Printer Friendly

Male and Female Gametophyte Development in Cichorium intybus.

Byline: ABDOLKARIM CHEHREGANI, FARIBA MOHSENZADEH AND MONA GHANAD

ABSTRACT

Gametophyte development and embryogenesis of Cichorium intybus L. were studied. The flowers and buds, in different developmental stages, were removed, fixed in FAA70, embedded in paraffin and sliced at 7-10 um. Staining was carried out with PAS and contrasted with Hematoxylin. Results showed that anther is ovoid-shaped and tetrasporangiated. Development of anther wall follows the dicotyledonous type, which is composed of an epidermal layer, an endothecium layer, one middle layer and tapetum. The tapetum is secretory type at the beginning and plasmodial type at the end of anther development. Microspore tetrads are tetragonal. Pollen grains are spherical, tricolpate and bi-cellular at the mature form. Ovule is anatropous, unitegmic and tenuinucellate. Development of ovule starts with the formation of primordium. In this primordium, an archeosporial cell produces a megaspore mother cell, which undergoes meiosis, forming a linear tetrad.

The micropylar cell is functional megaspore that survives and will function in megagametophyte development. Embryo sac development is of the Polygonum type. The mature embryo sac is composed of 7 cells, one central cell contained polar nuclei or secondary nucleus, two synergids and one egg cell that formed egg apparatus and three antipodal cells that are degenerate in the mature embryo sac before fertilization. (c) 2011 Friends Science Publishers

Key Words: Asteraceae; Male gametophyte; Female gametophyte; Cichorium intybus

INTRODUCTION

Asteraceae is the largest plant family. This family contained about 1600 genera and 23000 species (Kadereit and Jeffrey, 2007; Funk et al., 2009). Its abundant members, its global distribution and the fact that it comprises many medicinal species have made it the subject of many researches (Martin et al., 2009). The circumscription of the genera is often problematic and some of these have been frequently divided into minor subgroups (Hind et al., 1995). The principal taxonomic problems within the family are interrelationships amongst the genera, the circumscription of sub-tribal taxa and polymorphic species (Torrel et al., 1999; Inceer and Beyazoglu, 2004; Chehregani and Mehanfar, 2007; Arabaci and Yildiz, 2009).

Essential oils medicinally important compounds have been isolated from Asteracean species (Beerentrup and Robbelen,1987;Heywood and Humphries,1997).Many researchers have studied the karyological properties of the Asteracean species (Valles et al., 2005), but there are few embryological studies, so new studies are necessary to improve the embryological knowledge of the family (Valles et al., 2005). Based on present embryological studies, many exceptional events were reported in the members of this family, including Nemec phenomenon (Davis, 1968; Batygina, 1987), increasing of synergids (Cichan and Palser, 1982), increasing of antipodal cells (Richards, 1997; Pandey, 2001), four-celled female gametophyte (Harling, 1951) and apomixis (Davis, 1968; Chaudhury et al., 2001).

The aim of this study was to study of gametophyte and embryo development in Cichorium intybus. Although there are some reports about other members of Asteraceae (Lakshmi and Pullaiah, 1979; Pullaiah, 1979; Rangaswamy and Pullaiah, 1986; Hiscock et al., 2003) but this is the first embryological investigation in C. intybus.

MATERIALS AND METHODS

The Cichorium intybus L. plants were collected from the naturally growing area in Broujed. Voucher specimens are deposited in the local herbarium of the Islamic Azad University (Broujerd branch) and labeled as follows: Lorestan province of Iran, 15 km from Broujerd to Malayer, Alt. 2500 m. The florescence and buds, in different developmental stages, were removed, fixed in FAA70 (formalin, acetic acid and 70% ethanol, 1:1:17 v/v), stored in 70% ethanol, embedded in paraffin and sliced at 7-10 mm with a Micro DC 4055 microtome. Staining was carried out with PAS (Periodic Acid Schiff) according to the protocol suggested by Yeung (1984) and contrasted with Meyer's Hematoxylin (Chehregani and Sedaghat, 2009). For each developmentalstage,severalsectionsobservedundera Zeiss Axiostar Plus light microscope. Many samples were studied for each stage and photomicrographs were made from the best ones.

