TITLE:
How Betula ermanii Maintains a Positive Carbon Balance at the Individual Leaf Level at High Elevations
AUTHORS:
Koichi Takahashi, Sohei Otsubo
KEYWORDS:
Leaf Mass per Area, Leaf Nitrogen, Photosynthesis, Stable Carbon Isotope Ratio, Stomatal Conductance
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.8 No.3,
February
15,
2017
ABSTRACT: Generally, plant species with shorter leaf longevity
maintain a positive carbon balance by decreasing leaf mass per area (LMA) and
increasing photosynthesis. However, plants at high elevations need to increase
LMA against environmental stresses. Therefore, plants need to increase both LMA
and photosynthesis at high elevations. To examine how deciduous plants maintain
a positive carbon balance at high elevations, photosynthesis and related leaf
traits for deciduous broad-leaved tree Betula
ermanii were measured at three elevations. LMA was greater at middle and
high elevations than at low elevation. Leaf δ13C
was greater at higher elevations, and positively correlated with LMA,
indicating greater long-term deficiency of CO2 in leaves at higher
elevations. However, the Ci/Ca ratio at photosynthetic
measurement was not low at high elevations. Nitrogen content per leaf mass and
stomatal conductance were greater at higher elevations. Photosynthetic rates
and photosynthetic nitrogen use efficiency (PNUE) did not differ among the three
elevations. Photosynthetic rate showed a strong positive correlation with
stomatal conductance on a leaf area basis (R2 = 0.83, P B. ermanii compensates the deficiency of CO2 in leaves at high elevation by increasing
stomatal conductance, and maintains photosynthesis and PNUE at high elevation
as much as at low elevation.