TITLE:
Variation in Stomatal Characteristics of Bursera simaruba (L.) Sarg., a Dominant Tree Species of Tropical Hardwood Hammock Forest across a Habitat Gradient in the Florida Keys
AUTHORS:
Suresh C. Subedi, Michael S. Ross, Rosario Vidales, Jay P. Sah, Leonel Sternberg
KEYWORDS:
Stomatal Density, Stomatal Size, δ13C, Bursera simaruba, Dry Tropical Forest, Florida Keys
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.9 No.10,
September
30,
2018
ABSTRACT: Tree
species in coastal forests may exhibit specialization or plasticity in coping
with drought through changes in their stomatal morphology or activity, allowing
for a balance between gas exchange and water loss in a periodically stressful
environment. To examine these responses, we sought to answer two primary
research questions: a) how is variation in B. simaruba’s stomatal traits partitioned
across hierarchical levels, i.e., site, tree, and leaf; and b) is variation in
stomatal traits an integrated response to physiological stress expressed across
the habitat gradient of Florida Keys forests? At eight sites distributed throughout
the Keys, five leaves were collected from three mature trees for stomatal
analysis. Leaf carbon stable isotope ratio (δ13C) was
determined to infer the changes in water use efficiency caused by physiological
stress experienced by each tree. The
results showed that substantial proportions of the total variance in three
traits (stomatal density, stomatal size, and δ13C) were
observed at all levels, suggesting that processes operating at each scale are
important in determining trait values. A significant negative correlation
between stomatal density and size across scales was observed. Path model
analysis showed that environmental variables, distance to ground water and
ground water salinity, affect
leaf δ13C indirectly,
via its effects on stomatal traits, not directly to leaf δ13C.
Therefore, the combination of small and densely distributed stomata seems to
represent a strategy that allows B. simaruba to conserve water under conditions of physiological drought induced by
either higher ground water salinity or flooding stress at very low elevation.