Yoshida - 1981 - Fundamentals of Rice Crop Science

2 FUNDAMENTALS OF RICE CROP SCIENCE
1.1. Life history of a 120-day variety grown in the tropics under the transplanting cultivation
system (schematic).
the increase in tiller number per unit of time — is high. The maximum tiller number
stage follows active tillering. It is a stage when tiller number per plant or per square
meter is maximum — before or after the initiation of panicle primordia, depending
on a variety's growth duration. Because tiller number declines after the maximum
tiller number stage, there is a period before that stage (often called the end stage of
effective tillering) when the tiller number becomes numerically equal to panicle
number at maturity. That does not necessarily mean that tillers developed after the
end stage will not bear panicles. But tillers developed at early growth stages
normally produce panicles, while those developed later may or may not.
The reproductive growth stage is characterized by culm elongation (which
increases plant height), decline in tiller number, emergence of the flag leaf (the last
leaf), booting, heading, and flowering. Initiation of panicle primordia usually
dates back to about 30 days before heading. 1
Agronomists often refer to topdressing nitrogen fertilizer at panicle initiation –
a stage about 25 days before heading when the panicle has grown about 1 mm long
and can be recognized visually or with a magnifying lens. But initiation of panicle
primordia can be recognized only under a microscope. Internode elongation
1 Detailed studies have been done on development of rice panicles in Japan, which is in the temperate region
(Matsushima 1970). The results of these studies should perhaps be applied to tropical regions since temperature,
which is considered to have a great influence on initiation and subsequent growth of the panicle, is similar during the
reproductive growth stage in the temperate region and the tropics.