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Changes in fruit growth and pectic content in Coffea canephora (robusta) in relation to the exogenous application of ethylene
Kurze Mitteilungen' Short Communications Department of Biology, D. G. Vaishnav College, Madras-600 029, India and Central Coffee Research Institute, Coffee Research Station, Kamataka-577117, India
Changes in Fruit Growth and Pectic Content in Coftea canephora (Robusta) in Relation to the Exogenous Application of Ethylene G. SUDHAKARA RAO, D. VENKATARAMANAN and K. N. RAO Received January 7, 1977 . Accepted February 14, 1977
Summary Fruit ripening in robusta coffee induced chemically by ethylene (CEPA) is clearly manifested in enhanced growths of whole fruits and mesocarp and decreased pectic substances. Pectic changes in coffee appear to be directed by endogenous auxins. Foliar application of NPK prevented these changes at lower concentrations of ethylene (150 and 360 ppm) but the blockage was removed at higher doses (720 ppm). NPK treatment necessitates higher dosage of ethylene to obtain normal ripening, as these minerals increased the thresholds of ethylene in coffee fruits by some unknown mechanism.
Key words: Pectins, ethylene, fruits, Coffea canephora. Introduction Pre-harvest treatment of ethylene to synchronize and hasten the ripening of coffee fruits is gaining momentum. Ethylene effects on coffee have been investigated only in relation to abscission, ripening and quality of berries but not fruit metabolism (BROWNING and CANNELL, 1970 ; OYEADE, 1976). Studies concerning pectic metabolism in ethylene treated fruits are interesting (HULME, 1958; WOODMANSEE et aI., 1959) and they should be of special relevance to robusta coffee which contains the highest reported quantity of pectins (SUDHAKARA RAO, 1975). The present work concerns this aspect. Material and Methods Fruit bunches on field grown plants of Coffea canephora, Pierre ex Froehner (Robusta) were sprayed to the drip-point with the ethylene releasing liquid, 2-Chloroethane phosphoric acid (CEP A or Ethrel) (WARNER and LEOPOLD , 1969). The treatment consisted of a single spray without any wetting agent. CEPA was given in three different concentrations (150, 360 and 720 ppm) with or without the standard NPK dosage following a statistically Z. Pflanzenphysiol. Ed. 83. S. 459-461.1977.
460
G. SUDHAKARA RAo, D. VENKATARAMANAN and K. N. RAO
designed experiment (ANONYMOUS, 1974). Twenty plants were maintained for each of the two controls and six treatments. Thirty-three days after, when visual signs of ripening became evident, the fruits were harvested randomly. Pectic substances were assayed as described earlier (SUDHAKARA RAo, 1975).
Results and Discussion
Ethylene-induced increase in fresh weights of whole fruits and meso carp is roughly proportional to the intensity of treatment (Table 1). LEON and FOURNIER (1 %2) and WORMER (1964) have observed that fresh weight in arabica coffee increases most rapidly at the time of fruit ripening than at any other stage of berry growth. The present results of enhanced fresh weight in ethylene treated fruits and mesocarp appear to indicate the degree of fruit ripening. One useful method of determining the ripening of fruits is by following the quantitative changes in pectic compounds. In coffee, pectic content decreased with ethylene application (Table 2), which is consistent with the earlier work (HULME, 1958; WOODMANSEE et aI., 1959). Ethylene is known to influence pectic content by promoting the enzymatic hydrolysis (MCCREADY and MCCOMB, 1954; ARASIMOVICH, 1958) or inhibiting pectin synthesis. Table 1: Fresh weight changes in complete fruits and some fruit components of control and treated coffee berries (Mean of 5 replications with SE). mg fresh weight FRUIT Control CEPA 150 ppm CEPA 360 ppm CEPA 720 ppm NPK NPK + CEPA 150 ppm NPK + CEP A 360 ppm NPK + CEP A 720 ppm Table 2: Changes with SE).
