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Long‐term relationships among atmospheric CO 2 , stomata, and intrinsic water use efficiency in individual trees
Author(s) -
MillerRushing Abraham J.,
Primack Richard B.,
Templer Pamela H.,
Rathbone Sarah,
Mukunda Sharda
Publication year - 2009
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.0800410
Subject(s) - guard cell , stomatal density , carbon dioxide in earth's atmosphere , biology , water use efficiency , carbon dioxide , botany , herbarium , ecology , horticulture , atmospheric sciences , photosynthesis , geology
Leaf‐level responses to increases in atmospheric carbon dioxide (CO 2 ) concentrations could have large implications for water and carbon cycles. We investigated whether stomatal density, guard cell length, and intrinsic water use efficiency (iWUE) of 27 individual trees growing at the Arnold Arboretum in Boston, Massachusetts have responded to changing environmental conditions over the last 100 years. We examined leaves from 74 herbarium specimens collected from three genera— Acer (maples), Quercus (oaks), and Carpinus (hornbeams)—from 1893 to 2006. During this period, global average atmospheric CO 2 concentrations increased by approximately 29% (86 ppm), and temperatures in Boston increased by 1.8°C. Stomatal density and guard cell length were negatively correlated in oaks and hornbeams. Although stomatal density declined and guard cell length increased over time, the changes were not dependent on the magnitude of changes in CO 2 concentrations. Intrinsic WUE did not change significantly over time. Our findings suggest that iWUE may not respond to changes in CO 2 concentrations over the lifetimes of individual trees, possibly because of compensating changes in stomatal density and guard cell size. We provide an example of a method that can enable researchers to differentiate between genetic and plastic responses to global change in long‐lived trees.