RESULTS

Male gametophyte development: Results showed that the anther of Cichorium intybus is tetrasporangiate. Primary sporogenous cells (Fig. 1a) were developed directly as microsporocytes (Fig. 1b). Each microsporocyte undergoes meiosisandresultedinamicrosporetetrad.Meiosis staggers including prophase I, metaphase I (Fig. 1c), anaphase I and then telophase I (Fig. 1d), followed by prophase II, metaphase II, anaphase II (Fig. 1e), and telophase II (Fig. 1f) were observed clearly in the specimens.Cellwallwasnotformedbetweenthetwo newly formed nuclei in telophase I stage (Fig. 1d). In the all tetrads, the cytokinesis was done as simultaneous type. The final tetrads are recognized mostly as tetragonal (Fig. 1f, g). Callosic wall is formed around the tetrad and between each monad (Fig. 1g). In the two neighboring pollen sacs, microspores development is synchronized. The microspores when released from tetrad are non-vacuolated.

They have a dense cytoplasm with irregular shape and a prominent centrally placed nucleus (Fig. 1h). Its nucleus takes up a peripheral position together the central vacuole develops, i.e., forming a large vacuole squashes the cytoplasm and the nucleus toward the microspore margin. Nucleus of microspores then undergoes mitosis and resulted to form two unequal nuclei, a large vegetative and small generative one thus to form bi-nucleate pollens (Fig. 1i), further two- cellones.Pollengrains have a considerable thick exine (Fig. 1i).

Formation of anther wall: In early stage of development, several rows of archesporial cells differentiated beneath the epidermis of the anthers. They have dense cytoplasm and prominent nuclei. They are divided periclinally, cause to formation of inner sporogenous cells and outer parietal cells. Parietal cells are divided and cause to form anther wall that consists of three layers; the epidermis, endothecia, and tapetum (Figs. 1a-i). The tapetal cells are uni-nucleate, bi- nucleate or tri-nucleate at the stage of microsporocyte (Figs. 1 d, e). They have rapid mitosis and contained high level polyploidy (Fig. 1e), indicating their high metabolic activity, thatissimilartotheantipodalsintheembryosac. Extensions of tapetal cells are visible in the anther locule at the microspores releasing stage (Fig. 1h). The tapetal cells were degenerated at the stage of uni-cellular or bicellular pollen grains, and only relics of the tapetum are visible in the stage (Fig. 1i).

In this species, the middle layer is not developed. Female gametophyte development: Results showed that in C. intybus, ovary is composed of a single carpel and a locule with an ovule (Fig. 2a). The ovule is of anatropous type and unitegmic (Fig. 2a). During early ovular development, only a single hypodermal cell was observed. It is larger and differentiated from the neighboring cells and then become the megaspore mother cell (mc). The ovule contained small mass of nucellus (Fig. 2a). Megaspore mother cell (Figs. 2b, c) continues to growth, enters meiosis, produces dyad (Fig. 2d) and finally results in a linear-shaped tetrad of megaspores that the chalazal megaspore is functional one. Mitotic divisions take placed in the functional megaspore and resulted to form a two nucleated embryo sac (Fig. 2f), four nucleated embryo sac (Fig. 2g), and finally eight nucleate embryo sac was produced. Cell formation takes place in the embryo sac and mature embryo sac was formed (Fig. 2h).

Embryo sac formation and maturation follows as the Polygonum type. Egg cells are larger and distinguishable from synergids by its position (Fig. 2h). The two polar nuclei are fused and a large secondary nucleus was formed, before the formation of egg apparatus containing of egg cell and two synergids (Figs. 2h, i). The polar nuclei are visible in the center of embryo sac that are fussing just before fertilization and produced a secondary nucleus (Fig. 2i). Antipodal cells are degenerated in the studied flowers (Fig. 2i). Secondary nucleusismigratedtowardtheeggapparatus(Fig.2i). Some gametophyte characters were illustrated in Table I.

