In this paper, photosynthetic characteristics of green leaves (GL) and green pseudobulbs (GPSB) of C3 orchid Oncidium Golden Wish were first studied. Light saturation for photosynthesis and maximum photosynthetic rates (P
max) were significantly higher in GL than in GPSB. The results of the optimal PSII quantum yield (Fv/Fm ratio), electron transport rate (ETR), the effective photochemical quantum yield (ΔF/Fm′) and nonphotochemical quenching (NPQ) of Chl fluorescence revealed that GPSB had lower light utilization than that of GL.
Significantly higher photosynthetic pigments were found in GL than in GPSB. Alteration of source/sink ratio had no impact
on all photosynthetic parameters for both GL and GPSB after a short term of 3 days or even a long term of 2 weeks of treatments
although there were significant decreases in GL carbohydrate concentration of GL-darkened plants by the end of the day. However,
decreases of all photosynthetic parameters of GL were observed in GL-darkened plants after 4 weeks of treatment compared to
that of fully illuminated (FI)- and GPSB-darkened plant. These results indicate that the level of carbohydrates in GL plays
an important role in regulating their photosynthesis. Due to their lower photosynthetic capacities, GPSB function mainly as
sinks. Darkening GPSB up to 2 weeks did not affect their own P
max and the P
max of GL and thus, did not result in significant decreases of total carbohydrate concentration of GPSB. As GPSB store a large
amount of carbohydrates, it could also act as a source when the level of carbohydrates decreased. Thus, GL could depend on
GPSB carbohydrates to regulate their photosynthesis when their source capacity was removed. However, 4 weeks after treatments,
photosynthetic capacities of GL were significantly lower in GL- and GPSB-darkened plants than in FI-plants, which could be
due to the lower total soluble and insoluble sugar concentrations of both GL and GPSB in these plants.
Source-to-sink relationship between green leaves and green pseudobulbs of C 3 orchid in regulation of photosynthesis - ResearchGate. Available from: http://www.researchgate.net/publication/251244072_Source-to-sink_relationship_between_green_leaves_and_green_pseudobulbs_of_C_3_orchid_in_regulation_of_photosynthesis [accessed Sep 5, 2015].
In this paper, photosynthetic characteristics of green leaves (GL) and green pseudobulbs (GPSB) of C3 orchid Oncidium Golden Wish were first studied. Light saturation for photosynthesis and maximum photosynthetic rates (Pmax) were significantly higher in GL than in GPSB. The results of the optimal PSII quantum yield (Fv/Fm ratio), electron transport rate (ETR), the effective photochemical quantum yield (ΔF/Fm′) and nonphotochemical quenching (NPQ) of Chl fluorescence revealed that GPSB had lower light utilization than that of GL.Significantly higher photosynthetic pigments were found in GL than in GPSB. Alteration of source/sink ratio had no impacton all photosynthetic parameters for both GL and GPSB after a short term of 3 days or even a long term of 2 weeks of treatmentsalthough there were significant decreases in GL carbohydrate concentration of GL-darkened plants by the end of the day. However,decreases of all photosynthetic parameters of GL were observed in GL-darkened plants after 4 weeks of treatment compared tothat of fully illuminated (FI)- and GPSB-darkened plant. These results indicate that the level of carbohydrates in GL playsan important role in regulating their photosynthesis. Due to their lower photosynthetic capacities, GPSB function mainly assinks. Darkening GPSB up to 2 weeks did not affect their own Pmax and the Pmax of GL and thus, did not result in significant decreases of total carbohydrate concentration of GPSB. As GPSB store a largeamount of carbohydrates, it could also act as a source when the level of carbohydrates decreased. Thus, GL could depend onGPSB carbohydrates to regulate their photosynthesis when their source capacity was removed. However, 4 weeks after treatments,photosynthetic capacities of GL were significantly lower in GL- and GPSB-darkened plants than in FI-plants, which could bedue to the lower total soluble and insoluble sugar concentrations of both GL and GPSB in these plants. Source-to-sink relationship between green leaves and green pseudobulbs of C 3 orchid in regulation of photosynthesis - ResearchGate. Available from: http://www.researchgate.net/publication/251244072_Source-to-sink_relationship_between_green_leaves_and_green_pseudobulbs_of_C_3_orchid_in_regulation_of_photosynthesis [accessed Sep 5, 2015].
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