EFFECT OF PATULA PINE (Pinus patula) CONE PHYSICAL CHARACTERISTICS AND EXTRACTION PERIOD ON SEED YIELD AND GERMINATION IN LONDIANI, KENYA

Abstract

Pinus patula in Kenya is an exotic plantation tree species grown for commercial production of sawn wood and pulpwood. Propagation is by seed and grafted seedlings or cuttings for clonal seed orchards. The conventional way of P. patula seed extraction is by drying in beds in direct sunlight. This study was set up to investigate the interactions of cone physical characteristics, exposure duration to artificial seed extraction at a fixed extraction temperature and the germination temperature on seed release and subsequent seed germination. The hypothesis tested was that there was no relationship between cone characteristics, extraction exposure duration, seed yield and seed germination performance. Forty-five trees for cone collection were systematically selected with a random start from Kamara block, Londiani forest. Analysis of the difference in means from the three factor effects from ANOVA was performed using R Statistical software. Where significant differences were observed, post hoc tests were carried out to separate means using the Tukey test at 5 % significance level. Based on the variations in physical attributes and extraction exposure periods, seed extraction potential of cones and germination responses of seeds to thermal treatments was determined. The lowest mean number of seeds released observed was 28, from light cones, while the highest mean was 56 from wide cones. This study showed that for P. patula, cone width had a greater significant (p=0.001) influence on the amount of seed release than cone weight. There were significant differences (p=001) in germination performance as a result of cone characteristics, extraction exposure periods, and germination chamber conditions. Seeds extracted from heavy cones and exposed to germination temperature of 32℃ demonstrated the highest germination percent at 90% while the lowest was 20% from light cones exposed to similar germination temperature conditions. When considering efficiency in mechanized seed extraction, the first six hours were shown to be optimum for seed release. Thus, cone sorting for wider cones for extraction at 65oC for at least six hours would yield a greater part of the seeds in artificially heated timed kilns. Based on this study, foresters and germplasm producers can improve protocols for scoring of seed sources based on cone characteristics to infer germination potential of P. patula.