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Mycorrhizal abundance in aerial versus terrestrial roots among the climbing Araceae of the Monteverde Cloud Forest

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Mycorrhizal abundance in aerial versus terrestrial roots among the climbing Araceae of the Monteverde Cloud Forest
Translated Title:
La abundancia de micorrizas en las raíces aéreas versus terrestres en medio del Araceae trepadora del Bosque Nuboso de Monteverde ( )
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Mycorrhizal fungi   ( lcsh )
Roots (Botany)   ( lcsh )
Hongos Micorrizas
Raíces (Botánica)
Tropical Ecology 2007
Aerial roots
Terrestrial roots
Ecología Tropical 2007
Raíces aereas
Raíces terrestres
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Reports   ( lcsh )
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Abstract:
Climbing plants of the family Araceae are a prominent feature of the Monteverde Cloud Forest in Costa Rica. Aerial and terrestrial roots were collected from two species of climbing aroids Syngonium sp A (n = 15) and Philodendron aurantifolium (n = 17) and analyzed for mycorrhizae presence and abundance. Evidence of mycorrhizae infection was found in every plant sampled, and percent abundance of mycorrhizae in the aerial roots of Syngonium sp A ranged from 7.9-90%, while the mycorrhizal cover ranged from 5.3-38% in terrestrial roots. Mycorrhizal cover in the aerial roots of P. aurantifolium ranged from 8.2-57%, and from 4-33% in terrestrial roots. While a significant difference was not found between the aerial and terrestrial roots of P. aurantifolium (Paired t-test, t = 1.74, p = 0.10), mycorrhizae was significantly more abundant in the aerial roots of Syngonium sp A than in the terrestrial roots (Paired t-test, t = 3.11, p = 0.008). Additionally, individuals of the species Syngonium sp A experienced on average a greater percentage of mycorrhizal infections in their aerial roots than did P. aurantifolium individuals (Unpaired t-test, t = 2.19, p = 0.036). No difference in mycorrhizal infection was detected in terrestrial roots (Unpaired t-test, t = 0.19, p = 0.849). This report confirms the presence of mycorrhizae in two species of tropical climbing aroids, and suggests that aerial roots of an individual climbing plant may harbor on average more mycorrhizal infections than their respective terrestrial roots.
Abstract:
Las plantas escaladoras de la familia Araceae son una característica prominente del Bosque Nuboso de Monteverde en Costa Rica.
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Text in English.
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Mycorrhizal abundance in aerial versus terrestrial roots among the climbing Araceae of the Monteverde Cloud Forest Sydney Glassman Department of Biology, University of Pennsylvania Abstract Climbing plants of the family Araceae are a prominent feature of the Monteverde Cloud Forest in Costa Rica. Aerial and terrestrial roots were coll ected from two species of climbing aroids Syngonium sp A (n = 15) and Philodendron aurantifolium (n = 17) and analyzed for myco rrhizae presence and abundance. Evidence of mycorrhizae infection was found in every plant samp led, and percent abundance of mycorrhizae in the aerial roots of Syngonium sp A ranged from 7.9-90%, while the mycorrhizal cover ranged from 5.3-38% in terrestrial roots. Mycorrhizal cover in the aerial roots of P. aurantifolium ranged from 8.2-57%, and from 4-33% in terrestrial roots. While a significant difference was not found between the aerial and terrestrial roots of P. aurantifolium (Paired t-test, t = 1.74, p = 0.10), mycorrhizae was significantly more abundant in the aerial roots of Syngonium sp A than in the terrestrial roots (Paired t-test, t = 3.11, p = 0.008). Additionally, individuals of the species Syngonium sp A experienced on average a greater percentage of mycorrhizal infections in their aerial roots than did P. aurantifolium individuals (Unpaired t-test, t = 2.19, p = 0.036). No difference in mycorrhizal infection wa s detected in terrestrial roots (Unpaired t-test, t = 0.19, p = 0.849). This repo rt confirms the presence of mycorrhizae in two species of tropical climbing aroids, and suggests that aerial roots of an individual climbing plant may harbor on average more mycorrhizal infections than their respective terrestrial roots. Resumen Las plantas escaladoras de la familia Araceae son un a caracterstica prominente del Bosque Nuboso de Monteverde en Costa Rica. Las races aereas y terrestre s fueron tomadas de dos especies de araceas epifitas Syngonium sp. A (N = 15) y Filodendro aurantifolium (N = 17) y analizadas para medir la presencia de micorrizas y su abundancia. La evidencia de la inf eccin de micorrizas fue en contrada en cada planta prob, y por ciento abundancia de micorrizas en las races areas de Syngonium especia A el promedio de micorrizas fue de 7.9-90%, mientras la cubierta de mico rrizas en races terrestres fue 5.3-38%. La cubierta de micorrizas en las races areas de P. aurantifolium recorri de 8.2-57%, y de 4-33% en races terrestres. Mientras no fue encontrada una diferencia signi ficativa entre las races aereas y terrestres de P. aurantifolium (la T-prueba pareada, T = 1,74, P = 0,10), mi corrizas fue apreciable mente ms abundante en las races areas de Syngonium sp A que en las races terrestres (la Tprueba pareada, T = 3,11, P = 0,008). Adicionalmente, los individuos de la especie Syngonium sp A experimentaron en promedia un porcentaje ms grande de infecciones de micorrizas en sus races areas que hizo los individuos de P. aurantifolium (la T-prueba Irreparada, T = 2,19, P = 0,036). Ninguna diferencia en la infeccin de micorrizas fue discernida en races terrestres (la T-prueba Irreparada, T = 0,19, P = 0,849). Este informe confirma la presencia de micorrizas en dos especies de araceas escal adoras tropicales, y sugiere que races areas de un individuo planta es caladora puede abrigar en el promedio ms infecciones de micorrizas que sus races terrestres respectivas. 1

