Red Pine Needle Structure

Abstract

READERS of the recent article by Kozlowski and Clausen¹ on the anatomical responses of the needles of red pine (Pinus resinosa Ait.) to herbicides may have been confused by the extreme variations in needle structure which these authors described and illustrated. Kozlowski and Clausen attributed many of the anatomical differences between “needles” shown in their Fig. 1 to the effects of various herbicides applied to the soil in which the seedlings were grown. From what is known of the leaf structure of pine seedlings², however, we concluded that they had illustrated and described three different kinds of foliar appendages of red pine. Their Fig. 1A, a transection of a “needle” from a non-treated seedling, seems to be a primary leaf, as is Fig. 1D from a treated plant. Their Figs. 1B, C and E are cotyledons, and F resembles a shrivelled secondary leaf.