Inflorescences

Most bromeliads ower terminally, either just once if the genet is monocar-pic, or repeatedly in turn from each of a potentially in nite number of ramets produced by sympodial branching (Fig. 2.3A,B). Many fewer taxa produce lateral in orescences, i.e., are monopodial (Figs. 2.2B, 2.3C). Structure usually differentiates the vegetative from the reproductive portion of the shoot in the sense that the owers and oriferous branches of the more complex in orescences arise from the axils of bracts rather than from undiminished foliage (but see Cryptanthus; Fig. 3.2H). Racemes and spikes characterize an inordinate number of species; heads typify several more genera (e.g., Neoregelia, Nidularium). Panicles comprised of racemes and spikes occur among the larger-bodied members of all three subfamilies (Figs. 3.2 3.4). Architecture and peculiarities of development differ, sometimes even among closely related populations, indicating considerable evolutionary plasticity and reason for caution when choosing tax-onomic markers.

Tillandsioideae illustrate both the simplest and some of the most complex in orescences in the family (Fig. 3.3; Chapter 12). Reduction to a single ower occurs exclusively in Tillandsia (e.g., Tillandsia usneoides) where miniaturization associated with neoteny precludes more substantial reproductive efforts (Chapter 6; Fig. 2.1). Flowers and branches born on the more elaborate systems associate in either distichous (e.g., Vriesea bituminosa, V. hydrophora, many Tillandsia species; Figs. 3.3A, 3.5A,C) or polystichous arrangements (e.g., Catopsis, Guzmania, Tillandsia imperialis; Fig. 3.3G,H). Pedicles sometimes twist in one direction to produce a secund spike (e.g., Vriesea oligantha; Fig. 3.3E), or they align the owers in similar fashion along the subdivisions in branched systems (e.g., Tillandsia secunda). Internodes range from elongate (often true of the main axis) to telescoped (more often the ower-bearing axes), yielding arrays of relatively lax to more congested owers respectively. Tight heads surrounded by petal-like bracts (Fig. 3.3K) suggest the more familiar pseudanthium of Asteraceae.

Core Bromelioideae (e.g., Aechmea, Billbergia, Neoregelia; Fig. 3.2) exhibit similar variety, including many to few- owered forms (e.g., Aechmea pectinata, Neoregelia ampullacea respectively), condensed to spreading types (e.g., various Aechmea, Portea), and species with distichous (e.g., Aechmea tillandsioides) or polystichous (A. bromeliifolia) arrangements of owers. A few taxa produce pseudanthia (e.g., Canistrum). Much the same variety can be cited for Pitcairnioideae (Fig. 3.4). Architectural

Figure 3.2. Representative owers and in orescences of Bromelioideae. (A) Nidulate Neoregelia. (B) Aechmea fulgens. (C) Aechmea bracteata. (D) Aechmea setigera illustrating armed oral bracts. (E) Greigia sp., whole plant and axillary in orescence. (F) Billbergia amoena showing conspicuous ephemeral scape bracts. (G) Aechmeafasciata. (H) Cryptanthus correia-araujoi, owers subtended by foliose bracts.

Figure 3.2. Representative owers and in orescences of Bromelioideae. (A) Nidulate Neoregelia. (B) Aechmea fulgens. (C) Aechmea bracteata. (D) Aechmea setigera illustrating armed oral bracts. (E) Greigia sp., whole plant and axillary in orescence. (F) Billbergia amoena showing conspicuous ephemeral scape bracts. (G) Aechmeafasciata. (H) Cryptanthus correia-araujoi, owers subtended by foliose bracts.

Figure 3.3. Representative owers and in orescences of Tillandsioideae. (A) Tillandsia cyanea, prominent oral bracts. (B) Tillandsia argentea, oral bracts much reduced. (C) Tillandsia loliacea, miniaturized owers consistent with neoteny (arrow). (D) Guzmania wittmackii, foliose scape bracts. (E) Vriesea oligantha, secund spike. (F) Tillandsia xiphioides, mbriate corolla. (G) Guzmania globosa, head enveloped in mucilage. (H) Catopsis sessiliflora, staminate (below) and pistillate (above) plants, fruit, seed and structure of pistillate ower. Note vestigial stamens. (I) Tillandsia streptocarpa, mass owering species. (J) Alcantarea nevare-sii. (K) Guzmania lingulata, in orescence forms pseudanthium. (L) Tillandsia alber-tiana. (M) Tillandsia viridiflora, chiropterophilous.