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Introduction Mycorrhizae are symbiotic fungi associated with the roots of vascular plants (Lesica and Antibus 1990). The most common myco rrhizae are vesicula r-arbuscular (VAM) obligately symbiotic fungi in the order Glomales (Smith and Read 1997). Mycorrhizal fungi benefit their host plants by enhancing th e physiologically active area of the root system and increasing the plants ability to capture water and nutrients (Rains et al. 2003). VAM are widespread and common in many plants all over the world, especially in the tropics (Smith and Read 1997). As impor tant as mycorrhizal symbionts may be for plant growth, environmental c onditions must be correct for a mycorrhiza to develop because they prefer low nutrient soils (Alexopoulos et al. 199 6). Thus, not all vascular plants may harbor mycorrhizal infections. Arbuscular mycorrhizae have been observed in epiphytic aroids in the lower montane cloud forest canopy of Monteverde (Rains et al. 2003), an area that is characterized by an unmatched abundance of moss, epiphytes, and tree trunk climbers (Haber 2000). Climbers are plan ts that cannot suppor t themselves in an erect position at maturity, and epiphytes are plants dependent on trees and other plants for mechanical support but not nutrition (Ingr am 2000). While the presence of mycorrhizae in epiphytic aroids has been noted, infections in climbing aroids have yet to be studied. Most species of herbaceous tree trunk climbing epiphytes in the Monteverde cloud forest are of the family Araceae, which includes 32 species of the Philodendron Monstera and Syngonium genera (Haber 2000). Araceae is a primarily tropical and subtropical monocot family (Mabberley 1987), with a distinctive inflorescence called a spadix, covered in a bract called a sp athe (Zuchowski 2005). Aroids ha ve also evolved a plethora of growth forms. They can be found as scrambling shrubs, climbers with aerial roots, enormous herbs, and occasionally as a true ep iphyte or in the rare case, as a free floating aquatic plant (Mabberley 1987). Of the 80 species of aroids known in Monteverde, 44 are vines or hemiepiphytes (Haber 2000). Although VAM fungi are widely regarded as mutualistic and even indispensable symbionts, their extensive use of plant car bohydrates makes the continuum to parasitism unclear (Johnson et al. 1997). Because of this, a plant may preferentially allow infections in roots with less access to nutrient-rich substrates. Climbing plants possess terrestrial roots, but sequester additiona l nutrients from ambient mist via aerial roots, which are present along the stems, positioned at node s (Hinchee 1981). Thus, aerial roots of an individual may contain more my corrhizae than their terrestria l counterparts as they would presumably have less access to nutrient s than those rooted in the soil. The goal of this study is to determine the incidence of mycorrhizal infections in climbing species of aroids, which is a new ar ea of inquiry. Additionally, I am interested in the potential for differential abundance of mycorrhizae in aerial versus terrestrial roots. Due to their variation in location and access to nutrients, I expected a difference in the abundance of mycorrhizae between terrestrial an d aerial roots. I predicted that aerial aroid roots would have a higher abundance of mycorrhizae as they have less constant access to nutrients and would therefore be more likely to invest in the costly symbiont. 2

