would help predict the effects that it may suffer when struck by
the invasion front of A. dealbata. For these reasons, cell elongation
zone level and root cap were also observed. The cell elongation
zone thickness showed a significant increase (P < 0.05) induced by
the different A. dealbata parts (Fig. 1J–L) respect to control (Fig. 1I)
(Table 1). The seeds and leaves caused the greatest increase in thickness
of this zone; however, in previous studies found that those
are the two parts of the invasive plant that most inhibit radicle
growth in several native and non-native species (Aguilera, 2015c).
The reason for this unbalanced cell growth is uncertain, but it has
frequently been observed in relation to the action of several allelochemicals
(Burgos et al., 2004). It could be a combined effect of
growth retardation induced by auxin (Hoshi et al., 1994; Gra˜na
et al., 2013) and destabilization of cell walls due to the increased
peroxidase activity of the cell wall in response to phytotoxic compounds
(Gonzales and Rojas, 1999) released, in this study, by the
plant material of A. dealbata. Although meristem and immature
cells have small vacuoles, it has been shown that the presence of
allelochemicals can induce excessive vacuolization for lytic functions
and contribute to the degradation of phytotoxins