•or mu lo Teaching Flower Structure & Floral Formulae - A Mix of the Real & Virtual Worlds Ml aflheMllowini artfrom tpicitt inll i'ralooccao Thcoc Sfioeno gonoroHy I lice (>enanth segments Ihal hav« a zygumoiphic AnangArnfliii, four fil^mflns very short lilaminis thai its laintd lo Ihs penantti »gmanti. and a gynoecium consisiing at a single carpel wilh a tupei GEOFF BURROWS ovary They «N sh«r« tha llaral foimuli f>P4 A4 61 ABSTRACT Although DNA barcoding of plants is considered workable (Ausubel, 2009) and portable DNA analysis devices for nonexperts have been The stuii_y of/Irtwcr siruclure i.s essenlial in plant idenfi/itüliim and in unáersland\ng sexual reproáuaion in plünts, poíünalion syndromes, plant breeding, and/ruii simcture. suggested, plant species identification will continue to depend on Thus, sludv of flower sirutlure antl conslrucííon oj jïord jormulae are slandarà parts interpretation of flora! structure. offiru-yeai univcrsily boiany and biology tourses. These activiiies involve developing a complex sei aj skilh. and il is uscfiii for sludenis to review ¡fiis müíerial after practical se.ssiuns. The Virfuai floral Founula Web sile próvida sludenis wilh a unique resoune O Floral Formulae for practicing (heir jîoral sírucíure inlerprelíiíioti skills. Tïie site provides deltíiled dis- seclion phclogrtiphs d/ihe/lowers of 12 species, úndjloral/ormu/ac íJre progressively Construction of lloral formulae is a common acti%'ity in upper high assembled via drop-down menus. When sludenis arc satisfied with their answers, they school biology classes and a standard practical activity in many first- submit them, and any discrepancies from the "official'formula are hlghlighied. Students year university biology and botany classes. Floral formulae are a short- appreciate the inlf ratfiviiy (»flhe applitalion, Ihe/eedfccich íhe^í receive on any inacfura- hand way of summarizing the main features of a flower (Clarke &r Lee, i ies in (heir fonnulae, and the ahility to make progressive improvemenls in iheir sfíiíis. 2003; Judd et al,, 2008; Prenncr et al,, 2010). They have two main practical uses. First, when keying out a plant it is most efficient to fully Keywords: flower; jloral; slruí:[ure;/rtrmuía;/ormuiae; virlual; dissection. observe a flower's structure, prepare a lloral formula, and then progress to keying out. Almost all the features denoted in Flowers and iheir resulting fruils are a distin- a floral formula will be used in the identification guishing teamre of ihe angiosperms. Flower Floral formulae are process just to get to family level, This is more structure is a core component of biology and efficient than returning to the specimen to reex- botany curricula across the globe and is studied a shorthand way of amine it as eatb new pair of questions is encoun- al increasing levels of detail as students progress summarizing the main tered. Second, comparing the llora! formulae ol a from school to university. Ways to interest and variety of species in a family is an excellent way involve students in tbe study of plants through features of a flower. to find tbe main features of a family and tbe areas flower structure have been suggested over many of variation, if any years (e.g., Bernadette, Í958; Flannery, 1987; For better or worse, botanists have not stan- Marquard & Steinback, 2009). An understanding of ilower structure is dardized the format of floral formulae, although see the recent sug- important from many perspectives. gestions of Prenner et al. (2010). The three formulae in Figure 1 are • Tbe primary function of flowers is to faciliiate genetic recombina- for very similar flowers (Fucfisia. Ocnothera, and the Onagraceae in tion. By understanding flower structure, students can appreciate general), but at first inspection they appear to be quite different. Some diverse aspects of floral biology, such as bow a species with per- of tbe major differences in tbe fontiulac are related to the lact that spe- fect flowers can reduce self pollination and the different pollination cies in the Onagraceae have a floral tube or hypantbium, and this struc- syndromes. ture is represented in quite different ways in the tbree formulae. Even allowing for these differences, it is relatively easy to decipher most of • Understanding flower structure is tbe basis for appreciating fruit the botanical information contained within a fioral formula, no matter structure, including tbe differences between simple and aggregate what the format is. ' fruits and true and accessor}' fruits. • Understanding various aspects of plant breeding, sucb as artificial bybridization, depends on a correct interpretation of floral form O A Unique Web Resource and function- The Virtual Floral Formula is a Web bite thai lets students practice