Lignified Endocarp Research Articles

Carpological features of Iris hybrida Hort. (Rodion.) in the conditions of the M. M. Hryshko National Botanical Garden in Kyiv, Ukraine

The results of a morphological study of fruit and seed characteristics of Iris hybrida hort. are presented. The morphometric measurements of fruits and seeds are described including length and width. Such morphological features as the shape of fruits and seeds, hilum shape, the position and size of the seed embryo, endosperm features, the surface of the fruits and seeds are analyzed. Eleven tall bearded iris varieties of domestic and foreign selection were chosen from the collection fund of the M. M. Gryshko National Botanical Garden. The varieties selected are: ‘Alians’, ‘Amethyst Flame’, ‘Earth Song’, ‘Local Color’, ‘Mescalero Chief’, ‘Scintilation’, ‘Vanity’, ‘Violet Harmony’, ‘Zlatokudraya’, ‘Ayu-Dag’, and ‘Pryvit Z Ukrayiny’. These varieties are distinguished by their decorative qualities, are widely distributed and are promising candidates for further selection work. Among the researched varieties, fruit bodies of obovate, wide-oval, elongated-elliptic and rounded shapes were distinguished. Seeds of compressedprismatic, rounded, wedge-shaped, inverted ovoid and flattened-semicircular shapes were recorded. The surface of the seeds observed was spongy-wrinkled, hard, sometimes with narrow rims along the edge of the faces. The shape of the hilum showed slight variations. The described carpological features of the I. hybrida varieties align with literature data on the general morphology of the fruits and seeds of other types of irises. The varieties of I. hybrida studied were from the M. M. Gryshko National Botanical Garden collection fund, and when grown in the conditions of the forest-steppe, we’re able to form full viable seeds with free pollination, which indicates their high adaptability. According to the histogenetic classification, the fruits of the studied varieties belong to the Lilium type (with a lignified endocarp). The structure of the seed coat, consisting of the exo-, meso- and endotesta, differences in the size, shape of the seeds and the hilum were also noted. The morphological descriptions of the fruits and seeds of the investigated varieties provide additional data about the genus Iris L.

Hydrolyzable tannins are incorporated into the endocarp during sclerification of the water caltrop Trapa natans.

The water caltrop (Trapa natans) develops unique woody fruits with unusually large seeds among aquatic plants. During fruit development, the inner fruit wall (endocarp) sclerifies and forms a protective layer for the seed. Endocarp sclerification also occurs in many land plants with large seeds; however, in T. natans, the processes of fruit formation, endocarp hardening, and seed storage take place entirely underwater. To identify potential chemical and structural adaptations for the aquatic environment, we investigated the cell-wall composition in the endocarp at a young developmental stage, as well as at fruit maturity. Our work shows that hydrolyzable tannins-specifically gallotannins-flood the endocarp tissue during secondary wall formation and are integrated into cell walls along with lignin during maturation. Within the secondary walls of mature tissue, we identified unusually strong spectroscopic features of ester linkages, suggesting that the gallotannins and their derivatives are cross-linked to other wall components via ester bonds, leading to unique cell-wall properties. The synthesis of large amounts of water-soluble, defensive aromatic metabolites during secondary wall formation might be a fast way to defend seeds within the insufficiently lignified endocarp of T. natans.

Metabolomics Data Revealed Metabolite Changes during Endocarp Lignification in Kernel-Using Apricot

To understand the metabolite dynamics and genetic regulatory mechanism of apricot shell, a typical endocarp, before and after lignification are unknown, we investigated the metabolite differences of the endocarp of ‘Youyi,’ a popular kernel-using apricot cultivar, using ultra-performance liquid chromatography tandem mass spectrometry strategy. The endocarp thickness increased rapidly from 8 to 37 days after flowering (DAF) and lignin deposition began at 37 DAF. In total, 626 non-volatile metabolites were obtained from the endocarp tissues before (33 DAF) and after (41 and 45 DAF) lignification. The relative sugar and organic acid contents decreased continuously and those of L-phenylalanine and L-tyrosine increased after lignification. In the non-lignified endocarp, the phenylpropanoid metabolites were mainly in the form of p-coumaric acid, ferulic acid, neochlorogenic acid, dicumarol, coniferin, and some lignans. After lignification, the metabolites were mainly in the form of glycoside lignin or lactone coumarins, and the relative contents of L-asarinin and forsythin increased. The results of transcriptome confirmed the upregulation of genes related to lignin biosynthesis, including β-glucosidase and coniferyl-alcohol glucosyltransferase and laccases, accelerated lignification. This study provides insights into the formation of lignified endocarp in a kernel-using apricot and clarifies the role of monolignin transport and oxidative polymerization.

