Quantification of eccentricity in stems of Artemisia tridentata Nutt.

Previous research has shown that stems of Artemisia tridentata species exhibit extensive lobe formation. Twenty-two stem samples of Artemisia tridentata Nutt. ssp. wyomingensis (ARTRW) and 24 samples of A. t. ssp. tridentata (ARTRT) were investigated to quantify lobe formation characteristics. For samples of both subspecies, lobe formation values were constant for 8.3-cm-diameter stems. For the above samples, ARTRW had 14 xylem rings, while ARTRT had only 5 rings. Three stem samples (33 to 50 cm long) of ARTRW were cut into a series of 8-mm segments. For the 3 stems, the smallest ends had 8 xylem rings (10 mm² area), while the largest ends had 38 xylem rings (700-mm² area). Lobes were present in all samples with more than 10 xylem rings. Each stem segment was subdivided into 10 sectors. A difference of more than 10 rings was observed in 13% of all sectors from segment to segment, suggesting that eccentric growth and lobe formation was localized along stems. This is the first publication to quantify lobe formation characteristics in successive stem segments of A. tridentata.