Planta (Berl.)131, 203-205 (1976)
P I ~ H ~ 9 by Springer-Verlag 1976
Short Communication
The Effect of (2-Chloroethyl)phosphonic Acid on the Sink Strength of Developing Peach (Prunuspersica L.) Fruit D.J. Chalmers, B. van den Ende, and P.H. Jerie Horticultural Research Station, Victorian Department of Agriculture, Tatura, Vic. 3616, Australia
Summary. The sink strength of one of a pair of competing peach fruits was increased when the fruit was treated with (2-chloroethyl)phosphonic acid (Ethephon) and gibberellic acid. Ethephon increased the capacity of the treated fruit to attract 14C-labelled assimilates at most stages of fruit development and was most effective when the level of endogenous ethylene produced by the fruit was lowest. The results are discussed in relation to the hypothesis that ethylene participates in the control of sink strength of the fruit and of other competing organs of the tree.
Although the mechanism that controls sink strength in plants is unknown it is thought that it may be under the influence of the same hormones that regulate cell expansion [12]. However, the two processes cannot be separated for independent examination in most of the systems available for the study of plant growth. The growth curve of peach fruit has been traditionally divided into an initial stage of fast growth (stage 1), a period of slow growth (stage II), and a final period of rapid growth (stage III). Chalmers and van den Ende [3] found that the course of both dry-weight and fresh-weight increase of the peach fruit (cv. Golden Queen) followed a double sigmoid pattern but that dry-weight growth was substantially displaced in time from fresh-weight and volume growth. Dry-weight stages II (DWII) and III (DWIII) commenced some 2 ~ w e e k s later than fresh-weight stages II (FWII) and III (FWIII), respectively (see Fig. 1a). Thus fresh-weight growth and dry-weight growth are separate processes and can be studied independently. Since growth during the lag phase of dry-weight increase (DWII) is not limited by assimilate supply [2] it follows that dry-weight growth and cell expansion are controlled by different mechanisms
(probably hormonal) within the fruit. This is consistent with Crane's [4] suggestion that sink strength and growth may be separately controlled by the hormones in the fruit. The level of gibberellin (GA) in the mesocarp of peach fruit correlates with cell expansion [6] and it has been proposed [3] that ethylene controls dryweight growth. More recently it was shown that ethylene production and dry-weight growth increase simultaneously at the start of DWIII [7]. In this paper, we report a series of experiments in which the question whether ethylene is involved in 14C-incorporation by peach fruit was investigated. Peach trees flower on 1-year-old laterals and frequently have 2 or 3 flowers per node. Fertilization is usually good and frequently 2-3 fruits per node result. By selecting evenly sized pairs of fruits of the type described above and removing all other fruits and leaves but the terminal leaf cluster, one can obtain a system in which there are two independent but similar sinks competing for the same source of assimilate. In these experiments one fruit in each pair was selected at random and used as a control to compare the effect of Ethephon (2-chloroethyl)phosphonic acid and GA3 applied to the other fruit, on the amount of 14C (fed to the leaves at the shoot apex as 14CO2) incorporated by the fruit. Ethephon (Ciba-Geigy Australia, Ltd.) solutions between 1 and 200 ixg/ml containing a wetting agent were painted onto the surface of treated fruit. Gibberellic acid (GA3; 500 ~tg/ml) was applied in the same way. The concentration of Ethephon (A) and GA 3 (B) used in the experiment shown in Figure 1 b was: A1 200 ktg/ml, B 500 ~tg/ml, A2 100 ~tg/ml, A3 5 ~tg/ml, A4 50 ~tg/ml, A5 10 ~tg/ml. Higher concentrations of Ethephon were used in most experiments but they resulted in less stimulation of 14C uptake by the fruit than those used in the experiment reported above. The ethylene production after treatment with Ethephon was not measurable with our gas chromatograph (Shimadzu model GC-1C; detection limit < 0.02 ~tl/1)at 1 txg/ml Ethephon and increased proportionately with the Ethephon concentration from 0.027 ~tl kg -1 fr wt h -1
