Nitrite reductase (NiR) was extracted from seedlings of winter triticale cultivar Moreno in the form of homogenous protein fraction with molecular weight of about 61 kDa, characterised by maximum of absorption at 280 and 390 nm. Differences in specific activity of enzyme isolated from plants cultivated in different conditions (garden soil, Hoagland's diet) suggest that NiR may be induced by light and nitrate ions presence in arable medium.
The obtained results showed that grain aphid (Sitobion avenae Fabr.) feeding caused an increase of the total protein content and a decrease of soluble protein level in the ears of both studied winter triticale cultivars (i.e. susceptible cultivar Grado and relatively resistant- Lasko). Moreover, the content of amino acids in soluble protein increased in Grado plants infested with the aphid, and reduced - in Lasko.