Heat tolerance of rhizomes of several understory species

Abstract

Rhizomes of eight understory species: Gaultheria procumbens, Maianthemum canadense, Vaccinium angustifolium, Cornus canadensis, Pteridium aquilinum, Kalmia angustifolia, Chamaedaphne calyculata, and Rhododendron canadense were subjected to treatments of 45, 50, 55 and 60 °C for 5 min in a water bath. Selection of these species for study was based on differences in the depth of the rhizomes, in habitat, and in rhizome morphology. Samples were collected from study sites located near Halifax, in the Nova Scotia Acadian Forest region.Maximum shoot growth occurred at different temperatures for the various species: 45 °C for Cornus canadensis; 50 °C for Chamaedaphne calyculata, R. canadense, and V. angustifolium; 55 °C for G. procumbens and M. canadense. Death occurred at or below 60 °C for most species. For comparative purposes, a temperature tolerance index (TTI) was calculated for each species. The TTI indicated that R. canadense and V. angustifolium showed the greatest tolerance to higher temperatures and that K. angustifolia and P. aquilinum showed the least tolerance. Mean shoot number increased significantly following spring treatments for all species except for Cornus canadensis which showed greater increase following autumn treatments.