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STUDIES IN THE EMBRYOLOGY OF COMPOSITAE. IV. THE TRIBE INULEAE
Abstract
Embryology of Blumea malabarica, B. membranacea, Laggera pterodonta, Anaphalis busna and Vicoa auriculata has been studied. The anther is tetrasporangiate in all the members except in Blumea membranacea where it is bisporangiate. The anther tapetum is of the Periplasmodial type. Both tetrahedral and isobilateral pollen tetrads are found. Mature pollen grains are three-celled with thick spinous exine. The ovary is bicarpellary syncarpous and unilocular with a single basal ovule. In one instance in Blumea malabarica two ovules per ovary with a rudimentary septum separating them was observed. The single hypodermal archesporial cell functions directly as the megaspore mother cell. The embryo sac develops according to the Polygonum type. The synergids in Blumea malabarica are hooked while in other members they are pear shaped. There are three antipodal cells except in Blumea membranacea where they increase up to eight. Endosperm development in Blumea malabarica is of the Nuclear type while in Blumea membranacea and Laggera pterodonta it is of the Cellular type. One or two layers of endosperm persist up to maturity. Embryo development follows the Senecio variation of Asterad type. The embryological information of this tribe along with that of other tribes will be utilized in evaluating the interrelationships of the family Compositae in a later paper.
... diverSity And evOlutiOnAry trendS in embryOlOgicAl FeAtureS OF ASterAceAe Anther Tetrasporangiate anthers, as found in Stifftia and Wunderlichia, are common in Asteraceae (Davis, 1966;Johri et al., 1992;Jurukova-Grančarova, 1997, 2004Pandey, 2003;Ao, 2007;Deng et al., 2010;Rad & Hajisadeghian, 2014;Franca et al., 2015), Asterales (Johri et al., 1992;Tobe & Morin, 1996;and references therein), and are plesiomorphic, as in angiosperms as a whole (Davis, 1966;Johri et al., 1992;Doyle & Endress, 2000). The few reports of bisporangiate anthers in Asteraceae are restricted to some Asteroideae (Deshpande, 1960;Davis, 1962a, b;Sundara Rajan, 1974;Pullaiah, 1979Pullaiah, , 1982aPullaiah, , 1983Franca et al., 2015) and are apomorphic in Asteraceae. In most cases, it is unknown how the anthers became bisporangiate, by fusion or suppression of the sporangia of either the ventral or the dorsal theca. ...
... Secretory tapetum, as in Stifftia and Wunderlichia, also occurs in Goodeniaceae and Calyceraceae. It possibly appears as a plesiomorphic character state in Asteraceae being modified to periplasmodial in Mutisioideae (Maheswari Devi, 1957), Cichorioideae (Ahlstrand, 1985) and Asteroideae (Venkateswarlu & Maheswari Devi, 1955;Maheswari Devi, 1963;Davis, 1964;Sundara Rajan, 1968;Sharma & Murty, 1978;Pullaiah, 1978Pullaiah, , 1979Pullaiah, , 1981Pullaiah, , 1983Ahlstrand, 1985;Lakshmi & Pullaiah, 1986;Gotelli et al., 2008). The periplasmodial character state is not exclusive to these subfamilies and has probably appeared several times independently. ...
... Three-celled male gametophytes can be found in some Carduoideae (Yeung et al., 2011) and Pertyoideae (Kapil & Sethi, 1962). Two-and three-celled male gametophytes are found in Cichorioideae (Venkateswarlu & Maheswari Devi, 1955;Pullaiah, 1982b;Sood & Thakur, 1985;Jurukova-Grančarova, 1997;Yurukova-Grancharova, 2004;Yurukova-Grancharova & Dimitrova, 2006;Chehregani et al., 2011) and Asteroideae (Maheshwari & Roy, 1952;Venkateswarlu & Maheswari Devi, 1955;Davis, 1962a, b;Maheswari Devi, 1963;Davis, 1964;Misra, 1965;Sundara Rajan, 1968, 1974Eliasson, 1971;Sharma & Murty, 1978;Pullaiah, 1979Pullaiah, , 1981Pullaiah, , 1983Prakasa Rao et al., 1979;Laksmi & Pullaiah, 1986;Lersten & Curtis, 1990;Ao, 2007;Gotelli et al., 2008;Liu et al., 2012;Rad & Hajisadeghian, 2014;Franca et al., 2015). In contrast to the hypothesis of Lundberg (2009), the two-celled male gametophyte is plesiomorphic in Asteraceae, and the three-celled gametophyte is apomorphic. ...
