Content of total phenols in not treated plants of Chenopodium album biotype susceptible to atrazine was 40% higher compared to resistant one. Atrazine applied at 1 kg per hectare increased the amount of these compounds in both biotypes, especially as regards on the level of monophenols in susceptible biotype, which was 3 times higher than in untreated plants. Amount of monophenols in atrazine-resistant biotype increased slightly due to atrazine application. After application of atrazine the polyphenols/monophenols ratio decreased from 4.2 to 1.1 in susceptible biotype, while it was not much changed in resistant biotype. Atrazine increased the content of flavanols in S biotype eight-times compared with untreated plants, while in resistant one this phenomenon was not observed. IAA-oxidase activity measured in vitro was modified by leaf extracts from C. album and Echinochloa crus-galli. Than the extracts from triazine-treated resistant biotype were more capable of protecting the indoloacetic acid (IAA) against enzyme activity. It may suggest that the mechanism susceptibility or resistance to herbicide is not only involved with PS II complex, but consists also in formation in plant the systems which favour or protect the auxin degradation, respectively.

The invasion, development and number of generations of Heterodera goettingiana in pea plants were examined in a glasshouse experiment after plants were treated with herbicides, recommended for pea cultivation (terbutryn + terbuthylazine, methabenz rhiazuron, prometryne, bentazone, cyanazine, pendimethalin, benthiocarb and fluazifop-butyl). There was a non-target effect of herbicides. Prometryne, cyanazine and benthiocarb reduced female number in the roots. This effect may be due to the inhibition of hatching or/and retardation of female development.

The leaves of wheat infected by powdery mildew Erisiphe graminis var. tritici manifested repellent action against cereal aphids Rhopalosiphum padi and Sitobion avenae. Food (leaves) for aphids enriched in chemical components present in diseased leaves caused weaker reproduction of S. avenae and mortal i ty of R. pad i. It could be caused by post-infection increase of the level of monophenols and flavanoids in the leaves of wheat infected by powdery mildew (E. graminis var. tritici). These compounds increasing IAA-oxidase activity in plants can have a harmful influence on the cereal aphids.

Phenoxy acids significantly increased the number of Sitobion avenae F. and Rhopalosiphum padi L.on wheat treated with Aminopielik D and Illoxan 36 EC. This herbicidal effect could be caused directly by derivatives ofphenoxy acid or indirectly by altered metabolism of wheat plant.

The influence of cinnamic acid, 1-tryptophane, 3,4-dihydroxyphenylalanine, 2,4-dichlorophenol modifying IAA-oxidase activity and indoleacetic acid on the development and reproduction of cereal aphids in laboratory conditions was tested. We observed that IAA and Try stimulated the reproduction of cereal aphids whereas CA, DOPA and DCP decreased it.

The level of free (PAs) and conjugated (CPAs) soluble polyamines in leaves ofChenopodium album was determined using the fluorometric method for dansy lated derivatives. The tests made at the 4-6 leaf growth stage showed that the concentration of PAs in susceptible (S) and resistant (R) biotypes ranged between 32-43 μg and 45-56 μg per 100 μl of cell sap, respectively. The analyses performed later, namely at the beginning of flowering showed that the difference in the level of polyamines between Sand R biotypes was greater. In this case the amount of PAs in biotype S ranged between 15-34 μg and in biotype R between 51-73 μg per 100 μl of cell sap. Therefore, the level of PAs cans act as an indicator for susceptibility or resistance of C. album biotypes to atrazine.