© 1995 Heron Publishing—Victoria, Canada
The influence of magnesium deficiency on carbohydrate concentrations in Norway spruce (Picea abies) needles
Beate Mehne-Jakobs
Institut für Forstbotanik und Baumphysiologie, Albert-Ludwigs-Universität, Bertoldstrasse 17, D-79085 Freiburg, Germany / Received April 5, 1994
Summary
Both short- and long-term effects of Mg deficiency on carbohydrate metabolism were investigated in 6-year-old clonal Norway
spruce (Picea abies (L.) Karst.) trees cultivated in sand culture with an optimal supply of nutrients, except for Mg which was supplied at 0.203,
0.041 and 0.005 mM to provide optimal, moderately deficient and severely deficient Mg supply, respectively. Annual changes
in carbohydrate concentrations (starch, sucrose, glucose and fructose) were analyzed and diurnal changes were investigated
on a single day during the summer.
Older needles of trees in the moderate Mg-deficiency treatment developed tip-yellowing symptoms, whereas current-year needles
remained green. The severe Mg-deficiency treatment led to pronounced yellowing symptoms in needles of all ages. Increased
carbohydrate concentrations were observed before needle yellowing occurred. Diurnal and annual changes in carbohydrates were
similar in all treatments; however, carbohydrate concentrations were influenced by Mg supply. In both Mg-deficiency treatments,
starch concentrations increased in needles, especially during summer and autumn. Starch accumulation was more pronounced at
the beginning of the Mg-deficiency treatments than at the end of the treatments. Sucrose, and to a minor extent, glucose and
fructose concentrations tended to increase in response to Mg deficiency. The consequences of Mg deficiency on carbohydrate
metabolism are discussed with respect to reduced plant growth and decreased transport rates of carbohydrates to sink organs.
Keywords:
carbohydrate metabolism, fructose, glucose, growth, starch accumulation, sucrose.
