© 1989 Heron Publishing—Victoria, Canada
Response of Ulmus americana seedlings to varying nitrogen and water status. 1 Photosynthesis and growth
Michael B. Walters and Peter B. Reich
Department of Forestry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA / Received June 20, 1988
Summary
Well-watered American elm (Ulmus americana L.) seedlings responded to increased nitrate availability with increased leaf nitrogen (N) concentration and photosynthetic
rate, larger and more numerous leaves, greater total growth and greater proportional allocation of carbon to shoot than root.
Plasticity of growth and carbon allocation were greater than plasticity of N concentration and photosynthetic capacity. For
a given N availability, allocation of N per unit leaf area was positively correlated with dry mass per unit leaf area (specific
leaf mass), but these relationships differed with N availability. Rates of net photosynthesis and leaf conductance declined
logarithmically with decreasing predawn water status. Increased water stress resulted in a greater relative decline in net
photosynthesis and leaf conductance for high-N than low-N plants.
