Drought-induced changes in water relations in broom snakeweed ( Gutierrezia sarothrae) under greenhouse- and field-grown conditions

Abstract

Pressure-volume analyses were done on a half-shrub broom snakeweed ( Gutierrezia sarothrae) subjected to different soil water regimes under pot- and field-grown conditions. Under pot and field conditions, water deficit decreased water and osmotic potentials. In the severely droughted pot-grown, osmotic potential at full turgor (П 100) decreased by 0.44 MPa due to reduced symplastic volume, the result of a decreased leaf turgid to dry weight ( TW/DW) ratio. A reduction of 0.86 MPa in П 100 was observed in the field-grown plants subjected to the first drought cycle, but increased cell wall elasticity occurred in the second drought cycle. The lowered П 100 was attributed to osmotic adjustment and reduced symplastic volume. High cell wall elasticity in the second drought cycle led to a greater water loss and tissue desiccation. It is concluded that osmotic adjustment, increased apoplastic water fraction and more rigid tissue are important dehydration-avoidance mechanisms in broom snakeweed.