Latitudinal Differences in Coconut Foliar Spiral Direction: A Re-evaluation and Hypothesis

Abstract

Davis and Davis (Mathematical Modelling 8 : 730-733, 1987) have previously concluded, based on data collected from 42 locations around the world, that the ratio of right-handed to left-handed palm trees (Cocos nucifera L.) exhibits hemispheric differences : left-handed palms are in the majority in the Northern Hemisphere, and right-handed palms are in the majority in the Southern Hemisphere. Weighted and unweighted linear regression analyses of their data reveal that the skewing quotient [(left-handed-right-handed)\total] is better correlated with magnetic (dip) latitude than with geographic or geomagnetic (centred dipole) latitude. The hypothesis is advanced that latitude-dependent biases in foliar spiral direction may be associated with the temporally varying component of the earth's magnetic field. It is known that changes in the current strength of the ionospheric dynamo induce clockwise earth currents in the Northern Hemisphere and counterclockwise earth currents in the Southern Hemisphere. The hypothesis is advanced that these earth currents, which are measurable in trees, bias the diffusion of auxin (or auxin transport proteins) in young embryos such that left-handed trees are produced preferentially in the Northern Hemisphere and right-handed in the Southern Hemisphere. Some tests of the Induced Current Hypothesis are proposed.# 1998 Annals of Botany Company

Phyllotaxis and handedness in date palm (Phœnix dactylifera L.)

“…Davis and Davis [10] mentioned that phyllotaxis in coconut tree is influenced by magnetic latitude. Minorsky [15] explained that coconut trees with counterclockwise phyllotaxis predominate in the northern hemisphere because the auxin brought to the terminal bud tends to circulate in a counterclockwise direction, whereas in the southern hemisphere it turns in the opposite direction.…”

Do geomagnetic variations affect plant function?

“…Foliar spiral direction (FSD) would seem a random stochastic process unworthy of further study if not for the observation, based on data collected from over 70,000 coconut palms in over 40 locations around the world, that the FSD of coconut palms varies with latitude: R-trees predominate in the Northern Hemisphere and L-trees predominate in the Southern Hemisphere (Davis and Davis, 1987). A re-analysis of these data indicated that hemispheric asymmetries in FSD were significantly better correlated with magnetic latitude than with geographic or geomagnetic latitude, suggesting that latitudinal asymmetries in FSD might be associated with the temporally varying component of the Earth's magnetic field (Minorsky, 1998). Based on these findings, Minorsky (1998) proposed that asymmetries in coconut palm FSD result from the Earth currents induced by variations in the vertical Z component of the geomagnetic field that cause a rotational bias in the axial migration of morphogens (e.g., auxin transporters) in coconut palm embryos.…”

“…A re-analysis of these data indicated that hemispheric asymmetries in FSD were significantly better correlated with magnetic latitude than with geographic or geomagnetic latitude, suggesting that latitudinal asymmetries in FSD might be associated with the temporally varying component of the Earth's magnetic field (Minorsky, 1998). Based on these findings, Minorsky (1998) proposed that asymmetries in coconut palm FSD result from the Earth currents induced by variations in the vertical Z component of the geomagnetic field that cause a rotational bias in the axial migration of morphogens (e.g., auxin transporters) in coconut palm embryos. Minorsky and Bronstein (2006) presented two new lines of evidence that geomagnetic variations may underlie asymmetries in coconut palm FSD.…”

Natural Experiments Indicate That Geomagnetic Variations Cause Spatial and Temporal Variations in Coconut Palm Asymmetry

“…Davis, based on data collected from over 70,000 coconut palms in over 40 locations around the world, that the FSD of coconut palms varies with latitude: R trees predominate in the northern hemisphere and L trees predominate in the southern hemisphere (Davis and Davis, 1987). A reanalysis of Davis's data indicated that these hemispheric asymmetries in FSD are significantly better correlated with magnetic (dip) latitude than with geographic or geomagnetic (centered dipole) latitude, suggesting that latitudinal asymmetries in FSD might be associated with the temporally varying component of the Earth's magnetic field (Minorsky, 1998). Here, we report that asymmetries in FSD are also evident in populations of coconut palms on opposite sides of islands and that asymmetries between cohorts vary with an 11-year periodicity-two novel discoveries consistent with the hypothesis that geomagnetic variations underlie asymmetries in coconut palm FSD.…”

“…The induced current hypothesis proposes that asymmetries in coconut palm FSD result from earth currents in trees that are induced by variations in the vertical Z component of the geomagnetic field, and that these earth currents consequently cause a rotational bias in the axial electrophoresis of morphogens (e.g. auxin transporters) in coconut palm embryos (Minorsky, 1998).…”