The 3-year experiment was concerned with the response of spring forms of common wheat (Triticum aestivum L. subsp. aestivum), durum wheat (Triticum durum Desf.) and spelt wheat (Triticum aestivum subsp. spelta L. em. Thell.) to the foliar application of a plant growth stimulant (extract from marine algae Ecklonia maxima), with the commercial name of Kelpak SL (GS), as compared to control treatment (C). The following parameters were analysed: yield of grain, yield components (number of ears, weight of 1000 kernels, number and weight of kernels per ear) and physical indicators of grain quality (test weight, uniformity and vitreosity of grain). The study showed that the level of yielding and the yield components were related primarily with the wheat genotype, but they depended also on the agro-climatic conditions and on the algae extract and control experimental treatments. The application of algae extract, compared to the control, caused a significant increase in the yields of the spring wheat species under study, on average by 7.0%. Canopy spraying with algae extract had a favourable effect on the number of ears, on he number and weight of kernels per ear, but it had no effect on the weight of 1000 kernels. The grain quality of durum wheat, spelt wheat and common wheat was affected more strongly by the weather conditions in the successive years of the study and by the genotype than by the foliar application of algae extract. The spelt genotypes were characterised by lower yields and lower grain quality than common wheat and the durum wheat genotypes.
