Wpływ wieku drzew oraz wieku i lokalizacji igieł w koronie na zawartość związków fenolowych w igłach młodych sosen

We studied Scots pine stands differing in age to determine the influence of tree age (6−20−year−old), needle age, and needle location in the crown and on the shoot on total soluble phenolic compounds (TPh) content in needles. These compounds are secondary metabolites, which largely determine the resistance of plants to unfavorable biotic factors such as herbivorous insects and pathogenic fungi. Examining the constitutive resistance of needles (without indications of damage), we found a statistically significant positive effect of needles age (1−3−year) and a negative effect of whorl age on TPh content, but only in older needles. We found that in spite of the large influence of the needle's age, the light conditions have a significant positive influence on the TPh content, as indicated by changes in the level of phenols with whorl age, comparing needles of different ages. The tree's age was important, but only when the cleaning was carried out changing the light conditions of needle growth. Moreover, we revealed that in the oldest needles (3−year), the position on the shoot also has a significant influence on TPh content in the needles. The level of phenols is lower in the needles growing on the bottom part of the shoot, which are shaded by needles growing on the upper side of the shoot.