their • Surveys of plant diversity depend on accurate species identifica- floral structure interpretation skills using detailed dissection photographs tion, often based on an observer's assessment of flower structure. of the flowers of 12 species. It was constructed in ToolBook (SumTotal The American Bioh^y Teacher, Vol. 72, No. 5, pages 276-280. ISSN 0002-7685, eleclronk ISSN 1938-4211. ©2010 by National Assoclaiion of Biology Teachers. All rights reserved. Request permission to photocopy or reproduce arlicle conlent at the Universily of California Press's Rights and Permissions Web site at www.ucpressiournais.com/reprlntlnfo.asp. DOI: 10.1525/abt.2010.72.5.H THE AMERICAN BIOLOGY TEACHER VOLUME 72, NO. 5. MAY 2010 Systems), an e-leaming development application that allows for interac- taxonomy of the upper levels of the Lamiales is in a state of flux; Judd tive content- To access the site, go to hup://www.csu.edu.au/herbanunV etal., 2008.) and click on "The Virtual Floral Formula." After the opening page (Figure 2), which shows some of the floral The 12 species that are used cover a wide diversity of the eudicots diversity of the Australian Proteaceae (but with little or no variation in floral (Table 1). Each is from a different family, rcpresenling 10 different orders. formulae), users progress to a page where they can choose between (1) Three of the samples- Paulownia (Bignoniaceae or Faulowniaceae), Hebe learning about flower structure and floral formulae in general, (2) learning (Scrophulariaceae or Plantaginaceae), and Ercmophih (Myoporaceae or how to use ihe Virtual Floral Formula site, and (3) constmcting their own Scrophulariaceae) - are from the Lamiales, and their floral formulae floral formulae. Several aspects of interpreting flower structure are relatively (Table 1 ) show some diagnostic features of ihis order, such as two-lipped straightfoi'ward (e.g., counting numbers of parts or detcniiming whether zygomorphic flowers with two or four stamens Oudd et al., 2008). the same types of parls are free from each other or united), but others, such (Aliernative family names for these genera are given above because the as floral symmetry and gynoecium structure, are more complex. Links are provided to interactive tutorials and tests that I have developed lo help stu- dents wilh these topics (see bttp://www.csu.edu.au/herbanum/). At the "Seleci a Flower" page, students select one of the 12 flowers (Figure 3). They progress to a page where, in (he upper section, four to eight images of the flower are presented, showing different angles and dis- sections (Figure 4). At this stage the images are mostly unlalx-led, but in a very small number of cases some inionnation is supplied that cannot be ascertained from the images but is needed to construct the floral formula. Below the image window is the "backbone" of ihe floral formula (i.e., KCA G; calyx, corolla, androecium, and gynoecium, res[x^ctively), along with 13 drop-down menus (Figure 4). After assessing the images, the student uses K(4) C4 A4+4 G{4) the drop-down menus to select floral symmetry, ovary position, numbers B of parts in the various whorls, and fusion viàthin or between whorls. The floral tube present 13 menus allow all the major aspects of a flower to be recorded, although some more technical aspects (e.g., presence of staminodes, short and long stamens) that are found in some floral formulae cannot be recorded. The student progressively compiles the formula and submits it when complete. The submitted formula then appears above the "oiïidal" version, and any discrepancies are indicated by the presence oí blue arrows ihat show which features should be reexamined (Figure 5). The images now have text boxes Figure 1. Floral formulae for a very similar flower structure and/or labels to assist in the reexamination (Figure 5). from different sources, (A) Oenothera from the Digital Flowers website of the University of Illinois. (B) Fuchsia magellanica from Clarke and Lee (2003). (C) Onagraceae from Judd et al. {2008). O In the Classroom Much of the apparent variation derives from the different ways At Charles Stun University, first-year on-campus botany students (usually the floral tube has been expressed. enrolled in applied fields such as agriculture and horticulture) receive a Table 1. Genera used in the Virtual Floral Formula, with their family, order, and floral formula. Alternative family names are given where appropriate. Genus Family Order Floral Formula 1 Paulowr^ia Bignoniaceae, Paulowniaceae Lamiales t K(5) C(á AA G(2) 2 Hymenosporum Pittosporaceae Apiales • K5 C5 A5 G(2) 3 Cotyledor) Crassulaceae Saxif raga les * K(5) CiíT AÍO G¿ 4 Hebe Scrophulariaceae, Plantaginaceae Lamiales î K(4) CÍA) A2 G{2) 5 Prunus Rosaceae, Amygdalaceae Rosales * K5