An index for measuring the developmental age of a shoot, based on the number of leaves that are not less than some stated length, plus a fractional adjustment so calculated that the value of the index changes smoothly as the shoot grows.
Origin
1950s.
Definition of plastochron index in US English:
plastochron index
noun
Botany
An index for measuring the developmental age of a shoot, based on the number of leaves that are not less than some stated length, plus a fractional adjustment so calculated that the value of the index changes smoothly as the shoot grows.