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The mobilizing force of kinetin
Vol . 6, pp . 145-149, 1967 . LIFE SCIENCES Printed in Great Britain .
Pergamon Press Ltd .
TELE MOBILIZING FORCE OF KINPTIN H, B . hagerstedt* and R . G . Langaton Department of Plant Sciences, Texas A & M University, College Station
(Received 26 August 1966 ; in final form 14 October 1966) The movement of plant metabolites towards kinetin treated areas has created a great deal of interest among plant physiologists (1,2,3,4) . treated areas resemble metabolic sinks .
The kinetin
The manner in which sinks or kinetin
function in attracting metabolites has not yet been satisfactorily resolved . A variety of substances, endogeneous and exogenous, have been shown to accumulate in~kinetin treated areas (5,6),
This study was designed to
visually de~onatrate the mobilizing force of kinetin on radioactive indoleacetic acid (IAA-2- 14C),
The results were determined by radioautographa and
isotope counts of kinetin-treated and untreated leaf areas . Met ods and Materials The left
halves of leaves of Nicotiana tabacum 'Samson' were painted
with 40 mg/1 kinetin and Tween 20 .
The right, or control halves of the same
leaves were painted with water and the surfactant .
Twenty-four hours after
the kinetin treatment the leaf petioles were placed in IAA-2- 14 C at a concentration of 3 .5 mg/1 .
Petiole uptake of the radioactive material was allowed
to proceed for one hour . in orchid vials of water .
Following uptake the petioles were rinsed and placed The leaves were maintained in plastic boxes in the
dark for periods up to 13 days (7) .
The leaves were then heat killed, oven
dried and radiosutographed to show the results . To substantiate the radioautographa, ten 18 mm . disks were randomly * Present address :
Department of Horticulture, Oregon State University,
Corvallis, Oregon
145
J46
Vol . 6, No . 2
KINETIN
punched from each side of the radioautographed leaven and counted in a windowless .gas flow proportional counter .
The average relative counts were
corrected for background and graphed as are shown in Fig . 2 . These results were further substantiated by pressing all the tissue from each half leaf into 6 .6 cm 2 wafers, each exceeding 125 mg in weight .
Each
half leaf yielded two wafers which were considered infinitely thick and were counted once on each side with a micro-mil window Geiger-Müller counter .
No
correction for self absorption was made on these infinitely thick samples as only relative campariaona were sought .
Wafers from the kinetin treated half
leaf always produced counts indicating greater radioactivity on that side . This experiment was repeated with IAA-2- 14 C and DL- Alanine-1- 14 C with similar results .
In the latter case young tobacco leaves were used and only
minor differences could be observed on radioautographa .
However, counts of
wafers from such tissue always indicated a higher activity in the kinetin treated half leaf . Results and Discussion Figure 1 shows equally exposed radioautographa of representative leaves which were maintained in the dark for 1, 4, and 13 days .
It is assumed that
the radioactive IAA was passively taken up in the transpiration stream and equally distributed to both halves of the leaves .
Redistribution of the label
must have occurred subsequent to uptake and in response to the mobilizing force of kinetin .
The density of the radioautographa indicates two things :
Movement
of radioactivity into the interveinal parenchyma and more total radioactivity on the kinetin treated aide .
The latter ie verified by the data in Fig . 2
which shows that the kinetin treated half of the leaf yielded higher counts per minute than the control half .
Fig . 1 .
14 7
KINETIN
Vol . 6, No . 2
Radioautographs of tobacco leaves treated with a 40 mg/1
solution of kinetin on the left
half of the leaf .
being treated with water, nerved as a control .
The right half,
The leaves were
maintained in the dark for 1, 4, and 13 days following petiole uptake of 7AA-2- 14C .
The density of exposure indicates that more radio-
activity exists on the kinetin treated aide and that it has moved into the interveinal tissue .
Vol . 6, No . 2
KINETIN
148
300
KINETIN CONTROL
Zao
100
ao
Kn C I day
Fig . 2 .
Kn C 4 days
Kn C 13 doya
The average cpm obtained for 10 leaf diaka taken at random
from each half of 3 leaves maintained in the dark for 1, 4, and 13 days following petiole uptake of IAA-2- 14 C .
