stomatal aperture of tobacco leaves in the mid-day (about 11 a. m.) was observed every day in order to examine the time course of change on the stomatal movement after topping. In the early mature stage, the active stomatal movement in response to the change of environmental condition occurred in each position on stalk. After the leaves attained maturity, the stomata lost their active movement and remained almost closed. In the cutter leaves, the stomatal closre occurred around the time when the leaves became suitable for priming. In the smoking and tip leaves, on the other hand, it occurred about a week before priming.