204
D.J. Chalmers et al. : Effect of (2-Chloroethyl)phosphonic Acid on Peach Fruit
at 10 p.g/ml to 0.47 gl kg 1 fr wt h 1 with 100 gg/ml. To feed 14C the apical shoot was enclosed in a nylon bag sealed with cellulose tape and grafting mastic. Twenty mi of air containing 1.8 x 106 dpm of 14CO2 (generated from Na214CO3; 59 mCi/ mmole) was injected into the bag enclosing the terminal shoot at the same time as the fruits were treated with Ethephon or after 12, 24 and 72 h had elapsed after treatment with GA3. The bags were removed 1 h later; at this time, less than 1% of the original radioactivity remained in the bag. Eight hours after feeding 14CO2 the fruit were harvested, dried in a forced-draught oven at 103~ C, and ground in a mortar and pestle. After thorough mixing a subsample was pelletized and oxidized in a Packard model 305 tissue oxidizer. Radioactivity in the subsample was then measured with a Packard model 2003 scintillation spectrometer. The sum of the radioactivity recovered from both fruits at the completion of each experiment varied between 5 and 25% of the ~4CO2 initially fed to the shoot. This is consistent with the rates of ~4C export from individual peach leaves measured in previous experiments [2]. During DWI the abscission of peach fruits can be stimulated by Ethephon. However, this effect takes 5-10 days to occur and no abscission or skin damage occurred in the course of these experiments. E t h e p h o n s t i m u l a t e d 14C i n c o r p o r a t i o n into p e a c h fruit d u r i n g all stages o f f r u i t d e v e l o p m e n t . F i g u r e 1 a shows the stages o f fruit d e v e l o p m e n t a n d F i g u r e 1 b the effect o f E t h e p h o n on 14C i n c o r p o r a t i o n at various times. T h e c o n c e n t r a t i o n o f E t h e p h o n t h a t was m o s t effective in s t i m u l a t i n g 14C i n c o r p o r a t i o n v a r i e d w i t h the stage o f d e v e l o p m e n t . T h e level o f E t h e p h o n r e q u i r e d to s t i m u l a t e 14C u p t a k e was h i g h e r d u r i n g p e r i o d s o f h i g h e n d o g e n o u s ethylene. T o w a r d s the e n d o f D W I I , w h e n ethylene p r o d u c t i o n b y the fruit was a t its lowest [7], 1 I.tg/ml E t h e p h o n was sufficient to s t i m u l a t e t+C u p t a k e b y the fruit ( p < 0 . 0 5 ) even t h o u g h the s u m o f the ethylene p r o d u c e d e n d o g e n o u s l y a n d as a result o f the t r e a t m e n t was b e l o w the limit o f d e t e c t i o n o f o u r gas c h r o m a t o g r a p h . O n two occasions E t h e p h o n failed to s t i m u l a t e ~4C i n c o r p o r a t i o n . T o w a r d s the e n d o f F W I the rate o f t4C i n c o r p o r a t i o n was n o t affected b y E t h e p h o n b u t it was significantly s t i m u l a t e d b y G A 3 (p < 0.05). A t this time (pit h a r d e n ing) J a c k s o n [6] f o u n d t h a t G A 3 s t i m u l a t e d the g r o w t h o f p e a c h fruits. A l s o late in D W I I I E t h e p h o n d i d n o t effect ~+C i n c o r p o r a t i o n . A t this time the fruits g r o w very r a p i d l y [3] a n d have a high e n d o g e n o u s level o f ethylene [5, 8] w h i c h m a y have m a s k e d the effect o f a d d e d ethylene. The results indicate two p e r i o d s w h e n g r o w t h was limited by the c a p a c i t y to i n c o r p o r a t e assimilate, a n d also a p e r i o d w h e n cell e x p a n s i o n m a y have b e e n l i m i t e d b y gibberellin. R e c e n t evidence h a s s h o w n [11] t h a t ethylene c a n s t i m u l a t e c a r b o n m o b i l i z a t i o n in p l a n t tissues. F u r ther, ethylene as well as gibberellin is r e q u i r e d f o r g r o w t h o f Callitriche [10] a n d ethylene ( a p p l i e d as E t h e p h o n ) can s t i m u l a t e g r o w t h o f figs [9] a n d p e a c h e s in stage I I I [1, 13] quite s e p a r a t e l y f r o m its effect o n r i p e n i n g a n d senescence. T h e m e c h a n i s m
'
'
O _
g,
_
:
v--wm
i
I
i i
I I
[
i I
:
i
i 1
i
i
,
0.7--
,
,
I
I
9 I'
I I i I i I I i i i i i i
I I i I i
0.6
i I
~'0.s
I i i i i i I
4.0
"t3
i
I
C
"
:
i
I I I
!
