- Email: [email protected]
The effect of age and growing conditions on cyanide resistance in cultured tomato roots
Plant Science Letters, 23 (1981) 307--313 Elsevier/North-Holland Scientific Publishers Ltd.
307
THE EFFECT OF AGE AND GROWING CONDITIONS ON CYANIDE RESISTANCE IN CULTURED TOMATO ROOTS
HARRY W. JANES and CHEE-KOK CHIN
Department of Horticulture and Forestry, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, NJ 08903 (U.S.A.) (Received March 4th, 1981) (Revision received June 18th, 1981 ) (Accepted June 30th, 1981)
SUMMARY
Experiments were performed which demonstrate the existance of an alternative cyanide resistant electron transport pathway in aseptically cultured tomato roots. The capacity of this pathway was n o t altered by the age of the root, but stressing the root tissue by growth in various monosaccharides does result in a heightened alternative pathway capacity. It is further demonstrated that all root sections (primary tips, secondary tips, or axis tissue) possess similar potential alternative pathway activity. The results are discussed from the aspect of maintenance of cell reducing power.
INTRODUCTION
Cyanide resistant respiration (CRR) is a c o m p o n e n t of the total respiratory capacity of a large number of plants [1,2]. The importance of the low phosphorylating CRR in the heat production of the A r u m spadix is documented [3]. However, in most plants the existence of a highly inefficient (in terms of ATP production) alternative electron transport pathway is an enigma. It has been shown that many plants have the potential to develop CRR [ 2] and the development can be affected by age, type of tissue and cultural conditions. The capacity for increased CRR activity has been observed on several occasions to be associated with senescence and ripening [4,5] and stress (chemical irritants, ethylene, ethanol or fungal infection) [6--9]. A suggestion that CRR may serve as a sink for excess reducing power to prevent a change in redox state has been make [10]. However, the operaAbbreviation: CRR, cyanide resistant respiration.
0304--4211/81/0000--0000/$02.75 © 1981 Elsevier/North-Holland Scientific Publishers Ltd.
308
tion of the pathway in vivo under the conditions mentioned above is undocumented. Recently Flores and Chin [11] reported that excised tomato roots possessed CRR and that the presence of cyanide in the culture media greatly increased the CRR activity. The purpose of this investigation was to examine whether age, type of tissue and cultural conditions, had an effect on CRR activity of cultured tomato roots. Such information might shed some light on the possible role of this pathway. METHODS
Aseptic culture of tomato roots A tomato (Lycopersicon esculentum cv. Rutgers) seed was germinated and a 1-cm root tip was cultured in White's medium as modified by Street et al. [12] containing 1.5% sucrose. A clone was developed by subculturing root tips from this single culture. All roots used were, therefore, clones of the root from one seed. Roots were cultured in 25 ml of medium in 125 ml erlenmeyer flasks (1 root/flask) in the dark at 28°C. In experiments with roots cultured in glucose and fructose, the roots were grown for 3 days in sucrose medium and then transferred for 4 days to glucose and fructose media, respectively. Respiratory measurements 02 uptake was measured polar ographically using a YSI model 53 Oxygen monitor equipped with a Clark electrode. Root tissue from 5 flasks was cut into 1-cm long sections in a petri dish. A 0.5-g (fresh wt.) sample was placed in 4 ml of aerated medium in a 35-ml cuvette, into which a stirring bar and Clark electrode were placed. Respiratory determinations were carried out at 28°C with the aerated medium assumed to contain 240/~M 02. Respiratory inhibitors were injected into the cuvette and the altered respiratory rate was determined immediately. This method of determining root respiration is essentially the same as employed by Lambers and Steingrover [13] and Kano and Kageyana [14]. Respiration rates are usually expressed in nanomoles O2 consumed per rain/rag dry wt. except as noted in the text. Experiments were typically repeated 2--6 times. RESU L T S AND DISCUSSION
It has been suggested [15] that CRR pathway operates only on top of a fully active cytochrome oxidase pathway. This suggestion appears to be supported by data presented here. Figure 1A shows the effects of titration with various concentrations of cyanide in the p~Jence or absence of 10 -3 M SHAM on tomato root respiration. Figure 1B demonstrates the effect of SHAM at different concentrations plus 0, 10 -s or 10 -3 M KCN on respiration. This information along with that of Table I (SHAM inhibits r~pimtion 7~)
309
®
I
I
!
