ZLV Online

Abstrakt

The work evaluates the impact of simulated late frost and subsequent exposure to different irradiation on damage of the assimilation apparatus of fir (Abies alba Mill.) seedlings grown in different light conditions. Seedlings grown in shaded bed or in full sun were exposed for 5 hours to freezing temperatures with minimum temperature of -4.5 °C in a growth chamber. Subsequently, one part of seedlings was exposed to light intensity of cca 15,000 lux, and the other to 500 lux during 16 hours of simulated day (17 °C). Prior and after the application of frost, and then at weekly intervals chlorophyll fluorescence of one-year-old needles was measured. Analyzed parameters were as follows: maximum quantum yield of chlorophyll fluorescence (Fv/Fm), performance index on absorption basis (PIabs), absorptivity (Abs) and electron transport rate (ETR). Flushing seedlings were more susceptible to frost damage than seedlings that did not begin to flush yet. Unlike the flushing shoots, the frost damage of one-year-old needles was reversible, and their assimilation apparatus regenerated during 1–2 weeks. Assimilation apparatus of the seedlings exposed after frost to weak radiation was damaged significantly less than that of seedlings exposed to full light.