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Materials and Methods This study was conducted in lower montane rain forest ( sensu Holdridge, 1967) located behind the Estacion Biologia in Montever de, Costa Rica (elevation 1500-1600 m). I analyzed the aerial and terrestrial roots of two different species of climbing aroids, Philodendron aurantifolium (n = 17) and an unidentified species of Syngonium sp A (n = 15) Both species of aroids were chosen due to their abundance in the cloud forest and varying growth morphologies. Philodendron aurantifolium was more often found climbing on trees, while Syngonium sp A individuals were more often found climbing on the ground. However, individuals from both species were found in both environments. Samples were collected at the end of th e dry season, from April 11-May 5, 2007. Once collected, the roots were given an ini tial rinse in water to remove excess dirt and leaf matter. Next, the samples were soak ed in 10% KOH for one to seven days. The roots were then removed from KOH and s ubmerged in a 1% HCL solution for one hour in order to enhance the effici ency of dye absorption. After soaking in the acid solution, the roots were put in a solution containing a 4:2:1 ratio of 50% glycerol, 1% HCL, and 0.05% Trypan blue dye for a bout twenty five minutes. Stained roots were cut into very thin cross sections, mount ed onto slides, and observed under a 40x field view with a compound light microscope. Mycorrhizae presence or absence was recorded for every root sample. Pictures of each sliced and stained root cross section were taken with an Olympus 7.1 me ga pixel digital camera with an attached microscope adapter for use in quantification. Myco rrhizae abundance was recorded as the number of cross hairs c overing mycorrhizae divided by the number of cross hairs in the entire field of view us ing a transparent 1.0 cm x 1.0 cm grid sheet. Several aerial and terrestrial roots were used fo r each plant. Three to seven pictures from different sections of each aerial and each terre strial root sample were averaged to obtain more accurate abundance estimates across an entire root. The data were analyzed for deviatio n from a normal distribution using the Shapiro-Wilk W Test. I performed a paired ttest for each species to determine if mean percent abundance of mycorrhizae was significa ntly higher in the aerial or terrestrial roots. I checked for the eff ect of species on the mean pe rcent abundance of mycorrhizae using an unpaired t-test. I tested for e ffects of habit on mycorrhizal abundance using Wilcoxon sign-rank test. Results Mycorrhizal infections were observed in all 32 individuals sampled. The percent abundance of mycorrhizal cove r in the aerial roots of Syngonium sp A ranged from 7.990%, and from 5.3-38% in terrestrial roots (A ppendix 1). Mycorrhizal cover in the aerial roots of P. aurantifolium ranged from 8.2-57%, while terrest rial roots ranged from 4-33% (Appendix 2). All of the data were norm ally distributed (Shapiro Wilk W Test, Syngonium sp A aerial: w = 0.93, p = 0.07; Syngonium sp A terrestrial: w = 0.93, p = 0.26; Philodendron aurantifolium aerial: w = 0.923, p = 0.19; P. aurantifolium terrestrial, w = 0.92, p = 0.149). Because the data did not differ significan tly from a normal distribution, I tested for a difference in mycorrhizal abundance be tween aerial and terrestrial roots. While 3

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aerial roots were not found to differ appr eciably from the te rrestrial roots of P. aurantifolium (Paired t-test, t = 1.74, p = 0.10), a difference was found in the mycorrhizal abundance of Syngonium sp A (Figure 2) Mycorrhizae were significantly more abundant in the aerial roots of Syngonium sp A than in terrestrial roots (Paired t-test, t = 3.11, p = 0.008) (Figure 1). 0 10 20 30 40 50 60aerial terrestrial Root typeMean Mycorrhizal Abundance (%) FIGURE 1: Mean mycorrhizal abundance (percent of grid cells occupied; with standard error bars) in the aerial versus terrestrial roots in 15 individuals Syngonium sp A (Araceae) in the Monteverde cloud forest of Costa Rica. Mycorrhizae were significantly more abundant in aerial than terrestrial roots. 4

