Photosynthesis

All epiphytes photosynthesize, but certain life stages of several taxa are heterotrophic - for example, gametophytes of arboreal Lycopodium, Ophio-glossum, Psilotum, and Tmesipteris. Similarly, orchid seedlings remain ach-lorophyllous for weeks to months, subsisting on substrates provided by symbiotic fungi (Figs. 4.10, 4.12). Flow of fungal metabolites into adult orchids may also occur, but claims for epiparasitism in canopy-based Orchidaceae (e.g., Ruinen 1953 Johansson 1977) need...

Dispersal and establishment pattern

Madison's (1979b) study in North Borneo provides interesting commentary on wind versus animal dissemination in a heterogeneous group of 25 epiphytes. Although his survey was static in the sense that history was inferred from a single census, characteristics of the site eliminated much complicating postdispersal influence on plant distribution. Subjects were arrayed through an even-aged rubber tree plantation so that spacing, tree size, and type were relatively uniform (Fig. 5.5). Initial...

Broader effects of epiphyte nutrition on the forest

Epiphytes influence element apportionment and related aspects of plant community performance according to local circumstances. On stable sites heavily dependent on atmospheric deposition to balance outflow, a massive epiphyte-epiphyll presence may enhance the forest's storage and nutrient-capturing and -retaining capacities without depriving any community members (Nadkarni 1981). Here the negative connotation of piracy renders that term less appropriate for describing the epiphyte's role in...

Adaptive uniqueness

Some of the requirements for epiphytism can be rather straightforward -namely, aerial dispersal and holdfast. Other capacities - maintenance of adequate hydrature and nutrition, for instance - are more complex, and margins for error differ. Whereas acceptable mineral nutrition is no less imperative for success in tree crowns than elsewhere, maintenance of a favorable water balance requires quicker adjustment to more numerous and abrupt environmental challenges. Each time an epiphyte's moisture...

Hostmistletoe crypsis

Australian loranths are unique among mistletoes for their frequent resemblance to primary hosts (Fig. 6.1 A-C). Leaves in particular are so similar in form and presentation to a human eye several meters away that tree and parasite are indistinguishable, although closer examination often reveals less faithful coloration and texture. Amyema, Dendrophthoe, Diplatia, Lysiana, and Muellerina are mimetic mistletoes their hosts are most often Acacia, Casuarina, and Eucalyptus. Parasitic mimics with...

Leaf variegation and shoot architecture

Leafy rosulate shoots unavoidably self-shade all but the youngest foliage. A number of epiphytes, especially tank bromeliads, seem to respond to this type of archtecture with, among other qualities, elaborate ornamentation (Benzing 1986). Leaves of several taxa (e.g., Vriesea fosteriana Figs. 2.13, 2.19) are differentiated into regularly shaped and distributed zones, some Chl-rich (shutters) and others Chl-poor (windows or fenestrae). Shutter patterns are often copied by the aforementioned...

Nonorchid monocots

Bromeliaceae, with far fewer species and almost exclusively neotropical distribution, nevertheless rival Orchidaceae for variety of epiphytic mechanisms (Table 8.7) and vastly exceed the latter's biomass in tropical American forests. Tank habits have evolved independently in two brome-liad subfamilies, and in all three if sometimes-epiphytic Brocchinia (Fig. 4.25E) is correctly assigned to Pitcairnioideae (Benzing et al. 1985). A rosu-late shoot was required for each transference of absorptive...

Integration of flowering within the coihmunity

A 3.5-year study by Stiles (1978) of a mixed guild of ornithophilous taxa at Finca La Selva, Costa Rica focused on the group's sharing of pollinators in the face of climatic variation. The epiphyte contingent included one species from each of two bromeliad and three gesneriad genera most of the participating taxa rooted in the ground. Several points are worth noting. Canopy-adapted species flowered most abundantly during or just after the dry season (Fig. 5.1). On average, they were at the peak...

