Research

15 pages, 5868 KiB

Open AccessArticle

Secretory Patterns in Colleters of Apocynaceae

by Josiana Cristina Ribeiro, Elisabeth Dantas Tölke and Diego Demarco

Plants 2021, 10(12), 2770; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10122770 - 15 Dec 2021

Cited by 3 | Viewed by 2261

Colleters of Apocynaceae are glands related to different types of protection of vegetative and floral meristems through the production of mucilage or a mixture of many different compounds. Although several anatomical papers have shown histological and histochemical aspects of colleters of the family, [...] Read more.

Colleters of Apocynaceae are glands related to different types of protection of vegetative and floral meristems through the production of mucilage or a mixture of many different compounds. Although several anatomical papers have shown histological and histochemical aspects of colleters of the family, almost nothing is known about their secretory process. In this study, we analyzed two types of colleters in Apocynaceae: one produces mucilage and lipophilic compounds, while the other produces an exclusively mucilaginous secretion. The secretory epidermis of the colleters of Allamanda schottii and Blepharodon bicuspidatum has a dense cytoplasm with organelles responsible for the production of mucilage and lipids. This heterogeneous secretion is released through granulocrine and eccrine mechanisms and is temporarily stored in a subcuticular space before crossing the cuticle. Conversely, colleters of Mandevilla splendens and Peplonia axillaris produce only mucilage and have a very different secretory apparatus. The mechanism of secretion is granulocrine, and the exudate is firstly accumulated in a large periplasmic space and later in an intramural space before crossing the cuticle. Notably, the structure of the cuticle varies according to the secretion composition. Although the colleters of the family are histologically similar, this study demonstrates a metabolic and subcellular variability previously unknown for Apocynaceae. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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16 pages, 2662 KiB

Open AccessArticle

New Aspects of Secretory Structures in Five Alismataceae Species: Laticifers or Ducts?

by Flávia Maria Leme, João Pedro Silvério Pena Bento, Vitoria Silva Fabiano, Jean David Varilla González, Vali Joana Pott and Rosani do Carmo de Oliveira Arruda

Plants 2021, 10(12), 2694; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10122694 - 08 Dec 2021

Cited by 2 | Viewed by 2751

Abstract

The secretory structures of Alismataceae have been described as secretory ducts, laticifer ducts, laticifer canals or schizogenous ducts. However, these terms are not found in the specialized literature, and ontogenetic analyses for the exact classification of these structures are missing. Accordingly, more studies [...] Read more.

The secretory structures of Alismataceae have been described as secretory ducts, laticifer ducts, laticifer canals or schizogenous ducts. However, these terms are not found in the specialized literature, and ontogenetic analyses for the exact classification of these structures are missing. Accordingly, more studies regarding the secretory structures of Alismataceae are necessary to establish homology in the family or in the order. Thus, the aim of this study was to describe the anatomy, ontogeny, distribution in the organs and exudate composition of the secretory structures present in five Alismataceae species in order to determine whether the family has laticifers or secretory ducts. Samples of leaves, flowers and floral apices were processed for anatomical and histochemical analyses by light microscopy. The analysis indicated the presence of anastomosing secretory ducts in all species, occurring in both leaves and flowers. The exudate contains lipids, alkaloids, proteins and polysaccharides, including mucilage. The secretory duct structure, distribution and exudate composition suggest a defense role against herbivory and in wound sealing. The presence of secretory ducts in all species analyzed indicates a probable synapomorphy for the family. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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11 pages, 6498 KiB

Open AccessFeature PaperArticle

The Micromorphology and Histochemistry of Foliar Mixed Indumentum of Leucas lavandulaefolia (Lamiaceae)

by Yougasphree Naidoo, Thobekile Dladla, Yaser Hassan Dewir, Serisha Gangaram, Clarissa Marcelle Naidoo and Hail Z. Rihan

Plants 2021, 10(9), 1767; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10091767 - 25 Aug 2021

Cited by 7 | Viewed by 2372

Abstract

Leucas lavandulaefolia Sm. (Lamiaceae) is an important medicinal plant with a broad spectrum of pharmacological activities. This study aimed at characterizing the morphology, distribution, and chemical composition of the secretions of trichomes at different developmental stages on the leaves of L. lavandulaefolia, [...] Read more.

