Limitations to photosynthesis in coffee leaves from different canopy positions.
Plant Physiol Biochem
; 46(10): 884-90, 2008 Oct.
Article
em En
| MEDLINE
| ID: mdl-18603439
ABSTRACT
Limitations to photosynthesis were explored in leaves from four canopy positions of field-grown, unshaded coffee (Coffea arabica L.), a tropical tree species classified as shade-obligatory. Overall, compared to shade (lower) leaves, sun (upper) leaves had higher net carbon assimilation rate (A) (4.5 against 2.0 micromol m(-2)s(-1) at most) associated with higher electron transport rate (due to a greater irradiance availability) but unrelated to stomatal and mesophyll conductances, which were similar regardless of leaf position. Neither physiological variable directly involved with photosynthetic carbon gain nor those involved with light capture were able to adjust themselves to match the capacity of the photosynthetic machinery to the light supply. We concluded that (i) there was no major difference in photosynthetic capacity between sun and shade leaves; (ii) the intrinsic low A in coffee was greatly associated with remarkable low diffusive limitations rather than with biochemical or photochemical constraints; and (iii) morphological (e.g., variations in specific leaf area and leaf inclination) or anatomical plasticity should be of greater acclimative value than physiological plasticity as a mean of coffee leaves to respond to changing irradiance.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Fotossíntese
/
Café
/
Folhas de Planta
Idioma:
En
Revista:
Plant Physiol Biochem
Ano de publicação:
2008
Tipo de documento:
Article
País de afiliação:
Brasil