Small plants, large plants: the importance of plant size for the physiological ecology of vascular epiphytes

Abstract

Recently, a number of publications have reported that many physiological properties of vascular epiphytes are a function of plant size. This short review will summarize what is known to date about this phenomenon, describe the possible mechanism and will discuss the consequences for the present understanding of epiphyte biology. Size-related changes are also known from other plant groups and it is argued that close attention should be paid to the size of the organisms under study in order to understand the performance and survival of a species in the field. In the light of these findings, the results of many earlier studies on epiphyte ecophysiology are now difficult to interpret because essential information on the size of the specimens used is missing.

Ecophysiology and Plant Size in a Tropical Epiphytic Fern, Asplenium nidus, in Taiwan

“…For example, photosynthetic rates of leaves are not expected to vary dramatically, provided such rates are compared on an equal area or mass basis. Recent studies by Zotz and colleagues, however, indicate that ignoring plant size in physiological studies may lead to erroneous conclusions (Zotz 1997;Zotz et al 2001aZotz et al , 2001b. They provide convincing evidence that, at least in some epiphytic taxa, physiological parameters of leaves can vary depending on the size of the plant selected for measurement.…”

“…They provide convincing evidence that, at least in some epiphytic taxa, physiological parameters of leaves can vary depending on the size of the plant selected for measurement. The bulk of their evidence is derived from ecophysiological investigations of an epiphytic bromeliad, Vriesea sanguinolenta , although and Zotz et al (2001aZotz et al ( , 2001b provide some evidence that plant size affects the physiology of several epiphytic ferns, aroids, and orchids. In addition, results of other studies indicate that plant size, although not always clearly differentiated from plant age, can be an important variable influencing the physiology of terrestrial taxa, particularly trees (Kull and Koppel 1987;Miller et al 1990;Ryan and Waring 1992;Grulke and Miller 1994;Schoettle 1994;Yoder et al 1994;Smith and Resh 1999;Kolb and Stone 2000;Grulke and Retzlaff 2001).…”

Seed comas of bromeliads promote germination and early seedling growth by wick-like water uptake

“…Since water supply is arguably the most critical aspect of the ecology of vascular epiphytes, particularly during the early stages of ontogeny (Zotz et al 2001), this functional aspect (Zotz & Schultz 2008), where water supply even in the rainy season is highly fluctuating. Under such conditions, prolonging the time until a seed or a seedling loses the water that superficially adheres to it after a rain event, even for just a few minutes, may be highly critical for successful establishment.…”

Epífitas vasculares da Estação Ecológica Barreiro Rico, Anhembi, SP, Brasil: diversidade, abundância e estratificação vertical

“…A distribuição espacial das epífitas vasculares depende, em grande parte, da variabilidade estrutural dos forófitos (Arévalo & Betancur 2006), especialmente do incremento de tamanho destes (Zotz et al 2001), da qualidade do subosque (Krömer et al 2007), e da complexidade estrutural da floresta (Bennet 1996). Quanto mais complexo o tipo de floresta maior a proporção de forófitos e epífitas (Arévalo & Betancur 2006).…”

“…Nessas zonas o nível de luminosidade é razoavelmente alto, enquanto a presença de bifurcações ou inserção de galhos faz com que haja acúmulo de matéria orgânica, favorecendo a implantação das raízes das espécies epifíticas (Krömer et al 2007); a presença dessa matéria orgânica contribui para a manutenção da umidade, um dos principais fatores limitantes ao epifitismo (Nieder et al 1999, Zotz et al 2001. A presença de todas as famílias nas zonas próximas ao solo (Z1 e Z2) indica que nessa floresta não há restrições de luminosidade para as espécies epifíticas nas zonas mais próximas ao solo (figura 2a), entretanto, é notável a importância da umidade para a sinúsia que ocorre nessas zonas, especialmente pela maior abundância das famílias Orchidaceae e Piperaceae (figura 2b).…”