Photosynthetic limitations in coffee plants are chiefly governed by diffusive factors

摘要: It has long been held that the regulation of photosynthesis in source leaves may be controlled by carbohydrates. The mechanisms govern diurnal fluctuation and potential role feedback carbohydrates during coffee (Coffea arabica) were investigated three independent complementary experiments. An integrative approach using gas exchange measurements addition to carbon isotope labelling steady-state carbohydrate amino acid analysis was performed. Canonical correlation also In field-grown plants under naturally fluctuating environmental conditions (Experiment I), overall pattern characterised both low stomatal conductance (g s) net assimilation rate (A) afternoon; no apparent signs photoinhibition observed. Under air evaporative demand II), only slight decreases (~20%) A observed at end day, which associated with a reduction (~35%) g s. For conditions, any increase pools over course day small. from girdled branches III), remarkable decrease particularly s observed, as increases starch but not hexoses sucrose pools. Furthermore, 14CO2 uptake (assessed saturating CO2 conditions) partitioning recently fixed 14C affected girdling. is proposed oscillations differences non-girdled merely consequence diffusive limitations rather than photochemical constraints or direct metabolite-mediated down-regulation photosynthesis.