Humusbased nutrition

Humus-based epiphytes fall into two classes Class 1 are nonim-pounders that draw mineral ions from rotting wood, ant nests, or, more commonly, layers of suspended humus and the plant life clothing bark class 2 are impounders of litter or other nutritive solids which are then held against absorptive roots or leaves (e.g., Figs. 4.19, 4.25A). High humidity is required by most but not all humus epiphytes. Tank (phytotelm) bromeliads can inhabit drier sites because of their ability to intercept and...

Impounding epiphytes

As a rule, leaves provide impoundment capacity roots do so less often. Bromeliaceae illustrate the tank in its highest refinement about 1000 species, roughly half of the family, produce rosulate tank shoots comprised of tight, overlapping leaves with inflated bases (Fig. 1.2). Impoundment volume can be substantial a single large Glomeropitcairnia erectiflora has been said to contain several liters of fluid (Pittendrigh 1948), but the average for all species is on the order of a few hundred...

Inputs from fungi and diazotrophs

The nutrition of most terrestrial flora is aided by microbes, especially mutualistic fungi. A thin hyphal thread, finer than any rootlet, is the more cost-effective absorptive organ because the quantity of such immobile nutrients as P accessible to a plant is determined by the amount of substratum contacted, whether by roots or hyphae. Reports of epiphyte mycorrhi- Figures 4.3-4.9. (4.3) Microbiology of the epiphyte rhizosphere (4.3) multicellular rounded spores associated with root of...

The reductive pentose phosphate C3 pathway

Machinery for trapping radiant energy, perfected in plants long before land was colonized, required tailoring as the terrestrial flora developed. Light intensity and quality, supplies of moisture, nitrogen (N), and presumably other key nutritive elements, influenced selection during the subsequent radiation, up to and including colonization of tree crowns. Whereas the fundamental mechanisms of photosynthesis reflect ancient origins, today the forms and performances of green organs in epiphytes...

Atmospheric nutrition

Neither humus nor appreciable animal products are available to PS species. At the extreme, mist and root leaf tangle epiphytes of Orchidaceae barely contact host surfaces at all (Fig. 1.7). Certain atmospheric bromeliads possess roots that securely grip the substratum but are essentially nonab-sorptive (Fig. 1.11). Those of some other forms (e.g., certain ferns, Hoya) often seem too reduced to provide much benefit beyond mechanical support. As noted previously, the specialized shoot epidermis...

The origin and significance of phytotelm form

Abiotic factors must have influenced bromeliad habit, and thus the capacity to intercept and retain various resources. Particular shapes may exist primarily to accommodate specific degrees of drought or light exposure Deep tanks need replenishment less often than shallow, open ones the vertical leaves of tubular heliophilic billbergias (Fig. 4.25F) are spared direct-beam insolation at midday the flat, open rosettes (and therefore shallow axils) of shade-adapted shoots (Fig. 4.25G) maximize...

Ground soil conditions

Just one effort has been made to document the effect of earth-soil type or fertility on epiphyte development (Gentry and Emmons 1987), but there have been additional comments on the subject (Janzen 1974 Benzing and Seemann 1978 Gentry and Dodson 1987b). In fact, the situation probably varies, depending on the type of epiphyte and where it anchors. Because so many species are heliophilic by nature, opaque canopies promoted by moist, fertile substrata should limit colony growth in many instances....

Reproduction and life history

Constraints peculiar to forest canopy habitats helped shape epiphyte natural history, but the selective forces are not always apparent. Some characters and lineages appear to have been affected more than others for instance, iteroparity is nearly routine in the group, whereas breeding mechanisms and modes of pollen and seed dispersal are much more diverse. Multiple paths to similar ends complicate the search for a common theme. Enough data are available, however, to offer tentative judgments on...

Foliar trichomes

Foliar Trichomes

The second absorptive organ mentioned earlier is the trichomed leaf. Although several epiphytic ferns, Astelia, and perhaps some orchids bear absorptive foliar hairs, the trichome of Bromeliaceae, particularly of subfamily Tillandsioideae, exhibits the most elaborate structure. Scales (another term for these peltate hairs) feature shields made up of empty cells Figure 3.21. An absorbing bromeliad trichome in the dry and wet configuration. Arrows depict the route of water and solute movement...

