See discussions, stats, and author profiles for this publication at: http://www.researchgate.net/publication/223082185 Flower morphologic anatomy and embryological characteristics in Chrysanthemum multicaule (Asteraceae) ARTICLE in SCIENTIA HORTICULTURAE · MAY 2010 Impact Factor: 1.5 · DOI: 10.1016/j.scienta.2010.02.009 CITATIONS DOWNLOADS VIEWS 7 67 222 7 AUTHORS, INCLUDING: Sumei Chen Aiping Song Nanjing Agricultural University Nanjing Agricultural University 90 PUBLICATIONS 599 CITATIONS 28 PUBLICATIONS 114 CITATIONS SEE PROFILE SEE PROFILE Available from: Aiping Song Retrieved on: 11 July 2015 Scientia Horticulturae 124 (2010) 500–505 Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Flower morphologic anatomy and embryological characteristics in Chrysanthemum multicaule (Asteraceae) Yanming Deng, Sumei Chen, Nianjun Teng, Fadi Chen ∗, Fengtong Li, Aiping Song, Zhiyong Guan College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China article info abstract Article history: Chrysanthemum multicaule is an annual herbaceous ornamental species. The inflorescence is gynomo- Received 12 October 2009 noecious and consists of bisexual tubular florets and female ray florets. The pistils consist of two stigmas Received in revised form 8 February 2010 which are of the open type with a hollow stylar canal. At the base of the tubular floret style, the pistil is Accepted 9 February 2010 surrounded by oil gland cells. The anthers are tetrasporangiate and the young anther wall is composed of epidermis, endothecium, middle layer and tapetum. The mature anther wall comprises only thickened Keywords: endothecium after the release of the pollens. In the tubular florets, simultaneous microsporocyte meiotic Chrysanthemum multicaule cytokinesis results in mostly tetrahedral with a small proportion of decussate tetrads. The mature pollen Gametogenesis Sporogenesis grain is tricellular. The ovules are unitegmic and tenuinucellate, and the nucellus degenerates during the Embryogenesis development of the megasporocyte. The development of the embryo sac follows the Polygonum type. At Anatomy 4–6 days after blooming, the embryos reached the globular stage, thereafter passing through the heart- and torpedo-shape stages before maturing into the cotyledon embryos. From blooming to seed maturity, it takes about 3–4 weeks under our conditions. © 2010 Elsevier B.V. All rights reserved. 1. Introduction 2007). Here, we describe the morphology and anatomical structure of the florets of C. multicaule, and its sporogenesis, gametogenesis, Many Chrysanthemum species (Asteraceae-Anthemideae) are and embryogenesis, with a view to providing a firm basis for the exploited by the horticultural industry (Bremer and Humphries, utilization of this species. 1993). Chrysanthemum coronarium is a famous ornamental plant, while C. segetum is consumed as a common vegetable (Castellanos et al., 2001). The annual herbaceous species C. multicaule Desf. orig- 2. Materials and methods inates from Africa, and has been introduced to many countries. In China, it has become a particularly popular ornamental plant. The C. multicaule plants were grown at the Chrysanthemum species is highly fertile, flowers from mid-spring to early summer, Germplasm Resource Preserving Centre, Nanjing Agricultural Uni- grows to a height of 10–20 cm, and forms a dense mass of short versity, China. Inflorescences at various stages of development branches and leaves. As a result, it is an ideal subject for ground- were fixed in 5:5:90 formalin:acetic acid:70% ethanol (FAA), dehy- cover in borders, for filling flower beds and as a pot plant (Chen et drated through an alcohol series, infiltrated with xylene, and al., 1995; Zhao et al., 2009). The species has been shown to be highly embedded in paraffin wax as described by Li et al. (2009). Sections resistant to a spectrum of diseases and pests (Zhou et al., 2006). C. were cut to a thickness of 6–10 ␮m, stained in Heidenhain’s haema- multicaule is therefore regarded not only as a useful ornamental toxylin, and observed by optical microscope. The florets external plant in itself, but also as a potential reservoir of useful genetic morphology was observed directly under stereoscopic microscope. variation for chrysanthemum improvement via wide hybridization (Zhao et al., 2009). As far as we are aware, no systematic study has been made as 3. Results yet of either the reproductive organs of C. multicaule, or its embry- ological characteristics, even though this information is relevant 3.1. The morphology and anatomical structure of the flower to the understanding of angiosperm ontogenesis (Hu, 2005; Ao, The inflorescence is gynomonoecious, bearing both unisexual (female) ray florets and bisexual (hermaphroditic) tubular florets (Fig. 1A). The corolla of the ray floret consists of a single petal ∗ Corresponding author. Tel.: +86 25 84395231; fax: +86 25 84395266. (Fig. 1B), while the tubular bisexual florets are gamopetalous with E-mail address: [email protected] (F. Chen). five partially fused petals (Fig. 1C). 