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La presencia de muclago en las races areas en Monteverde, Costa Rica
Presence of mucilage on aerial roots in Monteverde, Costa Rica
Many hemiepiphytes produce aerial roots and some have mucilage on the growing tips of these roots. The purpose of this study was to determine if mucilage varies at different altitudes in the Monteverde Cloud Forest in Costa Rica. Mucilage may serve to protect the roots from the dry environments, or from altitudes more prone to fungal infections since it has both high water storing capacities and anti-fungal properties. Transects were run along different altitudes, and samples of plants mucilage were taken, measuring the weight and length of the mucilage. Monstera was the most common plant with mucilage found in the study and was found at all altitudes ranging from 1,400 m to 1,800 m. There were a total of 12 Monstera plants, two Pitcairnia plants, and one Philodendron plant with a total of 34 mucilaginous roots. Twenty-three of the mucilaginous aerial roots were found on the genus Monstera (Araceae), 4 on Pitcairnia brittoniana (Bromeliaceae) and 7 on Philodendron (Araceae). No correlation was found between the weight and length of mucilage, compared to altitude of all three genera (Spearman rank correlation, N = 32; R2 = 0.135; p = 0.44 and N = 32; R2 = 0,86; p = .62, respectively). No correlation was also found for Monstera roots only, for weight and length compared to altitude (Spearman rank correlation, N = 23; R2 = 0.10; p = .12 and N = 23; R2 = .004; p = .759, respectively). A trend could be seen in the total mucilage frequency for low and high altitudes for Monstera. In this case, 16 Monstera were found at low altitudes, and seven at high altitudes, but this difference was not statistically significant (chi-squared test, x2 = 3.52, df = 1, p = 0.06). In conclusion, no altitudinal difference was found in mucilage size, suggesting genetic determinants might be playing a role, but twice as many Monstera were found at low altitudes compared to high altitudes, although further studies need to be done to clarify the trend.
Algunas plantas hemiepfitas producen races areas y algunas de estas presentan mucilago en las puntas de estas races. El propsito de este estudio fue determinar si el mucilago vara en las diferentes altitudes en el bosque nuboso de Monteverde en Costa Rica.
Text in English.
Cloud forest ecology--Costa Rica
Ecologa del Bosque Nuboso--Costa Rica
Tropical Ecology 2008
Hemiepiphytes, Root development--Monteverde Cloud Forest Reserve
Ecologa Tropical 2008
Hemiepfitas, desarrollo de races--Reserva Bosque Nuboso de Monteverde
t Monteverde Institute : Tropical Ecology
1 Presence of mucilage on aerial roots in Monteverde, Costa Rica Chase Kincaid Department of Agriculture and Natural Resources, University of Wisconsin Madison _______________________________________________________________________ ABSTRACT: Many hemiepi phytes produce aerial roots and some have mucilage on the growing tips of these roots. The purpose of this study was to determine if mucilage varies at different altitudes in the Monteverde Cloud Forest in Costa Rica. Mucilage may serve to protect the root s from the dry environments or from altitudes more prone to fungal infections since it has both high water storing capacities and anti fungal properties. Transects were run along different altitudes, and samples of plants mucilage were taken, measuring t he weight and length of the mucilage. Monstera was the most common plant with mucilage found in the study and was found at all altitudes ranging from 1,400 m to 1,800 m. There were a total of 12 Monstera plants, two Pitcairnia plants, and one Philodendron plant with a total of 34 mucilaginous roots. Twenty three of the mucilaginous aerial roots were found on the genus Monstera Araceae, 4 on Pitcairnia brittoniana Bromeliaceae and 7 on Philodendron Araceae. No correlation was found between the weight and length of mucilage, compared to altitude of all three genera Spearman rank correlation, N = 32; R 2 = 0.135; p = 0.44 and N = 32; R 2 = 0, 86; p = .62, respectively. No correlation was