Low substrate temperature imposes higher limitation to photosynthesis of orange plants as compared to atmospheric chilling

Autor(es)

Santos, C. M. A. ^[1] ; Ribeiro, R. V. ^[1] ; Magalhes Filho, J. R. ^[1] ; Machado, D. F. S. P. ^[1] ; Machado, E. C. ^[1]

Afiliação do(s) autor(es)

^[1] Agron Inst IAC, Lab Plant Physiol Coaracy M Franco, BR-13012970 Campinas, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Photosynthetica; v. 49, n. 4, p. 546-554, DEC 2011.
• Citações Web of Science: 5

Resumo

The aim of this study was to evaluate the effects of low air temperature during nocturnal (T(N)) and diurnal (T(D)) periods as well as the substrate temperature (T(S)) on photosynthesis of `Valencia' orange tree grafted on Rangpur lime rootstock. The experiment was carried out in a growth chamber with seven-month-old plants. The plants were exposed to the following temperature regimes: low substrate temperature (LTS, with: T(D) = 28A degrees C, T(N) = 20A degrees C, T(S) = 10A degrees C); low air temperature during night (LT(N), with: T(D) = 28A degrees C, T(N) = 10A degrees C, T(S) = 26A degrees C); low temperature during nighttime and also low substrate temperature (LT(SN), with: T(D) = 28A degrees C, T(N) = 10A degrees C, T(S) = 10A degrees C); low air temperature during both diurnal and nocturnal periods (LT(ND), with: T(D) = 17A degrees C, T(N) = 10A degrees C, T(S) = 26A degrees C); and finally to low air temperature (night and day) and low substrate temperature (LT(SND), with: T(D) = 17A degrees C, T(N) = 10A degrees C, T(S) = 10A degrees C). As reference (control), plants were subjected to T(D) = 28A degrees C, T(N) = 20A degrees C, and T(S) = 26A degrees C. Measurements of leaf gas exchange, photochemical activity and carbohydrate concentrations were performed after six days of exposure to each thermal treatment. Compared to the control, all thermal regimes caused reductions in photosynthesis due to diffusive and metabolic limitations. The photoinhibition was transient in plants exposed to night and substrate low temperatures, whereas it was severe and chronic in plants subjected to chilling during the diurnal period. However, the lowest photosynthesis was observed in plants with low substrate temperature of 10A degrees C (in LT(S), LT(SND) and LT(SN) treatments), regardless of air temperature. The occurrence of cold night and/or its combination with low substrate temperature caused accumulation of starch in leaves. When considering carbohydrate concentrations in stems and roots, it was not possible to establish a clear response pattern to chilling. In conclusion, the low substrate temperature causes a greater reduction of CO(2) assimilation in citrus plants as compared to the occurrence of low air temperature, being such response a consequence of diffusive and biochemical limitations. (AU)

• Processo FAPESP: 05/57862-8 - Florescimento e frutificação em laranjeira Valência: aspectos anatômicos, fisiológicos, bioquímicos e moleculares
• Beneficiário: Marcelo Carnier Dornelas
• Modalidade de apoio: Auxílio à Pesquisa - Temático