In
1304 1568 1597 1655 1427 1471 1499 1683
EXOCARP
± 49
510 647 648 546 519 522 512 663
±
27 ± 34 ± 32 ± 29 ± 10 ± 12 ± 47
±
MESO CARP
17
244 253 264 365 272 278 308 305
± 12 ± 12 ± 6 ± 14 ± 17
±
±
10 8
± 10 ± 14 ± 6 ± 28
±
28
± 12 ± 5 ± 17
pectic content of control and treated fruits (Mean of 5 replications mg pectic compounds g fresh weight fruit
Control CEPA 150 ppm CEPA 360 ppm CEPA 720 ppm NPK NPK + CEPA 150 ppm NPK + CEP A 360 ppm NPK + CEP A 720 ppm
12.15 9.87 8.14 5.92 16.01 14.19 13.95 6.98
z. Pjlanzenphysiol. Bd. 83. S. 459-461.1977.
± 0.39
± 0.44 ± 0.63
± 0.07
±
0.33
± ±
0.32 0.29
± 0.49
15.84 15.48 12.94 9.50 22.83 20.89 20.82 11.74
± 0.92
± ±
0.53 0.74 ± 0.35 ± 0.41 ± 0.83 ± 0.62 ± 1.12
Effects of ethylene on coffee fruits
461
The latter is achieved by blocking endogenous auxins (BURG and BURG, 1967; MORGAN and GAUSMAN, 1966) which direct the synthesis of pectic substances (RAY and ABDUL-BAKI, 1968). The lowered pectins obtained here are due to the inhibition of pectin synthesis because endogenous auxins decreased with the ripening of coffee fruits (ANONYMOUS, 1973). Fruit ripening in coffee as influenced by ethylene, therefore, appears to be clearly associated with decreased pectin levels and increased fresh weights of complete fruits and mesocarp. Low concentrations of ethylene (150 and 360 ppm) when administered along with NPK prevented fresh weight accumulation in whole fruits and mesocarp, but at higher concentration (720 ppm) marked fresh weight increases were seen (Table 1). NPK also prevented ethylene-induced decreases in pectic content (Table 2). If pectins or even accumulation of fresh weight of berries are any indication of the degree of fruit ripening in coffee, then NPK treatments positively delay this process by increasing the thresholds of ethylene. Coffee plants treated earlier with NPK, therefore, should be given higher doses of ethylene to obtain the desired levels of ripening; the same effect would be achieved at lower concentration in fruits that have not been exposed to NPK treatments. The manner in which NPK, singly or in combination, affects fruit ripening and the thresholds of ethylene is not known (ABELES, 1973). Work in this direction would be highly useful because foliar application of NPK is one of the important cultural practices employed in coffee plantations. References ABELES, F. B.: Ethylene in Plant Biology. Academic Press, New York and London, 1973. ANONYMOUS: Twenty-sixth annual technical report. Coffee Board Research Department, India (1973). - Twenty-seventh annual technical report. Coffee Board Research Department, India
(1974).
ARASIMOVICH, C. c.: Biokhim. Plod. i. Ovosc. 4, 73-87 (1958). BROWNING, G ., and M. G. R. CANNELL: J. Hort. Sci. 45 , 223-232 (1970) . BURG, S. P ., and E . A. BURG: Pla nt Physiol. 42,1224-1228 (1967). HULME, A . c.: Advan. Food Res . 8,297-313 (1958). LEON, J., and L. FOURNIER: Turrialba 12, 65-74 (1962). MCCREADY, R. M., and E. A. MCCOMB: Food Res. 19, 530-535 (1954) . MORGAN, P. M., and H. W. GAUSMAN: Plant Physio!. 41, 45-52 (1966). OYEBADE, T.: Turrialba, 26, 86-89 (1976). RAY, P. M., and A. ABDUL-BAKI: In: WIGHTMAN, F., and G. SETTERFIELD (Eds.): Biochemistry and Physiology of Plant Growth substances, 647-658, The Runge Press, Ottawa,
1968.
SUDHAKARA RAo, G.: J. Coffee Res. 5, 29-35 (1975). WARNER, H. L., and A. C. LEOPOLD: Plant Physio!. 44,156-158 (1969). WOODMANSEE, C. W. , J. H . MCCLENDON and G. F. SOMERS: Food Res . 24, 503-514 (1959). WORMER, T. M .: Ann. Bot. (N. S.) 28, 47-55 (1964). G. SUDHAKARA RAo, Department of Biology, D. G. Vaishnav College, Madras 600 029, India.
