Well-documented shade adaptations include physiological and morphological traits of shoots and leaves. Belowground shade adaptations (roots or other buried structures) are rarely mentioned in the literature and have never been studied in tree seedlings. This study evaluates the functional role of adventitious roots developed by most balsam fir (Abies balsamea) seedlings under a closed canopy. Our goal was to describe the relationships between growth, biomass allocation, and adventitious root development in balsam fir seedlings (5–26 cm tall, 9 to 33 y old) excavated under a closed canopy (< 8% full sunlight). Seedling height, branch number and crown width increased linearly with stem diameter measured at ground level. The dry mass of stems and roots increased exponentially and tree vigour (photosynthetic/non-photosynthetic biomass ratio) decreased exponentially as stem diameter increased. Results indicate that shade tolerance is limited by size and concurrent radial increment at the stem base. Results also demonstrate that the proportion of adventitious roots and the number of annual growth units buried in humus (age of the belowground section) increased as seedlings aged. Therefore, the reverse taper phenomenon caused by the formation of adventitious roots simultaneously limits the radial expansion of the stem at ground level and the maximum size attainable by seedlings. Balsam fir's shade tolerance is attributable to root as well as shoot adaptations. The gradual burial of the stem in humus probably increases persistence in shade by limiting the plant's respiration costs.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 13 • No. 1