Growth and the chlorophyll and carotenoid contents were measured in greenhouse-grown yellow nutsedge (Cyperus esculentus L. ♯ CYPES), following treatment with glyphosate [N-(phosphonomethyl)glycine]. Herbicide was applied as a foliar spray at concentrations of 0.1, 1.0, 5.0, and 10.0 mM. After 2 weeks, growth was inhibited, and chlorosis and leaf apex necrosis were observed. Plant height was reduced, leaf fresh weight was decreased by 40%, and leaf dry weight was slightly affected. Rhizome, tuber, and secondary shoot formation was strongly inhibited, but root development was not affected by glyphosate treatment. With the 10-mM treatment, dry weight of the underground system was reduced by 80%. Chlorophyll and carotenoid levels were decreased by 52 and 54%, respectively, following glyphosate treatment.

Suitable winter wheat cultivars of different degree of resistance to cereal aphids, Sitobion avenae F. and Rhopalosiphum pali L. have been studied in the field conditions. The differences in the chemical composition of possible attractants and repellants have been analysed. The results confirm the inter-pendence between contents of yellow and orange plant pigments in the leaves of the studied varieties and their preference by the aphids. The leaves of the susceptible cultivars also had the highest level of sucrose. The number of the aphids was directly proportional to the total free amino acids content. The higher degree of resistance of the cultivars was related to the contents free phenols in their tissues and was also associated with a high value of ‘toxicity index’, which is the ratio of free phenols content to free amino acids content. Also the contents of structural polysaccharides (cellulose, hemicelluloses and pectins) of the investigated cultivars were inversely proportional to the degree of their infestation.