DISCUSSION

Results of this research showed that development of thethreelayeredantherwalloccurredasthe dicotelydonous-type in C. intybus (Davis, 1964). Archesporial cells are recognized by their prominent nuclei and compact cytoplasm. They are divided periclinaly resulted to form outer primary parietal and inner sporogenous cells that is accordance with the findings of Xue and Li (2005). The endothelial fibrous thickening is not as clearly observed as in the most representatives of Asteraceae (Yurukova-Grancharova et al., 2006). Although presence of middle layer was reported by Rangaswamy and Pullaiah (1986). It seems that there is no developed middle layer. A sharp correlation was observed between the meiotic division in pollen mother cells (PMCs) and development of anther's tapetum (Figs. 1b, g) that was reported for other Asteraceaen members (Gustafsson, 1946).

Tapetum cells have high level of polyploidy that is indicating their high metabolic activity (Maheshwari, 1950). Two basic types of tapetum are recognized in Angiosperms: secretory and amoeboid type (Pacini et al., 1985). In C. intybus the tapetum passes at the first a parietal (secretory) phase with multiplication of the nuclei (2-3 nuclei per cell) and later it changes in to amoeboidal (periplasmodial) type so that its periplasmodial extensions are observed toward the anther locule (Fig. 1h).

In C. intybus, the primary sporogenous cells become directly pollen mother cells (PMCs) that are as few rows of PMCsinthepollensac(Fig.1b).Therearefewplant species that have such character (Hu, 1982). The significance of this type of pollen mother cells development is not understood in plant phylogeny (Pan et al., 1997).

Table 1: Some gametophyte characters in C. intybus

Characters###Quantitv

Ovule number###1

Ovule length###260 im

Ovule width###140 im

Embryo sac length###180 jim

Ovary hair###Present

Number of nucellus layers in the wide of###12-14

embryo-sac

Position of megagametocyte###Second layer

Form of megaspore tetrads###Linear

Fusion lime of polar nuclei###Before emigration to

###micropylar end

Fusion position of polar nuclei###Center of embryo sac

Amyloplast accumulation in embryo sac###Weak

Growth pattern of integuments###Grow faster on opposite side of

###funicule

Number of layers in integument###4

Number of pollen grains in each anther###20-35

Polar length of mature pollen grains###60 um

Endothecium thickness###15 um

Each microsporocyte undergoes meiosis and produced microspore tetrad. The tetrads are mostly tetragonal (Fig. 1f, g). In two neighboring sporangia, microspores are synchronized development. The microspores at releasing time are non-vacuolated. They have compact cytoplasm, irregular shape, with a prominent and centrally located nucleus (Fig. 1h). The nucleus is then divided by the mitosis into two nuclei, a small generative and a large vegetative nucleus, so called bi-nucleated pollen grain, further two-cell onethatisdifferentfromtheresultsofLakshmiand Pullaiah (1979) in the other Asteracean member, that reported that pollen grains are 3-celled when shed.

In C. intybus, the chalazal megaspore of the linear- shaped tetrad gives rise to form Polygonum type of embryo sacasdescribedformorethan70%ofangiosperm (Maheshwari, 1950; Batygina, 1987). The other three megaspores were degenerated rapidly. Linear tetrads were reported by prior researchs in other species of Asteraceae(Lakshmi and Pullaiah, 1979; Kapil and Bhatnagar, 1981; Rangaswamy and Pullaiah, 1986). Remaining megaspore produced 8-nucleated and then cellulized embryo sac. In mature embryo sac three cells were differentiated at the micropylar end that consists of an Oospher and two Synergids. In this study, both synergid cells were seen in the embryo sac. It means that C. intybus is an allogamous species. In the plant, fertilization gives rise to degenerate one of the synergids, and the other synergid should be degenerated few days after the flower opening (Chehregani and Sedaghat, 2009).

Two free polar nuclei were located at thecenterofembryosacthatcametowardtheegg apparatus, fussing took place near the egg apparatus and just prior to fertilization and secondary nucleus was resulted.

