Abstract
Abstract
Leaf water relations and soil-to-leaf resistance were studied in 3-month-old pecan [
Carya illinoenis
(Wangenh.) C. Koch] seedlings as soil dried progressively to minimum water potentials of −0.3, −0.6, and −1.1 MPa in three separate tests. Leaf conductance, transpiration, and predawn leaf water potential declined with increasing soil water deficits, and only predawn leaf water potential fully returned to pre-stress levels after rewatering. Reduced levels of leaf conductance following water stress were apparently caused by internal factors other than leaf water potential. Leaf conductance of well-watered seedlings decreased logarithmically and with increasing leaf-to-air vapor pressure gradient. Soil-to-leaf resistance to water flow varied diurnally and generally increased following water stress at minimum soil water potentials of −0.6 and −1.1 MPa. Osmotic adjustment and changes in the distribution of water between the apoplast and symplast in leaves did not occur in response to soil water potentials of −0.6 MPa.