Research

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20 pages, 6748 KiB

Open AccessArticle

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

by Max Langer, Thomas Speck and Olga Speck

Plants 2021, 10(4), 774; https://doi.org/10.3390/plants10040774 - 15 Apr 2021

Cited by 14 | Viewed by 4498

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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13 pages, 2012 KiB

Open AccessArticle

Relationship between Vessel Formation and Seasonal Changes in Leaf Area of Evergreen and Deciduous Species with Different Vessel Arrangements

by Sayaka Takahashi and Erina Takahashi

Plants 2021, 10(1), 100; https://doi.org/10.3390/plants10010100 - 06 Jan 2021

Cited by 4 | Viewed by 2490

Abstract

To discuss the diversity of morphological traits and life strategies of trees, the functional relationship between leaf expansion and vessel formation must be clarified. We compared the temporal relationship among tree species with different leaf habits and vessel arrangements. Twigs, leaves, and trunk [...] Read more.

To discuss the diversity of morphological traits and life strategies of trees, the functional relationship between leaf expansion and vessel formation must be clarified. We compared the temporal relationship among tree species with different leaf habits and vessel arrangements. Twigs, leaves, and trunk core samples were periodically acquired from 35 sample trees of nine species in a temperate forest in Japan. We quantitatively estimated leaf expansion using a nonlinear regression model and observed thin sections of twigs and trunks with a light microscope. Almost all of the first-formed vessels in twigs, which formed adjacent to the annual ring border, were lignified with a leaf area between 0% and 70% of the maximum in all species. The first-formed vessels in trunks lignified between 0% and 95% of the maximum leaf area in ring-porous deciduous Quercus serrata and ring-(radial-)porous evergreen Castanopsis cuspidate. Their lignification occurred earlier than in diffuse-porous deciduous Liquidambar styraciflua, diffuse-porous evergreen Cinnamomum camphora and Symplocos prunifolia, and radial-porous evergreen Quercus glauca and Quercus myrsinifolia. The timing varied in semi-ring-porous deciduous Acanthopanax sciadophylloides and diffuse-porous evergreen Ilex pedunculosa. The observed differences in the timing of vessel formation after leaf appearance were reflected in their differing vessel porosities and were connected to the different life strategies among tree species. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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23 pages, 2686 KiB

Open AccessArticle

Pitfall Flower Development and Organ Identity of Ceropegia sandersonii (Apocynaceae-Asclepiadoideae)

by Annemarie Heiduk, Dewi Pramanik, Marlies Spaans, Loes Gast, Nemi Dorst, Bertie Joan van Heuven and Barbara Gravendeel

Plants 2020, 9(12), 1767; https://doi.org/10.3390/plants9121767 - 14 Dec 2020

Cited by 5 | Viewed by 4147

Abstract

Deceptive Ceropegia pitfall flowers are an outstanding example of synorganized morphological complexity. Floral organs functionally synergise to trap fly-pollinators inside the fused corolla. Successful pollination requires precise positioning of flies headfirst into cavities at the gynostegium. These cavities are formed by the corona, [...] Read more.

Deceptive Ceropegia pitfall flowers are an outstanding example of synorganized morphological complexity. Floral organs functionally synergise to trap fly-pollinators inside the fused corolla. Successful pollination requires precise positioning of flies headfirst into cavities at the gynostegium. These cavities are formed by the corona, a specialized organ of corolline and/or staminal origin. The interplay of floral organs to achieve pollination is well studied but their evolutionary origin is still unclear. We aimed to obtain more insight in the homology of the corona and therefore investigated floral anatomy, ontogeny, vascularization, and differential MADS-box gene expression in Ceropegia sandersonii using X-ray microtomography, Light and Scanning Electronic Microscopy, and RT-PCR. During 10 defined developmental phases, the corona appears in phase 7 at the base of the stamens and was not found to be vascularized. A floral reference transcriptome was generated and 14 MADS-box gene homologs, representing all major MADS-box gene classes, were identified. B- and C-class gene expression was found in mature coronas. Our results indicate staminal origin of the corona, and we propose a first ABCDE-model for floral organ identity in Ceropegia to lay the foundation for a better understanding of the molecular background of pitfall flower evolution in Apocynaceae. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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16 pages, 4733 KiB

Open AccessEditor’s ChoiceArticle

Ontogeny and Anatomy of the Dimorphic Pitchers of Nepenthes rafflesiana Jack

by Rachel Schwallier, Valeri van Wely, Mirna Baak, Rutger Vos, Bertie Joan van Heuven, Erik Smets, Rogier R. van Vugt and Barbara Gravendeel

Plants 2020, 9(11), 1603; https://doi.org/10.3390/plants9111603 - 18 Nov 2020

Cited by 5 | Viewed by 8655

Abstract

An enigmatic feature of tropical pitcher plants belonging to the genus Nepenthes is their dimorphic prey-capturing pitfall traps. In many species, the conspicuously shaped upper and lower pitchers grow from a swollen leaf tendril tip until finally opening as insect-alluring devices. Few have [...] Read more.

