Defence mechanisms in trees are not well understood. We assessed whether distribution of iron ions and their co-localisation with reactive oxygen species in Pinus sylvestris root cells reflect differential preferences of the pathogens Heterobasidion annosum sensu stricto, H. parviporum and H. abietinum to the host. Strains of H. annosum s.s. characterised by a greater preference for P. sylvestris induced accumulation of superoxide (O(2)(-)) in host cells 6 h after inoculation, whereas two peaks in accumulation of O(2)(-) (after 4 and 48 h) were observed after infection with strains of the pathogens H. parviporum and H. abietinum, which have a lower preference for P. sylvestris. Moreover, strains of H. annosum s.s. caused increased production of hydrogen peroxide (H(2)O(2)) in P. sylvestris cells, in contrast with strains of the other two species (H. parviporum and H. abietinum). Following inoculation with H. annosum s.s. strains, H(2)O(2) was correlated negatively with O(2)(-) and correlated positively with ferrous iron (Fe(2+)). Co-localisation of Fe(3+) with H(2)O(2) may suggest that they are involved in inducing hypersensitive responses and eventually cell death in roots inoculated with H. annosum s.s. strains, in contrast with H. parviporum, in which other mechanisms operate when the host is parasitised.

http://www.eje.cz riod of time (Šefrová & Laštůvka, 2001). The range of C. ohridella continues to expand; in 2003, it reached southern Sweden (Rämert et al., 2011), and a recent report indicates that this insect is in Kazakhstan (Gninenko et al., 2017). Its main host, horse chestnut Aesculus hippocastanum L., was introduced into central Europe in XVI c. (Ravazzi & Caudullo, 2016). Currently, trees of this species are common throughout the continent. They occur in both urban and rural environments and are commonly planted in lines or alleys. This species has high decorative value, especially during the fl owering period, and its chestnuts that fall to the ground attract the attention of children and, as described by Gwiazdowicz & Wiśniewski (2011) are also of interest to senior citizens. Escin, the mixture of triterpenoid saponins found in the tissues of A. hippocastanum, is used to treat chronic venous insuffi ciency, haemorrhoids and post-operative oedema (Sirtori, 2001). Escin also exhibits anti-cancer effects (Cheong et al., 2018). Fujimura et al.

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