Response of Buttonwood (Conocarpus erectus) Trees to Drought Conditions

Six-month-old buttonwood (Conocarpus erectus L.) seedlings were grown in containers under different soil water potentials (Ψsoil). The objective of the work was: 1) to determine the minimum soil water potential at which Conocarpus trees can survive and grow fairly well, 2) to study the soil-plant water relationship at different irrigation regimes, and 3) to examine the capacity of Conocarpus seedlings for osmotic adjustment via solute accumulation. Seedling growth was not affected significantly at soil water potential above –0.1 MPa (between 40 and 30% Field Capacity (FC). At lowerΨsoil, plant height, leaf area and shoot and root dry weights became disrupted by water deficit. Water stress decreased the osmotic potential (Ψπ) of leaves and roots. Leaves tended to osmoregulate their cell sap through osmotic adjustment processes as their content of soluble sugars increased. The positive survival under low Ψsoil could be related to increased osmotic adjustment. Ψsoil values were found to be more useful than FC values to estimate water requirements and use over an extended period of time, for plants grown under different soil types and different environmental conditions. Conocarpus seedlings can withstand reasonable water stress and can survive at moderately low water potential but, in contrast to other studies, this can not be classified as a high drought tolerant or resistant species.