Figure 3.3. Representative owers and in orescences of Tillandsioideae. (A) Tillandsia cyanea, prominent oral bracts. (B) Tillandsia argentea, oral bracts much reduced. (C) Tillandsia loliacea, miniaturized owers consistent with neoteny (arrow). (D) Guzmania wittmackii, foliose scape bracts. (E) Vriesea oligantha, secund spike. (F) Tillandsia xiphioides, mbriate corolla. (G) Guzmania globosa, head enveloped in mucilage. (H) Catopsis sessiliflora, staminate (below) and pistillate (above) plants, fruit, seed and structure of pistillate ower. Note vestigial stamens. (I) Tillandsia streptocarpa, mass owering species. (J) Alcantarea nevare-sii. (K) Guzmania lingulata, in orescence forms pseudanthium. (L) Tillandsia alber-tiana. (M) Tillandsia viridiflora, chiropterophilous.

Pitcairnioideae

Figure 3.4. Representative owers and in orescences of Pitcairnioideae. (A) Navia caulescens. (B) Navia linearis with isolated pistil. (C) Naviapolyglomerata with isolated pistil. (D) Entomophilous Fosterella penduliflora (below) and ornithophious Fosterella spectabilis (above). (E) Pitcairnia with radial ower and aring corolla. (F) Pepinia pruinosa. (G) Chiropterophilous Encholirium glasiovii. (H) Chiropterophilous Pitcairnia brongniartiana. (I) Sepal nectary of Dyckia floribunda in section. (J) Perennial in orescence of Deuterocohnia meziana; arrows indicate sites of proliferations for additional owering after the rst season. (K) Pitcairnia flammea with zygomorphic ower in cyme. (L) Pitcairnia bakeri showing dense spike. (M) Pitcairnia arcuata; stippling on older oral bracts indicates extent of progressive deliquescence.

Figure 3.4. Representative owers and in orescences of Pitcairnioideae. (A) Navia caulescens. (B) Navia linearis with isolated pistil. (C) Naviapolyglomerata with isolated pistil. (D) Entomophilous Fosterella penduliflora (below) and ornithophious Fosterella spectabilis (above). (E) Pitcairnia with radial ower and aring corolla. (F) Pepinia pruinosa. (G) Chiropterophilous Encholirium glasiovii. (H) Chiropterophilous Pitcairnia brongniartiana. (I) Sepal nectary of Dyckia floribunda in section. (J) Perennial in orescence of Deuterocohnia meziana; arrows indicate sites of proliferations for additional owering after the rst season. (K) Pitcairnia flammea with zygomorphic ower in cyme. (L) Pitcairnia bakeri showing dense spike. (M) Pitcairnia arcuata; stippling on older oral bracts indicates extent of progressive deliquescence.

redundancy across all three subfamilies reveals the distinctly homoplasious nature of the organization of the bromeliad in orescence.

Other groups of monocots, for example Poaceae, parallel Bromeliaceae for diverse in orescence structure, except that the small, wind-pollinated grass ower allows more compact arrangements, and the bracts tend to protect and help disperse seeds rather than attract pollinators and frugivores. Imperfect owers also occur in both families, but the bromeliads more often exhibit related dimorphism. Pistillate plants of dioecious Catopsis and Hechtia feature more abbreviated in orescences with fewer owers than their male counterparts (Fig. 3.3H). Pistillate Hechtia carlson-iae produces a spike, while its staminate counterpart is di- to tripinnately branched, presumably to enhance male relative to female function (assure high ratios of pollen to ovules).

Anthesis usually proceeds acropetally through spikes and cymes (e.g., Encholirium; Figs. 3.4G, 6.2A), and from the outside inward for heads (e.g., Neoregelia; Fig. 3.2A). Exceptions include certain Canistrum species where the buds in the middle of what approaches a capitulum open rst. Members of Aechmea section Ortgiesia ower basipetally, (from the top down), and occasionally from the middle in both directions. Deuterocohnia meziana lacks rivals for its shrubby in orescence that owers repeatedly for 6 8 years (Fig. 3.4J). Thick axes warrant closer inspection to con rm the reputed presence of a vascular cambium. Occasional proliferation of additional oral primordia around the periphery of spent infructescences allows some of the ramets of several members of Neoregelia subgenus Hylaeacium (e.g., N. eleutheropetala, N. myrmecophila) to reproduce during a second season.

