© 2000 Heron Publishing—Victoria, Canada
Physiological responses of radiata pine roots to soil strength and soil water deficit
Chris Zou (1), Roger Sands (1) and Osbert Sun (2)
1. School of Forestry, University of Canterbury, Private Bag 4800, Christchurch, New Zealand / 2. New Zealand Forest Research Institute Ltd., P.O. Box 29 237, Christchurch, New Zealand / Received August 18, 1999
Summary
We investigated physiological responses of radiata pine (Pinus radiata D. Don) roots to soil strength and soil water deficit by measuring the osmotic potential (Ψπ) and yield turgor (Y) in the elongation zone of root segments of seedlings growing (i) in polyethylene glycol 4000-containing rooting solution
of different water potentials (Ψs) and (ii) in soil of different soil strengths (Q) at the same soil matric potential (Ψm). Root elongation rate (Δl/Δt) decreased progressively with decreasing Ψs and was associated with decreased Ψπ and decreased turgor pressure (P). Osmotic adjustment occurred at Ψs < –0.2 MPa. Over a range in Ψs of –0.01 to –1.0 MPa, Ψπ fell 0.3 MPa whereas P fell 0.7 MPa. Mean Ψ in the solution experiment was 0.37 MPa and did not differ significantly with Ψs (P = 0.10). Root elongation rate decreased exponentially as Q increased from 0 to 3.0 MPa, and was associated with an increase in P of 0.11 MPa as a consequence of Ψπ decreasing by the same amount. Mean Y in the soil experiment was 0.49 MPa and did not change significantly with Q (P = 0.87).
Keywords:
osmotic adjustment, Pinus radiata, root elongation rate, turgor pressure, yield turgor.
