Outer Integument Research Articles

Origin of the outer integument and its implication for the angiosperm evolution

Summery: The origin of the outer integument, which is one of the prominent synapomorphies of angiosperms, was inferred to explore the phylogenetic origin of the angiosperms. Studies based on the ovules of“ANITA”, a group of early-diverged families, revealed that the ovules with the cup-shaped outer integument are derived from the ovules with hood-shaped outer integument. The morphological marker in the seed was sought for from which the outer integument morphology could be inferred because the seeds with more fossilized potential than flowers would be helpful in deducing the primitive morphology of the outer integument based on the fossil records. As a result, I found that the relative position of the micropyle to the hilum could be used as the marker for inferring the outer integument morphology(i. e., hood-shaped or cup-shaped). Based on this marker, it is inferred that the oldest seed fossils of angiosperms are derived from the ovules with the hood-shaped outer integument. Neo- and Paleo- botanical data suggests that the hood-shaped outer integument with bilateral symmetry is primitive. The bilaterally symmetrical nature is one of the characteristics of the leaf, thus the outer integument could be homologous to the leaf. Further to examine this hypothesis I analyzed the expression pattern of INO homologue of Nymphaea alba as molecular marker for the dorsiventrality. INO homologue was limitedly expressed in the outer epidermis of the outer integument, suggesting that the outer integument has the dorsiventrality. These results imply that the outer integument is derived from the leaf.In addition to this, the carpel is suggested to be homologous to sporophyll, thus the gynoecium of angiosperms is compared to the unitegmic orthotropous ovule enclosed in two leaf-like organs, which is known in some groups of the seed ferns.

Structure and development of the ovule and seed in Aristolochiaceae, with particular reference to Saruma

All members of Aristolochiaceae have anatropous, bitegmic, crassinucellate ovules, which are endostomic except in Saruma and Asarum arifolium where ovules are amphistomic. The outer integument is two cell-layered and the inner integument is three cell-layered. The chalazal megaspore is the functional one. All these conditions appear to be plesiomorphic for the order Piperales, which consists of five families, Aristolochiaceae, Hydnoraceae, Lactoridaceae, Piperaceae and Saururaceae. The embryo sac in Aristolochiaceae is eight-nucleate and corresponds to the Polygonum type; a hypostase is frequently present in this family. The seed coat of Aristolochia s.l., Asarum, Saruma and some Thottea species consists primarily of a two cell-layered testa, and a three cell-layered tegmen. In some species the cells of the outer epidermis become radially elongated, forming reticulate wall thickenings. Cells of the inner layer of the testa have crystals and thickened inner walls. The three layers of the tegmen are tangentially elongated, and become cross fibres at maturity, as fibres of the outer and inner layers are parallel to the seed axis, whereas those of the middle layer are perpendicular to it. This type of seed coat anatomy is synapomorphic for Aristolochiaceae. In addition, the gross morphology of the seed and elaiosome histology are remarkably similar in Asarum and Saruma, thus supporting a sister-group relationship between them. Embryological and seed characters do not supply any synapomorphy that support a close relationship between Aristolochiaceae, Hydnoraceae and Lactoridaceae. Instead, some seed features such as the absence of seed appendages and the collapsed cells of endotesta may indicate a close relationship of Lactoris with Piperaceae plus Saururaceae, although this is the subject of further analysis.

Ovules and seeds in Acalyphoideae (Euphorbiaceae): structure and systematic implications.

Acalyphoideae, the largest subfamily of Euphorbiaceae, are investigated with respect to ovule and seed structure on the basis of 172 species of 80 genera in all 20 tribes of Acalyphoideae sensu Webster. All species of Acalyphoideae examined have bitegmic ovules with a non-vascularized inner integument. However, noticeable differences exist among and sometimes within the genera in the thickness of the inner and outer integument, the presence or absence of vascular bundles in the outer integument, whether ovules are pachychalazal or not, the presence or absence of an aril, seed coat structure (in terms of the best-developed mechanical cell-layer), and the shape of cells constituting the exotegmen. For the latter two characters, two different types of seed coat (i.e., "exotegmic" and "exotestal") and three different types of exotegmic cell (i.e., palisadal, tracheoidal and ribbon-like) were distinguished. Comparisons showed that three tribes Clutieae, Chaetocarpeae and Pereae are distinct from the other Acalyphoideae as well as from the other Euphorbiaceae in having an exotestal seed coat with a tracheoidal exotegmen. The tribe Dicoelieae is also distinct from the other Acalyphoideae in having an exotegmic seed that is composed of ribbon-like cells of exotegmen (i.e., cells both longitudinally and radially elongated, sclerotic and pitted). The tribe Galearieae, which should be treated as a distinct family Pandaceae, is also distinct from the other Acalyphoideae in having an exotegmic seed with a tracheoidal exotegmen (i.e., cells longitudinally elongated, sclerotic and pitted). The remaining genera of Acalyphoideae always have an exotegmic seed with a palisadal exotegmen (i.e., cells radially elongated, sclerotic and pitted). The shared palisadal exotegmen supports the close affinity of Acalyphoideae (excluding five tribes) with Crotonoideae and Euphorbioideae. Within the remaining genera of Acalyphoideae, a significant diversity is found in ovule and seed morphology with respect to the thickness of the inner and outer integument, the size of chalaza, vascularization of an outer integument and an aril.