!
I
!
®
!
!
!
!
!
I
!
!
_'c 7 E6
d' 5 "3 e-
o, JL
0
10~
10"s 10" KCN, M
I
10"3 0
!
2
4 6 8 SHAM, XlO'4M
I
10
Fig. 1. A: Effects of various concentrations of KCN in the presence (O) or absence (o) of 10 -3 M SHAM. B: Effects o f various concentrations of SHAM in the absence (o) or presence of 10 -s M KCN (O) or 10 -3 M KCN (A).
indicate that in this tissue the alternative pathway may not be operating unless cytochrome oxidase is partially or fully inhibited or unless the cytochrome oxidase pathway is at saturation. If CRR operates only when the cytochrome pathway is at saturation, it may serve as a sink for excess reducing power and may prevent changes in the redox state of plant tissues. This is presumably important where there is an increase in respiratory activity (such as climacteric in fruit) or a decrease in biosynthetic processes or both. This presupposes that in tissues with an active CRR the normal respiratory feedback mechanisms are not in operation or possibly site I in the electron transport scheme is not under energy charge control. The alternative pathway with its low phosphorylating ability [16] might thus
TABLE I A C O M P A R I S O N O F T H E R E S P I R A T O R Y P A T T E R N S IN V A R I O U S R O O T SEGMENTS
R o o t segment
Whole r o o t Primary tip Secondary tip tissue
Control (nmol 0 2 rain-' mg -~ dry wt.)
% Inhibition KCN
SHAM
KCN + SHAM
6.9 6.8 6.6 6.3
46 49 56 53
7 6 7 8
95 90 90 89
310
serve as a safety valve to dispose of excess reduced pyridine nucleotides without the possible toxic build-up of ethanol or lactic acid. Indeed, increased CRR capacity has been observed to be associated with senescence and ripening [4,5] and stress [6--9] conditions. If this hypothesis is correct we would expect to see an increase in the activity of the C R R as the roots age. We observed during the first 7 days in culture that the roots are actively growing and that by 9 days the growth rate has slowed. By the time the roots are 2 weeks old browning has occurred and the tissue senesces (Fig. 2). Table II shows the change of r o o t respiratory c o m p o n e n t s over time. The data show that the percentage of the respiration inhibited by cyanide declined as the roots aged. Theologis and Laties [17] have shown that in many cases a portion of the respiration of whole tissues is insensitive to cyanide and salicylhydroxamic acid, an inhibitor of the alternative oxidase. They termed this respiratory c o m p o n e n t residual respiration. Therefore, lack of inhibition of cyanide does n o t necessarily mean alternative pathway activity. One way this can be determined is to subtract the percentage of respiration n o t inhibited by cyanide and SHAM from the rate when cyanide alone is present. The results (Table II) show virtually no change in the alternative pathway capacity from days 7--12, declining slightly on day 19, b u t rising again to 55% on day 35 (data n o t shown) and thus do n o t appear to support the contention that the CRR capacity increases as the tissue senesces. However, it was observed that as the roots aged the total respiration also declined. Thus, it is possible that due to the decline in total respiration no
E20 u18.16[-
/
g 14r
~
g
c 12~
¢
~
!
I
I
i
I
J
I
I
l
I
~ I
I,
0
!
1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 Days Fig. 2. The growth ~ttern, as me~und by an i=~e~e in length of tomato root~ ~ aseptically. Arrow ind/eatm point at which browning begin=.