The left half of each
leaf was treated with kinetin at 40 mg/1, while the right half served as control .
KINE1'IN
Vol . 6, No . 2
14 9
It is recognized that areas of rapid growth constitute a metabolic sink .
If a leaf is placed in the dark, growth is decelerated and there is
usually no movement of metabolites from the veins into the lamina or inter veinal areas .
Zimmerman (8) has suggested that this lack of movement may be
due to the fact that darkened parenchyma tissue does not represent a sink . The lack of movement of radioactivity into the lamina of the control halves of the leaves supports Zimmerman'e contention that darkened parenchyma does not represent a sink .
However, movement of radioactivity into the lamina
of kinetin treated halves of leaves indicates that this area was metabolically active even though being in the dark .
Thus the radioautographs in Fig . 1
actually represent pictures of a metabolic sink . Conrad (5), and Conrad and Engelbrecht (6) have done similar work using unphysiologically high levels of IAA (500 mg/1) over short time periods . They measured their results by leaf extractiona and subsequent bioassay on elongating hypocotyls .
The results reported here confirm those of Conrad's,
both visually and quantitatively, but were obtained with physiological levels of IAA, an increased time for mobilization, the use of two different labelled metabolites, and measurement by radiological techniques . References 1.
R, Mother and L . Engelbrecht, Phvtochemistrv , 1, 58 (1961),
2.
K . Mother and L, Engelbrecht, Life Sciences , No . 11, 852 (1963) .
3.
A Leopold and M . Kauvase, Ann . J, Bot ., 51, 294 (1963) .
4.
B, Gunning and W . Berkeley, Nature , 1~9, 262 (1963) .
5.
R, Conrad, F ors, 151, 345 (1961) .
6.
L, Engelbrecht and K . Conrad, Ber . Deutsch Bot . Gaz ., ~, (42) (1961) .
7,
H, Lageratedt, R, Halliwell, and R . Langstoa, HortSci . al , 21 (1966),
8.
M . Zimmermau, Ann . Rev . Plant Phve ., 11, 167 (1960) .
Pergamon Press Ltd .
TELE MOBILIZING FORCE OF KINPTIN H, B . hagerstedt* and R . G . Langaton Department of Plant Sciences, Texas A & M University, College Station
(Received 26 August 1966 ; in final form 14 October 1966) The movement of plant metabolites towards kinetin treated areas has created a great deal of interest among plant physiologists (1,2,3,4) . treated areas resemble metabolic sinks .
The kinetin
The manner in which sinks or kinetin
function in attracting metabolites has not yet been satisfactorily resolved . A variety of substances, endogeneous and exogenous, have been shown to accumulate in~kinetin treated areas (5,6),
This study was designed to
visually de~onatrate the mobilizing force of kinetin on radioactive indoleacetic acid (IAA-2- 14C),
The results were determined by radioautographa and
isotope counts of kinetin-treated and untreated leaf areas . Met ods and Materials The left
halves of leaves of Nicotiana tabacum 'Samson' were painted
with 40 mg/1 kinetin and Tween 20 .
The right, or control halves of the same
leaves were painted with water and the surfactant .
Twenty-four hours after
the kinetin treatment the leaf petioles were placed in IAA-2- 14 C at a concentration of 3 .5 mg/1 .
Petiole uptake of the radioactive material was allowed
to proceed for one hour . in orchid vials of water .
Following uptake the petioles were rinsed and placed The leaves were maintained in plastic boxes in the
dark for periods up to 13 days (7) .
The leaves were then heat killed, oven
dried and radiosutographed to show the results . To substantiate the radioautographa, ten 18 mm . disks were randomly * Present address :
Department of Horticulture, Oregon State University,
Corvallis, Oregon
145
J46
Vol . 6, No . 2
KINETIN
punched from each side of the radioautographed leaven and counted in a windowless .gas flow proportional counter .
The average relative counts were
corrected for background and graphed as are shown in Fig . 2 . These results were further substantiated by pressing all the tissue from each half leaf into 6 .6 cm 2 wafers, each exceeding 125 mg in weight .