Embryology of Siparunaceae (Laurales): characteristics and character evolution.

Embryological characters of Siparunaceae, which are poorly understood, were studied on the basis of two constituent genera, an African Glossocalyx and a South American Siparuna, to better understand their evolution within Laurales. These two genera have many embryological characteristics in common with the other lauralean families. Noticeably, they share the multi-celled ovule archesporium (uncertain in Glossocalyx) as a synapomorphy with all the other lauralean families except Lauraceae, the anthers dehisced by valves as a synspomorphy with all the other lauralean families except Calycanthaceae and Monimiaceae, and the bisporangiate anther as a synapomorphy with Gomortegaceae and Atherospermataceae. Siparunaceae are, however, distinct from all other laularean families in having unitegmic ovules that were derived from bitegmic ovules, probably due to an elimination of the outer integument. Likewise, the lack of the testa (i.e., developed outer integument), the "endotegmic" seed coat, and the perichalazal seed at maturity are also characteristics of Siparunaceae. Within the family, Siparuna differs from Glossocalyx in having plural tetrads of megaspores and plural, starchy-rich, one-nucleate, tubular embryo sacs (autapomorphies). On the other hand, Glossocalyx is characterized by having bilaterally flattened seeds (autapomorphy). Although functional aspects of those autapomorphies are uncertain, both Glossocalyx and Siparuna show evolution in different embryological characters.

Isolation and analyses of genes preferentially expressed during early cotton fiber development by subtractive PCR and cDNA array.

Cotton fibers are differentiated epidermal cells originating from the outer integuments of the ovule. To identify genes involved in cotton fiber elongation, we performed subtractive PCR using cDNA prepared from 10 days post anthesis (d.p.a.) wild-type cotton fiber as tester and cDNA from a fuzzless-lintless (fl) mutant as driver. We recovered 280 independent cDNA fragments including most of the previously published cotton fiber-related genes. cDNA macroarrays showed that 172 genes were significantly up-regulated in elongating cotton fibers as confirmed by in situ hybridization in representative cases. Twenty-nine cDNAs, including a putative vacuolar (H+)-ATPase catalytic subunit, a kinesin-like calmodulin binding protein, several arabinogalactan proteins and key enzymes involved in long chain fatty acid biosynthesis, accumulated to greater than 50-fold in 10 d.p.a. fiber cells when compared to that in 0 d.p.a. ovules. Various upstream pathways, such as auxin signal transduction, the MAPK pathway and profilin- and expansin-induced cell wall loosening, were also activated during the fast fiber elongation period. This report constitutes the first systematic analysis of genes involved in cotton fiber development. Our results suggest that a concerted mechanism involving multiple cellular pathways is responsible for cotton fiber elongation.

The outer integument and funicular outgrowth complex in the ovule of Magnolia grandiflora (Magnoliaceae).

The development of the outer integument and funicular outgrowth in the ovule of Magnolia grandiflora was examined by microtomy and scanning electron microscopy to reveal the morphology and evolution of the outer integument, a novel angiosperm structure. Early in development the outer integument is semiannular, decurrent to the lateral sides of the funiculus, and extends downwards beyond the funicular outgrowth that forms in the gap of the outer integument, and is transverse to the funiculus. The outer integument then overgrows the funicular outgrowth perpendicularly to the funiculus to form a micropyle together. The hood-shaped outer integument and the funicular outgrowth compose an envelope complex, and the interpretation of a single cupular outer integument is not supported. This envelope complex may differ from the cupular outer integument of other angiosperms, e.g., Nymphaeaceae, suggesting independent origin of apparently cupular outer integuments and hood-shaped outer integuments. Anatropous curving is due mainly to differential growth of the chalaza. The bistomic micropyle of Magnoliaceae seems to represent a derived character state, compared to an endostomic micropyle.