311
TABLE II THE E F F E C T OF AGE ON TOMATO ROOT RESPIRATION The % inhibition caused by KCN (10 -3 M) and KCN + SHAM (10 -3 M) on tomato root respiration was determined along with the alternative and residual respiratory activities (see text for details). Age of root (days)
7 9 12 19
Control (nmol 0 2 rain -I m g -I dry wt.)
% Inhibition
% Control rate
KCN
KCN + SHAM
Alternative pathway
Residual
7.1 4.9 4.9 1.7
46 38.9 31 36
95 89 80 78
49 50.1 49 42
5 11 20 22
excess reducing power was generated and hence no increase in C R R potential or activitywas observed since S H A M alone inhibitsonly approx. 7% at each age (data not shown). In tomato roots, cells at different stages of development are spatially separated along the root axis, with cell enlargement activitylocated in the terminal 5 nun of the root [18]. If the C R R pathway plays a role in maintaining the redox state of the tissue,it would follow that areas of the root with increased growth activity would demonstrate lower C R R pathway activity. The data presented here, however, shows no differences in C R R activity between the different root sections tested. The roots used in this study were 7 days old and growing vigorously and can be considered quite young. Therefore, not only the root tip tissue, because of its rapid cell enlargement, but the axis region due to biosynthetic processes possibly associated with cell wall deposition, m a y also be metabolically very active. Consequently, under such circumstances, no change in the redox potential of the tissue would be imminent and the alternative pathway's capacity would not change. The growth of tomato roots is greatly affected by the type of sugar in the growing media; the rates of growth are roughly 10 times greater with sucrose as the carbohydrate source than with fructose and glucose [19]. In addition, roots cultured in sucrose can be subcultured repeatedly but those cultured in glucose and fructose age irreversiblyand can only be subcultured once or twice before they die [19]. Thus, roots in glucose and fructose can be considered to be under stressconditions. Table III demonstrates that the C R R capacity is higher in glucose and fructose grown roots than in sucrose grown roots. This, therefore, appears to support the contention that stressed tissues m a y develop a higher C R R potential.However, here again S H A M inhibits the overallrespiration rate by <_7% in all cases and indicates that while the capacity is there, the actual operation of the C R R pathway is in doubt. Also,
312 TABLE III THE EFFECT OF CARBOHYDRATE SOURCE ON ROOT RESPIRATION Growing
Control
media
(nmol O 5 min-'
Surcrose Fructose Glucose
% Inhibition
% Control rate
mg-' dry wt,
KCN
KCN + SHAM
Alternative pathway
Residual
7.3 5.8 4.4
58 32 30
85 71 76
27 39 46
15 29 24
roots grown in all sugars have approximately the same absolute C R R capacity of 2 nmol O~ rain-' rag-' dry wt. with the apparent increase in C R R capacity noted in Table III being due to a drop in the cytochrome oxidase pathway. Clearly, the evidence in this study is indecisive in resolving whether a role of C R R is to serve as a sink for possible excess reducing power produced in senescence or stress.Although a correlation of stress and increase in C R R capacity appears to exist, no increase in C R R during aging was observed. Nevertheless, the latter m a y be explained by the fact that unlike some tissues, such as climacteric fruits which display high levels of respiration late in the senescence process, tomato roots show a decrease in respiration and, therefore, a reduction in reducing power generation as they age. In light of this, it is suggested that, to test the proposed hypothesis, tissues that can maintain relatively high respiration rates during senescence should be used. One interesting observation of this study is that the residual respiration increased when the roots aged or were stressed. This respiratory component is assumed to be non-mitochondrial and m a y reflect the activity of other cyanide resistant oxidases [20--22]. However, littleis k n o w n about residual respiration and it is not clear whether or not it is involved in senescence or stress. As the portion of residual respiration is considerable it is important that the nature and the possible role of this respiration be examined. ACKNOWLEDGEMENTS Paper of the Journal Series, New Jersey Agricultural Experiment Station, C o o k College, Rutgers University, N e w Brunswick, N e w Jersey. This w o r k was performed as a part of NJAES project 12144, supported by the New Jersey Agricultural Experiment Station and Hatch Act Funds. REFERENCES
