Effects of fragmentation on the growth and spread of the invasive plant Pistia stratiotes (water lettuce) in freshwater ecosystems

Recent introduction of Pistia stratiotes L. in the Al Jawahir wadi (Fez, Morocco) illustrates the growing threat posed by invasive alien species to Moroccan wetlands, despite in situ control measures. Surface aeration is one of the effective control methods tested ex situ , resulting in both partial breakage of stolons (fragmentation) and root systems of plants. This study aims to evaluate the independent effect of fragmentation on the development of this plant using different configurations of microcosm cultures under controlled conditions. The results show that the size of the single-cultivated parent rosettes is the largest (24.79±6.99 cm). The global diameter of the “leaf rosette and offspring ones” is also the most significant for this batch (20.29±6.02 cm); the total biomass is optimal as well (453.10 g dry weight·m -2 ). However, the absence of the parent rosette does not significantly affect the length of the outer leaves. The number of developed primary daughter rosettes differs depending on the test batch, but no significant differences were observed between the different configurations tested. Plant fragmentation significantly stimulates primary parent rosette growth, followed by mixed cultures of parent rosettes and separate daughter rosettes, which would promote rapid vegetative propagation of this species.