Asteraceae are one of the largest families of angiosperms and comprise > 1700 genera and 24 000 species currently in 13 subfamilies. However, despite recent and continuous improvement regarding their classification, little is known about their embryological diversity, especially in some of the early-diverging subfamilies including Stifftioideae and Wunderlichioideae. These subfamilies were previously considered to be similar, sharing several external features such as anther appendages, pollen grains, pappus bristles and cypsela trichomes. Ontogenetic and anatomical studies could reveal deeper levels of homology and expand the features of interest for the systematics of the family. Also, the lack of knowledge of the early-divergent subfamilies precludes the reconstruction of evolutionary trends in Asteraceae and Asterales. Here, we compared the anthers, ovaries, ovules, fruits and seeds of two Stifftia spp. and two Wunderlichia spp. to identify possible evolutionary trends. Our results show that embryology in these genera is similar, with slight differences in pollen grain ornamentation, types and distribution of ovary trichomes, antipodal persistence, pericarp tissue organization, occurrence of phytomelanin in the fruit wall, the form of the carpopodium, shape and lignification of carpopodial cells, form and distribution of pappus bristles, and lignification patterns of exotesta cells. The results also demonstrate novelties for the family, including Basic-type anther wall development and trichomes on the inner ovary epidermis of W. mirabilis, funicular trichomes in both Stifftia spp., and funicular stomata and phytomelanin in the pericarp of both Wunderlichia spp. Therefore, our data support Stifftioideae and Wunderlichioideae as distinct but closely related subfamilies. The results also open new perspectives on how anther, ovary and fruit evolved in the family. The occurrence of a Basic-type anther wall in early-divergent subfamilies may represent a symplesiomorphy or apomorphy for the family. This will depend on how the anther develops in the subfamilies related to Wunderlichioideae and Stifftioideae. Vascularization of the ovary was different from that previously known in the family and throws doubts upon its origin. Phytomelanin is a rare substance in plants, found only in seeds of most families of Asparagales and fruits of some Asteraceae; it had previously been found in fruits of Heterocoma (Cichorioideae) and some Asteroideae. We detected phytomelanin in Wunderlichia, indicating that presence of this substance has evolved independently three times in the fruits of the family.
ADDITIONAL KEYWORDS: cypselae-fruit anatomy-megagametogenesis-megasporogenesis-microgametogenesis-microsporogenesis-phytomelanin-seed anatomy.
... In H. annuus L. pollen mother cells undergo meiotic division simultaneously and produce tetrahedral microspore tetrads, as in Vernonia divergens and Adenostema lavenia, while in Elephantopus scaber (Vernonieae) and Adenostema rugosum (Euparieae), pollen tetrads have an isobilateral arrangement (Pullaiah, 1979). Mature pollen grains are suboblate, triporate and angulaperturate with spherical amb as specified by Gotelli et al. (2008). ...
In this study, anther ontogeny and microsporogenesis were analysed in Helianthus annuus L. The undifferentiated anther is ovoid-shaped and the differentiation starts with the appearance of archesporial cells. Mature anthers are tetrasporangiate. The anther wall is composed of epidermis, endothecium, middle layer and plasmodial tapetum. Endothecial cells show no fibrous thickening. Tapetum is amoeboid type with binucleate cells. Epidermal layer remains intact until anther dehiscence; however, middle layer, endothecium and tapetum disappear during development. At the end of regular meiotic division tetrahedral microspore tetrads are formed. Pollen grains are triporate, suboblate and angulaperturate.