-~0.3
I I I I
go.4 -
E
-
+6
~ 0-2
I
',
0.1
I I
I I
,
!
~
i', L
3-0? 2-0
"6
1"0
,,
I! 75 _ b
I i
B AT
L..
r- 50
-
' A/AS A3"ln ' l
.c_
.~
I I
I I i I
!
i i i i
I Ii 25 -
A2
I I '
:
[ i
Ii i
I I
I I I
i i i i i i
ii
i o
N
D
ii J
F
M
Fig. 1. a Changes in the growth rate of peach fruit in terms of fresh weight (light curve) and dry weight (heavy curve) throughout the growing season (abscissa=months) and the growth stages defined by the maximum and minimum growth rates, b 14C incorporated into control fruit (left-hand bars in histograms) and treated fruit (right-hand bars) after treatment with Ethephon (open histograms) and GA 3 (solid histograms). Fruit pairs were destructively sampled at the completion of each .labelling experiment. The concentration of Ethephon in the experiments A1-5 was: A1, 200 gg/ml; A2, 100 Ixg/ml; A3, 5 gg/ml; A4, 50 Ixg/ml; A5, 10 p.g/ ml. The concentration of GA3 (B) was 500 gg/ml. All differences significant at 5% level
b y w h i c h ethylene is i n v o l v e d in these effects has n o t been established. H o w e v e r , if c e l l - e x p a n s i o n " g r o w t h " a n d d r y - w e i g h t " g r o w t h " are s e p a r a t e l y c o n t r o l l e d [3] n e t g r o w t h c o u l d n o t c o n t i n u e indefinitely unless b o t h were active. A l t h o u g h there is a m p l e evidence t h a t G A m a y limit o r c o n t r o l the c a p a c i t y o f the cell to e x p a n d , this is the first evidence t h a t
D.J. Chalmers et al. : Effect of (2-Chloroethyl)phosphonic Acid on Peach Fruit
ethylene may have a direct role in controlling growth by controlling the rate at which the cell can gain access to the available assimilate. Such a mechanism could help to explain correlative growth in plants as a whole, where a sink is activated by stimulated ethylene production at a point. This could occur where ethylene synthesis was stimulated by auxin production in a meristem, or in experimental situations such as hormone-directed-transport. It could also be responsible for synergistic effects where sink-directed transport of a hormone further stimulates ethylene production or reduces the sensitivity of the tissue to the existing level of ethylene.
