ANNUAL GROWTH PATTERN OF THE TERMINAL SHOOT IN YOUNG TREES OF Pinus patula

Abstract

Pinus patula Schl. et Cham is a subtropical pine widely used in forest tree plantations. This species shows a relatively complex annual pattern of shoot growth, which might influence both productivity and adaptation on sites outside its natural distribution range. In order to determine the relationships between the annual growth pattern in the leader shoot and its components, leader elongation was periodically measured during two growing seasons in 101 four-year old saplings planted at Lomas de San Juan, State of México. The terminal shoot had a similar average number of growth cycles (4±1) during both years, but total length of the shoot and the average length of the growth cycles were drastically reduced during the second season. The growing season in the second year (1992) lasted over 300 days, and growth cycles overlapped in time, with durations ranging from 110 to 255 days and growth rates from 0.67 to 1.24 mm day-1. In both seasons, the main components of the annual shoot length were the length of growth cycles (r³0.70**) and the total number of stem units (r³0.76**). The number and length (distance) of stem units were negatively correlated (-0.26**>r>-0.51**).