Changes in the role of the seed coat during seed development have not been extensively examined, mainly because the greater emphasis is usually placed upon its function in the mature seed. Additionally, there have been few studies on the seeds of Asteraceae, and those that have been undertaken rarely addressed functional aspects of seeds. The present study examined seed ontogeny in species of Eupatorieae (Asteraceae) and investigated the role of the seed coat in seed nutrition and abortion. A new pattern of seed vasculature was encountered for the family, in addition to two other types previously described for other species. The most significant role of the seed coat among the species of Eupatorieae examined was in seed nutrition. The inner mesotesta is consumed during seed development, while the remaining layers collapse at maturity and cease to function. Seed abortion was observed in all of the species examined, varying from 95% in Symphyopappus reticulatus to 18.5% in Vittetia orbiculata. Changes in endothelial tissue were found in all episodes of abortion, although variation was observed concerning remnant structures and their degree of development. The young seed coat in Asteraceae has a nutritive role, while at maturation the pericarp serves a protective function.
The development of plant population biology (SOLBRIG et al., 1979) as a discipline which connects plant systematics with ecology has been one of the most important trends within recent years, though at present more questions have been asked than answered. Likewise, the study of reproductive biology, notably of tropical plants, has turned into a field of tremendous activity; most of it will be reviewed in this volume under pollination ecology, but the results are of course of great interest for the evolution and systematics of seed plants. Methodological progress has been made in the interpretation of phytochemical data. Apart from that, the trends mentioned in the last review (Progr. Bot. 41, 239) are still of interest. As to the problems of classification in general, the number of cladistic studies has increased, but it is still doubtful if they will have a major impact. Comprehensive, integrated approaches to the systematics and biology of major groups include the Solanaceae symposium (HAWKES et al., 1979), and the resumption of the Natürliche Pflanzenfamilien series with a multi-authored treatment of the Loganiaceae (LEEUWENBERG, 1980).
Genus Inula L. is paraphyletic and heterogeneous with respect to several diverse characters, which makes delimiting taxa difficult. Dittrichia Greuter, Limbarda Adans. and Pulicaria Gaertn. were previously located in different sections within Inula, and subsequently segregated into separate genera. According to the latest molecular phylogenetic analyses based on plastid and nuclear DNA sequence data, supported by morphological and karyological data, it is suggested that type species of genus, Inula helenium L., should be separated from the remaining species to form a separate genus. The goals of this research are to (1) perform comparative micro-morphological and anatomical analysis of fruit and receptacle of species belonging to Inula, Pulicaria, Dittrichia and Limbarda genera in order to estimate their systematic value; (2) define further characters that would be useful in taxonomic delimitation of species that are often misidentified due to their morphological similarities; (3) investigate whether all these characters support the segregation of I. helenium into a separate genus. Using stereoscopic, light and scanning electron microscope, micro-morphological and anatomical characters of cypsela and receptacle were revealed. Cross sections of mature fruit were obtained using cryotechnic procedure. This study pertains to the evaluation of examined characters using correspondence analysis. The species’ characters, as well as those specific to the genera are identified and described. The findings reveal that the organisation of sclerenchyma tissue in a fruit and receptacle characteristics are features that tend to be diagnostic for genera. The results yielded by this study provide valuable criteria for delimitation of taxa belonging to Compositae tribe Inuleae, which are often misidentified due to their morphological similarities. Our results, based on anatomical and micro-morphological characteristics of the fruit and receptacle, also revealed that I. helenium can be distinguished as a separate taxon with equally small percentage of statistical support as Dittrichia, Limabarda and Pulicaria had.
