Sensitivity of drought stress biomarkers tested on norway spruce | Citlivosť reakcie biomarkérov stresu zo sucha a smreka obyčajného

Spruce forests are in danger by drought on the present. It is caused by changes in climate and water distribution during the year and relative high requirement of spruce to soil moisture. This paper presents results from measurement set of parameters on 4-year-old Norway spruce seedlings growing in semicontrolled condition. The moisture content of the soil for severe water stress (ss) was limited to 20%-39% of the maximum capilar capacity (MCC), mild stress (ms) to 40%-59% MCC and control individuals c) were well watered (60%-80% MCC). During 48-days long treatment were measured this parameters: chlorophyll a fluorescence (Fv/Fm parameter), net photosynthesis (Pn), stomatal conductivity (gs), pigments content, concentration of free proline and water potential. We observed drought stress iduced changes in chlorophyll a fluorescence only for severe stressed (ss) seedling during 37-th day of treatment. It confirms assumption that proceses of primary photosynthesis are relatively low sensitive towards drought stress. Response of PN and gs was markedly effected by high temperature not only water defficit. Variant ms achieved even higher values of PN after watering in compare with c variant. Relationships between stomatal conductance and net photosynthesis was relatively tight for c variant (R=0,81), correlation coefficient for ss individuals was only 0,47. Is suggests that PN for ms but especially for ss variant was not reduced only by stomata activity. Long term water deficit decreased chlorophylls (chl a + chl b) and carotenoids (xantophylls and carotens) content for ss seedlings. There was no marked changes in chl/car and chl a/chl b ratios neither between variant ms and c. Significant difference in amino acid proline was determined during l2-th day for ss individuals, but changes between ms and s were not finded during treatment. Water potential values describe very shortly differences between various volume in water deficit.