Structural adaptations to drought

Vascular plants maintain serviceable water economy by utilizing a variety of coordinated structural and dynamic measures. The uncommon poikilohydrous epiphyte with its lightly insulated foliage loses water quickly desiccation is not fatal, however. The less tolerant homoiohydrous species must deploy special anatomical features (Fig. 3.1) as a first line of defense against lethal drying xerophytes possess stout-walled epidermal cells covered by a thick evaporation-retarding cuticle. Mesophyll is...

Historical notes

Columbus is credited with the first recorded comment on canopy-adapted vegetation he wrote that tropical trees have a great variety of branches and leaves, all of them growing from a single root (Gessner 1956). The earliest known picture of an epiphyte - or, for that matter, reference to American botany - appears in The Badianus Manuscript, a Mexican herbal of 1552, written and probably illustrated by the Aztec Indian physician Martinus de la Cruz and translated into Latin by his Indian...

The epiphytic habitat

Philodendron Epiphyte

Growing conditions in canopies - rooting media and microclimate - are diverse and often similar to those on the ground. Aerial substrata in arid woodlands, like dry sterile soils, probably impose comparable stresses on resident vegetation. Data presented later suggest that the sodden rotting trunks, ant nests, and continuously moist, debris-filled knotholes of an asea-sonal forest offer to certain epiphytes resources equal to those available in equable terrestrial habitats. In effect, the...

Ecology

Epiphyte ecology has been a recurrent topic throughout the preceding chapters but little or nothing has been said about community organization, succession, associated phytotelmata, phorophyte specificity, or influence of epiphytes on supports and other biota. Although documentation of cause and effect is scarce, it is clear that canopy-dwelling flora can help shape forest structure and economy processes as fundamental as community-wide mineral cycling and productivity are affected. Influence on...

Ferns

Small diaspores are an important attribute for pteridophytic epiphytism (Table 8.7) as are spongelike masses of finely divided, durable roots (e.g., Campyloneurum angustifolium (Fig. 1.19). Unique water and carbon balance mechanisms limit occurrence of many species to specific conditions, however. Poikilohydry is pronounced in exceptional taxa (e.g., Polypodium polypodioides Fig. 1.6), but many others also exhibit desiccation tolerance superior to that of most seed plants. A fern's xerophytism,...

Plastids In Root Of Taeniophyllum

Velamen Radicans

Photosynthetic roots deserve special mention in this discussion because they are featured by so many epiphytic orchids and aroids. Plastids responsible for the green color in an orchid root reside in cortical (Fig. 2.16) and less often stelar (Fig. 2.14) parenchyma, including the endodermis. Chloroplasts are scattered and relatively few per cell, much as they are in a CAM plant's succulent leaf and stem. If exposed on all sides, roots are uniformly pigmented. Those growing against solid objects...

Antguarded epiphytes

The incidents just described documenting ant protection of nestgardens and Schomburgkia tibicinis in tropical America demonstrate the overlap between animal-assisted categories. Another example is that of myr-mecophytic Dischidia plants rooted in carton runways sometimes house ants in pouch leaves (Weir and Kiew 1986). Some other ant-fed ant-house epiphytes also receive multiple benefits from mutualists. In Malaysia, inhabitants of rubiaceous myrmecophytes (mostly Iridomyrmex cordatus) clearly...

Mesophytes

Mesophytes are evergreen and vulnerable to all but modest drought. Their foliage is somewhat thicker and more resistant to desiccation than that of the hygrophytes. Moderate vigor is supported by C3 photosynthesis, Figures 3.5-3.11. (3.5) A mixed colony of bryophytes and filmy ferns growing on the base of a tree in primary Amazonian rain forest. (3.6) Absorbing trichomes with attenuated shields covering the leaves of the atmospheric bromeliad Tillandsia tectorum (X120). (3.7) Absorbing...