Metabolism of Stone Fruits: Reciprocal Contribution Between Primary Metabolism and Cell Wall.

Cell wall turnover and modification in its composition are key factors during stone fruit development and patterning. Changes in cell wall disassembly and reassembly are essential for fruit growth and ripening. Modifications in cell wall composition, resulting in the formation of secondary cell walls, are necessary for producing the most distinctive trait of drupes: the lignified endocarp. The contribution of primary metabolism to cell wall synthesis has been investigated in detail, while the knowledge on the contribution of the cell wall to primary metabolites and related processes is still fragmented. In this review, starting from peculiarities of cell wall of drupes cells (in mesocarp and endocarp layers), we discuss the structure and composition of cell wall, processes related to its modification and contribution to the synthesis of primary metabolites. In particular, our attention has been focused on the ascorbate synthesis cell wall-related and on the potential role of cyanogenic compounds in the deposition of the secondary cell wall.

Fruit fracture biomechanics and the release of Lepidium didymum pericarp-imposed mechanical dormancy by fungi

The biomechanical and ecophysiological properties of plant seed/fruit structures are fundamental to survival in distinct environments. Dispersal of fruits with hard pericarps (fruit coats) encasing seeds has evolved many times independently within taxa that have seed dispersal as their default strategy. The mechanisms by which the constraint of a hard pericarp determines germination timing in response to the environment are currently unknown. Here, we show that the hard pericarp of Lepidium didymum controls germination solely by a biomechanical mechanism. Mechanical dormancy is conferred by preventing full phase-II water uptake of the encased non-dormant seed. The lignified endocarp has biomechanically and morphologically distinct regions that serve as predetermined breaking zones. This pericarp-imposed mechanical dormancy is released by the activity of common fungi, which weaken these zones by degrading non-lignified pericarp cells. We propose that the hard pericarp with this biomechanical mechanism contributed to the global distribution of this species in distinct environments.

The Phylogenetic Significance of Fruit Anatomical and Micromorphological Structures in Chinese Heracleum Species and Related Taxa (Apiaceae)

Abstract Fruit anatomical and micromorphological structures from 28 species of Heracleum and three species of Angelica as outgroups were examined under light microscopy to identify characters useful in delimiting clades circumscribed in a previous molecular phylogenetic study. Maximum parsimony analyses of 20 fruit structural characters resulted in a generally poorly resolved strict consensus tree, yet one whose major clades matched those revealed previously. Angelica apaensis and Heracleum xiaojinense are best treated as the single species Angelica apaensis within Angelica s. s. All remaining Heracleum species share a highly lignified hypendocarp and a lignified endocarp, vascular bundles in marginal wings situated in the middle of the wing, and a commissure width the same as the mericarp width. These Heracleum species are recognized in four major clades with the following fruit structural features: (1) Heracleum s. s., having non-septate, clavate dorsal vittae that do not extend to the bottom of the see...

Seed germination of Phillyrea angustifolia L., a species of difficult propagation

Aim of study: The purpose was to determine the type of dormancy and the optimal germination conditions of Phillyrea angustifolia (Oleaceae) seeds.Area of study: Germination requirements of P. angustifolia seeds collected from wild plants growing in the province of Ávila (Central Spain) were studied.Materials and methods: Seed water uptake was measured. Seeds with and without an endocarp were germinated at different temperatures, and several treatments were tested.Main results: The lignified endocarp interferes mechanically with the emergence of the radicle, and the treatments that achieved the highest germination percentages were the total removal of the endocarp with pliers (84%) or the immersion in liquid nitrogen for 1 min (97%). Scarification with concentrated sulphuric acid did not significantly increase germination compared to the control seeds, and treatments with dry heat or wet heat were detrimental to seed germination. The optimum temperature for germination was 15 ºC. A pre-sowing treatment of soaking in distilled water for 24 h slightly increased germination speed. Neither cold stratification at 5 ºC nor soaking in a gibberellic acid solution improved seed germination. Research highlights: Phillyrea angustifolia seeds have physiological dormancy – that is, the embryo does not have enough growth potential to overcome the mechanical restriction of the lignified endocarp. The seeds do not exhibit physical dormancy, given their water-permeable lignified endocarp. Our results suggest that the optimum germination protocol for P. angustifolia would be the total removal of the endocarp or immersion in liquid nitrogen for 1 min, followed by immersion in distilled water for 24 h and then seed incubation at 15 ºC in light or darkness.

