Passage IV

A researcher investigated the growth of 6 specices of floodplain plants. Each species was classified as either flood-sensitive (S) or flood-tolerant (T) (see Table 1).

Experiment

Seeds from each of the 6 species were germinated in a growth chamber maintained at 25.5°C during the day and at 10°C at night.

After germination, the seedlings of each species were planted in separate 0.5 L pots and grown for 4 weeks.The seedlings were watered 3 times per week.

At the end of the 4 weeks, each plant was repotted into its own 4 L pot containing a substrate composed of a 4: 1 mixture, by mass, of sand to compost. The plants were grown for 2 more weeks; during this time, they were watered 3 times per week.

Next, the potted plants were placed in plastic tubs such that each tub contained 8 plants of each species. Each tub of plants was subjected to a different treatment (see Table 2) for 3 weeks.

At the end of the 3-week treatments, the plants were harvested, and their roots were washed. The roots were separated from the shoots, and then both were dried at 70°C for 48 hr. The average dry shoot biomass per plant and the average dry root biomass per plant were determined for each species and treatment combination (see Figures 1 and 2, respectively).