314
LIONEL F. JAFFE
and 6 X 10~
12 M or even 6 X 10"
13 M IAA sometimes induce spores of
the moss, Funaria, to generate first a rhizoid instead of a chloronema.
Gorter (1949) found application of 10~
3 M of the auxin antagonist, triiodobenzoic acid, to stop elongation of (but not terminal cellulose deposition by) Lepidium
root hairs. Jackson (1960) found that 10~
1 3
M IAA
speeds the elongation rate of root hairs of the grass, Agrostis, by about
20%.
Second, Davidson (1950) has reported that as little as 5XlO~
9 ^f
IAA greatly increases the number of rhizoids formed by Fucus embryo
during their first 40 days.
4
Third, the intensely studied, positive phototropic responses of oat
coleoptiles, known to be mediated by a photoinduced transport of IAA
to the dark side (Briggs, 1963, p. 329) show striking parallels to the
photoinduction of polarity in the Fucus egg. In both, greater rates of
cell wall expansion are induced at the darker side. Both show evidence of
two separate photosystems: a low-dosage system that obeys reciprocity
and is effective over an approximately 100 to 1000-fold range of doses
and a high-dosage one that does not obey reciprocity (Haupt and Bentrup, 1961; Bentrup, 1963; Briggs, 1963). The action spectra are similar.
The low-dosage system (Briggs' system I) in coleoptiles shows peaks in
the visible at 445 and 474 m/z, (Briggs, 1963, p. 341); relatively crude
action spectra for what appears to be the low-dosage system in Fucus
show a broad maximum at 460 imx, which, however, might be resolvable
into twin peaks (Jaffe, 1958; Bentrup, 1963).
When one adds these similarities to recent evidence that the active
step in polar auxin transport is a polar secretion rather than uptake of
IAA (Hertel, 1962; Christie and Leopold, 1965), the idea that rhizin is
IAA becomes even more attractive.
C. Electrical Currents
So far, efforts to measure the electrical potentials across individual
developing Fucus eggs have failed. However, if the order of a hundred
eggs are placed in a long, loose fitting capillary and so illuminated as to
form rhizoids toward one end of the tube—in short, if they are put in
series—then, as the population develops, this end becomes measurably
electronegative (Jaffe, 1966a). Details, e.g., perfusion independence,
indicate that these tube potentials are produced by the return past
4
Unfortunately, one cannot be sure whether these effects were due to the IAA
or to the ethanol first used to dissolve it.
LIONEL F. JAFFE
and 6 X 10~
12 M or even 6 X 10"
13 M IAA sometimes induce spores of
the moss, Funaria, to generate first a rhizoid instead of a chloronema.
Gorter (1949) found application of 10~
3 M of the auxin antagonist, triiodobenzoic acid, to stop elongation of (but not terminal cellulose deposition by) Lepidium
root hairs. Jackson (1960) found that 10~
1 3
M IAA
speeds the elongation rate of root hairs of the grass, Agrostis, by about
20%.
Second, Davidson (1950) has reported that as little as 5XlO~
9 ^f
IAA greatly increases the number of rhizoids formed by Fucus embryo
during their first 40 days.
4
Third, the intensely studied, positive phototropic responses of oat
coleoptiles, known to be mediated by a photoinduced transport of IAA
to the dark side (Briggs, 1963, p. 329) show striking parallels to the
photoinduction of polarity in the Fucus egg. In both, greater rates of
cell wall expansion are induced at the darker side. Both show evidence of
two separate photosystems: a low-dosage system that obeys reciprocity
and is effective over an approximately 100 to 1000-fold range of doses
and a high-dosage one that does not obey reciprocity (Haupt and Bentrup, 1961; Bentrup, 1963; Briggs, 1963). The action spectra are similar.
The low-dosage system (Briggs' system I) in coleoptiles shows peaks in
the visible at 445 and 474 m/z, (Briggs, 1963, p. 341); relatively crude
action spectra for what appears to be the low-dosage system in Fucus
show a broad maximum at 460 imx, which, however, might be resolvable
into twin peaks (Jaffe, 1958; Bentrup, 1963).
When one adds these similarities to recent evidence that the active
step in polar auxin transport is a polar secretion rather than uptake of
IAA (Hertel, 1962; Christie and Leopold, 1965), the idea that rhizin is
IAA becomes even more attractive.
C. Electrical Currents
So far, efforts to measure the electrical potentials across individual
developing Fucus eggs have failed. However, if the order of a hundred
eggs are placed in a long, loose fitting capillary and so illuminated as to
form rhizoids toward one end of the tube—in short, if they are put in
series—then, as the population develops, this end becomes measurably
electronegative (Jaffe, 1966a). Details, e.g., perfusion independence,
indicate that these tube potentials are produced by the return past
4
Unfortunately, one cannot be sure whether these effects were due to the IAA
or to the ethanol first used to dissolve it.