Leucas lavandulaefolia Sm. (Lamiaceae) is an important medicinal plant with a broad spectrum of pharmacological activities. This study aimed at characterizing the morphology, distribution, and chemical composition of the secretions of trichomes at different developmental stages on the leaves of L. lavandulaefolia, using light and electron microscopy. Morphological observations revealed the presence of bicellular non-glandular, glandular peltate, and capitate trichomes on both adaxial and abaxial leaf surfaces. The density of both non-glandular and glandular trichomes decreased with the progression of leaf development. Heads of peltate and short-stalked capitate trichomes were between 20.78–42.80 µm and 14.98–18.93 µm at different developmental stages. Furthermore, long-stalked capitate trichomes were rare and infrequent. Leaf sections revealed the presence of important secondary metabolites in glandular trichomes, i.e., terpenoids. This study represents the first report on the morphology and histochemistry of trichomes of L. lavandulaefolia; therefore, there is a great scope for further research in this field. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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10 pages, 2612 KiB

Open AccessArticle

Ultrastructural Alterations in Cells of Sunflower Linear Glandular Trichomes during Maturation

by Evelyn Amrehn and Otmar Spring

Plants 2021, 10(8), 1515; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10081515 - 23 Jul 2021

Cited by 1 | Viewed by 2399

Abstract

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of [...] Read more.

Sunflower and related taxa are known to possess a characteristic type of multicellular uniseriate trichome which produces sesquiterpenes and flavonoids of yet unknown function for this plant. Contrary to the metabolic profile, the cytological development and ultrastructural rearrangements during the biosynthetic activity of the trichome have not been studied in detail so far. Light, fluorescence and transmission electron microscopy were employed to investigate the functional structure of different trichome cells and their subcellular compartmentation in the pre-secretory, secretory and post-secretory phase. It was shown that the trichome was composed of four cell types, forming the trichome basis with a basal and a stalk cell, a variable number (mostly from five to eight) of barrel-shaped glandular cells and the tip consisting of a dome-shaped apical cell. Metabolic activity started at the trichome tip sometimes accompanied by the formation of small subcuticular cavities at the apical cell. Subsequently, metabolic activity progressed downwards in the upper glandular cells. Cells involved in the secretory process showed disintegration of the subcellular compartments and lost vitality in parallel to deposition of fluorescent and brownish metabolites. The subcuticular cavities usually collapsed in the early secretory stage, whereas the colored depositions remained in cells of senescent hairs. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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13 pages, 5704 KiB

Open AccessArticle

Two Origins, Two Functions: The Discovery of Distinct Secretory Ducts Formed during the Primary and Secondary Growth in Kielmeyera

by Ellenhise R. Costa, Marcelo M. P. Tangerina, Marcelo J. P. Ferreira and Diego Demarco

Plants 2021, 10(5), 877; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10050877 - 27 Apr 2021

Cited by 7 | Viewed by 2469

Abstract

Secretory ducts have been reported for more than 50 families of vascular plants among primary and secondary tissues. A priori, all ducts of a plant are of the same type, and only slight variations in the concentration of their compounds have been reported [...] Read more.

Secretory ducts have been reported for more than 50 families of vascular plants among primary and secondary tissues. A priori, all ducts of a plant are of the same type, and only slight variations in the concentration of their compounds have been reported for few species. However, two types of secretion were observed in primary and secondary tissues of Kielmeyera appariciana, leading us to investigate the possible influence of duct origins on the structure and metabolism of this gland. Kielmeyera appariciana has primary ducts in the cortex and pith and secondary ducts in the phloem. Both ducts are composed of uniseriate epithelium surrounded by a sheath and a lumen formed by a schizogenous process. Despite their similar structure and formation, the primary ducts produce resin, while the secondary ducts produce gum. This is the first report of two types of ducts in the same plant. The distinct origin of the ducts might be related to the metabolic alteration, which likely led to suppression of the biosynthetic pathway of terpenoids and phenolics in the secondary ducts. The functional and evolutionary implications of this innovation are discussed in our study and may be related to the diversification of Kielmeyera and Calophyllaceae in tropical environments. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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17 pages, 4970 KiB

Open AccessArticle

Uncovering the Neglected Floral Secretory Structures of Rhamnaceae and Their Functional and Systematic Significance

by Carimi Ribeiro, Cristina Marinho and Simone Teixeira

Plants 2021, 10(4), 736; https://0-doi-org.brum.beds.ac.uk/10.3390/plants10040736 - 09 Apr 2021

Cited by 4 | Viewed by 2397

Abstract

Rhamnaceae flowers are notably recognized by their fleshy nectary. Other types of floral secretory structures have been scarcely reported for this family. Thus, the objective of the present study was to update the occurrence of these structures in the family and to contribute [...] Read more.