Lateral in orescences characterize Greigia and certain members of Dyckia, Encholirium and Hechtia among others (Figs. 2.2B, 3.2E, 6.2B). Tillandsia complanata produces small, multiple spikes on lax scapes from axillary buds on indeterminate shoots; outwardly similar T. multicaulis and T. monstrum in fact remain cryptically sympodial as described in the previous chapter. Lateral owering occurs sporadically in the exceptional, sym-podially branched population, for example the occasional in orescence of Quesnelia lateralis that arises as a neotenic ramet devoid of expanded foliage. Discovery that conspeci cs ower from one or the other location obliged the synonymy of Q. centralis with Q. lateralis.

Bracts, which sometimes occur in several orders and sizes on the same in orescence, assist reproduction by targeting speci c pollen and/or seed dispersers. They also protect the developing owers and later sometimes the ripening fruit (Figs. 3.2 3.4). Sterile nodes below those bearing owers usually subtend the largest, most colorful appendages among Bromelioideae (e.g., Billbergia; Fig. 3.2F); similar organs tend to distribute more evenly through the in oresences of Pitcairnioideae and especially Tillandsioideae (Fig. 3.4L,M). A sterile 15 25 cm extension of the otherwise nidulate in orescence of Guzmania sanguinea var. comosa bears bright orange bracts whose purpose can only be attraction for birds.

Bracts may be elaborate and persistent (e.g., Aechmea fasciata; Fig. 3.2G), or much reduced and more ephemeral (e.g., Aechmea fulgens; Fig. 3.2B). Ancillary functions characterize the exceptional species, for example the red bracts that also secrete nectar to attract ant guards to Tillandsia bal-bisiana (see below). Floral bracts produced by Aechmea setigera bear a sharp terminal spine that seems not to impede either pollination or seed dispersal, but may deter large grazers (Fig. 3.2D).

In orescence bracts help identify tillandsioids dependent on certain kinds of pollinators (Chapter 6). Those of fundamentally ornithophilous Tillandsia subgenus Tillandsia both enclose the developing ower(s) and fruit(s) and provide the major visual signal for nectar-seekers (e.g., Tillandsia punctulata; Fig. 6.1B). The same appendages serve entomophi-lous and autogamous members of subgenus Anoplophytum and Diaphoranthema as the smaller, often less colorful organs needed primarily to insulate meristems and young oral buds (Fig. 3.3C,I). Aechmea fulgens (Fig. 3.2B) and various Pitcairnia (e.g., P. bakeri vs. P. flammea; Fig. 3.4K) exemplify the same arrangements in Bromelioideae and Pitcairnioideae respectively.

Visual attractants other than anthocyanins brighten the in orescence of some of the other bromeliads. Boat-shaped, foliaceous bracts covered with copious, re ective wax, combined with fragrant nocturnal owers, probably lure moths to Tillandsia heterophylla. The same appendage born by numerous other Tillandsioideae (e.g., Vriesea cylindrica; Fig. 3.5D) dries out to a light brown before the associated owers open. Persistent drops of water indicate that V. hydrophora features functional hydrathodes on its oral bracts (Fig. 3.5A). Appendages subtending the owers of some Cryptanthus species resemble foliage, as do those of Tillandsia brachycau-los and T. capitata, although the latter color up long enough to help attract pollinators (Fig. 3.2H).

Breeding system and other aspects of owers and the durability of bracts sometimes suggest greater importance for seed dispersal than for pollination. For example, the scape bracts of paniculate and autogamous Aechmea bracteata color up to a bright pink before anthesis and remain undimin-ished thereafter, apparently to act as fruit ags. Conversely, the colorful

Figure 3.5. Flowers and fruits of Bromeliaceae. (A) Guttating oral bracts of Vriesea hydrophora. (B) Nidulate in orescence of Neoregelia sp. with pollinator. (C) Sticky oral bracts of Vriesea bituminosa with captured insects. (D) Thief seeking nectar from base of corolla of Vriesea cylindrica. (E) Melaponid wasp visiting ower of chiropterophilous Vriesea atra at midmorning. (F) Pendant spike of Tillandsia dodsonii. (G) Ripe fruits of Billbergiaporteana photographed against the foliage of a shrub at dusk with ash to illustrate re ective trichomes. (H) Armed fruits of Aechmea angustifolia.