also found for Monstera roots only, for weight and length compared to altitude Spearman rank correlation, N = 23; R 2 = 0.10; p = .12 and N = 23; R 2 = .004; p = .759, respectively. A trend could be seen in the total mucilage frequency for low and high altitudes for Monstera. In this case, 16 Monstera were found at low a ltitudes, and seven at high altitudes, but this difference was not statistically significant chi squared test, x 2 = 3.52, df = 1, p = 0.06. In conclusion, no altitudinal difference was found in mucilage size, suggesting genetic determinants might be pla ying a role, but twice as many Monstera were found at low altitudes compared to high altitudes, although further studies need to be done to clarify the trend. RESUMEN: Algunas plantas hemiepÃfitas producen raÃces aÃ©reas y algunas de estas presentan muc Ãlago en puntas de estas raÃces. El propÃ³sito de este estudio fue determinar si el mucÃlago varÃa a diferentes altitudes en el bosque nuboso de Monteverde en Costa Rica. El mucÃlago puede servir para proteger la raÃz contra la sequedad o contra infeccion es por hongos en regiones de mayor altitud, ya que esta sustancia presenta tanto capacidad antifungÃca y de almacenamiento de agua. Se utilizaron transeptos a diferentes altitudes, y se tomaron muestras de plantas con mucÃlago, midiendo el peso y largo de l mismo. Monstera fue la planta mÃ¡s comÃºn encontrada con mucÃlago y fue encontrada a lo largo de todas las alturas desde 1400 m a 1800 m. Se encontraron un total de 12 plantas de Monstera , 2 plantas de Pitcarnia y una planta de Philodendron Arecaceae. No se encontrÃ³ ninguna correlaciÃ³n entre el peso y largo del mucÃlago, comparado con la altitud de los tres gÃ©neros CorrelaciÃ³n de Spearman, N = 32; R 2 = 0.135; p = 0.44 y N = 32; R 2 = 0,86; p = .62, respectivamente. No se encontrÃ³ correlaciÃ³n solament e para Monstera, para peso y largo comparado con la altitud CorrelaciÃ³n de Spearman, N = 23; R 2 = 0.10; p = .12 y N = 23; R 2 = .004; p = .759, respectivamente. Una tendencia se observa en la frecuencia total de mucÃlago para baja y mayor altitud para Mo nstera . En este caso, 16 plantas de esta especie se encontraron a menor altitud, y siete a mayor altitud, pero estas diferencias no son es tadÃsticamente significativas x 2 = 3.52, df = 1, p = 0.06. En conclusiÃ³n, no hay diferencias altitudinales in el tamaÃ±o del mucÃlago, sugiriendo que determinantes genÃ©ticos pueden jugar un papel, pero de nuevo al encontrar mÃ¡s plantas a menor altitud que a mayor altitud, se necesitan estudios posteriores para clarificar estÃ¡ tendencia.
2 INTRODUCTION: Hemiepiphytes have developed strategies to prevent desiccation of their aerial roots while growing towards the ground and mucilage is believed to serve this purpose. Gill 1969 Mucilage can commonly be found surrounding growing root tips. The mucilage has high water storage properties, which can help prevent desiccation by lengthening the time the aerial root has to absorb water. Darwin 1876 observed mucilage on Ficus ripens which remained wet for 128 days under hot and dry conditions. The mucilage has also shown t o prevent fungal infections, as spores were found on the mucilage but never germinated Ivey 1994. Mucilage is a polysaccharide that is secreted by Golgi vesicles in cells near the growing tips of roots. The mucilage is believed to lubricate root tips as they move through the soil, and also serves the purpose of sensing gravity. Hopkins, 1995 Mucilage is thought to protect the root tip from desiccation and aid in nutrient absorption by allowing the roots to be in contact with more soil. Russell, 1997 This mucilage is often invaded by bacteria, which may contribute to the roots by providing nutrients as metabolic byproducts in the soil and aerially. The mucilage, bacteria, and soil particle mixture is often called mucigel. Hopkins, 1995 If mucil age acts as an anti desiccant, more plants in dryer habitats would be expected to have mucilage and the amount of mucilage would be expected to be greater. On the other hand, if mucilage protects roots from fungal infections, which are more likely in wet habitats, more plants