Water requirements and use of Buttonwood (Conocarpus erectus) seedlings grown under arid conditions

Abstract: Six-month-old buttonwood (Conocarpus erectus L.) seedlings were grown in containers under different soil water potentials (soil), ) to 1) 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 until soil water potential was lower than -0.1 MPa (between 40 and 30% FC), after which, plant height, leaf area and shoot and root dry weights became disrupted by severe water deficit. Water stress decreased osmotic potential of leaves and roots. Leaves tended to osmoregulate their cell sap through osmotic adjustment process as their content of soluble sugars increased. The positive survival under low soil water potential could be related to increased osmotic adjustment. Soil water potential values seem more useful tool than FC values to estimate water requirements and use over an extended period of time, for plant grown under different soil types and different environmental conditions. The study indicate that Conocarpus seedlings can withstand reasonable water stress and can survive at moderately low water potential but, in contrast to other studies, can not be classified as a high drought tolerant or resistant species.