Seed germination characteristics of Phillyrea angustifolia L. and P. latifolia L. (Oleaceae), two Mediterranean shrub species having lignified endocarp

The aim of this study was to determine the germination characteristics of Phillyrea angustifolia L. and P. latifolia L. seeds in order to develop an optimized propagation protocol for Phillyrea species. Seeds of P. angustifolia and P. latifolia were collected from wild plants growing in Caceres province (CW Spain) and Andalucia (S Spain), respectively. Percentage o f water uptake for P. latifolia seeds was calculated. Seeds with and without endocarp were germinated at different constant and alternating temperatures. Seeds without endocarp were soaked in distilled water or gibberellic acid, and then set to germinate. Seeds with endocarp of both species were stratified at 5 oC for 30 or 90 days and then the endocarp was completely removed from the seeds before they were sowed. Chemical scarification with sulfuric acid and mechanical scarification were tested on P. angustifolia seeds with endocarp. Phillyrea endocarp was permeable to water, since Phillyrea seeds with endocarp imbibed water, but water uptake was faster when the endocarp was removed. Moreover, the encodarp could interfere mechanically in the emergence of the radicle, since seed germination of Phillyrea species was promoted by the complete removal of the lignified endocarp surrounding each seed. Optimal germination temperature for both species was 15 oC, and lower temperatures produced secondary dormancy. Soaking in distilled water or gibberellic acid did not significantly enhance seed germination. Cold stratification and chemical scarification treatments were detrimental for seed germination.

Fruit indehiscence caused by enhanced expression of NO TRANSMITTING TRACT in Arabidopsis thaliana.

In flowering plants, fruit dehiscence enables seed dispersal. Here we report that ntt-3D, an activation tagged allele of NO TRANSMITTING TRACT (NTT), caused a failure of fruit dehiscence in Arabidopsis. We identified ntt-3D, in which the 35S enhancer was inserted adjacent to AT3G-57670, from our activation tagged mutant library. ntt-3D mutants showed serrated leaves, short siliques, and indehiscence phenotypes. NTT-overexpressing plants largely phenocopied the ntt-3D plants. As the proximate cause of the indehiscence, ntt-3D plants exhibited a near absence of valve margin and lignified endocarp b layer in the carpel. In addition, the replum was enlarged in ntt-3D mutants. NTT expression reached a peak in flowers at stage 11 and gradually decreased thereafter and pNTT::GUS expression was mainly observed in the replum, indicating a potential role in fruit patterning. NTT:GFP localized in the nucleus and cytoplasm. FRUITFULL (FUL) expression was downregulated in ntt-3D mutants and ntt-3D suppressed upregulation of FUL in replumless mutants. These results indicate that NTT suppresses FUL, indicating a potential role in patterning of the silique. In seed crops, a reduction in pod dehiscence can increase yield by decreasing seed dispersal; therefore, our results may prove useful as a basis to improve crop yield.

The fruit of Bursera: structure, maturation and parthenocarpy

The deterioration of seasonally tropical dry forests will stop with the implementation of management plans for this ecosystem. To develop these plans, we require information regarding aspects such as germination and the presence of 'empty seeds' of representative species-like, for example, Bursera, a genus with a high number of endemic species of the Mesoamerican Hotspot-that would enable us to propagate its species. The main purpose of this study is to describe the phenological and structural characteristics of fruits of 12 Bursera species and provide useful data for future studies on germination and seed dispersal, and to acquire new and useful information to understand the phylogenetic relationships of the Burseraceae family. We described the phenology of fruit ripening in 12 species of Bursera. Fruits were collected from the study sites in three different stages of development. The histochemical and anatomical characteristics of fruits of all species were described with the use of inclusion techniques and scanning microscopy. There is a time gap between the development of the ovary and the development of the ovule in the 12 studied species. The exposed pseudoaril during the dispersion stage is an indicator of the seed's maturity and the fruit's viability. The Bursera fruit shows the same structural pattern as that of Commiphora, as well as many similarities with species of the Anacardiaceae family. All species develop parthenocarpic fruits that retain the structural characteristics of the immature fruits: soft tissues rich in nitrogen compounds and few chemical and physical defences. Insects were found mainly inside the parthenocarpic fruits in eight species of Bursera. The dispersion unit in Bursera consists of a seed, a lignified endocarp that protects the seed, and a pseudoaril that helps attract seed dispersers. The production of parthenocarpic fruits is energy saving; however, it is necessary to evaluate the potential benefits of this phenomenon.

