Effect of rhizome exposure to contrasting abiotic conditions on the performance of the invasive macrophyte Hedychium coronarium J. Koenig (Zingiberaceae)

We collected rhizomes of the invasive emergent macrophyte Hedychium coronarium from five sites in São Carlos, southeastern Brazil. The rhizomes were washed, dried at room temperature for 24h and divided into 10 cm fragments. Rhizome were used in three experiments aiming to assess the effect of ditinct temperature, desiccation and photoperiod treatments on the subsequent growth of ramets. For the desiccation experiment, we oven dried three rhizome fragments of each site at the average annual maximum temperature in the region (30°C) for 12 distinct time periods: 2h, 5h, 15h, 30h, 60h, 120h, seven days, 14 days, 21 days, 30 days, 60 days and 90 days. Three rhizome fragments from each site were then transplanted to 10 x 10 cm trays with a 5 cm layer of soil. These trays were maintained in a room at 24ºC and 12h:12h light-dark photoperiod for 60 days. Twice a week, we counted the number of emergent ramets and measured their heights. To assess the effect of rhizome exposure to distinct temperatures on ramet growth, we placed five 10 cm x 10 cm trays with five rhizome fragments in germination chambers at three conditions ((T1) 15oC, (T2) 25oC and (T3) 35oC) and a 12h:12h light-dark photoperiod. To assess the effect of light availability on ramet growth, five rhizome fragments from each site were transplanted to distinct 10 x 10 cm trays with a 5 cm layer of commercial soil rich, which were then exposed to four photoperiods: (L1) 24h light, (L2) 16h light, (L3) 12h light (L4) 0h light. In both experiments, samples also were watered with 500 mL water twice a week, and the abundance and height of emergent ramets was recorded weekly for 30 days. After this period the trays were transferred without removal of the already emerged ramets to a room at 24°C with a 12h:12h light:dark photoperiod, where they remained under the same watering regime for an additional 60 day period. At the end of all experiments, we oven dried all the ramets at 60°C for 48h and weighed the dry biomass.