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0 5 10 15 20 25 30 35aerial terrestrial Root typeMean Mycorrhizal Abundance (% ) FIGURE 2: Mean percent abundance of mycorrhi zae in the terrestrial and aerial roots of 17 individuals of Philodendron aurantifolium (Araceae) in the Monteverde cloud forest of Costa Rica. There was no significant difference in the mycorrhizae cover between aerial and terrestrial roots. St andard error bars are shown. Additionally, individuals of the species Syngonium sp A experienced on average a greater percentage of mycorrhizal inf ections in their aerial roots than did P. aurantifolium individuals (Unpaired t-test, t = 2.1 9, p = 0.036) (Figure 4). Although the abundance of mycorrhizae in aerial roots differed between species, no significant difference was detected betw een terrestrial roots (Unpair ed t-test, t = 0.19, p = 0.849) (Figure 3). 5

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0 5 10 15 20 25Philodendron aurantifolium Syngonium Aroid SpeciesMean mycorrhizal Abundance (%) FIGURE 3: Mean mycorrhizal abundance (percent of grid cells occupied; standard error bars shown) in the terrestrial roots of Philodendron aurantifolium (n = 17) and Syngonium sp A (n = 15) in the Monteverde cloud forest of Costa Rica. Mycorrhizae abundance in terrestrial roots did not differ significantly between species. 6

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0 5 10 15 20 25 30 35 40 45 50Philodendron aurantifolium Syngonium Aroid SpeciesMean Mycorrhizal Abundance (%) FIGURE 4: Mean mycorrhizal percen t abundance in the aerial roots of Philodendron aurantifolium (n = 17) and Syngonium sp A (n = 15) in the Monteverde cloud forest of Costa Rica. Aerial roots of Syngonium sp A had significantly more mycorrhizae than aerial roots of P. aurantifolium Standard error bars are shown. The plants I sampled from were eith er found climbing on the ground, on a tree, hanging from a tree, or climbing on a stump or dead log. To determine if proximity to the ground affected mycorrhizae, I separated the plants into either ground or climbing habits. No significant difference was found in mycorrhizal abundance in terrestrial or aerial roots between the various growth ha bits of either aroid species (Wilcoxon signrank test, Philodendron aurantifolium aerial: z = 1.59, p = 0.11; P. aurantifolium terrestrial: z = 1.06, p = 0.288; Syngonium sp A aerial: z = 0.67, p = 0.501; Syngonium sp A terrestrial: z = 0.43, p = 0.668)(Figures 5 and 6). Thus habit was not found to have an effect on mycorrhizal abundance in aerial or terrestrial roots in either species. 7

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0 10 20 30 40 50 60 70ground tree ground treeAerial TerrestrialMean Mycorrhizal Abundance (%)n = 10 n = 10 n = 5 n = 5 FIGURE 5: Mean mycorrhizal percent abundance (with standard error bars) in aerial and terrestrial roots of Syngonium sp A with respect to growth habit. Fifteen individuals were sampled in the Monteverde Cloud Forest, Costa Rica. Ten individuals were found climbing on the ground, five individuals were found climbing on a tree or dead log. No effects of habit on mycorrhizal abundance were found. 8

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0 5 10 15 20 25 30 35 40 45ground tree ground treeAerial TerrestrialMean Mycorrhizal Abundance (%)n = 9 n = 9 n = 7 n = 7 FIGURE 6: Mean mycorrhizal percent abundance (with standard error bars) in aerial and terrestrial roots of Philodendron aurantifolium with respect to growth habit. Seventeen individuals were sampled in the Monteverde Cloud Forest, Costa Ri ca. Seven individuals were found climbing on the ground, and nine indi viduals were climbing on trees or dead logs. No effects of habit on mycorrhizal abundance were found. Discussion My study confirms the presence of mycorrh izae in two species of climbing aroids. Current knowledge of the distribution of ar buscular mycorrhizae in natural areas remains limited; in fact, only a small fraction of th e known monocot species have been reviewed for mycorrhizal association (Santos et al. 2000). Cloud forest conditions such as low phosphorous concentration, elevated moisture level, and the pr esence of potential biotic spore dispersers may be particularly conduc ive to mycorrhizal co lonization in climbing plants (Rains et al. 2003). My data show that mycorrhizae are mo re abundant in the aerial roots of Syngonium sp A than P. aurantifolium, and mycorrhizae can be found at higher abundances in the aerial roots of Syngonium sp A than in the terrestrial roots. The developmental and growth processes in shoots are much better known than those of roots. The aerial root in particular is a developmen tal system that is of ten overlooked (Hinchee 1981). However, my results show that aerial roots may be essential to enhancing nutrient uptake in climbing plants. Aeri al roots sequester nutrients and water from ambient mist and debris. Many are able to gain more acc ess to nutrients by bu rrowing in mossy mats 9

