Phyllotaxis of the palmEuterpe oleraceaMart. at the level of the shoot apical meristem

Abstract

Previous studies on palm phyllotaxis deal mainly with the mature trunk. The goals of this study are (i) to determine the relationship between the number of parastichies, the divergence angle, and the plastochrone ratio at the level of the shoot apical meristem; (ii) to examine whether there are fluctuations in the divergence angle; (iii) to interpret the significance of phyllotactic parameters with respect to the mode of growth of the apex. The tubular base of the leaf primordium is more or less asymmetrical, and completely surrounds the shoot apical meristem. The phyllotactic system corresponds to a (2, 3) conspicuous parastichy pair. The mean divergence angle per apex varies between 126.98 ± 9.38 (mean ± SD) and 135. 88 ± 8.08. Divergence angles for all apices fluctuate within a range of 115.898 to 157.338. The mean plastochrone ratios between apices varies from 1.35 ± 0.18 to 1.58 ± 0.12. The plastochrone ratio at each plastochrone for all apices ranges from 1.09 to 2.00. There is no correlation between the angle of divergence and the plastochrone ratio. There is a fluctuation in the value of the divergence angle that falls within the range predicted by the fundamental theorem of phyllotaxis. The high value of the ratio of the diameter of leaf primordia over the diameter of the apex, and the long plastochrone might explain the lack of correlation between certain phyllotactic parameters.Résumé : Des études précédentes ont porté sur la phyllotaxie de palmier, mais surtout chez des tiges adultes. Le but de cette étude est de (i) déterminer la relation entre le nombre de parastiches, l'angle de divergence et le ratio du plastochrone, à la hauteur du méristème apical de la tige; (ii) de vérifier s'il y a des fluctuations dans l'angle de divergence; (iii) d'interpréter la signification des paramètres phyllotaxiques en relation avec le mode de croissance apicale. La base tubulaire du primordium foliaire est plus ou moins asymétrique et entoure complètement le méristème apical de la tige. Le système phyllotaxique correspond à une (2, 3) paire bien visible de parastiches. L'angle moyen de divergence par apex varie entre 126,98 ± 9,38 (moyenne ± DS) et 135,88 ± 8,08. La divergence des angles pour tous les apex fluctue régulièrement entre 115,898 et 157,338. Les ratios des plastochrones moyens entre les apex varient entre 1,35 ± 0,18 et 1,58 ± 0,12. Le ratio du plastochrone à chacun des plastochrone pour tous les apex va de 1,09 à 2,00. Il n'y a pas de corrélation entre l'angle de divergence et le ratio du plastochrone. On observe une fluctuation dans la valeur de l'angle de divergence qui se situe dans l'écart prédit par le théorème fondamental de la phyllotaxie. La valeur élevée du ratio du diamètre du primordium foliaire sur le diamètre de l'apex et le long plastochrone pourrait expliquer l'absence de corrélation entre certains paramètres phyllotaxiques.

Phyllotaxis transition over the lifespan of a palm tree using Magnetic Resonance Imaging (MRI) and Terrestrial Laser Scanning (TLS): the case of Jubaea chilensis

“…Conspicuous parastichy pairs were identified connecting the central points of the neighboring structures in both directions (clockwise and counterclockwise) in accordance with Jean’s definition [ 10 , 18 ] (Fig. 2 , third column, red and cyan lines show clockwise and counterclockwise spirals respectively).…”

“…Additionally, this average divergence angle is close to the range of other palm species. In Cocos nucifera , the divergence angle is between 136° and 137.9° [ 9 ]; in Euterpe oleracea it is between 126.9° and 135.8° [ 10 ], and in Calamus longipinna it is about 137.5° [ 54 ]. The section of the adult specimen of J. chilensis with the (8,5) parastichy pairs (below 9.0 m height) had a mean divergence angle of 137.0° (± 0.84 SD), which is in the range described by Mitchinson [ 14 ] for plants with contacts 5 and 8 (136.8° ± 1.8 SD); this finding is also consistent with results from other palm species [ 10 , 24 ].…”

“…Two parameters have been widely used for an objective study of phyllotaxis [ 6 – 10 ]: divergence angle and parastichy. The divergence angle, d , is the enclosed angle between two successive lateral organs (buds, shoots, leaves, labelled ij in Fig.…”

“…These arrangements are visible on the palms in three ways: scars from fallen leaves, the crown itself and in the apex [ 25 ]. The divergence angle tends to be regular, but there may be some variability within the same individual [ 10 ].…”

Vascular phyllotaxis transition and an evolutionary mechanism of phyllotaxis

“…As the evolutionary mechanism relies on statistical screening processes, it does not predict a limit divergence angle with unlimited precision. It is an empirical fact that divergence angles at the level of the shoot apex are regulated toward a mean value comparable with an ideal angle given by the formula (2) after some transient fluctuations (Davies (1939); Snow and Snow (1962); Barabé et al (2010)). Excepting initial fluctuations, the precision with which leaves are organized on the apical meristems is remarkable.…”