Conclusions
Cell wall and other anatomical properties can affect
Δ18OLW by manipulating Ethrough altering water flow along the transpiration stream andL v through altering water channeling out of the
xylem and to the stomata. This influence is apparent in variation in
Δ18OLW between C3 and
C4 grass species that can be attributed to differences
in vasculature that limit water flow out of the vasculature in
C4 species and may be an indication of differing
hydraulic attributes. Studying the interactions of anatomical features
and physiological traits in water movement through and outside of the
xylem can shed more light on Δ18OLWbecause either physiology or anatomy alone fails to capture the isotopic
implications of water movement. Consequently, stable isotopes can be
used to study this interaction. With the development of gene editing,
Δ18OLW can potentially be used to
better understand gene-phenotype relationships of traits related to
water movement in the leaf. For example, when studying genes associated
with Sd, differences in water movement may not be discernable from
measures of Sd per se , but nevertheless differences in Sd can
influence Δ18OLW and indicate a subtle
response of Sd to genotype or environmental conditions. Further
integration between leaf water transport through and outside the xylem
with stable isotope theory will facilitate the development of a
physiologically and anatomically explicit water transport model.