Agriculture Reference
In-Depth Information
1000
a
800
b
600
c
d
e
400
g
f
h
200
i
k
j
0
0
10
20
Leaf nitrogen (mmol g
−
1
)
30
40
50
Fig. 6.3
The increase of photosynthetic capacity with foliar nitrogen content; each
polygon
bounds observations collated from different studies. (From Field and Mooney 1986)
evolved differences in foliar design among species as well as in the ecophysio-
logical responses of single leaves in differing microenvironments within a plant
canopy (Fig.
6.4
). The photosynthetic return on nitrogen investment at the whole-
plant level is maximized when the tangents to the point where the curves for
individual leaves cross the linear leaf-level relationship between
A
max
and foliar
N
all pass through the origin (Hirose and Werger 1987a). Similarly, Koyama and
Kikuzawa (2009) observed this linear relationship applied to not only
A
max
but also
A
day
in leaves of
Helianthus tuberosus
.
Assembling the Elements of Foliar Function
By the early 1990s photosynthetic capacity was firmly linked to LMA and foliar
N
,
but it took a seminal paper by Peter Reich and his colleagues (Reich et al. 1997) to
focus attention on the high degree of coherence in the correlations among these
three foliar traits. They collated data for 280 plant species to show that there were
consistent correlations among
A
max
, LMA, and foliar
N
(Fig.
6.5
). As any one of
these traits characterizing foliar function varied from one species to another, they
varied in concert, and these relationships were conserved across and within growth
forms. This is compelling evidence that
A
max
, LMA, and foliar
N
are integral parts
of a unified suite of traits that affects the functionality of leaves.