in moister habitats would be expected to have more and larger mucilage secretions. Therefore, I examine the size and frequency of mucilage on aerial roots along an altitudinal gradient near and in the Monteverde Cloud Forest of Costa Rica. Here, lower altitudes are on the seasonal, dryer Pacific slope and represent areas likely to suffer some desiccation while higher altitudes are generally wetter and less seasonal. The objective of this study was to determine if mucilage production differs at varying altitudes. It was predicted that as altitude decreases, number of plant species with mucilage would increase as the environment becomes drier. MATERIALS AND METHODS: This study was conducted in the Monteverde Cloud Forest Reserve in C osta Rica between October 28 th and November 16 th , 2008. Altitudes ranged from 1,400 m. to 1,800 m. The general approach was to conduct the experiment by walking transects to observe/collect aerial roots with mucilage at different altitudes. Transects wer e run at 50 meter increments from 1,400 m to 1,800 m and altitude was measured using a hand held watch altimeter. Transect lengths were 133 m and I looked for the aerial roots with mucilage as I walked. The trails used were at the Monteverde Biological St ation and those of the Tropical Science Center the Monteverde Cloud Forest Reserve. Transects were run both on trail and off trail, although at high altitudes it was too difficult to run transects off trail. Once aerial roots with mucilage were found I recorded the number of mucilage masses per plant and the altitude the plant was found. I then measured the length of the mucilage on the root tip with a tape measure and collected the mucilage from the plant,
3 scraping off the mucilage into a cup to record its weight in grams using an electric, pocket sized scale. I brought back plant samples to be identified and also identified plant species in the field. Observations I recorded were: the mucilage s weight, which plant species the mucilage occurs, altitu de the mucilage was found at, and mucilage number per plant. RESULTS: A total of 125 transects were completed found a total of 34 aerial roots with mucilage. Twenty three of the mucilaginous aerial roots were found on the genus Monstera , and 4 on Pitca irnia brittoniana and 7 on Philodendron . There were a total of 12 Monstera plants, two Pitcairnia plants, and one Philodendron plant. Comparisons were made on total aerial roots from the three genera and also on Monstera alone since the majority of the d ata were on Monstera. There was no correlation between weight of the mucilage and altitude for the total mucilaginous roots Spearman rank correlation, N = 32; R 2 = 0.135; p = 0.44, as well as for Monstera roots Spearman rank correlation, N = 23; R 2 = 0. 10; p = .12. There was also no correlation between length of the mucilage and altitude for total roots Spearman rank correlation, N = 32; R 2 = 0, 86; p = .62 and for Monstera roots specifically Spearman rank correlation, N = 23; R 2 = .004; p = .759. Monstera roots were analyzed in low and high altitude ranges, with low altitudes ranging from 1,400 m to 1,600 m , and high altitudes ranging f ro m 1,600 m to 1,800 m. Monstera were found throughout the 1400m 1600m range, but no mucilaginous roots were f ound between 1600 and 1770 m for Monstera . Average weights for Monstera roots were compared at low and high altitudes and no difference was found Mann Whitney U test, U = 40.5, p = 0.30, N 1 = 16, N 2 =7. Fig. 1, a. I found no difference of lengths bet ween low and high altitude mucilage of Monstera Mann Whitney U test, U = 41.5, p = 0.33, N 1 = 16, N 2 =7. Fig 1, b The total mucilage number for low and high altitudes for Monstera was 16 found at low altitudes, and seven at high altitudes Fig. 2, a . Total mucilaginous roots were similar with 19 at high altitudes and 15 at low altitudes Fig. 2, b. There was no difference in Monstera mucilage between high and low altitudes x 2 = 3.52, df = 1, p = 0.06, although a trend can be seen with higher amo unts of mucilaginous roots at lower altitudes, with the p value being very close to the acceptable p value of "d 