| As urban infrastructure, the Viaduct has great significance of the city’s transportation and development. However, the construction of the viaduct makes the greening plant growth environment changing. Both weak light and air pollution have serious impact on plants. Therefore, it is very important to select adaptable greening plants under the viaduct. It will improve the urban greening quantity and road environment.We selected four viaducts of Wuhan City to carry out greening plants cultivation experiment and determine photosynthetic characteristics by employing Li-6400XT photosynthesis system. We had a preliminary study on shade tolerance of the typical greening plants to select the greening plants species suited to the light environment under the viaduct in Wuhan City. The main results are as follows:1.The diurnal changing curve of Pn of Fatsia japonica under full sunshlight presented doule-peak, and their maximum peak point was at11:00and14:00, peak value were5.77μmol·m-2·s-1and3.99μmol·m-2·s-1respectively. It presented single-peak curves under shade, and the maximum peak point was at12:00, peak value was2.49μmol·m-2·s-1. The diurnal changes of PAR was presented single-peak curves under shade and full sunlight, and the maximum peak point was at12:00, peak value were1669μmol·m-2·s-1and553μmol·m-2·s-1respectively.The diurnal changes of Ci under full sunlight was presented two extreme low point at11:00and15:00, while it had extreme low point at11:00under shade. The diurnal changes of Gs under full sunlight had a peak at10:00, and it was at12:00under shade. The diurnal changes of Tr were presented doule-peak curves and the maximum peak point was at11:00and14:00, peak value were2.64mmol·m-2·s-1and2.23mmol·m-2·s-1respectively, It presented single-peak curves under shade, and the maximum peak point was at12:00, peak value was2.21mmol·m-2·s-1. The diurnal changes of Ta were presented doule-peak curves under shade and full sunlight. The diurnal changes of RH under shade was higher than that under full sunlight, and it had maximum difference at12:00. The diurnal changes of Pn of Liriope muscari cv.Variegata under full sunlight were presented doule-peak curves and the maximum peak point was at10:00and15:00, peak value were4.33μmol·m-2·s-1and3.04μmol·m-2·s-1respectively,It presented single-peak curves under shade, and the maximum peak point was at12:00, peak value was2.99μmol·m-2-s-1. The diurnal changes of PAR was presented single-peak curves under shade and full sunlight, and the maximum peak point was at12:00, peak value were1423μmol·m-2·s-1and431μmol·m-2·s-1respectively.The diurnal changes of Ci under full sunlight was presented two extreme low point at10:00and15:00, and it had extreme low point at10:00and14:00under shade. The diurnal changes of Gs under full sunlight had a peak at9:00, and it was at8:00under shade. The diurnal changes of Tr were presented doule-peak curves and the maximum peak point was at11:00and15:00, peak value were2.87mmol·m-2·s-1and2.44mmol·m-2·s-1respectively, It presented single-peak curves under shade, and the maximum peak point was at12:00, peak value was1.98mmol·m-2·s-1. The diurnal changes of Ta were presented doule-peak curves under shade and full sunlight. The diurnal changes of RH presented a trend that the values in the morning and in the evening were higher than one at noon under shade and full sunlight.The diurnal changes of solar energy utilization efficiency of Fatsia japonica and Liriope muscari cv.Variegata performed a U line that the values in the morning and in the evening were higher, while the minimum was at noon. Higher sunlight, the smaller efficiency of solar energy utilization was. While when the sunlight was lower, solar energy utilization efficiency increased rapidly. There was a negative correlation between LUE and photosynthetically active radiation, and solar energy utilization efficiency under shade was higher than that was under sunshine.2. The main physio-ecological factors of Fatsia japonica and Liriope muscari cv. Variegata include photosynthetic active radiation(PAR), intercellular CO2concentration(Ci), stomatal conductance(Gs), transpiration rate(Tr), air temperature(Ta) and air relative humidity(RH). According to the principal component analysis, correlation analysis and path analysis of the physio-ecological factors, the main factor about Fatsia japonica net photosynthetic rate were PAR,Tr,Ci under full sunlight, and PAR,Tr,RH were the main factor under shade. The main factor about Liriope muscari cv. Variegata net photosynthetic rate were PAR,Tr,Ci under full sunlight, and PAR,RH,Ci were the main factor under shade.3. According to the cluster analysis of arbor、shrub、herbage、liana photosynthetic parameters, such as light compensation point(LCP), apparent quantum efficiency(cp), light saturation point(LSP) and maximum net photosynthetic rate(Amax)-The shade tolerance of the experimental plants can be divided into shade-tolerent extremely species, shade-tolerent species and shade-non-tolerent species. Among this, The shade-tolerent extremely species include Fatsia japonica, Fatshedera lizei, Camellia sasanqua, Euonymus fortunei, Parthenocissus tricuspidata; The shade-tolerent species include Osmanthus fragrans, Hypericum wilsonii, Liriope platyphylla, Gardenia jasminoides, Pittosporum brevicalyx, Nandina domestica, Aucuba japonica, Kerria japonica, Trachelospermumjasminoides, Campsis grandiflo, Hedera helixs. The shade-non-tolerent species include Acer palmatum, Lagerstroemia speciosa, Photinia-errulata, Photiniaxfraseri,Edgeworthia chrysantha, Viburnum odoratissimum var.awabuki. Rhododendron simsii, Mahonia fortunei, Buxus sinica, Nerium indicum, Yucca smalliana,Euonymus japonicas, Oxalis corymbosa. |
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