Forest Decline and Ionic Disturbances at the Histological and Cellular Levels in the Needles of Picea abies. An X-ray Microanalysis Study

1991

S. 321-332

5 Abb., 2 Tab., 36 Lit. Ang.

Unselbständiges Werk

200041331

Foliar yellowing in relation to mineral deficiencies has been observed in declining Norway spruce. To determine the causes of this phenomenon and to assess its physiological impact, the element contents at the histological and cytological level in green needles from declining spruce were studied by electron micro-probe. The microanalysis of different element shows that at the whole needle level the effects of decline on the mineral content resemble premature senescence. Decline as well as ageing lead to a decrease in potassium and an increase in calcium and manganese in the different tissues. This accurate technique indicates that at the cellular level, ageing or decline cause different ionic disturbances. Ageing mainly leads to high ionic disturbances at the vacular tissue level; however decline results in high decrease in potassium in the epidermis and stomata. At the same time a greater accumulation of calcium and manganese is observed in the stomatal complexes. The high ionic disturbances detected in the tissues situated near the surface of needles from declining spruce, provide good evidence that atmospheric parameters are involved (ozone, wet or dry acid deposition) in the forest decline phenomenon. In particular, by disturbing the stomatal movements these ionic modifications might be one of the causes involved in the decrease in water content observed by several authors in these needles.