Abstract
The relation between tiller age 'Yourei' and panicle growth stage (PS) in each tiller was investigated. Yourei is a scale of plant age expressed by leaf number. The first decimal place indicates the ratio of the length of the emerged part of the expanding leaf blade to its expected final length. Plants (cv. Sasanishiki, 3 plants/pot) were sampled at the panicle formation stage and observed under a dissecting microscope. For analysis we used the complementary age-scale Ho-Yourei (cA) which counted backwards from the flag leaf that just expanded (cA=LN-A, where LN is the total number of leaf on the tiller and A is Yourei). Panicle formation stage (from the differentiating stage of the flag leaf primordia to the late differentiating stage of flower primordia) was divided into 12 stages (pS 1∼pS l2). Variances of PS or cA in individual plants increased with time. The relationship between PS (y-axis) and cA (x-axis) is represented by the equation y=15.95-3.74x. In each tiller (LN=4 to 15), when half of the fourth leaf blade (counted from the flag leaf) expanded (cA 3.3∼3.6), the tiller began to initiate its panicle (PS 3: the increasing stage of bract primordia).
