Our thesis was that the presence of nodes in stems of Heteromeles arbutifolia plants would increase the mechanical strength of the xylem and the bark, allowing the stems to be better protected against harsh weather conditions during the severe California drought. We conducted research on two sample groups, one with nodes and one without nodes. An Instron machine tested the mechanical strength by bending the stems until the xylem broke. Values for MOR (modulus of rupture) and MOE (modulus of elasticity) were measured to determine the overall strength of both groups. We found that the xylem of the stems was stronger with nodes than without nodes. However, the inclusion of bark reduced the strength of the stems with nodes. The xylem results supported the idea that nodes would increase the stems’ mechanical strength, whereas the bark results suggested an alternate effect of nodes on the strength of stems.
Chan, Gabriella E.; Howard, Caleigh A.; and Shelley, Callie E., "Nodes Alter Stem Mechanical Strength in Heteromeles arbutifolia" (2016). Pepperdine University, Featured Research. Paper 191.