In Polygonum type development of embryo sac, antipodal cells are placed on the chalazal end of embryo sac. They are usually three and variable in size and number (Maheshwari, 1950; Cameron and Prakash, 1994; Xiao and Yuan, 2006), as reported in Asteraceae (Rangaswamy and Pullaiah, 1986). Our results indicated that the antipodal cells are degenerated in the late stages of embryo sac development. In this species, it seems that antipodal cells have not any specific role, but their function is importing of nutrients into the embryo sac at the early developmental stage (Diboll, 1968).

Acknowledgment: This study was supported by the grant provided by research and technology council of Islamic AzadUniversity,BroujerdBranch.Theauthorswishto thank Prof. Dr. Shahin Zarre, from the University of Tehran, for his valuable comments.

REFERENCES

Arabaci, T. and B. Yildiz, 2009. Taxonomy and threatened categories of three Achillea L. (Asteraceae-Anthemideae) species previously cited in the data deficient (DD) category. Turkish J. Bot., 32: 311-317

Batygina, T.B., 1987. Embryology of Flowering Plants: Terminology and Concepts. Science Publishers, USA

Beerentrup, H. and G. Robbelen, 1987. Calendula and Coriandrum-new potential oil crops for industrial uses. Fat. Sci. Technol., 6: 227-230

Cameron, B.G. and N. Prakash, 1994. Variations of the megagametophyte in the Papilionoidea. Advances in legume systematics. Str. Bot., 6: 97-115

Chaudhury, A.M., A. Koltunow, T. Payn, M. Luo, M.R. Tucker, E.S. Dennis and W.J. Peacock, 2001. Control of early seed development. Annu. Rev. Cell Dev. Biol., 17: 677-699

Chehregani, A. and N. Mehanfar, 2007. Achene Micro-morphology of Anthemis (Asteraceae) and itsAllies inIranwith Emphasis on Systematics. Int. J. Agric. Biol. Sci., 9: 486-488

Chehregani, A. and M. Sedaghat, 2009. Pollen grain and ovule development in Lepidium vesicarium (Brassicaceae). Int. J. Agric. Biol. Sci., 9: 486-488

Cichan, M.A. and B.F. Palser, 1982. Development of normal and seedless achenes in Cichorium intybus (Compositae). American J. Bot., 69: 885-895

Davis, G.L., 1968. Apomixis and abnormal anther development in Calotis lappulacea Benth. (Compositae). Australian J. Bot., 16: 1-17

Davis, G.L., 1964. Embryologicalstudies in the compositae. IV. Sporogenesis,gametogenesis,andembryogenyinBrachycome ciliaris (Labill.). Less. Australian J. Bot., 12: 142-151

Diboll, A.G., 1968. Fine structural development of the megagametophyte of Zea mays following fertilization. American J. Bot., 55: 787-806

Funk, V.A., A. Susanna, T. Stuessy and R. Bayer, 2009. Systematics, Evolution and Biogeography of the Compositae. International Association for Plant Taxonomy, Washington DC

Gustafsson, L., 1946. Apomixis in higher plants. Part I. The mechanism of apomixis. Acta University Lund, 42: 1-67

Harling, G., 1951. Embryological studies in the Compositae. 2. Anthemideae-Chrysantheminae. Acta Hortic. Bergiani, 16: 1-56

Heywood, V.H. and C.J. Humphries, 1997. Anthemideae. Systematic review. In: Heywood, V.H., J.B. Harborne and B.L. Turner (eds.), The Biology and Chemistry of the Compositae, Vol. II, pp: 851-898. London, New York, San Francisco: Academic Press

Hind, D.J.N., C. Jeffrey and G.V. Pope, 1995. Advances in Compositae Systematics, p: 469. Royal Botany Gardens Kew Hiscock, S.J., S.M. Mc Innis, D.A. Tabah, C.A. Henderson and A.C. Brennan, 2003. Saprophytic self-incompatibility in Senecio squalidus L. (Asteraceae). J. Exp. Bot., 54: 169-174

