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Article

Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait

by 1,2,*, 1,2 and 1,2
1
Plant Biomechanics Group @ Botanic Garden Freiburg, University of Freiburg, D-79104 Freiburg, Germany
2
Cluster of Excellence livMatS @ FIT—Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, D-79110 Freiburg, Germany
*
Author to whom correspondence should be addressed.
Academic Editor: Agnieszka Bagniewska-Zadworna
Plants 2021, 10(4), 774; https://doi.org/10.3390/plants10040774
Received: 22 March 2021 / Revised: 8 April 2021 / Accepted: 12 April 2021 / Published: 15 April 2021
(This article belongs to the Special Issue Plant Anatomy and Biochemistry)
Although both the petiole and lamina of foliage leaves have been thoroughly studied, the transition zone between them has often been overlooked. We aimed to identify objectively measurable morphological and anatomical criteria for a generally valid definition of the petiole–lamina transition zone by comparing foliage leaves with various body plans (monocotyledons vs. dicotyledons) and spatial arrangements of petiole and lamina (two-dimensional vs. three-dimensional configurations). Cross-sectional geometry and tissue arrangement of petioles and transition zones were investigated via serial thin-sections and µCT. The changes in the cross-sectional geometries from the petiole to the transition zone and the course of the vascular bundles in the transition zone apparently depend on the spatial arrangement, while the arrangement of the vascular bundles in the petioles depends on the body plan. We found an exponential acropetal increase in the cross-sectional area and axial and polar second moments of area to be the defining characteristic of all transition zones studied, regardless of body plan or spatial arrangement. In conclusion, a variety of terms is used in the literature for describing the region between petiole and lamina. We prefer the term “petiole–lamina transition zone” to underline its three-dimensional nature and the integration of multiple gradients of geometry, shape, and size. View Full-Text
Keywords: transition zone; foliage leaf; petiole; lamina; anatomy; morphology; Pilea peperomioides; Hemigraphis alternata; Hosta x tardiana ‘El Niño’; Caladium bicolor transition zone; foliage leaf; petiole; lamina; anatomy; morphology; Pilea peperomioides; Hemigraphis alternata; Hosta x tardiana ‘El Niño’; Caladium bicolor
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MDPI and ACS Style

Langer, M.; Speck, T.; Speck, O. Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait. Plants 2021, 10, 774. https://doi.org/10.3390/plants10040774

AMA Style

Langer M, Speck T, Speck O. Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait. Plants. 2021; 10(4):774. https://doi.org/10.3390/plants10040774

Chicago/Turabian Style

Langer, Max, Thomas Speck, and Olga Speck. 2021. "Petiole-Lamina Transition Zone: A Functionally Crucial but Often Overlooked Leaf Trait" Plants 10, no. 4: 774. https://doi.org/10.3390/plants10040774

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