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DIE ERNÄHRUNGSPHYSIOLOGIE DEr CHLOROPH YCEEN
2:5.")
( 1/jöo m°l- PH 6-5—7.0) and potassiuni nitrate as X-source the pH
ehanges in the solutions are insignificant.
4. Growth increases with rising pH. The liest growth was obtained
at pH 7.9; higher values were not tested. Even at so low a pH as 4.6
dislinct growth was obtained in several cases.
5. Iron may he indiscriminately added in the form of ferrie
Chloride. ferrie citrate or ferrous chloride if the solution is acid. In alkaline
solution ferrie citrate and ferrous chloride are preferable.
6. üifferences in the size of the inoculum are without significance
if the cell counts are made when growth in the cultures lias ceased. Two
species. however, Ankistrodesmus and Chlorella sp. A, differed in this
respect.
7. Glucose, galactose and maitose are good sources of carbon. Most
probably the last-mentioned may he utilized without previous
hydro-lysis. Sucrose cannot be utilized at all or only with difficulty, probably
owing to the absence of hydrolytic enzymes. Mannite and glycerol are
unserviceable as carbon sources, and the same is the case with ainino
acids, peptone and urea. Sodium acetate. ön the other hand, may be
used.
8. Glycocoll, as a source of nitrogen, may he considered as equal to
or even superior to nitrate. a-alanine is a verv good X-source, especially
for the Scenedesmus species. whereas asparagine bas in many cases given
a considerably inferior result to nitrate, glycocoll and alanine. Peptone is
advantageous for the Scenedesmus species, hut cannot be utilized by
the Chlorella species. Several species do not seem to be ahle to utilize
urea. It may be pointed ont that the amino acids are utilized under
liberation of ammonia, which renders the solution möre or less alkaline.
The Scenedesmus species have a great power of deamination.
9. Indole-3-acetic acid exercised a stimulatory effect ön cell
division in three of the species, viz. Chlorella sp. A. Chlorella vulgaris B
and Scenedesmus obliquus. The optimum concentration ranges from
0.1-—50 ppui., showing different levels for dit Terelit species. 100 ppm.
are without stimulatory effect or even poisonous. The number of cells
at optimum was 2—.3 times as great as in the control.
10. Indole-acetic acid affects cell division in acid solution hut not
in neutral, the reason doubtless being that it enters the cells in the form
of undissociated molecules. The best result was obtained at pl I 5.0.
which was the lowest pH value tested.
11. In order to investigate the stability of indole-acetic acid a
colo-rimetric method for quantitative determ i nation, founded ön a new
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