Yoshida - 1981 - Fundamentals of Rice Crop Science

GROWTH AND DEVELOPMENT OF THE RICE PLANT 21
1.19. Cross section of the left sheath (adapted from
Hoshikawa l975).
emergence is affected by temperature: an increase in temperature speeds leaf
emergence. In terms of the temperature summation index (see page 45). the
development of one leaf requires about 100 degree-days before the initiation of
panicle primordia and about 170 degree-days thereafter. Thus. when the rice plant
is grown at 20°C, leaves emerge every 5 days (100 degree-days/20°C = 5 days);
when it is grown at 25°C, they emerge every 4 days before panicle primordia
initiation. Leaves elongate quickly after emergence, complete their elongation,
and start functioning.
The life span of individual leaves after elongation differs widely among leaves
(Fig. 1.20). Upper leaves have longer life spans than lower ones; the flag leaf ha:,
the longest life span. From the initiation of panicle primordia to around heading,
the rice plant usually has five leaves that are functioning.
The rate at which the weight of individual leaves increases follows patterns shown
in Fig. 1.21. Leaf weignt increases sharply, reaches the maximum, and declines.
1.20. The life span of individual rice leaves (adapted from
Arashi 1955).