1 T. SolomoJ, Annu. Rev. Plant Phyaiol., 28 (1977) 279.
313 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
N.F. Henry and E.J. Nyns, Sub. Cell Biochem., 4 (1975) 1. B.J.D. Meeuse, Annu. Rev. Plant Physiol., 26 (1975) 117. T. Solomos and G.G. Laties, Nature, 245 (1972) 390. T. Solomos and G.G. Laties, Plant Physiol., 54 (1974) 506. D.L. Edwards and E. Rosenberg, Eur. J. Biochem., 62 (19"/6) 217. A. Rychter, H.W. Janes and C. Frenkel, Plant Physiol., 61 (1978) 667. A. Rychter, H.W. Janes, C. Chin and C. Frenkel, Plant Physiol., 64 (1979) 108. J.L. Harley and T. ApRees, New Phytol., 58 (1959) 364. H. Lambers and G. Smakman, Physiol. Plant., 42 (1978) 163. H. Flores and C. Chin, Plant Sci. Let., 17 (1980) 237. H.E. Street and J.S. Lowe, Ann. Bot., 14 (1950) 307. H. Lambers and E. Steingrover, Physiol. Plant., 42 (1978) 179. H. Kano and M. Kageyama, Plant Cell. Physiol., 18 (1977) 1149. J.T. Bahr and W.D. Bonner, Jr., J. Biol. Chem., 248 (1973) 3441. J.M. Plainer, Annu. Rev. Plant Physiol., 27 (1976) 133. A. Theologis and G.G. Laties, Plant Physiol., 62 (1978) 232. C.K. Chin and G.O. Weston, Phytochemistry, 12 (1973) 1229. G.D. Weston, New Phytol., 72 (1973) 61. D.J. Parrish and A.C. Leopold, Plant Physiol., 62 (1978) 470. L.R. DeChatelet, L.L. McPhail and P.S. Shirley, Blood, 49 (1977) 445. D. Reichhart, J.D. Salaum, I. Beneveniste and F. Durst, Plant Physiol., 66 (1980) 600.
307
THE EFFECT OF AGE AND GROWING CONDITIONS ON CYANIDE RESISTANCE IN CULTURED TOMATO ROOTS
HARRY W. JANES and CHEE-KOK CHIN
Department of Horticulture and Forestry, Cook College, New Jersey Agricultural Experiment Station, Rutgers University, New Brunswick, NJ 08903 (U.S.A.) (Received March 4th, 1981) (Revision received June 18th, 1981 ) (Accepted June 30th, 1981)
SUMMARY
Experiments were performed which demonstrate the existance of an alternative cyanide resistant electron transport pathway in aseptically cultured tomato roots. The capacity of this pathway was n o t altered by the age of the root, but stressing the root tissue by growth in various monosaccharides does result in a heightened alternative pathway capacity. It is further demonstrated that all root sections (primary tips, secondary tips, or axis tissue) possess similar potential alternative pathway activity. The results are discussed from the aspect of maintenance of cell reducing power.
INTRODUCTION
Cyanide resistant respiration (CRR) is a c o m p o n e n t of the total respiratory capacity of a large number of plants [1,2]. The importance of the low phosphorylating CRR in the heat production of the A r u m spadix is documented [3]. However, in most plants the existence of a highly inefficient (in terms of ATP production) alternative electron transport pathway is an enigma. It has been shown that many plants have the potential to develop CRR [ 2] and the development can be affected by age, type of tissue and cultural conditions. The capacity for increased CRR activity has been observed on several occasions to be associated with senescence and ripening [4,5] and stress (chemical irritants, ethylene, ethanol or fungal infection) [6--9]. A suggestion that CRR may serve as a sink for excess reducing power to prevent a change in redox state has been make [10]. However, the operaAbbreviation: CRR, cyanide resistant respiration.
0304--4211/81/0000--0000/$02.75 © 1981 Elsevier/North-Holland Scientific Publishers Ltd.
