© 2000 Heron Publishing—Victoria, Canada
Photosynthesis in Norway spruce seedlings infected by the needle rust Chrysomyxa rhododendri
Helmut Bauer (1), Karin Plattner (1) and Waltraud Volgger (1)
1. Institut für Botanik, Unversität Innsbruck, Sternwartestrasse 15, A-6020 Innsbruck, Austria / Received April 28, 1999
Summary
Chrysomyxa rhododendri (DC.) De Bary is a needle rust with a host shift between Rhododendron sp. and Norway spruce (Picea abies (L.) Karst.), penetrating only the new developing flushes of the conifer. Because little is known about its effects on trees,
we investigated several parameters related to photosynthesis in artificially infected 3-year-old Norway spruce seedlings.
The potential efficiency of photosystem II (PSII; derived from chlorophyll fluorescence measurements) was reduced in infected
current-year needles as soon as disease symptoms were visible, about three weeks after inoculation. Two weeks later, photosynthetic
O2 evolution (Pmax) of infected needles was less than 20% of control needles, whereas respiratory O2 uptake (RD) was about three times higher than that of control needles. Nonstructural carbohydrate concentrations were about 60% of control
values in all parts of the shoots of infected trees. Photosynthetic inhibition was associated with marked decreases in chlorophyll
concentration and chlorophyll a/b ratio but only a small reduction in carotenoid concentration. In infected trees, Pmax of noninfected 1-year-old and 2-year-old needles was 50 and 80% higher than in the corresponding age class of needles of
control trees. Estimation of potential daily net dry mass production, based on Pmax, RD, specific leaf area, carbon content and needle biomass, indicated that seedlings infected once were able to produce 60%,
and those infected twice only 25%, of the dry mass of controls. We conclude that afforestation and regeneration of Norway
spruce is seriously impaired in regions where seedlings are frequently attacked by Chrysomyxa.
Keywords:
chlorophyll, dark respiration, fluorescence, needle age, nonstructural carbohydrates, photosynthetic O2 evolution, photosynthetic pigments, Picea abies.