Types of interaction

Diverse biota are drawn to epiphytes for many reasons. Visitation by animals to collect floral rewards and edible fruit has already been considered, as have occupancy of ant-fed ant-house taxa and creation of ant nestgardens, but enemies and protective symbiosis were barely mentioned. Very little is known about herbivory or pathogens in nature. Janzen (1974) and Huxley (1978) noted insects consuming Hydnophytum foliage in Malaysia. Signs of predation are common among additional taxa, but...

The case for parasitism

Authors of textbooks who consider nonhaustorial epiphytes at all, routinely describe them as plants that grow upon other plants but have no significant effect on hosts. In A Dictionary of Biology, Abercrombie, Hickman, and Johnson (1970) described an epiphyte as a plant attached to F.PARAENSIS F. PERFORATA FS F.COLUBRMAE g F. THIGONATA JTJ F. COSTARICA * fJl F. OBTUSFOLIA Figures 7.18-7.20. Distribution of individual stranglers within the crowns of trees in a Panamanian humid forest 1, Below...

Circumscribing labeling and documenting the epiphyte community

Concepts of how epiphytes should be organized into phytosocietal units have varied with historical period and an author's broader views on classification of vegetation. Complicating the issue have been differing emphases on dynamism. Some workers recognized ecological succession, whereas others offered no judgments about age or serai stage. Epiphyte associations were circumscribed according to composition and location without regard to history or potential for change. Every approach has taken...

Orchids and mycotrophy

Orchids deserve special note for the unique way they reap some of the advantages of large seeds without bearing the associated cost. Recall that juveniles succeed without reserves because germination and early growth are symbiotic. Establishment begins with invasion of the rudimentary endosperm-free embryo by a septate fungus, usually not a specific species (Fig. 5.2C Hadley 1982). Development takes place for a time, nurtured through fungal saprophytism or perhaps by attack on adjacent living...

Influence of microhabitat

Because dispersal mode and seed size influence seed mobility and seedling establishment, they should be prominent factors in plant distribution within epiphyte communities. Two studies dealt with these phenomena and illustrate how additional parameters may alter expected patterns. Kelly (1985) found a marked correlation between vertical zoning and dispersal type in Jamaican wet montane forest. Nearly all the epiphytes anchored above 16 m (mostly orchids and tillandsioid bromeliads) bore small...

Table 42 Chemical characteristics of mineral soil and suspended substrata one sample each in wet forest at Rio Palenque

Species, even among members of the same community. Diverse epiphytes in a single tree crown, for example, draw on different nutrient sources Tables 4.2-4.4 and employ key elements with characteristic mineral use efficiency MUE . Plant chemistry as an index of nutritional sufficiency, MUE, or habitat fertility is less reliable for comparisons between than within species. For instance, robust bromeliads whose vigor results from abundant resources in tanks or ground soil may concentrate foliar N...

Velamentous roots

Vanda Roots

Several families contain members equipped with velamentous roots an example is the aroid genus Anthurium. But this character is particularly refined in xeric Orchidaceae Barthlott and Capesius 1975 , both drought endurers and avoiders Fig. 3.19A-G thus it serves the majority of the epiphyte flora. The specialized nonliving rhizodermis velamen forms an insulating but permeable mantle, 1-24 cells thick, around a living core comprised of an often chlorophyllous cortex Fig. 2.16 and central...

Mistletoes

Floral Diagram Sapota

Mistletoes are unique enough among canopy flora to merit separate treatment. Certain relic terrestrial forms parasitize roots of other plants, but they will be mentioned only in passing the principal focus will be on aerial mistletoes which are here defined as shrubby hemiparasites growing attached to branches. These unusual plants deviate from true epiphytes in form, diversity, physiology, and impact on hosts. Most mistletoes belong to San-talales, a sizable, predominantly tropical, order....

Glossary

Accidental epiphyte A typically terrestrial species with occasional members that grow to maturity anchored in a tree crown. Allelopathy The process whereby one plant inhibits or kills another through the production of toxic compounds. Allogamy Seed production resulting from pollen flow between different plants. Anemochory The dispersal of seeds by wind. Ant-fed ant-house epiphyte A species that produces hollow organs doma-tia specifically for housing ant colonies. Ant nest-garden epiphyte A...