The study of a SPATULA-like bHLH transcription factor expressed during peach (Prunus persica) fruit development

Extensive studies on the dry fruits of the model plant arabidopsis (Arabidopsis thaliana) have revealed various gene regulators of the development and dehiscence of the siliques. Peach pericarp is analogous to the valve tissues of the arabidopsis siliques. The stone (otherwise called pit) in drupes is formed through lignification of the fruit endocarp. The lignified endocarp in peach can be susceptible to split-pit formation under certain genetic as well as environmental factors. This phenomenon delays processing of the clingstone varieties of peach and causes economical losses for the peach fruit canning industry. The fruitfull (FUL) and shatterproof (SHP) genes are key MADS-box transcription protein coding factors that control fruit development and dehiscence in arabidopsis by promoting the expression of basic helix-loop-helix (bHLH) transcription factors like Spatula (SPT) and Alcatraz (ALC). Results from our previous studies on peach suggested that temporal regulation of PPERFUL and PPERSHP gene expression may be involved in the regulation of endocarp margin development. In the present study a PPERSPATULA-like (PPERSPT) gene was cloned and characterized. Comparative analysis of temporal regulation of PPERSPT gene expression during pit hardening in a resistant and a susceptible to split-pit variety, suggests that this gene adds one more component to the genes network that controls endocarp margins development in peach. Taking into consideration that no ALC-like genes have been identified in any dicot plant species outside the Brassicaceae family, where arabidopsis belongs, PPERSPT may have additional role(s) in peach that are fulfilled in arabidopsis by ALC.

Developmental Anatomy and Morphology of the Ovule and Seed of Heliconia (Heliconiaceae, Zingiberales)

The developmental anatomy and morphology of the ovule and seed in several species of Heliconia were investigated as part of an embryological study of the Heliconiaceae and to provide a better understanding of their relationships with the other families of the Zingiberales. Heliconia species have an ovule primordium with an outer integument of both dermal and subdermal origin. The archesporial cell is divided into a megasporocyte and a single parietal cell, which in turn are divided only anticlinally to form a single parietal layer, disintegrating later during gametogenesis. The embryo sac was fully developed prior to anthesis. In the developing seed, the endosperm was nuclear, with wall formation in the globular stage; a nucellar pad was observed during embryo development, but later became compressed. The ripe fruit contained seeds enveloped by a lignified endocarp that formed the pyrenes, with each pyrene having an operculum at the basal end; the embryo was considered to be differentiated. Most of these characteristics are shared with other Zingiberales, although the derivation of the operculum from the funicle and the formation of the main mechanical layer by the endocarp are unique to the Heliconiaceae.

ONTOGENY OF THE FRUITS OF TWO ANOMALOUS AFRICAN WOODY GENERA, POLEMANNIOPSIS AND STEGANOTAENIA (APIACEAE), AND THEIR PHYLOGENETIC RELATIONSHIP

The fruits of two anomalous African woody Apiaceae, Polemanniopsis marlothii and Steganotaenia araliacea, differ in structure when mature though the ovaries are very similar, both being heteromorphic in young flower stage. This unexpected heteromorphism in S. araliacea has important implications for future studies of basal genera and the interpretation of fruit characters in general. Both taxa also have unique ‘intrajugal cavities’ in the ovaries and fruits, which supports the idea that the two genera are closely related, sharing some characters with the Hydrocotyloideae and Saniculoideae. This provides morphological and anatomical evidence to support the previous hypotheses on their relationship with Saniculoideae. Their basal position is also supported by characters shared with other basal genera previously included in Hydrocotyloideae, such as the lateral wings and slightly lignified endocarp in Polemanniopsis and Steganotaenia.

