Spiral phyllotaxis of needle fascicles on branches and scales on cones in Pinus contorta var. latifolia: Are they influenced by wood-grain spiral?

Abstract

Neither the relationship between the chirality of spiral phyllotaxis and spiral wood grain nor the cause or ontogeny of such a relationship has been examined previously. To this end, chirality of the spiral in phyllotaxis of needle fascicles and cone scales were contrasted with wood-grain spiral in seedlings, young, and mature trees of Rocky Mountain lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) in central British Columbia. To assess chirality of phyllotaxis, the relationship between numbers of contact parastichies and chirality of phyllotaxis in scales on cones and needle fascicles on branchlets was determined. Three or 8 clockwise acropetal contact parastichies were indicative of a clockwise generative spiral, while totals of 2, 5, or 13 clockwise acropetal parastichies were indicative of a counter-clockwise generative spiral. Lodgepole pine trees were nearly always chimeric, i.e., having clockwise and counter-clockwise phyllotaxis on the same individual, but there was a high overall correspondence between the chirality of phyllotaxis in cone scales and subtending needle fascicles. Seedlings (<1.5 years old) had no measurable wood-grain angle and clockwise and counter-clockwise phyllotaxis occurred in equal proportions. However, young trees (13-15 years since planting) had a pronounced clockwise bias to their wood-grain spiral in contrast with a counter-clockwise bias in phyllotaxis. In contrast, mature trees (≥100 years old) had the reverse trend and exhibited a counter-clockwise bias in wood-grain spiral but a clockwise bias in phyllotaxis. A model is proposed to explain how chirality of spiral wood grain could generate an inverse bias in the chirality of phyllotaxis in lodgepole pine.Résumé : Jusqu'ici, on a jamais examiné la relation entre la chiralité de la spirale phyllotaxique et celle de la spirale du grain du bois, et encore moins la cause ou l'ontogénèse de ces relations. A cette fin, les auteurs ont comparé la chiralité de la spirale phyllotaxique des faisceaux foliaires et les écailles des cônes, avec la spirale des grains du bois chez des plantules, chez de jeunes arbres et chez des arbres adultes du pin lodgepole des Montagnes Rocheuses (Pinus contorta var. latifolia), au centre de la Colombie-Britannique. Pour évaluer la chiralité de la phyllotaxie, les auteurs ont déterminé la relation entre le nombre de parastiches contactées et la chiralité de la phyllotaxie des écailles des cônes et des faisceaux foliaires sur des rameaux. La présence de 3 ou 8 parastiches contactées dans le sens des aiguilles de la montre en direction acropète indique une spirale générative dans le sens des aiguilles de la montre, alors que des totaux de 2, 5 ou 13 parastiches acropètes indiquent une spirale générative dans le sens contraire des aiguilles de la montre. Les tiges du pin lodgepole sont presque toujours chimériques, à savoir qu'elles possèdent à la fois des phyllotaxies dans le sens et contre le sens des aiguilles de la montre sur le même individu, mais on retrouve généralement une fort...

Antisymmetry in female strobili of Pinus taeda

“…Also, both orientations were equally as frequent in cones of the same trees ( Table 1), indicating that, contrary to other asymmetries such as the apical-basal axis, which are strongly influenced by maternal effects and are determined even before fertilization (Hudson 2000), the orientation of the spiral in pine cones seems to be environmentally determined. Similar results have been recorded for Pinus contorta (Fredeen et al 2002).…”

Fibonacci or quasi-symmetric phyllotaxis. Part I: why?

“…Botanists relate this geometric choice to the chirality of the generative spiral (that connects successive primordia) of the plant, and it is widely believed that plants of a same species exhibit the two chiralities with the same frequency [40] -as reflected by the symmetry of the initial condition of our model. However, some observations show that it might not be the case, or more precisely that the initial conditions might not be symmetric themselves [41].…”

Asymmetry in Food Handling Behavior of a Tree-Dwelling Rodent (Sciurus vulgaris)

“…pinea cones on rocks or stumps in the ground, employing a procedure to extract the seeds that is not observed for cones of other pine tree species [ 52 ]. Besides, pine cones contain unequal numbers of clockwise and counter-clockwise acropetal generative spirals, and the number of spirals differs among pine species [ 53 ]. Thus, handling asymmetries exhibited by squirrels in our study might also reflect a way to deal with naturally asymmetrical pine cones.…”