308
tion of the pathway in vivo under the conditions mentioned above is undocumented. Recently Flores and Chin [11] reported that excised tomato roots possessed CRR and that the presence of cyanide in the culture media greatly increased the CRR activity. The purpose of this investigation was to examine whether age, type of tissue and cultural conditions, had an effect on CRR activity of cultured tomato roots. Such information might shed some light on the possible role of this pathway. METHODS
Aseptic culture of tomato roots A tomato (Lycopersicon esculentum cv. Rutgers) seed was germinated and a 1-cm root tip was cultured in White's medium as modified by Street et al. [12] containing 1.5% sucrose. A clone was developed by subculturing root tips from this single culture. All roots used were, therefore, clones of the root from one seed. Roots were cultured in 25 ml of medium in 125 ml erlenmeyer flasks (1 root/flask) in the dark at 28°C. In experiments with roots cultured in glucose and fructose, the roots were grown for 3 days in sucrose medium and then transferred for 4 days to glucose and fructose media, respectively. Respiratory measurements 02 uptake was measured polar ographically using a YSI model 53 Oxygen monitor equipped with a Clark electrode. Root tissue from 5 flasks was cut into 1-cm long sections in a petri dish. A 0.5-g (fresh wt.) sample was placed in 4 ml of aerated medium in a 35-ml cuvette, into which a stirring bar and Clark electrode were placed. Respiratory determinations were carried out at 28°C with the aerated medium assumed to contain 240/~M 02. Respiratory inhibitors were injected into the cuvette and the altered respiratory rate was determined immediately. This method of determining root respiration is essentially the same as employed by Lambers and Steingrover [13] and Kano and Kageyana [14]. Respiration rates are usually expressed in nanomoles O2 consumed per rain/rag dry wt. except as noted in the text. Experiments were typically repeated 2--6 times. RESU L T S AND DISCUSSION
It has been suggested [15] that CRR pathway operates only on top of a fully active cytochrome oxidase pathway. This suggestion appears to be supported by data presented here. Figure 1A shows the effects of titration with various concentrations of cyanide in the p~Jence or absence of 10 -3 M SHAM on tomato root respiration. Figure 1B demonstrates the effect of SHAM at different concentrations plus 0, 10 -s or 10 -3 M KCN on respiration. This information along with that of Table I (SHAM inhibits r~pimtion 7~)
309
®
I
I
!
!
I
!
®
!
!
!
!
!
I
!
!
_'c 7 E6
d' 5 "3 e-
o, JL
0
10~
10"s 10" KCN, M
I
10"3 0
!
2
4 6 8 SHAM, XlO'4M
I
10
Fig. 1. A: Effects of various concentrations of KCN in the presence (O) or absence (o) of 10 -3 M SHAM. B: Effects o f various concentrations of SHAM in the absence (o) or presence of 10 -s M KCN (O) or 10 -3 M KCN (A).
indicate that in this tissue the alternative pathway may not be operating unless cytochrome oxidase is partially or fully inhibited or unless the cytochrome oxidase pathway is at saturation. If CRR operates only when the cytochrome pathway is at saturation, it may serve as a sink for excess reducing power and may prevent changes in the redox state of plant tissues. This is presumably important where there is an increase in respiratory activity (such as climacteric in fruit) or a decrease in biosynthetic processes or both. This presupposes that in tissues with an active CRR the normal respiratory feedback mechanisms are not in operation or possibly site I in the electron transport scheme is not under energy charge control. The alternative pathway with its low phosphorylating ability [16] might thus
TABLE I A C O M P A R I S O N O F T H E R E S P I R A T O R Y P A T T E R N S IN V A R I O U S R O O T SEGMENTS
R o o t segment
Whole r o o t Primary tip Secondary tip tissue
Control (nmol 0 2 rain-' mg -~ dry wt.)
