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ABSTRACTTo investigate the effects of gibberellic acid (GA) on photosynthesis, nutrient partitioning and endogenous hormones at different leaf locations (1 and 6), Camellia oleiferawas treated with four levels of GA (0, 100, 200 and 300 mg L−1) during the flower bud physiological differentiation stage. GA increased the net photosynthetic rate (Pn), chlorophyll content and chlorophyll fluorescence parameters of 1st and 6th leaves. The 100 mg L−1dose was most effective for increasing the total chlorophyll content and Pn, which increased by 100.00% and 59.55%, respectively, in the 1st leaf, and 110.18% and 44.90%, respectively, in the 6th leaf compared with the control. The 100 and 200 mg L−1GA solutions decreased the starch and soluble sugar levels in both 1st and 6th leaves, but increased those of the 1st and 6th buds which suggested that exogenous GA promotes the transportation of photosynthetic products from leaves to buds with the regulation of a sink–source relationship. Endogenous levels of gibberellin and auxin increased, but abscisic acid decreased in the 1st and 6th leaves after GA applications. The Pn was positively correlated with the total chlorophyll content (0.922 for 1st leaf and 0.944 for 6th leaf) and fluorescence parameters, but negatively correlated with soluble sugar and starch contents in 1st (−0.940 and −0.875, respectively) and 6th (−0.866 and −0.854, respectively) leaves. The difference in responses of leaves at different positions to exogenous GA due to the physiological differences of the leaves themselves.

In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalisand Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalisand Pinus tabulaeformis. But peak times and stopping times of sap flow varied considerably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalisand Pinus tabulaeformiswere about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized.In order to explore the relationship between the time processes of solar radiation and sap flow, sap flow velocity (SFV) of Platycladus orientalisand Pinus tabulaeformis, effective solar radiation (ESR) and other environmental factors were synchronously monitored for one year in the Beijing Western Mountains by using a thermal dissipation probe (TDP) system and an automatic weather station. Results showed significant differences between changes in diurnal characteristics of ESR and sap flow in sunny days during three seasons. Starting times of sap flow occurred generally 1.5–3 hours later than those of solar radiation and there were small differences between Platycladus orientalisand Pinus tabulaeformis. But peak times and stopping times of sap flow varied considerably with large contrasts in ESR. The duration of sap flow showed clear differences among the seasons owing to the variable rhythms of climate factors in Beijing. Fluctuation amplitude in the duration of sap flow remained relatively stable during the autumn but changed greatly during spring and summer. Changes in diurnal sap flow velocity of both Platycladus orientalisand Pinus tabulaeformiswere about 0–3 hours later than those of ESR but with the same configuration. The start of sap flow was mainly induced by the sudden intensification of ESR (sunrise effect). Seasonal models of SFV indicated that a cubic equation had the best fit. It was more practical to simulate seasonal water consumption models of trees with ESR. In further investigations, these models should be optimized.