Anthers are tetrasporangiate inEmilia sonchifolia andNotonia grandiflora and bisporangiate inGynura nitida. The male archesporium consists of a single row of 6–8 hypodermal cells. Development of anther walls is according to the Dicotyledonous type. The tapetum corresponds to the periplasmodial type. Both tetrahedral and isobilateral pollen tetrads are produced. The pollen grains at the time of anther dehiscence are three-celled inG. nitida andE. sonchifolia;N. grandiflora is male sterile. All the three species have Polygonum type embryo sacs with variable antipodal cells. InG. nitida andE. sonchifolia fertilization is porogamous, endosperm development is of the cellular type, and embryo development closely follows that ofSenecio vulgaris (Souèges 1920a, b).
It appears that the tapetum is universally present in land plants, even though it is sometimes difficult to recognize, because it serves mostly as a tissue for meiocyte/spore nutrition. In addition to this main function, the tapetum has other functions, namely the production of the locular fluid, the production and release of callase, the conveying of P.A.S. positive material towards the loculus, the formation of exine precursors, viscin threads and orbicules (= Ubisch bodies), the production of sporophytic proteins and enzymes, and of pollenkitt/tryphine. Not all these functions are present in all land plants:Embryophyta. Two main tapetal types are usually distinguished in theSpermatophyta: the secretory or parietal type and the amoeboid or periplasmodial type; in lower groups, however, other types may be recognized, with greater or lesser differences. A hypothetical phylogenesis of the tapetum is proposed on the basis of its morphological appearance and of the nutritional relations with meiocytes/spores. The evolutionary trends of the tapeta tend towards a more and more intimate and increasingly greater contact with the spores/pollen grains. Three evolutionary trends can be recognized: 1) an intrusion of the tapetal cells between the spores, 2) a loss of tapetal cell walls, and 3) increasing nutrition through direct contact in narrow anthers.
The embryology ofLagascea mollis, Zinnia angustifolia andGalinsoga parviflora has been studied. The anther archesporium is hypodermal and consists of a single row of 6–8 cells, there are two layers below the epidermis of the anther and a periplasmodial tapetum. Ripe pollen grains are tricolpate and 3-celled. The ovary contains a single ovule, but in a few cases ofGalinsoga parviflora two ovules have been found. The female archesporium is unicellular, but sometimes more than one archesporial cell occurs inLagascea mollis andZinnia angustifolia. The embryo sac development is of the Polygonum type, the synergids are hooked, antipodal cells show great variation. The endosperm development is cellular inGalinsoga parviflora and peripheral layer persists in the mature seed. The embryo development conforms to the Senecio variation of the Asterad type. The pericarp structure and cmbryological features support the disputed systematic position ofLagascea withinHeliantheae.
The male and female gametophytes formation, fertilisation, and embryo development were observed inSolidago canadensis andConyza stricta. The anther is tetrasporangiate and its wall development conforms to the Dicotyledonous type. Simultaneous cytokinesis in
pollen mother cells results in tetrahedral or isobilateral tetrads. Pollen polymorphism is a common feature inS. canadensis. The ovule is anatropous, unitegmic and tenuinucellate showing an ovular vascular strand. The female archesporium is hypodermal
and single celled. The development of the embryo sac is of the Polygonum type. InS. canadensis seed set is completely absent and multiplication occurs by vegetative propagation. InC. stricta fertilisation is progamous. Triple fusion and syngamy occur more or less simultaneously. Endosperm is cellular and the embryogeny
corresponds to the Asterad type.
Ammobium alatum is a perennial herb whose discoid-homogarnous capitula are
surrounded by several rows of involucral bracts with white radiating laminae.
Four microsporangia are present in each anther and their development and
dehiscence are described.
The ovule is anatropous, unitegmic, and tenuinucellate. The archesporial cell
is hypodermal in origin and, following considerable increase in size, it functions directly
as the megaspore mother cell. Cytokinesis and wall formation are postponed until
after Meiosis 11 and a dyad is formed in which each cell is binucleate. The embryo sac
is bisporic and its development is a variation of the Allium type. After fertilization,
the surviving synergid may increase greatly in size but it does not extend into the
micropyle and it collapses when the embryo reaches the seventh cell generation.
Embryogeny is of the Asterad type and the sequence of events leading up to
maturation of the embryo and of the fruit is described.
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