Morphological asymmetry and chlorophyll fluorescence in Scots pine (Pines sylvestris): responses to variation in soil moisture, nutrients and defoliation

摘要

The effects of different levels of watering, nutrients and defoliation on two-year-old Scots pine (Pines sylvestris) seedlings were examined. Two indicators of stress, chlorophyll fluorescence and morphological asymmetry, were also compared. Reduced watering and low levels of nutrients increased relative biomass and the length of the current year shoot, respectively, while both decreased current year needle biomass. In the defoliation gradient, an extensive defoliation resulted in reduced root biomass. Chlorophyll fluorescence was highest with the highest level of nutrients. In the moisture and defoliation experiments, different parts of the seedlings (current year leader vs. lateral shoot) showed significantly different fluorescence; there was no significant trend along the gradients. Both fluctuating (FA) and directional (DA) asymmetry in needle length increased significantly with increasing nutrient levels. In the defoliation experiment, both FA and DA increased with an increased percentage of defoliation. In the moisture gradient, no significant trend was found. Although the defoliation experiment confirmed that FA and DA correlate with stress intensity, the results on nutrient levels were contradictory: FA and DA increased with nutrient levels while chlorophyll fluorescence indicated no stress.