References 1. Byers, R.E., Dostal, H.E., Emerson, F.H. : Regulation of fruit growth with 2-chloroethane-phosphoric acid. BioScience 19, 903 904 (1969) 2. Chalmers, D.J., Canterford, R.L., Jerie, P.H., Jones, T.R., Ugalde, T:D. : Photosynthesis in relation to growth and distribution of fruit in peach trees. Aust. J. Plant Physiol. 2, 635~45 (1975) 3. Chalmers, D.J., van den Ende, B. : A reappraisal of the growth and development of peach fruit. Aust. J. Plant Physiol. 2, 623634 (1975) 4. Crane, J.C. : Growth substance in fruit setting and development. Ann. Rev. Plant Physiol. 15, 303 336 (1964)
205
5. Iwata, I., Omata, I., Ogata, K. : Relationship between the ripening of harvested fruits and the respiratory pattern. III. Changes in ethylene concentration in fruits and responses to applied ethylene with relation to the respiratory pattern. J. Jap. Soc. Hort. Sei. 38, 3 5 0 0 5 8 (1969) 6. Jackson, D.I. : Gibberellin and the growth of peach and apricot fruits. Aust. J. Biol. Sci. 2 1 , 2 0 9 ~ 1 5 (1968) 7. Jerie, P.H., Chalmers, D.J.: Ethylene as a growth hormone in peach fruit Prunus persica L. Aust. J. Plant Physiol. 3 (in press) 8. Looney, N.E., McGlasson, W.B., Coombe, B.G.: Control of fruit ripening in peach, Prunus persica : action of succinic acid2,2-dimethylhydrazide and (2-chloroethyl)phosphonic acid. Aust. J. Plant Physiol. 1, 77 86 (1974) 9. Marei, N., Crane, J.C.: Growth and respiratory response in fig (Ficus carica L. cv. Mission) fruits to ethylene. Plant Physiol. 48, 249-254 (1971) 10. Musgrave, A., Jackson, M.B., Ling, E. : Callitriche stem elongation is controlled by ethylene and gibberellin. Nature New Biol. 238, 94-96 (1972) 11. Nichols, R., Ho, L.C. : An effect of ethylene on the distribution of 14C-sucrose from the petals to other flower parts in the senescent cut inflorescence of Dianthus caryophyllus. Ann. Bot. 39, 4 3 3 4 3 8 (1975) 12. Phillips, I.D.J. : Apical dominance. Ann. Rev. Plant Physiol. 26, 341-367 (1975) 13. Stembridge, G.E., Raff, J.W. : Ethephon and peach fruit development. Hort. Sci. 8, 500-501 (1973)
Received 16 February; accepted 12 April 1976
P I ~ H ~ 9 by Springer-Verlag 1976
Short Communication
The Effect of (2-Chloroethyl)phosphonic Acid on the Sink Strength of Developing Peach (Prunuspersica L.) Fruit D.J. Chalmers, B. van den Ende, and P.H. Jerie Horticultural Research Station, Victorian Department of Agriculture, Tatura, Vic. 3616, Australia
Summary. The sink strength of one of a pair of competing peach fruits was increased when the fruit was treated with (2-chloroethyl)phosphonic acid (Ethephon) and gibberellic acid. Ethephon increased the capacity of the treated fruit to attract 14C-labelled assimilates at most stages of fruit development and was most effective when the level of endogenous ethylene produced by the fruit was lowest. The results are discussed in relation to the hypothesis that ethylene participates in the control of sink strength of the fruit and of other competing organs of the tree.
