INFLUENCE OF THE APPLICATION OF CYTOKININ AND NITROGEN-FERTILIZATION ON SPRING WHEAT

In the years 1993 to 1995 the effect of postfloral application of cyto kinin N-6-m (hydroxybenzyl) adenosine and two nitrogen doses (40 kg/ha and 70 kg/ha in the form of calcium nitrate applied before anthesis) as exerted on the formation of yield-forming components, height of eco nomic yield and spring wheat quality was studied in spring wheat, cv. Sandra. Six treatments were evaluated: control, control + cytokinin, 4 0 kg N, 40 kg N + cytokinin, 70 kg N and 70 kg N + cytokinin (Tab. II) . Besides length of stem, number of tillers and dry matter, leaf area index LAI as well as tillering potential OP during the growing season were evaluated. In postfloral period, roughly six weeks after applicat ion of cytokinin, spectrophotometrical methods were used to determine activity of glutamate kinase in upper two flag leaves. Grain quality a fter harvest was assessed from wet gluten content (fixed on the Glutom atic device) and from the value of falling number (fixed on the device Falling Number manufactured by the Swedish company Perten). Nitrogen and cytokinin fertilization had a positive effect on the yield and qua lity of grain, particularly in the years 1994 and 1995. Both years dif fer by weather conditions (Fig. 1). Data on yield components are summe d up in Tabs III to V. Out of yield-forming components (Tabs VI and VI I) the number of grains per spike was the most affected, while TKW at least. Nitrogen fertilization and cytokinin application limited the re duction of tillers and reduced potential spike productivity (numbers o f established spikelets and florets in spikes to actual number of grai ns per spike). The effect of cytokinin on glutamate kinase enzyme acti vity, on the value of falling number and wet gluten content (Figs 2 to 5) is evident. Treatments of 40 kg N + cytokinin and 40 kg N were man ifested most. An analysis of production-ecological and yield component s in different years indicates that the effect of treatment was manife sted significantly particularly in less favourable years when cytokini n aided to plants to overcome the stress, e.g. in 1994 stress from dro ught (Tab. IV). In this weather unfavourable year the effect of treatm ent was most marked for the whole evaluated period. In 1993 higher dos e of nitrogen decreased grain yield (Tab. III). Length of stems, numbe r of tillers and leaf area index (which were different in wetter and w arm year of 1995 and in more arid year of 1994) differed significantly along with integral characteristics, leaf area index LAI and tillerin g potential. In treatments 40 kg N + cytokinin increased activity of g lutamate kinase (Tab. VIII) was recorded. Results presented in Figs 2 to 5 indicate some relations between glutamate kinase activity, fallin g number and gluten content. In addition, they also indicate significa nt effects of a year (weather conditions), in concrete terms - formati on of progression of yield-forming components in time, and quality of production as well. Ecophysiological manifestations of growth are in c ongruency with literature.