Aroid Seeds from the Middle Eocene Princeton Chert (Keratosperma allenbyense, Araceae): Comparisons with Extant Lasioideae

A reinvestigation of more than 200 new specimens of Keratosperma allenbyense Cevallos-Ferriz et Stockey from the Middle Eocene Princeton chert allows a more detailed comparison with living Araceae and provides evidence for the evolution of the lasioid clade. The anacampylotropous seeds possess a warty seed coat, single dorsal ridge, and two lateral ridges. Idioblasts that may have contained raphides are scattered in the outer integument. The seed has a thin micropylar cover and an epistase, with evidence of mucilage in the space between these two structures. The raphe is embedded in the seed coat and parallels the concave surface of the seed. At the chalazal end of the seed, there is a prominent hypostase and podium. Endosperm tissue with dark contents and monocotyledonary embryo are present, but in most specimens these tissues are replaced by fungal hyphae. Anatomical comparisons with the extant lasioid taxa Cyrtosperma merkusii (Hassk.) Schott and Urospatha sagittifolia (Rudge) Schott were made. A reconstruction of K. allenbyense constructed from serial sections allowed the fossil to be compared with the extant genera of Araceae, subfamily Lasioideae, on the basis of external seed morphology of 22 taxa. Keratosperma appears to be a distinct genus among aroids having many shared characters with extant Lasioideae and represents the oldest known member of the lasioid clade.

Metal uptake from soils and soil–sediment mixtures by larvae of Tenebrio molitor (L.) (Coleoptera)

Bioassays were performed to evaluate the impact of soil characteristics on Cd, Cu, Pb, and Zn uptake by larvae of Tenebrio molitor. Metal accumulation was determined in 13 natural field soils, one metal-spiked field soil, four soil–sediment mixtures, and Cd- or Zn-spiked OECD artificial soil. Statistical analyses were used to investigate covariation of accumulation patterns with various soil metal pools and soil properties. Body concentrations of Cu and Zn in Zn-spiked OECD soils, field soils, and soil–sediment mixtures mostly remained constant. Considerable variation was noted for all Cd and Pb steady-state body concentrations among field soils and soil–sediment mixtures. For the spiked field soil and in the Cd-spiked OECD soil, body concentrations increased almost linearly with time. For the nonessential metals Cd and Pb, larval body concentrations correlated mainly to the total metal pool of the soil. Cd uptake at similar total Cd concentrations was within the same range among spiked OECD soils, field soils, and mixtures. A comparison of the findings with studies on other soil-inhabiting species shows that metal uptake patterns depend on metal type, soil type, and exposed species. It is suggested that soil organisms can be categorized according to gross divergence in ecophysiological characteristics, determined by, for instance, (non)permeability of the outer integument. These characteristics appear as similarities among multivariate functions as derived for the beetle.

Seed development in two species of medifixed hairy Astragalus (Fabaceae)

Summary Anatomical aspects of ovule, embryo and endosperm development are described for the zygote to cotyledon embryo stages in A. demavendicus and A. latifolius . Nucellar cells disappear during an early stage of development. The inner integument differentiates into an endothelium and an exterior layer of cells at the zygote stage. The primary endosperm nucleus divides before the zygote nucleus, forming a nuclear endosperm. In A. latifolius the polar nuclei fuse immediately after cellularization of the embryo sac, whereas in A. demavendicus they remain separated until fertilization. Endosperm cellularization begins when the embryo has developed the early globular stage in A. latifolius and the late globular stage in A. demavendicus . The inner integument is degraded at early heart stage in A. latifolius and at late heart stage in A. demavendicus , then the outer integument adjoins the embryo sac. The outer integument consists of three different tissues at this stage. As expected, the studied species which both belong to the same section of Astragalus , show major similarities in seed development. The remarked differences should be considered as variations among the species of this section.