Rhamnaceae flowers are notably recognized by their fleshy nectary. Other types of floral secretory structures have been scarcely reported for this family. Thus, the objective of the present study was to update the occurrence of these structures in the family and to contribute to the knowledge of their morphology and systematic significance. To this end, we carried out an extensive bibliographic search on the secretory structures of the family and obtained data for 257 taxa. Additionally, we presented here novel data (surface, anatomy, and ultrastructure) for six species belonging to the main clades within Rhamnaceae. The family has a wide diversity of types of mucilage-secreting structures: epidermis, hypodermis, idioblasts, cavities, and ducts. Mucilage and phenolic idioblasts are widely distributed among the floral organs. Colleters are present in all sampled species, and these are the first reports of their occurrence in floral organs of Rhamnaceae. The information obtained about the structure, secreted content, and occurrence of the secretory structures of Rhamnaceae helped us to understand the assertive folk use of its species. The absence of mucilage and the presence of resin or mucilage cavities and ducts in some taxa may have intrafamily systematic significance. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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15 pages, 8073 KiB

Open AccessArticle

More than Scales: Evidence for the Production and Exudation of Mucilage by the Peltate Trichomes of Tillandsia cyanea (Bromeliaceae: Tillandsioideae)

by Igor Ballego-Campos, Rafaela C. Forzza and Elder A. S. Paiva

Plants 2020, 9(6), 763; https://0-doi-org.brum.beds.ac.uk/10.3390/plants9060763 - 18 Jun 2020

Cited by 12 | Viewed by 3864

Abstract

Bromeliad scales have been investigated extensively due to their recognition as a key ecological and evolutionary feature of Bromeliaceae. However, much remains unknown about such trichomes and only recently mucilage exudation was described for them in a species of the subfamily Bromelioideae. The [...] Read more.

Bromeliad scales have been investigated extensively due to their recognition as a key ecological and evolutionary feature of Bromeliaceae. However, much remains unknown about such trichomes and only recently mucilage exudation was described for them in a species of the subfamily Bromelioideae. The present study aimed to investigate the secretion present in inflorescences of Tillandsia cyanea Linden ex K. Koch (Tillandsioideae) to determine whether the scales of this species also produce and release secretions. Samples of young and mature portions of inflorescences were collected and prepared according to standard methods for light and electron microscopy. Anatomical and ultrastructural results indicate that the secretion is produced by the wing portion of typical peltate trichomes on the adaxial surface of bracts. The secretory activity begins in the early stages of trichome expansion and characteristically occurs in cells exhibiting a porous cuticle and dense cytoplasm with numerous mitochondria and dictyosomes. Histochemical tests confirmed mucilage secretion and revealed proteins in the exudate. These data comprise the first record of mucilage exudation by trichomes within Tillandsioideae and indicate that this capacity may be more relevant to bromeliad biology than previously considered. Functional aspects and colleter-like activity are also discussed. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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17 pages, 18458 KiB

Open AccessArticle

The Secretory Apparatus of Tabernaemontana ventricosa Hochst. ex A.DC. (Apocynaceae): Laticifer Identification, Characterization and Distribution

by Clarissa Naidoo, Yougasphree Naidoo and Yaser Hassan Dewir

Plants 2020, 9(6), 686; https://0-doi-org.brum.beds.ac.uk/10.3390/plants9060686 - 28 May 2020

Cited by 10 | Viewed by 4431

Abstract

Due to the inconsistencies in the interpretation of laticifers within the Apocynaceae, the current study aimed to distinguish, for the first time, the type and distribution of the laticifers in the embryos, seedlings and adult plants of Tabernaemontana ventricosa (Forest Toad tree). The [...] Read more.

Due to the inconsistencies in the interpretation of laticifers within the Apocynaceae, the current study aimed to distinguish, for the first time, the type and distribution of the laticifers in the embryos, seedlings and adult plants of Tabernaemontana ventricosa (Forest Toad tree). The characterization and distribution of laticifers were determined using light and electron microscopy. The findings revealed the presence of articulated anastomosing laticifers. The laticifers were found to have originated from ground meristematic and procambium cells and were randomly distributed in all ground and vascular tissue, displaying complex branching conformations. The presence of chemical constituents within the laticifers and latex determined by histochemical analysis revealed the presence of alkaloids, phenolics, neutral lipids, terpenoids, mucilage, pectin, resin acids, carboxylated polysaccharides, lipophilic, and hydrophilic substances and proteins. These secondary metabolites perform an indispensable role in preventing herbivory, hindering and deterring micro-organisms and may possibly have medicinal importance. The outcomes of the present study outlined the first micromorphology, anatomy, ultrastructural and chemical analysis of the laticifers of T. ventricosa. In addition, this investigation similarly established the probable functions of latex and laticifers. Full article

(This article belongs to the Special Issue Plant Secretory Structures)

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