Discriminacao isotópica do carbono e trocas gasosas em espécies de Coffea crescidas em diferentes regimes de irradiancia
Two coffee species (Coffea arabica L. cv. Catuai Vermelho and Coffea canephora L. cv. Apoata) were grown in pots placed outdoor under three irradiance regimes, full sunlight (S), 50 percent of shade (50 percent S) and 80 percent of shade (80 percent S), and evaluated for stable carbon isotope discrimination ( ), photosynthetic gas exchange, and growth. The rate of CO2 assimilation in S and 50 percent S plants was higher in C. arabica than in C. canephora, but there was no difference between the two species in 80 percent S. Both species showed similar response to the irradiance regimes. CO2 assimilation rate at 80 percent S was 0.49 and 0.58 of CO2 assimilation in full sunlight, respectively, for C. arabica and C. canephora. There was no significant difference in CO2 assimilation between S and 50 percent S plants for either species. Stomatal conductance in C. arabica increased with the irradiance level, but the increase was less evident than that observed for CO2 assimilation. Consequently, the CO2 assimilation/stomatal conductance ratio (A/g) expressing intrinsic water use efficiency, was greater in the S plants and 50 percent S plants than in the 80 percent S plants. Irradiance regime did not affect stomatal conductance in C. canephora, which had a lower A/g ratio than C. arabica for the same irradiance regime. Leaf values were lower in S plants than in the 80 percent S plants for both species, but there was no difference between S and 50 percent S treatments. The decrease in was associated with a greater increase in the CO2 assimilation rate (106 percent) than in the stomatal conductance (54 percent) in C. arabica. In C. canephora the decrease in was associated with an increase in CO2 assimilation (73 percent), because stomatal conductance values were not influenced by the irradiance regime. Leaf tissue was negatively correlated with instantaneous measurements of CO2 assimilation (r=-0.92; P=0.0109) and with stomatal conductance (r=0.80; P=0.0570). Full sunlight grown plants exhibited higher leaf nitrogen content than 80 percent S plants. The increase in leaf nitrogen content with increasing irradiance levels was strongly correlated with CO2 assimilation rate (r=0.99, P=0.0007) and negatively with (r=-0.94, P=0.0071)
| Main Authors: | , , , |
|---|---|
| Format: | biblioteca |
| Published: |
Ago
|
| Subjects: | COFFEA ARABICA, COFFEA CANEPHORA, FOTOSINTESIS, INTERCAMBIO DE GASES, CONTENIDO DE NITROGENO, NUTRICION DE LAS PLANTAS, CRECIMIENTO, NITROGENO, HOJAS, ESTOMATA, CONDUCTIVIDAD, ISOTOPOS, IRRADIACION, |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Two coffee species (Coffea arabica L. cv. Catuai Vermelho and Coffea canephora L. cv. Apoata) were grown in pots placed outdoor under three irradiance regimes, full sunlight (S), 50 percent of shade (50 percent S) and 80 percent of shade (80 percent S), and evaluated for stable carbon isotope discrimination ( ), photosynthetic gas exchange, and growth. The rate of CO2 assimilation in S and 50 percent S plants was higher in C. arabica than in C. canephora, but there was no difference between the two species in 80 percent S. Both species showed similar response to the irradiance regimes. CO2 assimilation rate at 80 percent S was 0.49 and 0.58 of CO2 assimilation in full sunlight, respectively, for C. arabica and C. canephora. There was no significant difference in CO2 assimilation between S and 50 percent S plants for either species. Stomatal conductance in C. arabica increased with the irradiance level, but the increase was less evident than that observed for CO2 assimilation. Consequently, the CO2 assimilation/stomatal conductance ratio (A/g) expressing intrinsic water use efficiency, was greater in the S plants and 50 percent S plants than in the 80 percent S plants. Irradiance regime did not affect stomatal conductance in C. canephora, which had a lower A/g ratio than C. arabica for the same irradiance regime. Leaf values were lower in S plants than in the 80 percent S plants for both species, but there was no difference between S and 50 percent S treatments. The decrease in was associated with a greater increase in the CO2 assimilation rate (106 percent) than in the stomatal conductance (54 percent) in C. arabica. In C. canephora the decrease in was associated with an increase in CO2 assimilation (73 percent), because stomatal conductance values were not influenced by the irradiance regime. Leaf tissue was negatively correlated with instantaneous measurements of CO2 assimilation (r=-0.92; P=0.0109) and with stomatal conductance (r=0.80; P=0.0570). Full sunlight grown plants exhibited higher leaf nitrogen content than 80 percent S plants. The increase in leaf nitrogen content with increasing irradiance levels was strongly correlated with CO2 assimilation rate (r=0.99, P=0.0007) and negatively with (r=-0.94, P=0.0071) |
|---|