【Objective】The study aimed to explore the effects of the combined application of nitrogen (N), phosphorus (P), and potassium (K) fertilizers on the growth and photosynthetic characteristics of the ‘Yuanhua’ and ‘Yueshuo Bodhi’ of Sapindus saponaria, and to provide a theoretical basis for the scientific fertilization of disease-free clones.【Method】Using the S. saponaria ‘Yuanhua’ and ‘Yueshuo Bodhi’ as the experimental materials, the “3414” field experimental method was used to study the effects of different N, P, and K fertilization regimes on the growth and photosynthetic characteristics of the S. saponaria.【Result】The tree heights of the offspring of S. saponaria were greatest following treatment with N2P1K2 and N2P2K3, being 28.42% and 39.14% higher, respectively, than that of the control, and the differences were found to be significant (P < 0.05). The ground diameter was largest following treatment with N1P2K1 and N2P3K2, and increased by 16.11% and 32.93%, respectively, compared to that of the control (N0P0K0). The tree heights and ground diameters of the ‘Yuanhua’ were in the following order: P > N > K, under different fertilization treatments, while those of the ‘Yueshuo Bodhi’ were in the order: N > K > P. The net photosynthetic rate of the ‘Yuanhua’ and ‘Yueshuo Bodhi’ was highest following treatment with N2P2K2 under different fertilization regimes, and increased significantly by 42.19% and 53.01%, respectively, compared to that of the control. The net photosynthetic rate, intercellular CO2 concentration, rate of transpiration, and foliar water use efficiency of the treatment groups improved significantly; however, the stomatal conductance of the ‘Yuanhua’ did not alter significantly, and the stomatal conductance of the ‘Yueshuo Bodhi’ differed significantly, The quantity of N fertilizer applied exhibited a significant positive correlation with the tree heights and ground diameters of ‘Yuanhua’ and ‘Yueshuo Bodhi’ trees. The growth and photosynthetic indicators of the ‘Yuanhua’ and ‘Yueshuo Bodhi’ under different fertilization regimes were comprehensively evaluated using the entropy weighted TOPSIS method. The findings revealed that N2P1K2 and N1P2K2 were superior for the fertilization of ‘Yuanhua’ trees, while N1P1K2 and N2P2K2 were superior for the fertilization of the ‘Yueshuo Bodhi’.【Conclusion】The application of N, P and K at an appropriate ratio can effectively promote the growth and photosynthetic characteristics of ‘Yuanhua’ and ‘Yueshuo Bodhi’ trees. The optimal strategy for the application of N, P, and K fertilizers is that the quantities of N, P and K should be 115.26, 64.14 and 44.37 kg/hm2, respectively, for the ‘Yuanhua’, and 117.90, 87.65 and 36.11 kg/hm2, respectively, for ‘Yueshuo Bodhi’ trees.
【Objective】The present study aimed to investigate the characteristics of sap flow velocity of Sapindus saponaria and its response pattern to pruning and meteorological factors during the key phenological periods, and to provide a theoretical reference for scientific water management during key reproductive phenological periods of Sapindus.【Method】The present study was conducted in the experimental area of the Sapindus National Forest Germplasm Repository in Jianning County, Sanming City, Fujian Province. Using five-year-old S. saponaria ‘Yuanhua’. Thermal dissipation probes (TDPs) and automatic weather stations were utilized to monitor sap flow and meteorological data from April 20, 2021 to November 9, 2021. The probes were installed approximately 30 cm above the ground to ensure that all probes were installed under the first branch. Sample trees in the pruning group were pruned once after inflorescence growth at the inflorescence growth period to remove branches and leaves that shaded the inflorescence from sunlight. Trees in the control group were left unpruned for comparison.【Result】The average daily sap flow velocity of S. saponaria showed a decreasing-increasing-decreasing trend over time during the seven key reproductive phenological periods. The strongest transpiration activities were (1.13±0.05)×10-3 cm/s (pruning) and (1.48±0.05)×10-3 cm/s (CK) in the early ovary growing period, while the weakest transpiration activities were (0.15±0.02)×10-3 cm/s (pruning) and (0.26±0.03)×10-3 cm/s (CK) in the fruit maturity period. Pruning significantly reduced the sap flow velocity of S. saponaria in all phenological periods, except for the bud swelling period. This reduction effect was more pronounced on sunny days when the tree was actively growing and was strongest at the end of the fruit development period. In addition, solar radiation, air temperature, wind speed and vapor pressure deficit (VPD) were the main drivers of sap flow velocity, while precipitation and air humidity were the main limiting factors. Meteorological factors, such as persistent rainfall, were the main limitations of the transpiration activity of S. saponaria from the bud swelling period to the early flowering period and middle fruit development period. Leaf aging and gradual dormancy of the tree were the main reasons for low sap flow velocity during the fruit maturity period.【Conclusion】Pruning significantly reduced the transpiration, with the reduction effect becoming more pronounced as the phenological periods progressed. There were large fluctuations in sap flow velocity throughout the reproductive growth of S. saponaria. Thus, these findings suggested that the water demand for tree and fruit growth is closely related to the water consumption behavior of trees. Meteorological factors, such as persistent excessive rainfall, during inflorescence growth and development are not conducive to transpiration.
【Objective】This study aims to investigate the time lag characteristics of sap flow during reproductive phenological periods in Sapindus saponaria and the effect of shading inflorescence branching and leaf pruning on the time lag of sap flow.【Method】In the experimental area of the Sapindus saponaria National Forest Germplasm Repository in Jianning County, Fujian Province, five-year-old S. saponaria ‘Yuanhua’ asexual lines were employed as experimental materials. Sap flow was measured using a thermal diffusion probe, and environmental factors including photosynthetically active radiation (PAR), air temperature (Ta), and relative air humidity (RHa) were simultaneously measured during the reproductive growing season.Time lags between sap flow velocity and the dominant environmental factors were analyzed using the mismatch correlation method.【Result】PAR and VPD were the dominant environmental factors affecting sap flow, independent of pruning treatments. On typical sunny days, the relationship between sap flow and these environmental factors showed a “hysteresis loop”, with PAR responsed in a counterclockwise direction and VPD responsed in a clockwise direction. Across six reproductive phenological periods (bud swelling, flowering, early ovary growing, fruit developmet, fruit colour change, fruit ripening), the control (CK) and pruning group sap flow lagged PAR by 10, 10, 0, 10, 20, 50 min and 0, 20, 10, 10, 20, 50 min, respectively; and advanced VPD by 160, 120, 90, 90, 130, 100 min and 190,110, 70, 90, 130, 100 min at six key reproductive phenological periods.【Conclusion】The time lag between sap flow and dominant environmental factors varied across different reproductive phenological periods. Pruning impacted these time lags differently: it reduced the time lag of Fd-PAR during bud swelling and increased it during the flowering and early ovary growing periods, while it had the opposite effect on Fd-VPD. This study provides a scientific foundation for accurately evaluating the influence of environmental factors on the water consumption of forest trees and contributes to the development of more precise models to simulate daytime transpiration processes.