0304-4238/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.scienta.2010.02.009 Y. Deng et al. / Scientia Horticulturae 124 (2010) 500–505 501 Fig. 1. Flowers of C. multicaule. ov, ovary; pe, petal; st, stigma. (A) A flower. (B) A ray floret. (C) A tubular floret. Scale bars: A = 10 mm, B=5mm,C=1mm. Fig. 2. The anatomical structures of tubular and ray florets in C. multicaule. ova, ovary; ovu, ovule; pe, petal; sta, stamen; stb, style branch; sty, style. (A) The ray floret is composed of a single petal and two style branches. The arrow shows the hollow stylar canal. (B) The tubular floret has five stamens and five petals. The arrow shows the hollow stylar canal. (C) A tubular floret with five split stamens. The arrows indicate the ruptured anther walls. (D) A longitudinal section of a ray floret showing the unilocular ovary with an anatropous ovule. (E) A longitudinal section of a tubular floret showing the unilocular ovary with no ovule. (F) A longitudinal section of a tubular floret showing the oil gland cells with dense cytoplasm (arrowhead). (G) Transection of a tubular floret showing the oil gland cells (arrowheads) surrounding the style. Scale bars = 100 ␮m. Each style of both tubular and ray florets has two stigmas and 3.2. Microsporogenesis, male gametogenesis and the formation of is of the open (or hollow) type with a circular and hollow stylar the anther wall canal (Fig. 2A–C). Every tubular floret contains five tetrasporangiate anthers, which is typical type for dicotyledonous species according At an early developmental stage, rows of archesporial cells dif- to Hu (2005) (Fig. 2B and C). The normal ovary of tubular and ray ferentiate beneath the anther epidermis, and divide periclinally to floret is unilocular with an anatropous ovule (Fig. 2D), but about form the outer primary parietal and the inner primary sporogenous 7% ovaries of the tubular florets is female sterile where ovule is cells. The archesporial cells can be recognized by their dense cyto- absent at pollen shed stage (Fig. 2E). At the base of the tubular floret plasm and conspicuous nuclei (Fig. 3A). The primary sporogenous style, oil gland cells with dense cytoplasm and conspicuous nuclei cells divide to form the secondary sporogenous cells (Fig. 3B) and surround the pistil (Fig. 2F and G). then develop into pollen mother cells (PMCs) (Fig. 3C and D). Meio- 502 Y. Deng et al. / Scientia Horticulturae 124 (2010) 500–505 Fig. 3. Microsporogenesis, male gametogenesis and the development of anther wall in tubular florets of C. multicaule. en, endothecium; ep, epidermis; ml, middle layer; pg, pollen grain; pmc, pollen mother cell; ta, tapetum; tt, tetrad. (A) A young anther showing several archesporial cells (arrowed). (B) An anther with several sporogenous cells, shortly after the differentiation of the middle layer (arrowhead) and tapetum (arrow). (C) An anther with several microsporocytes, and a developed tapetum. The immature anther wall consists of epidermis, endothecium, middle layer and tapetum (arrowed). (D–M) Various stages of meiosis in a microsporocyte. (D) Microsporocyte. (E) Prophase I. (F) Metaphase I (polar view). (G) Metaphase I (side view). (H) Anaphase I. (I) Telophase I. (J) Prophase II. (K) Metaphase II. (L) Anaphase II forming a tetrahedral tetrad. (M) Anaphase II forming a decussate tetrad. (N) Tetrahedral and decussate tetrads. (O) Microspores freshly released from a tetrad, and tapetal cells entering the anther locule. (P–T) Development in a microspore. (P) Uninucleate microspore with no vacuole. The aperture is indicated by an arrowhead. (Q) Uninucleate microspore with a large vacuole. (R) Mitotic nucleus of a microspore with a large vacuole. (S) A bicellular pollen grain with a large vegetative cell and a small generative cell. (T) A tricellular pollen grain with two sperm cells and a vegetative cell. (U) Mature pollen grain with three germinal apertures (indicated by arrowheads). (V) Radially elongated tapetal cells with two nuclei (arrowed). The arrowhead shows a mitotic anaphase in a tapetum cell. (W) Tapetal cells entering the anther locule. The arrowhead shows the tapetal periplasmodia surrounding the tetrad. The arrow shows the degenerating middle layer. (X) Once the pollen is shed, the ruptured anther wall is composed of only epidermis (indicated by arrowhead). Scale bars = 10 ␮m. sis in each PMC passes through prophase I (Fig. 3E), metaphase I but lack the vacuole (Fig. 3O). Subsequently, the exine develops and (Fig. 3F and G), anaphase I (Fig. 3H), telophase I (Fig. 3I), prophase II the germinal apertures begin to form (Fig. 3P). Later, a large vacuole (Fig. 3J), metaphase II (Fig. 3K), anaphase II (Fig. 3L) and telophase II pushes the cytoplasm and the nucleus against the wall (Fig. 3Q). (Fig. 3M), to form mostly tetrahedral, but occasionally also decus- The first mitosis of the microspore nucleus produces two differ- sate tetrads (Fig. 3N). Thus, the cytokinesis is of the simultaneous ently sized nuclei, one of which is the vegetative, and the other is type.