Yoshida - 1981 - Fundamentals of Rice Crop Science

42 FUNDAMENTALS OF RICE CROP SCIENCE
1.38. Variations in daylength at different northern latitudes.
b. Basic vegetative phase. The vegetative growth stage is divided into the basic
vegetative phase (BVP) and the photoperiod-sensitive phase (PSP).
Because the very young plant is insensitive to photoperiod, the early growth
stage that must occur before floral initiation can be triggered by short days has been
termed the BVP. The length of the BVP ranges from 10 to 63 days; a BVP longer
than 100 days has not yet been found in rice varieties. One simple way to estimate
the BVP is to subtract 35 days from the growth duration (days to flower) at the
optimum photoperiod, i.e., the shortest growth duration. This assumes that the
period from the initiation of panicle primordia to flowering is 35 days (Vergara and
Chang 1976).
c. Photoperiod-sensitive phase. After the BVP, the plant enters the PSP during
which floral initiation can be triggered by short days. The PSP of photoperiodinsensitive
varieties is less than 30 days; that of sensitive varieties, longer than 31
days.