Z. PJlanzenphysiol. Ed. 83. S. 459-461.1977.
Changes in Fruit Growth and Pectic Content in Coftea canephora (Robusta) in Relation to the Exogenous Application of Ethylene G. SUDHAKARA RAO, D. VENKATARAMANAN and K. N. RAO Received January 7, 1977 . Accepted February 14, 1977
Summary Fruit ripening in robusta coffee induced chemically by ethylene (CEPA) is clearly manifested in enhanced growths of whole fruits and mesocarp and decreased pectic substances. Pectic changes in coffee appear to be directed by endogenous auxins. Foliar application of NPK prevented these changes at lower concentrations of ethylene (150 and 360 ppm) but the blockage was removed at higher doses (720 ppm). NPK treatment necessitates higher dosage of ethylene to obtain normal ripening, as these minerals increased the thresholds of ethylene in coffee fruits by some unknown mechanism.
Key words: Pectins, ethylene, fruits, Coffea canephora. Introduction Pre-harvest treatment of ethylene to synchronize and hasten the ripening of coffee fruits is gaining momentum. Ethylene effects on coffee have been investigated only in relation to abscission, ripening and quality of berries but not fruit metabolism (BROWNING and CANNELL, 1970 ; OYEADE, 1976). Studies concerning pectic metabolism in ethylene treated fruits are interesting (HULME, 1958; WOODMANSEE et aI., 1959) and they should be of special relevance to robusta coffee which contains the highest reported quantity of pectins (SUDHAKARA RAO, 1975). The present work concerns this aspect. Material and Methods Fruit bunches on field grown plants of Coffea canephora, Pierre ex Froehner (Robusta) were sprayed to the drip-point with the ethylene releasing liquid, 2-Chloroethane phosphoric acid (CEP A or Ethrel) (WARNER and LEOPOLD , 1969). The treatment consisted of a single spray without any wetting agent. CEPA was given in three different concentrations (150, 360 and 720 ppm) with or without the standard NPK dosage following a statistically Z. Pflanzenphysiol. Ed. 83. S. 459-461.1977.
460
G. SUDHAKARA RAo, D. VENKATARAMANAN and K. N. RAO
designed experiment (ANONYMOUS, 1974). Twenty plants were maintained for each of the two controls and six treatments. Thirty-three days after, when visual signs of ripening became evident, the fruits were harvested randomly. Pectic substances were assayed as described earlier (SUDHAKARA RAo, 1975).
Results and Discussion
Ethylene-induced increase in fresh weights of whole fruits and meso carp is roughly proportional to the intensity of treatment (Table 1). LEON and FOURNIER (1 %2) and WORMER (1964) have observed that fresh weight in arabica coffee increases most rapidly at the time of fruit ripening than at any other stage of berry growth. The present results of enhanced fresh weight in ethylene treated fruits and mesocarp appear to indicate the degree of fruit ripening. One useful method of determining the ripening of fruits is by following the quantitative changes in pectic compounds. In coffee, pectic content decreased with ethylene application (Table 2), which is consistent with the earlier work (HULME, 1958; WOODMANSEE et aI., 1959). Ethylene is known to influence pectic content by promoting the enzymatic hydrolysis (MCCREADY and MCCOMB, 1954; ARASIMOVICH, 1958) or inhibiting pectin synthesis. Table 1: Fresh weight changes in complete fruits and some fruit components of control and treated coffee berries (Mean of 5 replications with SE). mg fresh weight FRUIT Control CEPA 150 ppm CEPA 360 ppm CEPA 720 ppm NPK NPK + CEPA 150 ppm NPK + CEP A 360 ppm NPK + CEP A 720 ppm Table 2: Changes with SE).
