作 者 ：王云贺,韩忠明,韩梅,杨利民*
期 刊 ：生态学报 2010年 30卷 24期 页码：6762~6770
Keywords:shading, net photosynthetic rate, diurnal changes, chlorophyll, biomass,
摘 要 ：遮荫处理对东北铁线莲生长发育和光合特性的影响
Abstract:The experiments took Clematis manshurica Rupr. a medicinal plant, as material, studied the effects of five different shading levels (Shading of 0, 30%, 50%, 70% and 90%) on its growth and photosynthetic characteristics, and it is essential for its normalized cultivation in Jilin Province, Northeast China. The photosynthetic parameters, dry matter accumulation as well as chlorophyll contents in the leaves of C. manshurica were measured. The results indicated that the contents of total chlorophyll, chlorophyll a and chlorophyll b in leaves under the shading conditions were significant higher than under the full daylight; the chlorophyll contents increased with the increasing of shading levels, and it reached the top point under the shading of 90%. However, the variation trend of chlorophyll a/b was contrary. The specific leaf area of C. manshurica increased with the weakening of light intensity, so the accumulation of photosynthetic products was produced by increasing the total photosynthetic area under lower light intensity. The diurnal changes in the net photosynthetic rate of C. manshurica in full light could be expressed as two-hump curves, reflecting a significant middy depression at noon, but the middy depression was not obvious in the shading of 30%; the effects of shading treatments on transpiration rate and stomatal conductance were different significantly, and the values of transpiration rate and stomatal conductance of C. manshurica decreased with the increasing of shading levels; the diurnal average of net photosynthetic rate and module biomass of C. manshurica were increased firstly, and then decreased along the shading gradient. There were significant effects of shading on the net photosynthetic rate, the biomass of the root and rhizomes, stems and leaves of C. manshurica. A sharp increase dry matter accumulation of C. manshurica was observed in the shading of 30% compared with the other levels. The light intensity and the canopy temperature were markedly reduced in the shading of 30%, but the relative humidity was increased. Consequently, the temperatures of leaf surface were decreased, which can improved canopy microclimate conditions and eliminated the phenomenon of “midday depression” effectively. At the same time it increased the net photosynthetic rate and the module biomass of C. manshurica, in other words, appropriate shading was conducive to its matter production. But the net photosynthetic rate and the total accumulation of photosynthetic products of C. manshurica were decreased with the increasing of shading levels. The stems were short, the biomass of the root, rhizomes, stems and leaves were decreased. The diurnal changes in the net photosynthetic rate in the shading of 50%, 70% and 90% could be expressed as the single peak curve, and the overhead shading could effectively overcome the harm caused by high temperature and strong light, but the photosynthetic efficiency of C. manshurica was deceased because of lower light. The excess shading significantly decreased the photosynthesis and module biomass, and it could bring unfavorable effects to the growth of C. manshurica. In conclusion, the above experiment showed that appropriate shading was propitious to increase the net photosynthetic rate of C. manshurica in the practical production, which is the important measure to increase the output of C. manshurica.
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