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on tree trunks, eventually beco ming terrestrial, picking up dead leaf matter, or perhaps by increasing their rate of inf ection by symbiotic fungi. Because mycorrhizae are costly for plants to support, one would expect plants to only allow fungal infections in roots needi ng extra access to nutrients and water. A symbiosis with mycorrhizae may bring these necessary nutritional benefits. One study estimated that external hyphae of VAM f ungi can deliver up to 80% of a plants phosphorous requirements and 25% of a plants nitrogen requirements (Maschner & Dell 1994). However, at high fertility levels so me plants may reject mycorrhizal infection, choosing rather to employ more root hairs than pay the carbon cost of the fungi (Janos 1983). Thus, aerial roots may harbor more my corrhizae than terrestrial roots because terrestrial roots have access to soil nutrients and may thus shed excess mycorrhizae. Surprisingly, while individuals of Syngonium sp A followed the expected pattern, root location did not appear to affect mycorrhizal abundance in the roots of P. aurantifolium individuals. Philodendron aurantifolium appear to overall invest less in their aerial roots. These sp ecies belong to different genera, which could affect their ability to sequester nutrients. Philodendron aurantifolium individuals appear to have thicker stems on average than the Syngonium sp A. Perhaps they have an increased capacity to transport water and nutrients se questered from the terrestrial roots than Syngonium sp A individuals, causing less dependen ce on their aerial roots for nutrition Furthermore, the presence of aerial root s appeared to be highly variable; many individuals lacked aerial roots completely or all were dedicate d to structural support. It is also possible that the P. aurantifolium individuals simply could not afford the extra mycorrhizae. The presence of mycorrhizae in terrestrial roots did not differ between species. This finding is not surprising as VAM are generally considered ubiquitous in terrestrial soils (Janos 1993). As all terrest rial roots have the same acce ss to the nutrient poor lower montane cloud forest soils, they experien ce no significant difference in nutrient availability. Similar vectors of spore disp ersal could potentially reach all species of terrestrial roots, while spore dispersers may have more difficulty reaching aerial roots of varying levels of accessibilit y. Thus it makes sense that aerial roots, with their differential access to nutrients and spore dispersers, show a difference in percent mycorrhizal infection between species while terrestrial roots do not. An ecological factor that could poten tially contribute to differences in mycorrhizal abundance is the variation in grow th habit of individua l climbers. A plants substrate could potentially affect the need for mycorrhizae or access of roots to spore dispersers. However, growth habit was not found to affect signifi cantly the pe rcent of mycorrhizal coverage in either terrestrial or ae rial roots. This appa rent lack of difference in mycorrhizal infection could potentially be due to the special mobility of climbing plants. The climbing habit of the Araceae is expressed in elongated and relatively unbranched stems, which results in a plant w hose one apical shoot meristem is displaced relatively rapidly through the fo rest, while the trailing stem eventually senesces behind it (Ray 1992). This type of growth results in a mobility that is unique to plants, which are usually considered sessile organisms. For inst ance, aroids are able to orient themselves towards trees through skototropism (Str ong and Ray 1975 in Ray 1992). A plant I found climbing on the ground during the dry season could very well make it to a tree by the wet season. Therefore, mycorrhiza l infection may not differ si gnificantly across species and 10