Each
half leaf yielded two wafers which were considered infinitely thick and were counted once on each side with a micro-mil window Geiger-Müller counter .
No
correction for self absorption was made on these infinitely thick samples as only relative campariaona were sought .
Wafers from the kinetin treated half
leaf always produced counts indicating greater radioactivity on that side . This experiment was repeated with IAA-2- 14 C and DL- Alanine-1- 14 C with similar results .
In the latter case young tobacco leaves were used and only
minor differences could be observed on radioautographa .
However, counts of
wafers from such tissue always indicated a higher activity in the kinetin treated half leaf . Results and Discussion Figure 1 shows equally exposed radioautographa of representative leaves which were maintained in the dark for 1, 4, and 13 days .
It is assumed that
the radioactive IAA was passively taken up in the transpiration stream and equally distributed to both halves of the leaves .
Redistribution of the label
must have occurred subsequent to uptake and in response to the mobilizing force of kinetin .
The density of the radioautographa indicates two things :
Movement
of radioactivity into the interveinal parenchyma and more total radioactivity on the kinetin treated aide .
The latter ie verified by the data in Fig . 2
which shows that the kinetin treated half of the leaf yielded higher counts per minute than the control half .
Fig . 1 .
14 7
KINETIN
Vol . 6, No . 2
Radioautographs of tobacco leaves treated with a 40 mg/1
solution of kinetin on the left
half of the leaf .
being treated with water, nerved as a control .
The right half,
The leaves were
maintained in the dark for 1, 4, and 13 days following petiole uptake of 7AA-2- 14C .
The density of exposure indicates that more radio-
activity exists on the kinetin treated aide and that it has moved into the interveinal tissue .
Vol . 6, No . 2
KINETIN
148
300
KINETIN CONTROL
Zao
100
ao
Kn C I day
Fig . 2 .
Kn C 4 days
Kn C 13 doya
The average cpm obtained for 10 leaf diaka taken at random
from each half of 3 leaves maintained in the dark for 1, 4, and 13 days following petiole uptake of IAA-2- 14 C .
The left half of each
leaf was treated with kinetin at 40 mg/1, while the right half served as control .
KINE1'IN
Vol . 6, No . 2
14 9
It is recognized that areas of rapid growth constitute a metabolic sink .
If a leaf is placed in the dark, growth is decelerated and there is
usually no movement of metabolites from the veins into the lamina or inter veinal areas .
Zimmerman (8) has suggested that this lack of movement may be
due to the fact that darkened parenchyma tissue does not represent a sink . The lack of movement of radioactivity into the lamina of the control halves of the leaves supports Zimmerman'e contention that darkened parenchyma does not represent a sink .
However, movement of radioactivity into the lamina
of kinetin treated halves of leaves indicates that this area was metabolically active even though being in the dark .
Thus the radioautographs in Fig . 1
actually represent pictures of a metabolic sink . Conrad (5), and Conrad and Engelbrecht (6) have done similar work using unphysiologically high levels of IAA (500 mg/1) over short time periods . They measured their results by leaf extractiona and subsequent bioassay on elongating hypocotyls .
The results reported here confirm those of Conrad's,
both visually and quantitatively, but were obtained with physiological levels of IAA, an increased time for mobilization, the use of two different labelled metabolites, and measurement by radiological techniques . References 1.
R, Mother and L . Engelbrecht, Phvtochemistrv , 1, 58 (1961),
2.
K . Mother and L, Engelbrecht, Life Sciences , No . 11, 852 (1963) .
3.
A Leopold and M . Kauvase, Ann . J, Bot ., 51, 294 (1963) .
4.
B, Gunning and W . Berkeley, Nature , 1~9, 262 (1963) .
5.
R, Conrad, F ors, 151, 345 (1961) .
6.
L, Engelbrecht and K . Conrad, Ber . Deutsch Bot . Gaz ., ~, (42) (1961) .
7,
H, Lageratedt, R, Halliwell, and R . Langstoa, HortSci . al , 21 (1966),
8.
M . Zimmermau, Ann . Rev . Plant Phve ., 11, 167 (1960) .