Seasonal variation in radial growth and phloem activity of Terminalia ivorensis A. Chev

Abstract

Radial growth in five Terminalia ivorensis trees has been recorded from dendrometer reading for a period of 12 months. The duration of the growing season was 7-9 months. Variation in annual radial increment between individual trees was observed to be due both to differences in the length of the growing season and the rate of growth during that period. Seasonal changes in the diameter of sieve elements, and the extent of callose deposition on the sieve plates have also been investigated. Sieve element diameters were smallest in the dry season, possibly because of shrinkage. The width of phloem tissue showing definitive callose was fairly constant throughout the year, but the zone with open pores on the sieve plates changed, being widest in September, and narrowest in March when the trees were almost bare. There were two peaks of cambial activity, indicated by an increase in width of the 'open pore zone', one in April at the time of bud break, and a second in September.The sugar concentration of the phloem exudate obtained from small cuts into the bark of the trees varied throughout the year. Concentrations were highest in March, during the dry season, and lowest in May, when the young leaves were expanding. © 1981 Annals of Botany Company.