Developmental morphology of ovules and seeds of Austrobaileyales

Development of ovules of Illicium anisatum (Illiciaceae), Trimenia moorei (Trimeniaceae), and Austrobaileya scandens (Austrobaileyaceae) (Austrobaileyales) was observed. In Austrobaileya scandens and Trimenia moorei the outer integument is hood-shaped, while it is cup-shaped in Illicium anisatum. On the basis of a phylogeny, the ovule with the hood-shaped outer integument is suggested to be primitive in Austrobaileyales. Seed development of Austrobaileyales was also examined. In Austrobaileya scandens the seed is mesotestal, ruminated, not pachychalazal, and has a micropyle–hilum complex. In Trimenia moorei the seed is exotestal, perispermous, not pachychalazal, and has a micropyle–hilum complex and a circular cap. The seed of Illicium anisatum is exotestal, not pachychalazal, and has a circular cap. Taking the character states of other basal angiosperms into account, primitive seeds of angiosperms are inferred to have such characters as the unilayered exotestal mechanical tissue, circular cap, micropyle–hilum complex and non-pachychalazy. The inferred primitive seed is very simple, suggesting that a great diversity of seeds is established through elaboration of organs/tissues of seeds, and not through reduction as hypothesised previously.

A suppressed gene in integument cells of a fiberless seed mutant in upland cotton

A fiberless seed mutant (fl) was identified in a commercial cotton (Gossypium hirsutum L.) variety Xu-Zhou 142 (FL). This phenotype is associated with lack of fiber cell initiation in the outer integument of the ovule, as was characterized by analysis of genes related to fiber differentiation and development. Two genes, fl-E6 and FL-E6, were cloned from fl-integument cells and FL-fiber or integument cells, respectively. Compared with FL-E6, fl-E6 showed a dramatic change in nucleotide sequence: (1) FL-E6 contained a tandem repetitive sequence in which GGCTCA (Gly-Ser) is repeated five times between the 82nd and the 93rd codon from the first ATG codon, while in fl-E6 the same sequence is repeated four times; (2) The fl-E6 gene encodes a polypeptide of 241 amino acids but lacks two codons between the 90th and 93rd codon and three between the 171st and 174th relative to FL-E6; (3) There are also 12 nucleotide substitutions which would result in 7 amino acid differences between fl-E6 and FL-E6. Analysis of RT-PCR and Northerm Blot showed that expression of the fl-E6 gene is suppressed in the fl-integument cells, but highly expressed in FL-fiber cells. The difference between fl-E6 and FL-E6 may be associated with lower expression of fl-E6 in the fl-integument cells. Searches of protein databases with the FL-E6 gene sequence showed similarity to the protein backbones of two arabinogalactan-proteins (AGPs), one from the filtrate of suspension-cultured cells ofPyrus cornmunis (AGPPc2) and the other fromNicotiana alata (AGPNa2). Although the function of the FL-E6 protein in differentiation and development of cotton fiber cells is not known, the data indicate that the mutation of fl-E6 gene from FL-E6 gene may inhibit the fiber cell initiation from epidermal cells of the outer integument of the ovule.

Ovules and seeds in Euphorbioideae (Euphorbiaceae): structure and systematic implications.

Ovule and seed structure in Euphorbioideae, one of the five euphorbiaceous subfamilies, is surveyed to evaluate its systematic implications on the basis of 79 species representing four of five tribes. All Euphorbioideae, like two other "uniovulate" subfamilies Acalyphoideae and Crotonoideae, but unlike most of two "biovulate" subfamilies Oldfieldioideae and Phyllanthoideae, consistently have a persistent and palisadal exotegmen composed of radially elongate, sclerotic, and pitted cells. Within Euphorbioideae, the tribe Stomatocalyceae (also with the palisadal exotegmen) is unusual in having vascular bundles in outer integument and clearly distinct from the remaining Euphorbioideae and the other "uniovulate" subfamilies. With the exclusion of Stomatocalyceae, Euphorbioideae are not anatomically divided into major groups such as a pseudanthial and a non-pseudanthial clade, but instead have some remarkable diversity within a tribe, a subtribe, and even a genus in the three ovule and seed characters: (1) the thickness of the inner integument, (2) the thickness of the outer integument, and (3) the presence or absence of an aril. Groups of genera and species wrapped by different combinations of their characteristics, however, are not necessarily harmonized with tribal or subtribal classifications available. Anatomical similarities and dissimilarities presented in this paper, as well as relationships among taxa presented in the classifications available, will be critically evaluated in the light of results of ongoing molecular phylogenetic analyses.

