Foliar Nutrient Concentrations and Epicuticular Wax Formation of Scots Pine Needles

1993

S. 189

Unselbständiges Werk

200077390

The relationship between nutrient status and epicuticular wax formation of needles of Pinus sylvestris L. seedlings was studied experimentally by inducing differences in foliar N, K, Mg, and Ca concentrations and subsequently analyzing the surface structure of the needles by scanning electron microscopy (SEM). The induced concentrations were either normal or excessive for N and normal or deficient for K, Mg and Ca. The experiment for N was a completely randomized factorial (2hoch4) design with 16 foliar nutrient combination. For SEM, smples of current needles and subtending bracts were taken systematically from 10 seedlings from each foliar nutrient combination. The quantity and quality of epicuticular waxes were estimated from bracts and needle convex surfaces, stomatal furrows and epistomatal chambers. All the bracts and convex surfaces examined were almost free of wax structures. In the stomatal furrows and epistomatal chambers, wax quantity decreased towards the needle tip. In needles with nutrient imbalances, a general decline of wax in the stomatal furrows was observed. This phenomenon was most evident in the needles with K, Mg and Ca deficiencies in combination. While the quantity of the wax decreased, the quality of the wax tended to change from the normal tube-like structures to more granulated and fused structures. The results are discussed with special reference to disease resistance.