Poster: Ecophysiology

Abs # 3: Asymmetry in the Handedness of Coconut Spiral Leaf Attachment on Opposite Sides of the Big Island of Hawaii and Puerto Rico: A Role for Tradewinds?

Presenter:	Minorsky, Peter V, peminorsky@aspb.org
Authors	Minorsky, Peter V (A)   Bronstein, Natalie B (A)
Affiliations:	(A): Mercy College

Like other plants with alternate foliage, the leaves of coconut palms (Cocos nucifera) are attached to the stem in either an ascending clockwise (left-handed or L) or counter-clockwise (right-handed or R) spiral. Foliar spiral direction is not a genetically determined trait in coconut palms: all crosses (R X R; R X L; L X R; L X L) yield R- and L- progeny in approximately equal numbers. Based on an analysis of 71,640 trees in 42 different locales around the globe, Davis & Davis (Math. Modeling 8: 730-737, 1987) reported the occurrence of a latitude-dependent asymmetry in the ratio of L to R coconut palms. L palms were more prevalent in the Northern Hemisphere, whereas R palms were more predominant in the Southern Hemisphere. Here, we report our on scoring of L and R palms around the circumferences of the Big Island of Hawaii (3500 trees) and Puerto Rico (4311 trees). We show that the asymmetry of handedness varies on different sides of these two islands. In both cases, R palms were more prevalent on the N and E sides of the islands whereas L palms more prevalent on the S and W sides. For example, above the diagonal from Luquillo (NE Puerto Rico), to Boqueron (SW Puerto Rico), we counted 744 L palms and 577 R palms. Below this diagonal, we counted 845 L palms and 1120 R palms. This diagonal corresponds closely with the direction of the NE tradewinds, suggesting that the asymmetry may arise from wind effects on morphogenesis. We offer a re-interpretation of the findings of Davis and Davis’s (1987) findings in view of our results.