Morphological studies on the regularity of shoot development in rice plants. VII. The mechanism controlling the start of internodal elongation and the regular distribution of elongated internodes on stems.

摘要

A comparison was made of the distribution of elongated internodes on main shoots and tillers of rice plants, and GA3 was applied to determine which internode primordia are sensitive to growth regulators. The main shoots had five or six elongated internodes. The total leaf number was one less on shoots with five internodes than on shoots with six internodes. The position of the lowest elongated internode was the same tillers and the main shoot, or it was one internode lower on tillers. Tillers had five or six elongated internodes. The time lag between the first bract (b1) initiation on the main shoot and the fourth tiller was estimated to be about 10 days. Primordia of GA3-sensitive internodes were positioned in the main shoots under the leaf whichwas newly emerging at the time of GA3 treatment. Moreover, at the first bract initiation stage, there were two young leaves and two leaf primordia (including b1) inside the newly emerging leaf. Hence, it was concluded that because growth substances affect the tissues of the sensitive internode primordia between the initiation stages for the flag leaf and the first bract, the number of internodes elongated consecutively is either five or six.