% Inhibition KCN
SHAM
KCN + SHAM
6.9 6.8 6.6 6.3
46 49 56 53
7 6 7 8
95 90 90 89
310
serve as a safety valve to dispose of excess reduced pyridine nucleotides without the possible toxic build-up of ethanol or lactic acid. Indeed, increased CRR capacity has been observed to be associated with senescence and ripening [4,5] and stress [6--9] conditions. If this hypothesis is correct we would expect to see an increase in the activity of the C R R as the roots age. We observed during the first 7 days in culture that the roots are actively growing and that by 9 days the growth rate has slowed. By the time the roots are 2 weeks old browning has occurred and the tissue senesces (Fig. 2). Table II shows the change of r o o t respiratory c o m p o n e n t s over time. The data show that the percentage of the respiration inhibited by cyanide declined as the roots aged. Theologis and Laties [17] have shown that in many cases a portion of the respiration of whole tissues is insensitive to cyanide and salicylhydroxamic acid, an inhibitor of the alternative oxidase. They termed this respiratory c o m p o n e n t residual respiration. Therefore, lack of inhibition of cyanide does n o t necessarily mean alternative pathway activity. One way this can be determined is to subtract the percentage of respiration n o t inhibited by cyanide and SHAM from the rate when cyanide alone is present. The results (Table II) show virtually no change in the alternative pathway capacity from days 7--12, declining slightly on day 19, b u t rising again to 55% on day 35 (data n o t shown) and thus do n o t appear to support the contention that the CRR capacity increases as the tissue senesces. However, it was observed that as the roots aged the total respiration also declined. Thus, it is possible that due to the decline in total respiration no
E20 u18.16[-
/
g 14r
~
g
c 12~
¢
~
!
I
I
i
I
J
I
I
l
I
~ I
I,
0
!
1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 Days Fig. 2. The growth ~ttern, as me~und by an i=~e~e in length of tomato root~ ~ aseptically. Arrow ind/eatm point at which browning begin=.
311
TABLE II THE E F F E C T OF AGE ON TOMATO ROOT RESPIRATION The % inhibition caused by KCN (10 -3 M) and KCN + SHAM (10 -3 M) on tomato root respiration was determined along with the alternative and residual respiratory activities (see text for details). Age of root (days)
7 9 12 19
Control (nmol 0 2 rain -I m g -I dry wt.)
% Inhibition
% Control rate
KCN
KCN + SHAM
Alternative pathway
Residual
7.1 4.9 4.9 1.7
46 38.9 31 36
95 89 80 78
49 50.1 49 42
5 11 20 22
excess reducing power was generated and hence no increase in C R R potential or activitywas observed since S H A M alone inhibitsonly approx. 7% at each age (data not shown). In tomato roots, cells at different stages of development are spatially separated along the root axis, with cell enlargement activitylocated in the terminal 5 nun of the root [18]. If the C R R pathway plays a role in maintaining the redox state of the tissue,it would follow that areas of the root with increased growth activity would demonstrate lower C R R pathway activity. The data presented here, however, shows no differences in C R R activity between the different root sections tested. The roots used in this study were 7 days old and growing vigorously and can be considered quite young. Therefore, not only the root tip tissue, because of its rapid cell enlargement, but the axis region due to biosynthetic processes possibly associated with cell wall deposition, m a y also be metabolically very active. Consequently, under such circumstances, no change in the redox potential of the tissue would be imminent and the alternative pathway's capacity would not change. The growth of tomato roots is greatly affected by the type of sugar in the growing media; the rates of growth are roughly 10 times greater with sucrose as the carbohydrate source than with fructose and glucose [19]. In addition, roots cultured in sucrose can be subcultured repeatedly but those cultured in glucose and fructose age irreversiblyand can only be subcultured once or twice before they die [19]. Thus, roots in glucose and fructose can be considered to be under stressconditions. Table III demonstrates that the C R R capacity is higher in glucose and fructose grown roots than in sucrose grown roots. This, therefore, appears to support the contention that stressed tissues m a y develop a higher C R R potential.However, here again S H A M inhibits the overallrespiration rate by <_7% in all cases and indicates that while the capacity is there, the actual operation of the C R R pathway is in doubt. Also,