An enigmatic feature of tropical pitcher plants belonging to the genus Nepenthes is their dimorphic prey-capturing pitfall traps. In many species, the conspicuously shaped upper and lower pitchers grow from a swollen leaf tendril tip until finally opening as insect-alluring devices. Few have studied the ontogeny of these traps from an anatomical and quantitative morphological perspective. We investigated whether the anatomy and development of lower and upper type pitchers of N. rafflesiana differ or overlap in terms of 3D geometric morphology and microstructure progression and presence. We hypothesized that there is an overlap in the initial, but not all, developmental stages of the two pitcher types and that one pitcher type is suspended in development. We identified four important morphological changes of pitcher ontogeny and defined these as curvation, elongation, inflation and maturation phases. Pitcher length indicated progress through developmental phases, and we propose to use it as a tool for indication of developmental stage. Microstructure development coincided with the developmental phases defined. Additionally, we discovered a new anatomical feature of extrafloral nectariferous peristomal glands between the inner peristome ridges of upper and lower pitchers being hollow and analyze the chemistry of the sugars on the outside of these glands. Ontogenetic shape analysis indicated that upper and lower pitcher types develop with similar phase progression but have no directly overlapping morphology. This means that upper pitchers are not a derived state from lower pitchers. Independent developmental programs evolved to produce distinctly shaped upper and lower pitchers in Nepenthes, likely to exploit different food sources. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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18 pages, 5566 KiB

Open AccessArticle

Solanales Stem Biomechanical Properties Are Primarily Determined by Morphology Rather Than Internal Structural Anatomy and Cell Wall Composition

by Ilana Shtein, Alex Koyfman, Amnon Schwartz, Zoë A. Popper and Benny Bar-On

Plants 2020, 9(6), 678; https://doi.org/10.3390/plants9060678 - 27 May 2020

Cited by 3 | Viewed by 2724

Abstract

Self-supporting plants and climbers exhibit differences in their structural and biomechanical properties. We hypothesized that such fundamental differences originate at the level of the material properties. In this study, we compared three non-woody members of the Solanales exhibiting different growth habits: (1) a [...] Read more.

Self-supporting plants and climbers exhibit differences in their structural and biomechanical properties. We hypothesized that such fundamental differences originate at the level of the material properties. In this study, we compared three non-woody members of the Solanales exhibiting different growth habits: (1) a self-supporting plant (potato, Solanum tuberosum), (2) a trailing plant (sweet potato, Ipomoea batatas), and (3) a twining climber (morning glory, Ipomoea tricolor). The mechanical properties investigated by materials analyses were combined with structural, biochemical, and immunohistochemical analyses. Generally, the plants exhibited large morphological differences, but possessed relatively similar anatomy and cell wall composition. The cell walls were primarily composed of hemicelluloses (~60%), with α-cellulose and pectins constituting ~25% and 5–8%, respectively. Immunohistochemistry of specific cell wall components suggested only minor variation in the occurrence and localization between the species, although some differences in hemicellulose distribution were observed. According to tensile and flexural tests, potato stems were the stiffest by a significant amount and the morning glory stems were the most compliant and showed differences in two- and three-orders of magnitude; the differences between their effective Young’s (Elastic) modulus values (geometry-independent parameter), on the other hand, were substantially lower (at the same order of magnitude) and sometimes not even significantly different. Therefore, although variability exists in the internal anatomy and cell wall composition between the different species, the largest differences were seen in the morphology, which appears to be the primary determinant of biomechanical function. Although this does not exclude the possibility of different mechanisms in other plant groups, there is apparently less constraint to modifying stem morphology than anatomy and cell wall composition within the Solanales. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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16 pages, 2574 KiB

Open AccessArticle

Exodermis and Endodermis Respond to Nutrient Deficiency in Nutrient-Specific and Localized Manner

by Jiří Namyslov, Zuzana Bauriedlová, Jana Janoušková, Aleš Soukup and Edita Tylová

Plants 2020, 9(2), 201; https://doi.org/10.3390/plants9020201 - 06 Feb 2020

Cited by 14 | Viewed by 4447

Abstract

The exodermis is a common apoplastic barrier of the outer root cortex, with high environmentally-driven plasticity and a protective function. This study focused on the trade-off between the protective advantages provided by the exodermis and its disadvantageous reduction of cortical membrane surface area [...] Read more.

