3 0 6
L I O N E L F . J A F F E
FIG. 9 . The positive group effect. (Redrawn from Whitaker, 1937.)
duce respiratory C 0 2 at a rapid rate (Whitaker, 1931a). H e , therefore,
suggested that rhizin was H + a n d / o r C 0 2. However, it was later found
that the positive group effect is unaffected b y the replacement of respiratory C 0 2 emission b y photosynthetic C 0 2 uptake and is also unaffected
by a 500-fold change in buffer capacity (Jaffe, 1955). So rhizin is not
H +, C 0 2, or for that matter 0 2.
During this same period Olson and du B u y reported that eggs tend to
germinate toward locally applied indoleacetic acid ( I A A ) (Olson and
du B u y , 1937). Although their data were somewhat limited, they seemed
FIG. 1 0 . Group effect in Fucus as a function of p H and group size. ( 1 ) From
Whitaker and Lowrance, 1 9 4 0 (and Whitaker, 1 9 3 7 ) ; ( 2 ) each group of 2 0 0 0 eggs was
arranged as a close-packed, disc-shaped monolayer. The medium was strongly
buffered with 0.05 M tris. Despite the crowding, almost all of the interior eggs germinated normally. The ordinate refers to the response of the peripheral eggs, all of
which germinated normally. ( F r o m Jaffe, unpublished.)
RHIZOIDS DIRECTED TOWARD
OTHER EGG(S)
pH of MEDIUM
L I O N E L F . J A F F E
FIG. 9 . The positive group effect. (Redrawn from Whitaker, 1937.)
duce respiratory C 0 2 at a rapid rate (Whitaker, 1931a). H e , therefore,
suggested that rhizin was H + a n d / o r C 0 2. However, it was later found
that the positive group effect is unaffected b y the replacement of respiratory C 0 2 emission b y photosynthetic C 0 2 uptake and is also unaffected
by a 500-fold change in buffer capacity (Jaffe, 1955). So rhizin is not
H +, C 0 2, or for that matter 0 2.
During this same period Olson and du B u y reported that eggs tend to
germinate toward locally applied indoleacetic acid ( I A A ) (Olson and
du B u y , 1937). Although their data were somewhat limited, they seemed
FIG. 1 0 . Group effect in Fucus as a function of p H and group size. ( 1 ) From
Whitaker and Lowrance, 1 9 4 0 (and Whitaker, 1 9 3 7 ) ; ( 2 ) each group of 2 0 0 0 eggs was
arranged as a close-packed, disc-shaped monolayer. The medium was strongly
buffered with 0.05 M tris. Despite the crowding, almost all of the interior eggs germinated normally. The ordinate refers to the response of the peripheral eggs, all of
which germinated normally. ( F r o m Jaffe, unpublished.)
RHIZOIDS DIRECTED TOWARD
OTHER EGG(S)
pH of MEDIUM