The influence of the method of silver fir growing and nutrition on sprouting and chlorophyll fluorescence during spring

Abstract

To compare breaking of dormancy in relation with climatic conditions and reaction to late frost fir plants growing in sun, in shade and at magnesium deficiency were evaluated. Sprouting and chlorophyll a fluorescence of needles were evaluated from March to May 2011. As a consequence of May frost 100% of plants from sunny treatments and 70% of firs shaded with shade cloth were affected by necrosis of sprouting shoots; fir-trees shaded by the stand remained fully intact. No relationship between the index of shoot sprouting and damage was confirmed. Firs with Mg deficiency had the lowest maximum quantum yield of PSII photochemistry of the dark-adapted tissue (FV/FM) and performance index on absorption basis (PIabs) in the long term. Regression models of FV/FM and PIabs and selected environmental parameters showed that chlorophyll fluorescence was influenced to the largest extent by minimum temperature of the day of measurement and also by acclimation to the light environment. The process of breaking of dormancy increased fir vulnerability to thermal stresses of the environment - late frosts.