| Tinospora sagittata is a vine of Tinospora(Menispermaceae)that grows vigorously and has excellent clingability.The underground roots of it can be used as medicine,and is one of the basic source plants of the common Chinese medicinal materia ’Tinosporae radix’.T.sagittata has great research potential in the development of medicinal value and plant landscape landscaping.However,the main source of T.sagittata is still dependent on field collection at present,which has caused resource slack due to long-term over-excavation.In response to this situation,this study explored the effects of different light intensities on the growth and physiological indicators of T.sagittata,as well as the influence of photosynthetic index,which has important theoretical basis and practical value for the large-scale artificial cultivation and quality control of T.sagittata.In this study,two-year-old T.sagittata was taken as the research object,and 4 light intensity ranges under the forest were set for shading treatment.The following conclusions are drawn in the research.(1)In the condition of 50%～70%light transmittance,the plant height of T.sagittata was suitable.Furthermore,the number and the area of leaves were increased,and the accumulation of underground material together with the number of tubers were enhanced.Higher yield can also be obtained under this condition.(2)As the light transmittance decreases,the SOD,POD,CAT activities and the soluble protein content of T.sagittata all showed a significant increase trend,and the change trends were basically the same.It shows that under shading treatment,the defense mechanism of T.sagittata is rapidly activated.Therefore,proper shading can improve the activity of antioxidant enzymes,increase the production of soluble protein,and reduce the content of MDA of T.sagittata.(3)The trends of the photosynthetic pigments of T.sagittata were similar.With the deepening of shading degree,the chlorophyll content increased,the value of chlorophyll a/b decreased,and the ratio of carotenoid to chlorophyll increased,which indicated the adaptability of T.sagittata to low light.(4)In August and September,The light saturation point is 657～797 μmol·m-2·s-1,the light compensation point is 5.68～12.92 μmol·m-2·s-1,and the CO2 saturation point is 1192～1755 μ mol·m-2·s-1,The CO2 compensation point is 74～123 μ mol·m-2·s-1.It indicates that T.sagittata has a wide range of light adaptation and strong carbon sequestration ability.Under the light transmittance of 50%～70%,there is no ’midday depression of photosynthesis’phenomenon,the water use efficiency and apparent quantum efficiency are high,and the transpiration rate is low.The results showed that moderate shading is beneficial to improve the photosynthetic of T.sagittata and promotes its growth and development.(5)The Fv/Fm of the maximum photosynthetic efficiency of PSII was significantly different among all treatments.The Fv/Fm of the 10%～50%transmittance and 70%～90%transmittance were between 0.81～0.823,and the Fv/Fm of the 50%～70%transmittance was between 0.835～0.84.However,the threshold of photoinhibition is 0.832,which indicated that moderate shading would not lead to photoinhibition of plants and could increase the maximum photosynthetic efficiency of plants.(6)Under the transmittance of 10%～30%,the correlation between the aboveground growth index and the underground growth index was the highest,and the correlation between the growth index and the antioxidant enzyme activity was also high.Moreover,with the decrease of shading degree,the correlation between the indexes of T.sagittata seedlings was gradually weakened.It showed that there was a complex synergistic growth relationship between the growth factors of T.sagittata under severe shading stress.In summary,50%～70%light transmittance is most conducive to the growth of two-year-old T.sagittata especially the tubers. |
PDF Full Text Request