Histochemical features of wall appositions inAsparagusroot meristems infected byFusarium

Primary roots of Asparagus officinalis cv. Viking seedlings were inoculated with the pathogen Fusarium oxysporum f.sp. asparagi. The meristematic region of the root was the major infection site. Meristematic cells were the first barrier to fungal advance. Colonized cells and uninfected cells contiguous with infected cells revealed many cytological changes, the most conspicuous of which was an accumulation of material in the paramural space. These wall appositions consisted of three main substances: an amorphous substance, an electron-lucent material and an electron-dense material. Histochemical tests showed that polysaccharides, acid mucopolysaccharide, callose, and phenolic substances were present in the wall appositions.