This stage may begin before panicle initiation or it may occur during the latter part of the tillering stage. Thus, there may be an overlap of stages 2 and 3.
The tillers continue to increase in number and height, with no appreciable senescence of leaves noticeable. Ground cover and canopy formation by the growing plants have advanced.
Growth duration is significantly related to stem elongation. Stem elongation is more in varieties with longer growth duration. In this respect, rice varieties can be categorized into two groups: the short-duration varieties which mature in 105-120 days and the long-duration varieties which mature in 150 days.
In early-maturing semidwarfs like IR64, the fourth internode of the stem, below the point where the panicle emerges, elongates only from 2 to 4 cm before panicle initiation becomes visible. This slide shows stems which have been dissected to show the length of the fourth internode at the panicle initiation stage.
Maximum tillering, stem elongation, and panicle initiation occur almost simultaneously in short-duration varieties (105-120 days).
In long-duration varieties (150 days), there is a so-called lag vegetative period during which maximum tillering occurs. This is followed by stem or internode elongation, and finally by panicle initiation.