In
1304 1568 1597 1655 1427 1471 1499 1683
EXOCARP
± 49
510 647 648 546 519 522 512 663
±
27 ± 34 ± 32 ± 29 ± 10 ± 12 ± 47
±
MESO CARP
17
244 253 264 365 272 278 308 305
± 12 ± 12 ± 6 ± 14 ± 17
±
±
10 8
± 10 ± 14 ± 6 ± 28
±
28
± 12 ± 5 ± 17
pectic content of control and treated fruits (Mean of 5 replications mg pectic compounds g fresh weight fruit
Control CEPA 150 ppm CEPA 360 ppm CEPA 720 ppm NPK NPK + CEPA 150 ppm NPK + CEP A 360 ppm NPK + CEP A 720 ppm
12.15 9.87 8.14 5.92 16.01 14.19 13.95 6.98
z. Pjlanzenphysiol. Bd. 83. S. 459-461.1977.
± 0.39
± 0.44 ± 0.63
± 0.07
±
0.33
± ±
0.32 0.29
± 0.49
15.84 15.48 12.94 9.50 22.83 20.89 20.82 11.74
± 0.92
± ±
0.53 0.74 ± 0.35 ± 0.41 ± 0.83 ± 0.62 ± 1.12
Effects of ethylene on coffee fruits
461
The latter is achieved by blocking endogenous auxins (BURG and BURG, 1967; MORGAN and GAUSMAN, 1966) which direct the synthesis of pectic substances (RAY and ABDUL-BAKI, 1968). The lowered pectins obtained here are due to the inhibition of pectin synthesis because endogenous auxins decreased with the ripening of coffee fruits (ANONYMOUS, 1973). Fruit ripening in coffee as influenced by ethylene, therefore, appears to be clearly associated with decreased pectin levels and increased fresh weights of complete fruits and mesocarp. Low concentrations of ethylene (150 and 360 ppm) when administered along with NPK prevented fresh weight accumulation in whole fruits and mesocarp, but at higher concentration (720 ppm) marked fresh weight increases were seen (Table 1). NPK also prevented ethylene-induced decreases in pectic content (Table 2). If pectins or even accumulation of fresh weight of berries are any indication of the degree of fruit ripening in coffee, then NPK treatments positively delay this process by increasing the thresholds of ethylene. Coffee plants treated earlier with NPK, therefore, should be given higher doses of ethylene to obtain the desired levels of ripening; the same effect would be achieved at lower concentration in fruits that have not been exposed to NPK treatments. The manner in which NPK, singly or in combination, affects fruit ripening and the thresholds of ethylene is not known (ABELES, 1973). Work in this direction would be highly useful because foliar application of NPK is one of the important cultural practices employed in coffee plantations. References ABELES, F. B.: Ethylene in Plant Biology. Academic Press, New York and London, 1973. ANONYMOUS: Twenty-sixth annual technical report. Coffee Board Research Department, India (1973). - Twenty-seventh annual technical report. Coffee Board Research Department, India
(1974).
ARASIMOVICH, C. c.: Biokhim. Plod. i. Ovosc. 4, 73-87 (1958). BROWNING, G ., and M. G. R. CANNELL: J. Hort. Sci. 45 , 223-232 (1970) . BURG, S. P ., and E . A. BURG: Pla nt Physiol. 42,1224-1228 (1967). HULME, A . c.: Advan. Food Res . 8,297-313 (1958). LEON, J., and L. FOURNIER: Turrialba 12, 65-74 (1962). MCCREADY, R. M., and E. A. MCCOMB: Food Res. 19, 530-535 (1954) . MORGAN, P. M., and H. W. GAUSMAN: Plant Physio!. 41, 45-52 (1966). OYEBADE, T.: Turrialba, 26, 86-89 (1976). RAY, P. M., and A. ABDUL-BAKI: In: WIGHTMAN, F., and G. SETTERFIELD (Eds.): Biochemistry and Physiology of Plant Growth substances, 647-658, The Runge Press, Ottawa,
1968.
SUDHAKARA RAo, G.: J. Coffee Res. 5, 29-35 (1975). WARNER, H. L., and A. C. LEOPOLD: Plant Physio!. 44,156-158 (1969). WOODMANSEE, C. W. , J. H . MCCLENDON and G. F. SOMERS: Food Res . 24, 503-514 (1959). WORMER, T. M .: Ann. Bot. (N. S.) 28, 47-55 (1964). G. SUDHAKARA RAo, Department of Biology, D. G. Vaishnav College, Madras 600 029, India.
Z. PJlanzenphysiol. Ed. 83. S. 459-461.1977.