0.05. DISCUSSION: Monstera was the most prevalent plant in the study, therefore would have been the most likely to show trends in the data. Mo nstera was found at both low and very high altitudes. No Monstera roots were found between 1600 m and 1770 m. Results comparing mucilage length and weight for both Monstera plants alone and total aroid species showed no correlation with altitude. Monstera plants may always produce the same amount of mucilage on an aerial root, as the amount of mucus may be genetically determined. This does not support that the aerial roots in lower drier habitats would produce more mucilage per root to prevent desiccation. In all comparisons of
4 weight or length to altitude, there was a considerable amount of overlap in the results with no statistical differences. The results showed some relationship in mucilage number of Monstera in low altitudes versus high altitudes. The re was over twice as many roots with mucilage on them in lower elevations compared with high elevation; supporting the prediction that there will be more mucilaginous aerial roots at lower elevations since the climate in the lower elevations is drier, and there would be more advantages for the plant to protect its aerial roots from desiccation. This appears to be a trend, but is not statistically significant as the p value was over 0.05, though it was very close at 0.06. This suggests that if there was a l arger sample size, results may show a significant difference between low and high elevations. If the mucilage is serving two functions, fungal protection and desiccation prevention, there may be no difference in mucilage between low and high altitudes. Lo w altitudes may be more susceptible to desiccation since they are drier, but high altitudes may be more susceptible to fungal infections since they are wetter, so mucilage would be necessary in all ranges of altitudes. Further studies need to be done to c larify the trend seen by increasing sample sizes. ACKNOWLEDGEMENTS: I would like to thank my advisor Tania ChavarrÃa for her help with my project statistics. Also to Alan and Karen Masters in their guidance throughout the project. I am also grateful to the Monteverde Cloud Forest reserve and the Biological Station in the use of their trail systems to conduct my project. LITERATURE CITED: Darwin, C. 1876. The movements and habits of climbing plants. D. Appleton & Company, New York Gill, A. M. 1969. The ecology of an elfin forest in Puerto Rico: 6 aerial roots. Journal of the Arnold Arboretum 50: 197 209 Hopkins, G. W. 1995. Introduction to Plant Physiology. John Wiley & Sons, Inc. Pp. 96, 275 Ivey, C. T. 1994. Experimental evidence concerning th e function of mucilage on aerial root tips. Pp. 115 116 in Young, B. E. & Gilbert, G. eds. Tropical biology: an ecological approach. Organization for Tropical Studies, Durham, NC. Russell, R. S. 1977. Plant Root Systems. Their Function and Interaction with the Soil. McGraw Hill, London. in Taiz, L. and Zeiger, E. 1991. Plant Physiology. The Benjamin/ Cummings Publishing Company, Inc., Redwook City, California. Pp. 102
5 a b Figure 1. Avera ge weight and length of mucilage and altitude are shown for Monstera at low 1,400 1,600 m and high altitudes 1,600 1,800 m. a Avg. mucilage weight, standard deviation = .12 for low altitude, .42 for high altitude Mann Whitney U test, U = 40.5, p = 0.30, N 1 = 16, N 2 =7 b Avg. mucilage length, standard deviation = 2.6 for low altitude, 2.8 for high altitude Mann Whitney U test, U = 41.5, p = 0.33, N 1 = 16, N 2 =7. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Average mucus weight g Low altitude High altitude 0 1 2 3 4 5 6 7 8 9 10 Average Length cm Low Altitude High Altitude
6 a b Figure 2. Mucilage frequencies at low and high altitudes. Low altitude range is 1,400 1,600 m and high altitude range is from 1,600 1,800 m. a Mucilage frequency of Monstera at low altitude n =16, and high altitude n = 7. b Total aroid muci lage frequency at low altitude n =19, and high altitude n = 15. 0 2 4 6 8 10 12 14 16 18 low altitude high altitude Monstera mucus # 0 2 4 6 8 10 12 14 16 18 20 Low altitude High altitude Total mucus #