Isolation of genes preferentially expressed in cotton fibers by cDNA filter arrays and RT-PCR

Cotton fibers are single-cell trichomes derived from the outer integument cells of ovules. Recent studies showed that the rapid elongation of fibers was coordinated with the expression of a subset of fiber-specific genes. Here we report the use of filter arrays of cDNAs to identify genes preferentially expressed in cotton fibers. An array of 1536 clones was hybridized with cDNA probes prepared from wild type (fiber-containing) and fl mutant (naked) ovules at 5 days post-anthesis (DPA), respectively. Subsequent RT-PCR analyses of 14 genes identified ten that were highly transcribed in cotton fibers. Among them, an RD22-like protein ( GhRDL), a putative acyltransferase ( GhACY), a Fiddlehead homolog ( GhFDH), a serine carboxypeptidase-like protein ( GhSCP), two tubulin components ( GhTUA6 and GhTUB1) and the previously reported gene encoding fiber protein E6, showed a fiber-enriched expression pattern. The other three genes, including an actin ( GhACT), a putative cellulose synthase catalytic subunit ( GhCesA-5) and a putative 24-sterol- C-methyltransferase ( GhSMT), were actively transcribed in fibers during the elongation stage, but their transcripts were also clearly present in other tissues. The possible roles of these proteins in cotton fiber development and growth are discussed.

SUPERMAN attenuates positive INNER NO OUTER autoregulation to maintain polar development of Arabidopsis ovule outer integuments.

The outer integument of Arabidopsis ovules exhibits marked polarity in its development, growing extensively from the abaxial side, but only to a very limited extent from the adaxial side of the ovule. Mutations in two genes affect this asymmetric growth. In strong inner no outer (ino) mutants outer integument growth is eliminated, whereas in superman (sup) mutants integument growth on the adaxial side is nearly equal to wild-type growth on the abaxial side. Through complementation and reporter gene analysis, a region of INO 5'-flanking sequences was identified that contains sufficient information for appropriate expression of INO. Using this INO promoter (P-INO) we show that INO acts as a positive regulator of transcription from P-INO, but is not sufficient for de novo initiation of transcription in other plant parts. Protein fusions demonstrate nuclear localization of INO, consistent with a proposed role as a transcription factor for this member of the YABBY protein family. Through its ability to inhibit expression of the endogenous INO gene and transgenes driven by P-INO, SUP is shown to be a negative regulator of INO transcription. Substitution of another YABBY protein coding region (CRABS CLAW) for INO overcomes this negative regulation, indicating that SUP suppresses INO transcription through attenuation of the INO positive autoregulatory loop.

SCB1, a BURP-domain protein gene, from developing soybean seed coats.

We describe a gene, SCB1 (Seed Coat BURP-domain protein 1), that is expressed specifically within the soybean (Glycine max [L.] Merrill) seed coat early in its development. Northern blot analysis and mRNA in situ hybridization revealed novel patterns of gene expression during seed development. SCB1 mRNA accumulated first within the developing thick-walled parenchyma cells of the inner integument and later in the thick- and thin-walled parenchyma cells of the outer integument. This occurred prior to the period of seed coat maturation and seed filling and before either of the layers started to degrade. SCB1 may therefore play a role in the differentiation of the seed coat parenchyma cells. In addition, the protein product appears to be located within cell walls. The SCB1 gene codes for a new member of a class of modular proteins that possess a carboxy-terminal BURP domain and a variety of different repeated sequences. The sequence of the genomic clone revealed the insertion of a Tgm transposable element in the upstream promoter region but it is not certain whether it contributes to the tissue-specific pattern of SCB1 expression.

Ovule, seed and seedling characters in Acharia (Achariaceae) with evidence of myrmecochory in the family

An investigation of mature seed structure in Guthriea capensis and ovule-to-seed development in Acharia tragodes indicate that the two species are herbaceous myrmecochores with similar adaptations for seed dispersal and germination. The development and structure of the modified seed tissues, namely a sarcotestal elaiosome, a fringe layer in the mesotesta, endotestal-exotegmic mechanical layers and a chalazal seed lid are described. Additional embryological similarities between the two taxa include, amongst others, sessile ovules, distally lobed outer integuments, zigzag micropyle canals formed by both integuments, bisporic Allium Type embryo sacs, suspensorless embryos belonging to the Penaea Variation of the Asterad Type, and small embryos in the mature seed. In Acharia intraseminal embryo growth occurs before radicle emergence, germination is epigeal and seedlings belong to the Macaranga Type.