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root types based on growth habit because that growth habit is most likely an ephemeral condition. Climbers are abundant in tropical forests, and mycorrhizae may very well be essential to their growth. Mycorrhizal fungi ha ve been shown to almost completely close tropical rain forest nutrient cycles by their efficient uptake of nutrients from soil in addition to their advantageous position for scavenging nutrients from dying roots (Janos 1983, from C.F. Jordan 1985). Although they ma y be a huge factor contributing to the efficiency and productivity of tropical forests, we often underestimate the ecological complexity of mycorrhizal systems (Johnson et al. 1997). A study in the nutritional and distributional differences in r oot substratum would be helpful for the future. Investigating plant physiology with respect to patterns of nutrient approp riation and transport would help explain why species differ in their pa tterns of mycorrhizal infection, and perhaps further elucidate the specifics of plant-VAM interactions. Much controversy remains even over the basics of mycorrhizal iden tification, although some hope lies in the new molecular techniques being developed (R owe and Pringle 2005). Understanding why aerial roots may harbor more mycorrhizal infec tions than their terres trial counterparts can have implications in the evolution of the mycorrhizal-plant mutualism, in addition to adding to the basic knowledge of how myco rrhizae function. Mycorrhizae have the potential to impact hugely tropical landscapes; because of this, more research on these influential fungi is warranted. Acknowledgments: Thank you so much to Karen Masters, Tom Mcfarland, Cam Pennington, all of whom were essential to the completion of this report. Thank you to Laura Garrison for helpful comments and revisions. Also thanks to Bill Haber and Willow Zuchowski for help in plant identification, and Estacion Biologica de Monteverde for use of the forest. Literature Cited Alexopoulos, C.J., C.W. Mims, and M. Blackwell. 1996. Introductory Mycology. D. Harris, ed. John Wiley and Sons, United States. Pp. 515. Allen, M.F., E. Rincon, E.B. Allen, P. Huante and J. J. Dunn. 1993. Observations of canopy bromeliad roots compared with plants rooted in soils of a seas onal tropical forest, Ch amela, Jalisco, Mexico. Mycorrhiza 4: 27-28. Eaton, D.A.R. 2005. Mycorrhizal fungi in aerial and terrestrial roots of an epiphytic and two terrestrial species of Orchidaceae. CIEE Fall 2005. Haber, W. 2000. Plants and Vegetation. In: Monteverde: Ecology and Conservation of a tropical cloud forest. Nadkarni N. and N.T. Wheelwright, ed. The Oxford University Press, New York. pp. 3940, 54. Hinchee, M.A.W. 1981. Morphogenesis of Aerial and Subterranean Roots in Monstera deliciosa Botanical Gazette 142: 347-359. Ingram, S. 2000. Epiphytes. In: Monteverde: Ecology and Conservation of a tropical cloud forest. Nadkarni N. and N.T. Wheelwright, ed. Oxford Un iversity Press, Ne w York. pp. 72-73. Janos, D.P. 1993. Vesiculararbuscular mycorrhizae of ep iphytes. Myco rrhiza 4:1-4. Janos, D.P. 1983. Vesicular-Arbuscular Mycorrhizal Fungi In: Costa Rica Natural History D.H. Janzen, ed. The University of Chicago press, Chicago, IL. pp. 340-345. Johnson, N.C., J.H. Graham, and F.A. Smith. 1997. Fu nctioning of Mycorrhizal Associations along the Mutalism-Parasitism Continuum. New Phytologist 135: 575-586. Jordan, C.F. 1985. Nutrient Cycling in Tropical Forest Ecosystems. John Wiley & Sons Ltd., Great Britain. 11

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Lee, Y.C. Mycorrhizae concentration and fitness of ca nopy orchids in the Cloud forest of Monteverde, Costa Rica. CIEE Fall 2006. Lesica, P. and R.K. Antibus. 1990. The Occurrence of Mycorrhizae in Va scular Epiphytes of Two Costa Rican Rain Forests. Biotropica 22: 250-258. Mabberley, D.J. 1987. The Plant-Book: A portable dictionary of the higher plants. Cambridge University Press, Great Britain. pp. 39. Marschner, H., and B. Dell. 1994. Nutrient uptake in mycorrhizal symbiosis. Plant and Soil 159: 89-102. Rains, K.C., N.M. Nadkarni, and C.S. Bledsoe. Epiphytic and terrestrial mycorrhizas in a lower montane Costa Rican cloud forest Mycorrhiza 13: 257-264. Ray, T.S. 1992. Foraging Behavior in Tropical Herbaceous Climbers (Araceae). Th e Journal of Ecology 80: 189-203. Rowe, A.R. and A. Pringle. 2005. Morphological and molecular evidence of arbusc ular mycorrhizal fungal associations in Costa Rican epiphytic bromeliads. Biotropica 37: 245-250. Santos, B.A., G.A. Silva, L.C. Maia, and M.V. Alves. 2000. Mycorrhi zae in Monocotyledonae of Northeast Brazil: subclasses Alismatidae, Arecid ae, and Zingiberidae. Mycorrhiza 10: 151-153. Smith, S.E. and D.J. Read. 1997. Mycorrhizal Symbiosis Academic Press, London. Zuchowski, W. 2005. A Guide to Tropical Plants of Costa Rica. Zona Tropical Publication, Costa Rica. 12