Figure 3.5. Flowers and fruits of Bromeliaceae. (A) Guttating oral bracts of Vriesea hydrophora. (B) Nidulate in orescence of Neoregelia sp. with pollinator. (C) Sticky oral bracts of Vriesea bituminosa with captured insects. (D) Thief seeking nectar from base of corolla of Vriesea cylindrica. (E) Melaponid wasp visiting ower of chiropterophilous Vriesea atra at midmorning. (F) Pendant spike of Tillandsia dodsonii. (G) Ripe fruits of Billbergiaporteana photographed against the foliage of a shrub at dusk with ash to illustrate re ective trichomes. (H) Armed fruits of Aechmea angustifolia.

primary bracts of usually ornithophilous Billbergia fade within days to pale pastels, sometimes even before the youngest owers open (Fig. 3.2F). Signi cantly, the sometimes strong-smelling brown to yellow or trichome-covered fruits on pendant spikes attract bats (e.g., B. porteana; Fig. 3.5G). Even more curiously ephemeral, the pink and imbricated bracts of Pepinia fimbriatobracteata soon degrade to a glutinous blackish-brown residue reminiscent of a deliquescent sporocarp of the fungus Coprinus. Several related species (e.g., Pitcairnia arcuata; Fig. 3.4M) engage in less pronounced autolysis.

Extra oral nectaries help deter herbivores and perhaps distract nectar thieves for members of at least three genera in two subfamilies. Koptur (1992) photographed ants collecting nectar on the immature bracts of Tillandsia balbisiana, a likely bird-pollinated epiphyte in southern Florida. Galetto and Bernardello (1992) described secretions from glands located on the calyx of nine species of Dyckia and a Deuterocohnia native to northeastern Argentina (Figs. 3.4I, 8.2E). Regular ant-nest users (certain members of Aechmea, Neoregelia) also merit inclusion in this group if they, like so many of the nonbromeliads that share the same media, also produce ant food. Glands reported so far differ from those located in the ovary, conforming instead to the easily overlooked "formless type (Fig. 3.4I).

Orientation, timing, and rates of maturation further distinguish bromel-iad in orescences, and help promote relationships with speci c kinds of pollinators and seed dispersers. Those of the epiphytes often hang below the shoot, while the same organs of the terrestrials almost always stand upright (Figs. 3.5F,G, 6.2A,B). Oddly deviant Pitcairinia corallina produces a bright red spike that, unexpectedly for its color and presumed pollinators, sprawls along the ground seemingly out of range of most nectar-feeding birds.

Many months pass before some of the largest and usually monocarpic Tillandsioideae (e.g., Tillandsia grandis, Alcantarea regina) and Pitcairnioideae (e.g., Puya raimondii) with erect, multibranched in orescences exhaust complements of hundreds to tens of thousands of owers. Certain one to few- owered relatives (neotenic Tillandsia) must set fruit within a few days, but typically dense populations of somewhat asynchronous individuals or attached ramets assure more extended opportunities to set fruit (Chapter 6).

Weeks to several months pass between the rst visible signs of bolting and the rst ower opening, and growth often accelerates as anthesis approaches. Downs (1974) reported that Billbergia elegans required nearly a month to emerge from the funnelform shoot, but just four more days to expand to nal size and present the rst ower. Scapes elongated at rates of up to 10 cm day~1. At the other extreme, the short, capitate in orescence of Neoregelia exhibits more conservative and precisely regulated growth, extending just enough to allow the tubular owers to emerge above the phy-totelmata and assure the resulting inferior-ovaried fruits opportunity to develop submerged, perhaps to avoid predators (Figs. 3.2A, 3.5B). Fruits of some species elongate enough at the base to protrude several centimeters above the waterline at ripeness (Fig. 3.6F).

In orescences produced by species with phytotelm shoots pose interesting questions about morphogenesis. Speci cally, does ethylene play a regulatory role similar to that responsible for the measured elongation of the shoots and leaves of certain emergent aquatics (e.g., Nymphaeaceae)? Would the in orescences of the nidulate bromelioids still end up just long enough to position the owers just above the waterline if they developed while tanks were empty?

Agents other than water may also impede gas exchange with different consequences. Copious mucilage, presumably secreted from the oral bracts or buds, insulates the fruits of Guzmania globosa (Fig. 3.3G) until capsules dehisce after which the plumose seeds require drier conditions to take ight. Lesser secretions characterize many additional Tillandsioideae, and these products sometimes cause the leaves and oral bracts to "quill i.e., stick together (e.g., Vriesea glutinosa).

Quite likely, growth factors synthesized in the developing in orescence, or the absence of substances formerly produced by the vegetative apex, activate one or more of the axillary buds programmed to produce ramets. Anthocyanins that temporarily suffuse the shoots of many bird-pollinated types probably owe their synthesis to light and chemical signals originating in the embryonic in orescence. Those scattered taxa (e.g., several Orthophytum, Tillandsia flexuosa, T. paucifolia; Fig. 2.11A) that produce offshoots from buds subtended by oral bracts raise additional questions about the involvement of hormones in bromeliad reproduction.

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