Hu, S.Y., 1982. Embryology of Angiosperm, p: 30. High Education Press, Beijing, China Inceer,H.andO.Beyazoglu,2004.Karyological studiesin Tripleurospermum (Asteraceae, Anthemideae) from north-east Anatolia. Bot. J. Linnean Soc., 146: 427-429

Kadereit, J. and C. Jeffrey, 2007. Flowering Plants, Vol. VIII. Eudicots. Asterales, Springer-Verlag Press, Berlin Heidelberg, Germany Kapil, R.N. and A.K. Bhatnagar, 1981. Ultra-structure and biology of female gametophyte in flowering plants. Cytology, 70: 291-337

Lakshmi, S.P. and T. Pullaiah, 1979. Embryology of Senecio tenuifolius Burm. F. (Asteraceae). Taiwania, 32: 208-213

Maheshwari, P., 1950. An Introduction to the Embryology of Angiosperms, p: 453. Mc Graw-Hill, New York

Martin, E., M. DinC and A. Duran, 2009. Karyological study of eight Centarea L. taxa (Asteraceae) from Turkey. Turkish J. Bot., 33: 97- 104

Pacini, E., G.G. Franchi and M. Hesse, 1985. The tapetum: its form, functionandpossiblephylogenyinEmbryo-phyta.PlantSys. Evolut., 149: 155-185

Pan, K.Y., J. Wen and S.L. Zhou, 1997. Embryological study on Mosla chinensis (Lamiaceae). Acta Bot. Sin., 39: 111-116

Pandey,B.P.,2001.ATextbookofBotany,Angiosperms.Taxonomy, Anatomy, Embryology (Including TissueCulture) andEconomic Botany. McGrew Hill, New York

Pullaiah, T., 1979. Studies in the Embryology of Compositae. IV. The Tribe Inuleae. American J. Bot., 66: 1119-1127

Rangaswamy, V.and T. Pullaiah, 1986. Studies inthe embryology of Senecio candicans Dc. (Compositae). J. Indian Bot. Soc., 65: 509-512

Richards, A.J., 1997. Plant Breeding Systems. Chapman and Hall Torrel, M., N. Garcia-Jacas, A. Susanna and J. Valles, 1999. Phylogeny of Artemisia(Asteraceae-Anthemideae)inferredfromnuclear ribosomal DNA (ITS) sequences. Taxon, 48: 721-736

Valles, J., T. Garnatje, S. Garcia, M. Sanz and A.A. Korbkov, 2005. ChromosomenumbersinthetribesAnthemideaeandInuleae (Asteraceae) in Kazakhstan. Bot. J. Linnean Soc., 148: 77-85

Xiao, D.X. and Z. Yuan, 2006. Embryogenesis and seed development in Sinomanglietia glauca (Magnoliaceae). J. Plant Res., 119: 163-166

Xue, C.Y. and D.Z. Li, 2005. Embryology of Megacodon stylophorus and Veratrilla baillonii (Gentianaceae): descriptions and systematic implications. Bot. J. Linnean Soc., 147: 317-331

Yeung, E.C., 1984. Histological and histochemical staining procedures. In: Vasil, I.K. (ed.), Cell Culture and Somatic Cell Genetics of Plants, pp: 689-697. Orlando, Florida: Academics Press Yurukova-Grancharova, P., P. Robeva-Davidova and V. Vladimirov, 2006. On the embryology and mode of reproduction of selected diploid species of Hieracium s.l. (Asteraceae) from Bulgaria. Flora, 8: 668- 675
COPYRIGHT 2011 Asianet-Pakistan
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2011 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Chehregani, Abdolkarim; Mohsenzadeh, Fariba; Ghanad, Mona
Publication:International Journal of Agriculture and Biology
Article Type:Report
Geographic Code:1USA
Date:Aug 31, 2011
Words:2763
Previous Article:Effect of Heavy Metals Pollution on Pistachio Trees.
Next Article:Chemical Variation on the Essential Oil of Thymus praecox ssp. scorpilii var. laniger.
Topics:

Terms of use | Privacy policy | Copyright © 2022 Farlex, Inc. | Feedback | For webmasters |