Water use patterns of eastern black nightshade (Solanum ptycanthum) and hairy nightshade (Solanum sarrachoides) in response to shading and water stress

Greenhouse and growth room experiments were conducted to determine the effects of shading and water stress on transpiration of eastern black nightshade (Solanum ptycanthum) and hairy nightshade (S. sarrachoides). Transpiration rates were estimated using heat balance stem flow gauges. Eastern black nightshade transpired significantly more water than hairy nightshade given ample water and light. Eastern black nightshade also transpired more water than hairy nightshade when shaded. Transpiration of both species increased with light intensity and was relatively insensitive to changes in soil volumetric water content above 0.10 m 3 m −3 , but declined sharply below that level. Eastern black nightshade had significantly more stomata than hairy nightshade, particularly on the lower leaf surface. Key words: Sap flow, stomata