| Popis: |
Frost resistance was compared in five species of different life forms in the neotropical woody bamboo genus Chusquea growing along a cloud forest-paramo gradient, between 2250-4010 m a.s.l. in the Venezuelan Andes. C. multiramea and C. serrulata are viny bamboos of the upper montane cloud forest-treeline ecotone (2400-2900 m); whereas C.angustifolia C. spencei and C. guirigayensis are shrublike bamboos associated to swampy low elevation paramos (2525 m) in the first case, a broad range of paramo ecosystems (2670-3600 m) in the second, and dry high elevation paramos in the third (3800-4010 m). Intercellular ice nucleation and 50% tissue injury temperatures were estimated in these five species under laboratory conditions in order to determine frost resistance mechanisms. No significant differences were observed among ice nucleation and tissue injury temperatures in any of these species, indicating that all avoid intercellular ice nucleation through supercooling (-12.3 to -10.1 ºC). We conclude that variations in supercooling capacity and freezing injury are not related to life form, habitat or elevation and that freezing temperatures are not a determining factor in the altitudinal distribution of tropical Andean bamboos. 247-257 fely@ula.ve, fely@intercable.net.ve frada@ula.ve |
