Department of Agriculture, Annamalai University.
Observation on the extension growth of shoots of certain species and varieties of citrus, within a year after planting in the Experimental Orchard of the Annamalai University Agriculture Department, during the rainy seasons of 1956 showed a definite cyclic pattern of growth ie, a period of growth alternated by a period of no growth or quiescence.
Between August 29th and December 12th, there were two distinct cycles or periods of shoot growth; and the daily increment of growth in the second cycle was generally more than in the first cycle.
There was wide variation in the date of initiation duration, and cessa-tion of shoot growth among the species and varieties.
It has also been brought out that there are differences in timing of the cycles of growth between those under tropical conditions such as around the Annamalai University and those under sub-tropica] conditions prevailing in Arizona and southern California, which have been explained in this paper.
It has also been observed that the sum total of shoot growth in each variety and species increased with the accumulated rainfall