Petunia actin-depolymerizing factor is mainly accumulated in vascular tissue and its gene expression is enhanced by the first intron

Actin-depolymerizing factor (ADF) is one of the actin cytoskeleton-modulating proteins. We have characterized the accumulation pattern of petunia ADF proteins. PhADF proteins are accumulated in every petunia organ and their accumulation is differentially regulated by developmental signals. Their cellular localization is vascular tissue-preferential in vegetative organs, whereas somewhat different in reproductive organs. In reproductive organs, PhADFs are present in outer integument, endocarp of ovary wall, transmitting tissue of style, and epidermis and endothecium of young anther. From a petunia genomic library, we have isolated a genomic clone encoding PhADF1. Comparison to complementary DNA sequence revealed that the coding region of PhADF1 gene consists of three exons and two introns. Analysis of chimeric gene expression using β-glucuronidase as a reporter gene in transgenic Arabidopsis revealed that PhADF1 was strongly expressed in every vegetative tissue except petal. In addition, expression of the gene was highly enhanced by its first intron. These results suggest that PhADF1 gene of petunia is mainly expressed in vascular tissues and its expression is regulated by intron-mediated enhancement mechanism.

Environmental factors affecting germination of apple of Peru

Abstract Laboratory and field experiments were conducted to determine the effects of several environmental factors on seed germination and seedling emergence of the invasive weed, apple of Peru. The anatomy of the seed was also investigated in this study. The anatomy of the seed is similar to that of an eggplant (Solanum melongena L.) seed. The seed is albuminous, and consists of a seed coat, endosperm, and an embryo. The seed coat, which consists of both outer and inner integuments, is relatively thick. Fresh and dry stored seeds exhibited strong dormancy. Hot water treatment did not affect the seed germination in the light, but significantly (P < 0.05) reduced the germination rate in the dark. Dry-heat treatment had no significant effect on seed germination in the dark, but it significantly (P < 0.05) increased the germination rate in the light. Cold stratification alone did not influence seed germination under constant temperature (25 C) but affected it under alternating temperature (25–15 C). However,...

CDNA cloning and expressions of cytochrome P450 1A in zebrafish embryos.

Cytochrome P450 1A (CYP1A) is well known for being induced by aromatic hydrocarbons, including 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD). We determined the complete cDNA sequence of a CYP1A open reading frame with both 5'- and 3'-ends in zebrafish (zfCYP1A), a useful model for environmental toxicology. zfCYP1A shows high percentage identity with CYP1As of mammals, domestic fowl and xenopus (51.9-60.4%), as well as the other fish species (63.8-89.2%). As revealed by in situ hybridization and immunohistochemistry, zfCYP1A was scarcely detected in control embryos but was markedly induced by TCDD especially in heart, vascular endothelial cells, intestinal epithelium, pronephros and outer integument in both prehatched and hatched embryos. These expression patterns are consistent with possible involvement of zfCYP1A in TCDD-induced toxicities.

Seed Coat Anatomy and Its Relationship to Seed Dispersal in Subfamily Lecythidoideae of the Lecythidaceae (The Brazil Nut Family)

The seed coat anatomy of representative species from all 10 Neotropical genera of Lecythidaceae subfamily Lecythidoideae and from the Paleotropical Barringtonia (Lecythidaceae subfamily Planchonioideae) was studied. The seed coat is mainly composed of the testa, which is developed through moderate or intensive multiplication of the outer integument of the ovule. The tegmen, derived from the inner integument of the ovule, is mostly crushed at seed maturity. Barringtonia and Grias, with fruits as diaspores, have an unspecialized exotesta and a poorly differentiated seed coat. In contrast, species of Lecythidoideae, with seeds as diaspores, possess well-differentiated seed coats with diversified protective mechanisms. Examples include: an expanded and lignified exotesta that serves as a water barrier and protects the embryo; an extensive area of tannin cells that provides a chemical defense against pathogens and predators; a thick and sclerotic mesotesta that protects the embryo; and large fibers surrounding and supporting the vascular bundles. In addition, other modifications of the seed coat are probably adaptations for seed dispersal by different dispersal agents. These include the exotestal hairs of Couroupita guianensis, which possibly protect the embryos as they pass through the digestive tracts of peccaries; an extension of the seed coat into a wing in species of Cariniana and Couratari, which facilitate wind dispersal; the papillate exostestal cells of Allantoma lineata, which probably promote dispersal by water; the well-developed arils of species of Corythophora and Lecyt his, probably sought after by animals, which in turn disperse the seeds; and the sarcotesta of Eschweilera ovalifolia, consumed by fish, which in turn disperse the seeds. We conclude that the highly diversified anatomy and morphology of the seed coat of the Lecythidoideae has evolved from relatively homogeneous ovules in response to pathogens and predators as well as to abiotic and biotic dispersal agents.