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Appendix 1 Abundance of mycorrhizae found in aer ial and terrestrial roots of Syngonium sp A (Araceae). Collected April 11May 5, 2007 in the Monteverde cloud forest of Costa Rica. Individual Aerial roots (% abundance) Terrestrial roots (% abundance) 1 7.9 38 2 33 22 3 82 22 4 28 24 5 22 6.8 6 25 28 7 46 8.0 8 31 7.5 9 53 14 10 86 6.0 11 34 33 12 39 29 13 90 17 14 43 13 15 15 5.3 Appendix 2 Abundance of mycorrhizae found in aer ial and terrestrial roots of Philodendron aurantifolium (Araceae). Collected April 11May 5, 2007 in the Monteverde cloud forest of Costa Rica. Individual Aerial roots (% abundance) Terrestrial roots (% abundance) 1 42 33 2 27 6 3 14 18 4 15 6.4 5 8.2 25 6 37 28 7 0 26 8 54 4 9 14 29 10 11 20 11 39 19 12 57 16 13 42 33 14 15 6 15 32 13 16 18 9.6 17 14 7.6 13

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Appendix 3 Sample mycorrhizae pictures taken from Oy mpus 7.1 camera with microscope adapter under 40x magnification with compound microscope. A. Philodendron aurantifolium terrestrial (29A terrestrial) 29% average abundance B. Syngonium sp A terrestrial (3C terrestrial) 22% average abundance 14

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C. Syngonium sp A aerial (13 C aerial) 90% average abundance D. Syngonium sp A terrestrial (13 C terrest rial) 17% average abundance 15

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16 E. Syngonium sp A aerial (8C aerial) 82% average abundance D. Syngonium sp A terrestrial (5C terrestria l) 8% average abundance


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La abundancia de micorrizas en las races areas versus terrestres en medio del Araceae trepadora del Bosque Nuboso de Monteverde
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Climbing plants of the family Araceae are a prominent feature of the Monteverde Cloud Forest in Costa Rica. Aerial and terrestrial roots were collected from two species of climbing aroids Syngonium sp A (n = 15) and Philodendron aurantifolium (n = 17) and analyzed for mycorrhizae presence and abundance. Evidence of mycorrhizae infection was found in every plant sampled, and percent abundance of mycorrhizae in the aerial roots of Syngonium sp A ranged from 7.9-90%, while the mycorrhizal cover ranged from 5.3-38% in terrestrial roots. Mycorrhizal cover in the aerial roots of P. aurantifolium ranged from 8.2-57%, and from 4-33% in terrestrial roots. While a significant difference was not found between
the aerial and terrestrial roots of P. aurantifolium (Paired t-test, t = 1.74, p = 0.10), mycorrhizae was significantly more abundant in the aerial roots of Syngonium sp A than in the terrestrial roots (Paired t-test, t = 3.11, p = 0.008). Additionally, individuals of the species Syngonium sp A experienced on average a greater percentage of mycorrhizal infections in their aerial roots than did P. aurantifolium individuals
(Unpaired t-test, t = 2.19, p = 0.036). No difference in mycorrhizal infection was detected in terrestrial roots (Unpaired t-test, t = 0.19, p = 0.849). This report confirms the presence of mycorrhizae in two species of tropical climbing aroids, and suggests that aerial roots of an individual climbing plant may harbor on average more mycorrhizal infections than their respective terrestrial roots.
Las plantas escaladoras de la familia Araceae son una caracterstica prominente del Bosque Nuboso de Monteverde en Costa Rica.
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Hongos Micorrizas
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653
Tropical Ecology 2007
Aerial roots
Terrestrial roots
Ecologa Tropical 2007
Races aereas
Races terrestres
655
Reports
720
CIEE
773
t Monteverde Institute : Tropical Ecology
856
u http://digital.lib.usf.edu/?m39.142