Sprouting of seedlings of three Quercus species in relation to repeated pruning and the cotyledonary node

Abstract

We studied sprouting of three oak species (Quercus humilis Miller, Q. ilex L. and Q. suber L.) at the seedling stage to examine the role of the cotyledonary node in the production of new shoots after disturbance. The aerial biomass was removed three successive times above and below the point of attachment of the cotyledons. All three Quercus species produced new shoots when the aerial biomass was removed above the cotyledonary node. However, the number of sprouts per seedling, the length and leaf number of the sprouts, and root diameter decreased with repeated pruning. Because of their underground dormant buds only Q. suber seedlings could sprout and survive when the aerial biomass was removed below the cotyledons. These results show that in Q. suber seedlings the cotyledonary node forms a true functional lignotuber and suggest that the presence of clusters of hidden underground cotyledonary dormant buds is limited to Q. suber.