312 TABLE III THE EFFECT OF CARBOHYDRATE SOURCE ON ROOT RESPIRATION Growing
Control
media
(nmol O 5 min-'
Surcrose Fructose Glucose
% Inhibition
% Control rate
mg-' dry wt,
KCN
KCN + SHAM
Alternative pathway
Residual
7.3 5.8 4.4
58 32 30
85 71 76
27 39 46
15 29 24
roots grown in all sugars have approximately the same absolute C R R capacity of 2 nmol O~ rain-' rag-' dry wt. with the apparent increase in C R R capacity noted in Table III being due to a drop in the cytochrome oxidase pathway. Clearly, the evidence in this study is indecisive in resolving whether a role of C R R is to serve as a sink for possible excess reducing power produced in senescence or stress.Although a correlation of stress and increase in C R R capacity appears to exist, no increase in C R R during aging was observed. Nevertheless, the latter m a y be explained by the fact that unlike some tissues, such as climacteric fruits which display high levels of respiration late in the senescence process, tomato roots show a decrease in respiration and, therefore, a reduction in reducing power generation as they age. In light of this, it is suggested that, to test the proposed hypothesis, tissues that can maintain relatively high respiration rates during senescence should be used. One interesting observation of this study is that the residual respiration increased when the roots aged or were stressed. This respiratory component is assumed to be non-mitochondrial and m a y reflect the activity of other cyanide resistant oxidases [20--22]. However, littleis k n o w n about residual respiration and it is not clear whether or not it is involved in senescence or stress. As the portion of residual respiration is considerable it is important that the nature and the possible role of this respiration be examined. ACKNOWLEDGEMENTS Paper of the Journal Series, New Jersey Agricultural Experiment Station, C o o k College, Rutgers University, N e w Brunswick, N e w Jersey. This w o r k was performed as a part of NJAES project 12144, supported by the New Jersey Agricultural Experiment Station and Hatch Act Funds. REFERENCES
1 T. SolomoJ, Annu. Rev. Plant Phyaiol., 28 (1977) 279.
313 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
N.F. Henry and E.J. Nyns, Sub. Cell Biochem., 4 (1975) 1. B.J.D. Meeuse, Annu. Rev. Plant Physiol., 26 (1975) 117. T. Solomos and G.G. Laties, Nature, 245 (1972) 390. T. Solomos and G.G. Laties, Plant Physiol., 54 (1974) 506. D.L. Edwards and E. Rosenberg, Eur. J. Biochem., 62 (19"/6) 217. A. Rychter, H.W. Janes and C. Frenkel, Plant Physiol., 61 (1978) 667. A. Rychter, H.W. Janes, C. Chin and C. Frenkel, Plant Physiol., 64 (1979) 108. J.L. Harley and T. ApRees, New Phytol., 58 (1959) 364. H. Lambers and G. Smakman, Physiol. Plant., 42 (1978) 163. H. Flores and C. Chin, Plant Sci. Let., 17 (1980) 237. H.E. Street and J.S. Lowe, Ann. Bot., 14 (1950) 307. H. Lambers and E. Steingrover, Physiol. Plant., 42 (1978) 179. H. Kano and M. Kageyama, Plant Cell. Physiol., 18 (1977) 1149. J.T. Bahr and W.D. Bonner, Jr., J. Biol. Chem., 248 (1973) 3441. J.M. Plainer, Annu. Rev. Plant Physiol., 27 (1976) 133. A. Theologis and G.G. Laties, Plant Physiol., 62 (1978) 232. C.K. Chin and G.O. Weston, Phytochemistry, 12 (1973) 1229. G.D. Weston, New Phytol., 72 (1973) 61. D.J. Parrish and A.C. Leopold, Plant Physiol., 62 (1978) 470. L.R. DeChatelet, L.L. McPhail and P.S. Shirley, Blood, 49 (1977) 445. D. Reichhart, J.D. Salaum, I. Beneveniste and F. Durst, Plant Physiol., 66 (1980) 600.