Fine-Root Responses of Two Maple and Two Magnolia Species to Waterlogging

Apparent mortality during waterlogging and subsequent regrowth of fine roots during the 7-week recovery period. Examples of waterlogged (left) and control (right) plants are shown for saucer magnolia. Note the much smaller root system of the waterlogged plant that resulted from high-mortality rates of the fine roots during waterlogging. Also note the proliferation of new, healthy root tips emerging around the root ball. Similar amounts of new fine-root growth were observed on all waterlogged saucer and star magnolia individuals (Figure S2), but not for sugar maple (Figure S4).

Peroxidase activity (POX) and lipid oxidative damage (LOD) in control and waterlogged fine roots of 4 tree species measured immediately after a 2-week period of waterlogging and again after a 7-week recovery period (9 weeks total). Significant differences between control and treatment for a given species and sample date are indicated by an asterisk (P < 0.05). Dots indicate outliers, and numbers indicate the number of individual trees for each measurement, respectively.

Reductions in carbon assimilation and stomatal conductance for waterlogged individuals compared to control individuals measured immediately after a 2-week period of waterlogging and again after a 10-day recovery period (3.5 weeks total). Error bars represent standard error. Asterisks indicate significant (P < 0.05) differences between the treatment and control for a given species and sample date.

Leaf loss and stem growth of control and waterlogged trees of 4 tree species. Trees were measured before a 2-week waterlogging period and again after a 7-week recovery period. Asterisks indicate significant (P < 0.05) differences between the treatment and control trees for a given species.

“Rhizopots” were constructed from standard nursery pots: four flaps (11 cm × 16 cm) were cut into each pot, and clear acetate was glued into the cutouts. Green and yellow colors indicate different tracing sessions; differentiating in this way allowed us to monitor root growth and sample roots produced before and after waterlogging. When pots were not being actively traced or imaged, the flaps were closed, and each rhizopot was placed inside a second, uncut pot to prevent light penetration through the windows.