Although the mechanism that controls sink strength in plants is unknown it is thought that it may be under the influence of the same hormones that regulate cell expansion [12]. However, the two processes cannot be separated for independent examination in most of the systems available for the study of plant growth. The growth curve of peach fruit has been traditionally divided into an initial stage of fast growth (stage 1), a period of slow growth (stage II), and a final period of rapid growth (stage III). Chalmers and van den Ende [3] found that the course of both dry-weight and fresh-weight increase of the peach fruit (cv. Golden Queen) followed a double sigmoid pattern but that dry-weight growth was substantially displaced in time from fresh-weight and volume growth. Dry-weight stages II (DWII) and III (DWIII) commenced some 2 ~ w e e k s later than fresh-weight stages II (FWII) and III (FWIII), respectively (see Fig. 1a). Thus fresh-weight growth and dry-weight growth are separate processes and can be studied independently. Since growth during the lag phase of dry-weight increase (DWII) is not limited by assimilate supply [2] it follows that dry-weight growth and cell expansion are controlled by different mechanisms
(probably hormonal) within the fruit. This is consistent with Crane's [4] suggestion that sink strength and growth may be separately controlled by the hormones in the fruit. The level of gibberellin (GA) in the mesocarp of peach fruit correlates with cell expansion [6] and it has been proposed [3] that ethylene controls dryweight growth. More recently it was shown that ethylene production and dry-weight growth increase simultaneously at the start of DWIII [7]. In this paper, we report a series of experiments in which the question whether ethylene is involved in 14C-incorporation by peach fruit was investigated. Peach trees flower on 1-year-old laterals and frequently have 2 or 3 flowers per node. Fertilization is usually good and frequently 2-3 fruits per node result. By selecting evenly sized pairs of fruits of the type described above and removing all other fruits and leaves but the terminal leaf cluster, one can obtain a system in which there are two independent but similar sinks competing for the same source of assimilate. In these experiments one fruit in each pair was selected at random and used as a control to compare the effect of Ethephon (2-chloroethyl)phosphonic acid and GA3 applied to the other fruit, on the amount of 14C (fed to the leaves at the shoot apex as 14CO2) incorporated by the fruit. Ethephon (Ciba-Geigy Australia, Ltd.) solutions between 1 and 200 ixg/ml containing a wetting agent were painted onto the surface of treated fruit. Gibberellic acid (GA3; 500 ~tg/ml) was applied in the same way. The concentration of Ethephon (A) and GA 3 (B) used in the experiment shown in Figure 1 b was: A1 200 ktg/ml, B 500 ~tg/ml, A2 100 ~tg/ml, A3 5 ~tg/ml, A4 50 ~tg/ml, A5 10 ~tg/ml. Higher concentrations of Ethephon were used in most experiments but they resulted in less stimulation of 14C uptake by the fruit than those used in the experiment reported above. The ethylene production after treatment with Ethephon was not measurable with our gas chromatograph (Shimadzu model GC-1C; detection limit < 0.02 ~tl/1)at 1 txg/ml Ethephon and increased proportionately with the Ethephon concentration from 0.027 ~tl kg -1 fr wt h -1
204
D.J. Chalmers et al. : Effect of (2-Chloroethyl)phosphonic Acid on Peach Fruit
