Cell wall elasticity and water index (R970 nm R900 nm) in wheat under different nitrogen availabilities

New data showing the importance of cell wall elasticity in the expression of the Water Index (WI) (R970/R900) as an indicator of plant water status are presented. We studied wheat under five different nitrogen (N) fertilization treatments (0 to 200kg ha(-1)) to test N-availability effects on tissue structural changes such as cell wall composition and elasticity, and the corresponding effects on WI. Although water was amply supplied in all the plots, WI, CWSI (Crop Water Stress Index) and delta T (canopy minus air temperature) were all highest in the N-0 (no fertilization) treatment. Plants in this treatment had the most xeromorphic characteristics. Their specific leaf weight (SLW) and leaf cellulose contents were higher and their cell wall elasticities were lower than in the other N treatments. WI was a useful water status indicator (even of mild water stress conditions) at ground level when elasticity was low. WI may also become an indicator of cell wall elasticity of leaves when plant water status is known.