Seed Germination and Viability of Bursera Species of Moreios, Mexico

摘要

Tropical dry forest restoration in Mexico is hindered by poor germination of Burs-era copallifera and other common Bursera. Fungal infections of the seeds are common. Preliminary work on B. copallifera found that the stony endoearp was water-permeable. One germination experiment on a mixed collection of 6. copallifera seed tested treatments with (1) deionized water, (2) 4-h soak in 3% hydrogen peroxide, (3) mechanical scarification by cracking, and (4) 4-h soak in 3% hydrogen peroxide plus mechanicalscarif ication.There was no statistical difference between the treatments, although mechanical scarification alone appeared to encourage fungal infection. A second experiment with individual seed collections of several B. copallifera trees tested: (1) deionized water (control), (2) moist pre-chili for 6 days at 4 deg C preceded by a 48-h imbibition period at room temperature, (3) 250 uM GA_3, (4) 600 muM benzyladenine (BA), and (5) 125 muM GA_3 plus 300 uM BA. Logistic regression analysis found that the most important effects on germination were the variation between the seed collections of each tree (p = 0.05 < 0.0001) and the tree-by-treatment interaction (p = 0.0005). Treatment effect was minimal (p = 0.0432). While the seeds of each tree respondeddifferentially to the treatments, none of the treatments improved germination to a statistically significant extent. Pre-chilling decreased germination of the seeds of one tree. Most of the remaining seeds were dead at the end of the test period. The proportion of viable seeds varied widely among the trees. Low viability and vigor appeared to be the most important factors limiting germination in B, copaillfera.The results suggested a possible relationship between tree density and seed viability that should be examined more closely.