at 10 p.g/ml to 0.47 gl kg 1 fr wt h 1 with 100 gg/ml. To feed 14C the apical shoot was enclosed in a nylon bag sealed with cellulose tape and grafting mastic. Twenty mi of air containing 1.8 x 106 dpm of 14CO2 (generated from Na214CO3; 59 mCi/ mmole) was injected into the bag enclosing the terminal shoot at the same time as the fruits were treated with Ethephon or after 12, 24 and 72 h had elapsed after treatment with GA3. The bags were removed 1 h later; at this time, less than 1% of the original radioactivity remained in the bag. Eight hours after feeding 14CO2 the fruit were harvested, dried in a forced-draught oven at 103~ C, and ground in a mortar and pestle. After thorough mixing a subsample was pelletized and oxidized in a Packard model 305 tissue oxidizer. Radioactivity in the subsample was then measured with a Packard model 2003 scintillation spectrometer. The sum of the radioactivity recovered from both fruits at the completion of each experiment varied between 5 and 25% of the ~4CO2 initially fed to the shoot. This is consistent with the rates of ~4C export from individual peach leaves measured in previous experiments [2]. During DWI the abscission of peach fruits can be stimulated by Ethephon. However, this effect takes 5-10 days to occur and no abscission or skin damage occurred in the course of these experiments. E t h e p h o n s t i m u l a t e d 14C i n c o r p o r a t i o n into p e a c h fruit d u r i n g all stages o f f r u i t d e v e l o p m e n t . F i g u r e 1 a shows the stages o f fruit d e v e l o p m e n t a n d F i g u r e 1 b the effect o f E t h e p h o n on 14C i n c o r p o r a t i o n at various times. T h e c o n c e n t r a t i o n o f E t h e p h o n t h a t was m o s t effective in s t i m u l a t i n g 14C i n c o r p o r a t i o n v a r i e d w i t h the stage o f d e v e l o p m e n t . T h e level o f E t h e p h o n r e q u i r e d to s t i m u l a t e 14C u p t a k e was h i g h e r d u r i n g p e r i o d s o f h i g h e n d o g e n o u s ethylene. T o w a r d s the e n d o f D W I I , w h e n ethylene p r o d u c t i o n b y the fruit was a t its lowest [7], 1 I.tg/ml E t h e p h o n was sufficient to s t i m u l a t e t+C u p t a k e b y the fruit ( p < 0 . 0 5 ) even t h o u g h the s u m o f the ethylene p r o d u c e d e n d o g e n o u s l y a n d as a result o f the t r e a t m e n t was b e l o w the limit o f d e t e c t i o n o f o u r gas c h r o m a t o g r a p h . O n two occasions E t h e p h o n failed to s t i m u l a t e ~4C i n c o r p o r a t i o n . T o w a r d s the e n d o f F W I the rate o f t4C i n c o r p o r a t i o n was n o t affected b y E t h e p h o n b u t it was significantly s t i m u l a t e d b y G A 3 (p < 0.05). A t this time (pit h a r d e n ing) J a c k s o n [6] f o u n d t h a t G A 3 s t i m u l a t e d the g r o w t h o f p e a c h fruits. A l s o late in D W I I I E t h e p h o n d i d n o t effect ~+C i n c o r p o r a t i o n . A t this time the fruits g r o w very r a p i d l y [3] a n d have a high e n d o g e n o u s level o f ethylene [5, 8] w h i c h m a y have m a s k e d the effect o f a d d e d ethylene. The results indicate two p e r i o d s w h e n g r o w t h was limited by the c a p a c i t y to i n c o r p o r a t e assimilate, a n d also a p e r i o d w h e n cell e x p a n s i o n m a y have b e e n l i m i t e d b y gibberellin. R e c e n t evidence h a s s h o w n [11] t h a t ethylene c a n s t i m u l a t e c a r b o n m o b i l i z a t i o n in p l a n t tissues. F u r ther, ethylene as well as gibberellin is r e q u i r e d f o r g r o w t h o f Callitriche [10] a n d ethylene ( a p p l i e d as E t h e p h o n ) can s t i m u l a t e g r o w t h o f figs [9] a n d p e a c h e s in stage I I I [1, 13] quite s e p a r a t e l y f r o m its effect o n r i p e n i n g a n d senescence. T h e m e c h a n i s m
'
'
O _
g,
_
:
v--wm
i
I
i i
I I
[
i I
:
i
i 1
i
i
,
0.7--
,
,
I
I
9 I'
I I i I i I I i i i i i i
I I i I i
0.6
i I
~'0.s
I i i i i i I
4.0
"t3
i
I
C
"
:
i
I I I
!
-~0.3
I I I I
go.4 -
E
-
+6
~ 0-2
I
',
0.1
I I
I I
,
!
~
i', L
3-0? 2-0
"6
1"0
,,
I! 75 _ b
I i
B AT
L..
r- 50
-
' A/AS A3"ln ' l
.c_
.~
I I
I I i I
!
