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Begonia heracleifolia
Stomata and stomatal clusters in Begonia: Ecological response in two Mexican species.
by Hoover W. S. (1986)
W. Scott Hoover
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in Biotropica. 1986;18(1):16–21. – DOI: 10.2307/2388356 –
https://www.jstor.org/stable/2388356?seq=1#page_scan_tab_contents
Abstract
Many species in the genus Begonia have stomata that occur in clusters; stomatal clusters are an unusual character and have an extremely limited distribution among the higher plants.
Six populations of Begonia heracleifolia Cham. et Schlecht. and nine populations of B. nelumbiifolia Cham. et Schlecht. were sampled from tropical forests in Mexico to determine the ecological response of the stomata and stomatal clusters of these species.
Several stomatal characters, including mean cluster size, number of stomata/cluster, stomatal length, and number of stomata/mm$^2$, were analyzed to determine variation within and between populations; the latter three characters are responsive to elevation in B. nelumbiifolia, but only mean cluster size and number of stomata/mm$^2$ are responsive to elevation in B. heracleifolia.
Ecological evidence from this study supports the hypothesis that stomatal clusters in Begonia assist in water conservation. A distributional analysis of sympatric populations of these species at a waterfall site in Chiapas indicates that the relative density of B. nelumbiifolia is greater near the pool formed by the falls, and that the relative density of B. heracleifolia is greater away from the pool.
B. nelumbiifolia has a lower mean cluster size and a lower range of cluster sizes than B. heracleifolia.
The hypothesis is further supported by differences in the range of cluster sizes between populations occupying different habitats and substrate types: populations growing on rocks near waterfalls have larger stomatal clusters than populations collected from soil substrates.
PLANT STOMATA ENCYCLOPEDIA 