E. Ringo et al., EFFECTS OF EXTRACTS OF ALNUS-GLUTINOSA SEEDS ON GROWTH OF FRANKIA STRAIN ARI3 UNDER STATIC AND FERMENTER CULTURE CONDITIONS, Plant and soil, 176(2), 1995, pp. 283-288
In the present study, the effect of Alnus glutinosa seed extract on th
e in vitro growth of Frankia strain ArI3 was investigated under variou
s culture conditions. Frankia filaments grown in static cultures showe
d a very slow growth with doubling time of 12 days. However, under the
same growth conditions but with seed extract added to the medium, the
doubling time was reduced to 6 days. A further reduction in doubling
time (2.5 days) was obtained without seed extract when Frankia strain
ArI3 was grown in a fermenter with continuous stirring. Under these cu
lture conditions, seed extract did not influence the Frankia growth ra
te. In all our studies, Na-propionate was used as the only carbon sour
ce. Gradual addition of Na-propionate to Frankia cultures in the ferme
nter sustained exponential growth of the filaments over a prolonged pe
riod. The complete consumption of Na-propionate was the limiting growt
h factor under fermenter growth conditions. The mechanism of growth st
imulation by Alnus glutinosa seed extract under growth limiting condit
ions in static cultures and its possible ecological significance is di
scussed.