The exodermis is a common apoplastic barrier of the outer root cortex, with high environmentally-driven plasticity and a protective function. This study focused on the trade-off between the protective advantages provided by the exodermis and its disadvantageous reduction of cortical membrane surface area accessible by apoplastic route, thus limiting nutrient acquisition from the rhizosphere. We analysed the effect of nutrient deficiency (N, P, K, Mg, Ca, K, Fe) on exodermal and endodermal differentiation in maize. To differentiate systemic and localized effects, nutrient deficiencies were applied in three different approaches: to the root system as a whole, locally to discrete parts, or on one side of a single root. Our study showed that the establishment of the exodermis was enhanced in low–N and low–P plants, but delayed in low-K plants. The split-root cultivation proved that the effect is non-systemic, but locally coordinated for individual roots. Within a single root, localized deficiencies didn’t result in an evenly differentiated exodermis, in contrast to other stress factors. The maturation of the endodermis responded in a similar way. In conclusion, N, P, and K deficiencies strongly modulated exodermal differentiation. The response was nutrient specific and integrated local signals of current nutrient availability from the rhizosphere. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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Review

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25 pages, 3652 KiB

Open AccessEditor’s ChoiceReview

Xylem Parenchyma—Role and Relevance in Wood Functioning in Trees

by Aleksandra Słupianek, Alicja Dolzblasz and Katarzyna Sokołowska

Plants 2021, 10(6), 1247; https://doi.org/10.3390/plants10061247 - 19 Jun 2021

Cited by 33 | Viewed by 12713

Abstract

Woody plants are characterised by a highly complex vascular system, wherein the secondary xylem (wood) is responsible for the axial transport of water and various substances. Previous studies have focused on the dead conductive elements in this heterogeneous tissue. However, the living xylem [...] Read more.

Woody plants are characterised by a highly complex vascular system, wherein the secondary xylem (wood) is responsible for the axial transport of water and various substances. Previous studies have focused on the dead conductive elements in this heterogeneous tissue. However, the living xylem parenchyma cells, which constitute a significant functional fraction of the wood tissue, have been strongly neglected in studies on tree biology. Although there has recently been increased research interest in xylem parenchyma cells, the mechanisms that operate in these cells are poorly understood. Therefore, the present review focuses on selected roles of xylem parenchyma and its relevance in wood functioning. In addition, to elucidate the importance of xylem parenchyma, we have compiled evidence supporting the hypothesis on the significance of parenchyma cells in tree functioning and identified the key unaddressed questions in the field. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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18 pages, 965 KiB

Open AccessReview

Responses to Cadmium in Early-Diverging Streptophytes (Charophytes and Bryophytes): Current Views and Potential Applications

by Erika Bellini, Camilla Betti and Luigi Sanità di Toppi

Plants 2021, 10(4), 770; https://doi.org/10.3390/plants10040770 - 14 Apr 2021

Cited by 13 | Viewed by 2660

Abstract

Several transition metals are essential for plant growth and development, as they are involved in various fundamental metabolic functions. By contrast, cadmium (Cd) is a metal that can prove extremely toxic for plants and other organisms in a dose-dependent manner. Charophytes and bryophytes [...] Read more.

Several transition metals are essential for plant growth and development, as they are involved in various fundamental metabolic functions. By contrast, cadmium (Cd) is a metal that can prove extremely toxic for plants and other organisms in a dose-dependent manner. Charophytes and bryophytes are early-diverging streptophytes widely employed for biomonitoring purposes, as they are able to cope with high concentrations of toxic metal(loid)s without showing any apparent heavy damage. In this review, we will deal with different mechanisms that charophytes and bryophytes have evolved to respond to Cd at a cellular level. Particular attention will be addressed to strategies involving Cd vacuolar sequestration and cell wall immobilization, focusing on specific mechanisms that help achieve detoxification. Understanding the effects of metal(loid) pollution and accumulation on the morpho-physiological traits of charophytes and bryophytes can be in fact fundamental for optimizing their use as phytomonitors and/or phytoremediators. Full article

(This article belongs to the Special Issue Plant Anatomy and Biochemistry)

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