Gas exchange and hydraulic function in seedlings of three basal angiosperm tree-species during water-withholding and re-watering

Basal angiosperms have relatively primitive hydraulic systems and may be vulnerable to drought. The coordination in hydraulic function between leaf, stem and root of a plant during and after a drought is not well understood. Here, we examined the interaction between gas exchange and hydraulic function in the leaves, stems, and intact root systems of potted-seedlings of three evergreen basal angiosperm tree-species exposed to a cycle of severe water stress and subsequent rewatering. In all three species, stomatal closure occurred at water potentials before 50% loss of stem hydraulic conductivity, because their leaves and roots were more vulnerable to drought than the stems. Manglietia insignis that has scalariform perforatiom plates was more vulnerable to drought than the other two species that have simple porforation plates. During rewatering, water potentials of D. chinensis and C. camphora were recovered after 10 days, their gas exchange were gradually recovered and reached to pre-drought levels after 3 weeks, whereas, the recovery of hydraulic function in their leaves, stems and roots lagged behind but also reached pre-drought levels after 3 weeks. Manglietia insignis displayed poor recovery in both gas exchange and hydraulic function and a high mortality. Our results reveal that drought-induced severe embolism can be recovered even in seedlings of basal angiosperms depending on species if a drought does not persist long, and earlier recovery in xylem water potential and gas exchange than hydraulic function.