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Leaf water use in heterobaric and homobaric leafed canopy tree species in a Malaysian tropical rain forest

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Photosynthetica

Abstract

Tropical canopy tree species can be classified into two types by their heterobaric and homobaric leaves. We studied the relation between both leaf types and their water use, together with the morphological characteristics of leaves and xylem, in 23 canopy species in a tropical rain forest. The maximum rates of photosynthesis and transpiration were significantly higher in heterobaric leaf species, which also underwent larger diurnal variations of leaf water potential compared to homobaric leaf species. The vessel diameter was significantly larger and the stomatal pore index (SPI) was significantly higher in heterobaric than that in homobaric leaf species. There was a significant positive correlation between the vessel diameter, SPI, and maximum transpiration rates in all the studied species of both leaf types. However, there was no significant difference in other properties, such as leaf water-use efficiency, leaf mass per area, leaf nitrogen content, and leaf δ13C between heterobaric and homobaric leaf species. Our results indicate that leaf and xylem morphological differences between heterobaric and homobaric leaf species are closely related to leaf water-use characteristics, even in the same habitat: heterobaric leaf species achieved a high carbon gain with large water use under strong light conditions, whereas homobaric leaf species can maintain a high leaf water potential even at midday as a result of low water use in the canopy environment.

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Abbreviations

BSE:

bundle-sheath extension

DBH:

stem diameter at breast height

D v :

vessel diameter

E max :

maximum transpiration rate

GCL:

guard cell length

g s :

stomatal conductance at P max

LMA:

leaf mass per area

Narea :

nitrogen per unit leaf area

Nmass :

mass-based leaf nitrogen concentration

PIC:

phylogenetically independent contrast

P max :

maximum photosynthetic rate

PNUE:

the ratio of CO2 assimilation rate to leaf organic nitrogen content

RGR:

relative growth rate

SD:

stomatal density

SPI:

stomatal pore index

V d :

vessel density

VPD:

vapor pressure deficit

W d :

wood density

WUE:

intrinsic water-use efficiency

δ13C:

stable carbon isotope ratio

ΔΨL :

diurnal variation in the leaf water potential

Ψmid :

leaf water potential at midday

Ψpd :

leaf water potential at predawn

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Correspondence to Y. Inoue.

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Acknowledgements: We are grateful to the Forest Department, Sarawak, and Prof. N. Yamamura for their kind support of this study. We thank Prof. S. Fujiwara for his help with microscopic analysis, Dr. M. Nakagawa for providing tree census data, and Dr. Kume for providing meteorological data. We also thank two anonymous reviewers for constructive critique. This research was partly supported by the Grant-in-Aid for Scientific Research from JSPS (No. 23255002, 244050321), the Research Institute for Humanity and Nature (project No. D-04), and the Environment Research and Technology Development Fund (RF-1010, S-9) of the Ministry of the Environment, Japan.

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Inoue, Y., Kenzo, T., Tanaka-Oda, A. et al. Leaf water use in heterobaric and homobaric leafed canopy tree species in a Malaysian tropical rain forest. Photosynthetica 53, 177–186 (2015). https://doi.org/10.1007/s11099-015-0105-6

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