i i i i
I Ii 25 -
A2
I I '
:
[ i
Ii i
I I
I I I
i i i i i i
ii
i o
N
D
ii J
F
M
Fig. 1. a Changes in the growth rate of peach fruit in terms of fresh weight (light curve) and dry weight (heavy curve) throughout the growing season (abscissa=months) and the growth stages defined by the maximum and minimum growth rates, b 14C incorporated into control fruit (left-hand bars in histograms) and treated fruit (right-hand bars) after treatment with Ethephon (open histograms) and GA 3 (solid histograms). Fruit pairs were destructively sampled at the completion of each .labelling experiment. The concentration of Ethephon in the experiments A1-5 was: A1, 200 gg/ml; A2, 100 Ixg/ml; A3, 5 gg/ml; A4, 50 Ixg/ml; A5, 10 p.g/ ml. The concentration of GA3 (B) was 500 gg/ml. All differences significant at 5% level
b y w h i c h ethylene is i n v o l v e d in these effects has n o t been established. H o w e v e r , if c e l l - e x p a n s i o n " g r o w t h " a n d d r y - w e i g h t " g r o w t h " are s e p a r a t e l y c o n t r o l l e d [3] n e t g r o w t h c o u l d n o t c o n t i n u e indefinitely unless b o t h were active. A l t h o u g h there is a m p l e evidence t h a t G A m a y limit o r c o n t r o l the c a p a c i t y o f the cell to e x p a n d , this is the first evidence t h a t
D.J. Chalmers et al. : Effect of (2-Chloroethyl)phosphonic Acid on Peach Fruit
ethylene may have a direct role in controlling growth by controlling the rate at which the cell can gain access to the available assimilate. Such a mechanism could help to explain correlative growth in plants as a whole, where a sink is activated by stimulated ethylene production at a point. This could occur where ethylene synthesis was stimulated by auxin production in a meristem, or in experimental situations such as hormone-directed-transport. It could also be responsible for synergistic effects where sink-directed transport of a hormone further stimulates ethylene production or reduces the sensitivity of the tissue to the existing level of ethylene.
References 1. Byers, R.E., Dostal, H.E., Emerson, F.H. : Regulation of fruit growth with 2-chloroethane-phosphoric acid. BioScience 19, 903 904 (1969) 2. Chalmers, D.J., Canterford, R.L., Jerie, P.H., Jones, T.R., Ugalde, T:D. : Photosynthesis in relation to growth and distribution of fruit in peach trees. Aust. J. Plant Physiol. 2, 635~45 (1975) 3. Chalmers, D.J., van den Ende, B. : A reappraisal of the growth and development of peach fruit. Aust. J. Plant Physiol. 2, 623634 (1975) 4. Crane, J.C. : Growth substance in fruit setting and development. Ann. Rev. Plant Physiol. 15, 303 336 (1964)
205
5. Iwata, I., Omata, I., Ogata, K. : Relationship between the ripening of harvested fruits and the respiratory pattern. III. Changes in ethylene concentration in fruits and responses to applied ethylene with relation to the respiratory pattern. J. Jap. Soc. Hort. Sei. 38, 3 5 0 0 5 8 (1969) 6. Jackson, D.I. : Gibberellin and the growth of peach and apricot fruits. Aust. J. Biol. Sci. 2 1 , 2 0 9 ~ 1 5 (1968) 7. Jerie, P.H., Chalmers, D.J.: Ethylene as a growth hormone in peach fruit Prunus persica L. Aust. J. Plant Physiol. 3 (in press) 8. Looney, N.E., McGlasson, W.B., Coombe, B.G.: Control of fruit ripening in peach, Prunus persica : action of succinic acid2,2-dimethylhydrazide and (2-chloroethyl)phosphonic acid. Aust. J. Plant Physiol. 1, 77 86 (1974) 9. Marei, N., Crane, J.C.: Growth and respiratory response in fig (Ficus carica L. cv. Mission) fruits to ethylene. Plant Physiol. 48, 249-254 (1971) 10. Musgrave, A., Jackson, M.B., Ling, E. : Callitriche stem elongation is controlled by ethylene and gibberellin. Nature New Biol. 238, 94-96 (1972) 11. Nichols, R., Ho, L.C. : An effect of ethylene on the distribution of 14C-sucrose from the petals to other flower parts in the senescent cut inflorescence of Dianthus caryophyllus. Ann. Bot. 39, 4 3 3 4 3 8 (1975) 12. Phillips, I.D.J. : Apical dominance. Ann. Rev. Plant Physiol. 26, 341-367 (1975) 13. Stembridge, G.E., Raff, J.W. : Ethephon and peach fruit development. Hort. Sci. 8, 500-501 (1973)
Received 16 February; accepted 12 April 1976
