Study On Photosynthetic And Stomatal Characteristics Of Two Kinds Of Liriopogons

Liriope platyphylla and Ophiopogon japonicus are perennial evergreen herbs,belong to Liriope and Ophiopogon respectively.They are widely distributed in China and are often used in landscape architecture and medicinal material production.In order to develop undergrowth planting on a large scale and provide a theoretical basis for the practice of production in the future,it is necessary to know the adaptability about photosynthetic and stomatal characteristics of Liriopogons in different habitats（forestry gap and forestry canopy）.In this study,the adaptability of L.platyphylla and O.japonicus to seasons and habitats was studied by measuring the photosynthetic parameters,chlorophyll fluorescence parameters,photosynthetic pigments content and stomatal characteristics.The main results are as listed.（1）L.platyphylla only appeared“midday depression of photosynthesis”in summer,and O.japonicus appeared“midday depression of photosynthesis”in both summer and winter.The reason of“midday depression of photosynthesis”appeared under the forest gap of L.platyphylla and under the forestry canopy of O.japonicus was combined effect of stomatal and non-stomatal restrictions.The reason of“midday depression of photosynthesis”appeared under the forestry canopy and the forest gap of L.platyphylla in summer,and under the shade of O.japonicus in winter was stomatal limitation.In the two environments,the photosynthetic potential and the ability of utilizing weak light of L.platyphylla were both reached to the highest in autumn,and L.platyphylla can adapt to the largest range of light intensity in summer.In the same environments,the photosynthetic potential of O.japonicus was reached to the largest in autumn,and utilization of light energy was reached the largest in winter.The photosynthetic capacity of O.japonicus under the forestry canopy was stronger than that under the forest gap.（2）In L.platyphylla,the main direct effect on net photosynthetic rate was temperature in summer forest gap,while in summer forestry canopy was stomatal conductance;the transpiration rate was the main factor in autumn forest gap,while in autumn forestry canopy was temperature.In O.japonicus,the main direct effect on net photosynthetic rate was stomatal conductance in summer forest gap,while in summer forestry canopy was photosynthetic active radiation;the relative humidity was the main factor in autumn forest gap and winter forestry canopy,while in autumn forestry canopy was external CO₂ concentration;and in winter forest gap was photosynthetic active radiation.（3）The optimal/maximal quantum yield of PSⅡ（Fv/Fm）values of the two Liriopogons were stable in all seasons,and the non-photochemical quenching（NPQ）value was increased gradually with the seasonal variation and reached the highest in winter.The results suggested that L.platyphylla and O.japonicus both have adaptability under forestry environment.The Fv/Fm and photochemical quenching（q P）value of L.platyphylla was higher than O.japonicus under forest gap in summer.The result suggested that adaptability to high temperature and high light of L.platyphylla was stronger than that of O.japonicus.The q P and relative electron transfer rate（ETR）values of O.japonicus in the two environments had little difference.The light use and electron transfer efficiency of PSII were less affected by the changes of light environment,suggested that O.japonicus could adapt to various light environments.（4）The contents of chlorophyll b and chlorophyll a+b in L.platyphylla and O.japonicus were reached the highest under the forestry canopy in autumn,while the chlorophyll a/b value was the lowest.The result suggested that the two plant could adapt to the decrease of light intensity by optimizing the ratio of photosynthetic pigments.The content of chlorophyll b and chlorophyll a+b in L.platyphylla was lower than in O.japonicas,but the content of carotenoids was opposite,suggested the adaptability of L.platyphylla to weak light environment was not as good as that of O.japonicas,however its light protection ability is stronger than O.japonicas.（5）L.platyphylla and O.japonicus adapted to the forest gap environment by increasing stomatal density and reducing stomatal area.The correlation analysis of stomatal width and stomatal conductance between L.platyphylla and O.japonicus in different seasons and habitats reached a significant positive correlation.The results suggested stomatal opening of Liriopogons coudle directly effect net photosynthetic rate by regulate its stomatal conductance and transpiration rate.