Drought until death do us part: a case study of the desiccation-tolerance of a tropical moist forest seedling-tree, Licania platypus (Hemsl.) Fritsch.

Studies of the desiccation tolerance of 15-month-old Licania platypus (Hemsl.) Fritsch seedlings were performed on potted plants. Pots were watered to field capacity and then dehydrated for 23-46 d to reach various visible wilting stages from slightly-wilted to dead. Root hydraulic conductance, k_r, was measured with a high-pressure flow meter and whole-stem hydraulic conductance, k_ws, was measured by a vacuum chamber method. Leaf punches were harvested for measurement of leaf water potential by a thermocouple psychrometer and for measurement of fresh- and dry-weight. L. platypus was surprisingly desiccation-tolerant, suggesting that most species of central Panama may be well adapted to the seasonality of rainfall in the region. The slightly-wilted stage corresponded to leaf water potentials and relative water contents of -2.7 MPa and 0.85, respectively, but plants did not die until these values fell to -7.5 MPa and 0.14, respectively. As desiccation proceeded k_r and k_ws declined relative to irrigated controls, but k_ws was more sensitive to desiccation than k_r. Values of k_ws declined by 70-85% in slightly-wilted to dead plants, respectively. By comparison, k_r showed no significant change in slightly-wilted plants and fell by about 50% in plants having severely-wilted to dead shoots. [ABSTRACT FROM AUTHOR]