Critical water stress levels in Pinus patula seedlings and their relation to measures of seedling morphology

  • CA Rolando
  • NW Pammenter
  • KM Little

Abstract

A pot trial was implemented to determine the effect of soil water stress following transplanting on shoot water potential and stomatal conductance of Pinus patula seedlings. The relationship of seedling morphology to measures of water stress was also investigated. The trial consisted of two watering treatments: a control (no water stress) and a severe water stress (no further water after planting). The treatments were applied to recently transplanted seedlings selected to reflect a range of sizes typical in an operational environment. Measures of shoot water potential and stomatal conductance, root and shoot growth and environmental variables were made. The results indicated that P. patula seedlings tolerated high air and soil temperatures (above 35 °C) and low soil water availability (-1.5 MPa). The water potential threshold for changes in stomatal conductance was in the region of -0.8 to -0.9 MPa and stomatal closure had occurred at a shoot water potential of between -1.8 and -2.1 MPa. Mortality occurred when shoot water potential declined to below -3.0 MPa. There was variability between seedlings in their potential for survival and growth. Inherently bigger seedlings had a greater capacity for new root growth following planting. Mass of new roots was significantly and positively related to higher rates of transpiration under conditions of low soil moisture.

Keywords: growth, mortality root mass, Pinus patula, seedling quality, soil water stress

Southern Forests 2011, 73(1): 41–49

Author Biographies

CA Rolando
Scion, PO Box 3020, Rotorua 3046, New Zealand
NW Pammenter
School of Biological and Conservation Sciences, South Ring Road, Westville Campus, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa
KM Little
Institute for Commercial Forestry Research, PO Box 100281, Scottsville 3209, South Africa
Section
Articles

Journal Identifiers


eISSN: 2070-2639
print ISSN: 2070-2620