© 1993 Heron Publishing—Victoria, Canada
Vascular tissue anatomy of Norway spruce needles and twigs in relation to magnesium deficiency
A. F. Hannick (1), L. Waterkeyn (2), F. Weissen (3, 4) and H. J. van Praag (3)
1. Department of Forestry, Université Catholique de Louvain, Place Croix du Sud, B-1348 Louvain-la-Neuve, Belgium / 2. Department of Biology, Université Catholique de Louvain, Place Croix du Sud, B-1348 Louvain-la-Neuve, Belgium / 3. Forest Soils and Tree Nutrition (IRSIA), Faculty of Agronomy, Avenue Maréchal Juin 27, B-5030 Gembloux, Belgium / 4. Author to whom correspondence should be addressed / Received June 10, 1992
Summary
Vascular tissues of needles and twigs of Norway spruce with low foliar magnesium concentrations were examined by light microscopy.
Observations were made on samples from (1) apparently healthy trees, (2) trees exhibiting progressive symptoms of decline,
including the yellowing and fall of needles and the death of twigs and branches in the subapical canopy, and (3) trees recovering
from symptoms of decline after fertilization with magnesium sulfate. Abnormalities in cambium and phloem anatomy, which were
apparent in 2-year-old needles of declining trees, were seen only in needles at least 4 years old in healthy trees, suggesting
that needles of declining trees are susceptible to precocious aging. Abnormalities in xylem anatomy were observed in needles
3 years or more in age in declining trees, but were never seen in needles of healthy trees. Over time, anatomical abnormalities
in declining trees were seen in progressively younger twigs, which may explain the acropetal development of decline symptoms.
After fertilization with magnesium sulfate, normal phloem and xylem were observed in the newly formed tissues.
Keywords:
forest decline, needle anatomy, needle longevity, phloem, Picea abies, twig anatomy, xylem.