Ontogeny and Structure of the Pericarp of Schinus terebinthifolius Raddi (Anacardiaceae)

The fruit of Schinus terebinthifolius Raddi is a globose red drupe with friable exocarp when ripe and composed of two lignified layers: the epidermis and hypodermis. The mesocarp is parenchymatous with large secretory ducts associated with vascular bundles. In the mesocarp two regions are observed: an outer region composed of only parenchymatous cells and an inner region, bounded by one or more layers of druse-like crystals of calcium oxalate, composed of parenchymatous cells, secretory ducts and vascular bundles. The mesocarp detaches itself from the exocarp due to degeneration of the cellular layers in contact with the hypodermis. The lignified endocarp is composed of four layers: the outermost layer of polyhedral cells with prismatic crystals of calcium oxalate, and the three innermost layers of sclereids in palisade.

Endocarp Structural Components of Insect Resistance in Almond

Almond, as with other stone fruit, possesses a highly lignified endocarp or shell. The dominant hard-shelled trait (D-) is positively associated with greater resistant to insect infestation than nuts expressing the paper-shelled (dd) trait. Hard-shelled genotypes have undesirable effects, including a lower kernel meat-to-nut crack-out ratio, greater kernel damage during mechanical shelling, and a reduction in plant energy available to kernel development. Histogenic analysis shows that the almond endocarp, unlike peach, has a tri-partite structure. Insect feeding studies have subsequently demonstrated that the inner endocarp layer, which is similar in both hard and paper-shelled types, is the most important structural barrier to insect infestation. Shell-seal integrity and X-ray studies have confirmed that discontinuities at the inner endocarp suture seal are the primary, though not the sole site of entry for insect pests. Paper-shelled almond selections with highly lignified and well-sealed inner endocarps show resistance levels comparable to hard shelled types but with crack-out ratios 30% to 40% higher. Pseudo-paper-shelled types have also been selected, in which a highly lignified outer endocarp is formed, but is retained by the fruit hull at dehiscence. An understanding of endocarp morphology and development is thus important in breeding for insect resistance as well as the commercial utilization of both kernel and hull.

Solution calcium concentration and application date effects on pod calcium uptake and distribution in florunner and tifton‐8 peanut

Abstract Calcium is known to be passively absorbed by developing peanut pods directly from the soil solution. However, the factors influencing the distribution of Ca in the hull and seed have not been thoroughly studied. In this study of two peanut cultivars (Florunner and Tifton‐8) differing in hull and seed size, pod zones containing differing solution concentrations of Ca (0.025, 0.625, 1.875 and 3.75 mM) were separated from the rooting medium. The increased pod surface area, and hull thickness of Tifton‐8 resulted in greater uptake of Ca (mg pod‐1) and higher hull Ca concentrations when compared to Florunner. However, the thin hull of Florunner (0.59 nun, compared to 1.04 mm for Tifton‐8) resulted in a mean seed Ca contribution to total pod Ca uptake of 62.5% compared to 46.5% for Tifton‐8. Increasing the calcium level in the pod zone increased pod dry weight in both Florunner and Tifton‐8. Pods grown in 3.75 mM Ca for the first 30 days after initial pegging, followed by no Ca in the pod zone until 30 days after initial pegging, had significantly lower seed and hull Ca when compared to pods grown in a continuous supply of Ca. Electron microprobe analysis of pod sections revealed high Ca levels in the exocarp, mesocarp and the outer and inner surfaces of the testa. Both the highly lignified endocarp and the seed were significantly lower in Ca concentration than other pod layers. These results were confirmed by direct analysis of the tissue.

A preliminary study on the germination of Sclerocarya birrea subsp. caffra

Seeds of Sclerocarya birrea (A. Rich.) Hochst. subsp. caffra (Sond.) Kokwaro, commonly known as marula, occur in locules within a hard lignified endocarp. The endocarp appears to restrict germination mainly by offering mechanical resistance. It may also restrict the leaching of germination inhibitors and possibly serve as a barrier to oxygen diffusion. The endocarp does not restrict water uptake. High germination counts were only obtained by removing opercula. Leaching slightly improved germination of seeds in intact endocarps. The optimum germination temperature of opercula-removed seeds was between 27° and 37°C. Storage improved rate of germination.