Effect of embryo and exogenous GA3 on endospermic endo-{DF}-mannase activity of Coffea arabica L. during germination and early seedling growth
Endo-ß-mannanase (EC 3.2.1.78) is produced by the cells of the endosperm of coffee (Coffea arabica L.) seeds. During germination of intact seeds the enzyme activity was not detected prior to radicle emergence (0-10 days) and increased several fold over the following stage of radicle emergence and post- radicle emergence (10-25 days). Enzyme activity increases from the micropylar end to the opposite end of the seed and correlates with the growth of the cotyledons. When endosperms are isolated just prior to the time when radicle emergence begins (8th day) and left intact. or incubated in a large volume of water for 48 h, no endo-ß-mannanase activity is detected over the following period. When isolated endosperms are incubated in the presence of growth regulators only gibberellic acid promotes an enhancement of enzyme activity. Abscisic acid or cycloheximide completely inhibit endo-ß-mannanase production in intact germinating seeds or inhibit the promoting effect of gibberellic acid in isolated endosperms. It is concluded that the activity of endo-ß-mannanase, and thus the mobilization of galactomannan in C. arabica seed, is essentially a post-germinative phenomenon and may be under the strict control of the embryo-axis. Possible roles of gibberellins and ABA are discussed.
| Main Authors: | , |
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| Format: | biblioteca |
| Published: |
Abr
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| Subjects: | COFFEA ARABICA, SEMILLA, ENDOSPERMA, AMINOAZUCARES, GERMINACION, PLANTULAS, |
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| Summary: | Endo-ß-mannanase (EC 3.2.1.78) is produced by the cells of the endosperm of coffee (Coffea arabica L.) seeds. During germination of intact seeds the enzyme activity was not detected prior to radicle emergence (0-10 days) and increased several fold over the following stage of radicle emergence and post- radicle emergence (10-25 days). Enzyme activity increases from the micropylar end to the opposite end of the seed and correlates with the growth of the cotyledons. When endosperms are isolated just prior to the time when radicle emergence begins (8th day) and left intact. or incubated in a large volume of water for 48 h, no endo-ß-mannanase activity is detected over the following period. When isolated endosperms are incubated in the presence of growth regulators only gibberellic acid promotes an enhancement of enzyme activity. Abscisic acid or cycloheximide completely inhibit endo-ß-mannanase production in intact germinating seeds or inhibit the promoting effect of gibberellic acid in isolated endosperms. It is concluded that the activity of endo-ß-mannanase, and thus the mobilization of galactomannan in C. arabica seed, is essentially a post-germinative phenomenon and may be under the strict control of the embryo-axis. Possible roles of gibberellins and ABA are discussed. |
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