
TY  - JOUR
A1  - Jensen, CR 
A1  - Mogensen, VO 
A1  - Mortensen, G 
A1  - Andersen, MN 
A1  - Schjoerring, JK 
A1  - Thage, JH 
A1  - Koribidis, J 
T1  - Leaf Photosynthesis and Drought Adaptation in Field-Grown Oilseed Rape (<I>Brassica napus</I> L.)
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1996
VL  - 23
IS  - 5
SP  - 631
EP  - 644
KW  - age effects; canola; osmotic adjustment; photosynthetic nitrogen use efficiency; photosynthetic water use efficiency; pressure-volume curves
UR  - https://doi.org/10.1071/PP9960631 
N2  - Photosynthesis and drought adaptation in leaves of field grown rape (Brassica napus L. cv. Global) were investigated in 1992 under temperate climatic conditions in plants grown in lysimeters in a sand and in a loam soil. Light-saturated net photosynthesis (Amax), leaf conductance to water vapour (ge), leaf water potential (&#936;e), leaf osmotic potential at full turgor (&#936;&#960;100), specific leaf area (SLA), spectral reflection index (RI) used as a measure of leaf area, and leaf nitrogen content, were determined in irrigated plants and in plants exposed to soil drying.     In the early growth stages before flowering, Amax was 35-45 &#956;mol m-2 s-1 and ge was 1-1.5 mol m-2 s-1. Maximum rates of CO2 assimilation greater than 30 &#956;mol m-2 s-1 were obseved for up to 19 days. Stomata partly closed in ageing leaves maintaining a constant CI/Ca ratio. Both photosynthetic nitrogen use efficiency (NUE; Amax per unit of nitrogen) and photosynthetic water use efficiency (WUE; Amax/ge) were high compared with efficiencies of stems and husks and of other C3 plants. In bracts Amax and ge were 10-15 &#956;mol m-2 s-1 and 0.2-0.7 mol mol m-2 s-1, respectively. Both Amax and ge varied linearly with leaf nitrogen content.     When soil water was depleted, both &#936;&#960;100 and RI decreased relative to controls on both soil types before any significant decrease in &#936;&#960; occurred. On loam with slow soil drying SLA, ge and Amax decreased before any significant decrease in &#936;e occurred. We suggest that these responses might have been triggered by a non-hydraulic signal transmitted from the roots. When water was more depleted, rape maintained positive turgor down to &#936;e of -1.6 MPa. Rape had a high TW/DW ratio (9-11) and a 6 limited ability to adjust osmotically, &#916;&#936;e100 being at most 0.3-0.4 MPa. 
ER  -

