
TY  - JOUR
A1  - Ghannoum, Oula 
A1  - Caemmerer, Susanne von 
A1  - Conroy, Jann P. 
T1  - The effect of drought on plant water use efficiency of nine NAD&#8211;ME and nine NADP&#8211;ME Australian C<emph type="8">4</emph> grasses
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 2002
VL  - 29
IS  - 11
SP  - 1337
EP  - 1348
KW  - C4 photosynthesis, drought, water use efficiency, &#948;13C, &#948;18O.
UR  - https://doi.org/10.1071/FP02056 
N2  - We investigated the response to drought of nine NAD&#8211;malic enzyme (NAD&#8211;ME) and nine NADP&#8211;malic enzyme (NADP&#8211;ME) C4 grasses. Species were grown from seeds in potted soil in a glasshouse. Seedlings were either watered regularly or exposed to two successive drying cycles of 8&#8211;10 d each, after which plants were harvested. Under well-watered conditions, average water use efficiency (WUE; dry mass gain per unit water transpired) was similar for NAD&#8211;ME and NADP&#8211;ME C4 grasses, and ranged between 6.0 and 8.7 g dry mass kg&#8211;1 H2O. Drought enhanced WUE of most species, but to a significantly greater extent in NAD&#8211;ME (1.20-fold) than NADP&#8211;ME (1.11-fold) grasses. Inhibition of dry matter accumulation (average of 12%) and shoot elongation under drought was similar among the C4 grasses. Leaf dry matter carbon (&#948;13C) and oxygen (&#948;18O) isotope compositions were significantly different between the two C4 subtypes. Leaf &#948;13C averaged &#8211;13.3 and &#8211;12.2, and leaf &#948;18O averaged 26.0 and 26.9 in well-watered NAD&#8211;ME and NADP&#8211;ME grasses, respectively. Drought significantly reduced leaf &#948;13C in most C4 grasses by an average 0.5. Leaf &#948;18O was not significantly affected by drought, indicating that leaf &#948;18O does not reflect drought-induced changes in leaf transpiration of C4 grasses. In the experiment reported here, NAD&#8211;ME grasses increased their WUE under drought to a greater extent than their NADP&#8211;ME counterparts. Increased WUE of the C4 grasses under drought was primarily related to control of water loss relative to carbon gain at the leaf, rather than the plant, level. 
ER  -

