Research On The Photosynthetic Physiological Characteristics Of Leymus Chinensis From Leaf-colored Gradient Populations

In the natural grassland of Leymus chinensis,we can often see the scattered patches distribution of L.chinensis populations with different-colored leaves.The morphological structure and other aspects of L.chinensis populations had occured stable genetic differences of L.chinensis due to adapting to various complex ecological conditions in the natural world for a long period of time,resulted in distinct leaf-colored gradient populations with different-colored leaves phenotypes.In this experiment,three leaf-colored Leymus chinensis populations were studied.The diurnal variation of photosynthetic activity and its relationship with environmental factors,the relationship between photosynthetical active radiations and net photosynthetic rates,and photosynthetic activity of leaves of different leaves positions were studied.The results provide a scientific basis for more in-depth and systematic understanding of the photosynthetic mechanism of different-colored leaves Leymus chinensis populations,exploring the photosynthetic physiological changes of Leymus chinensis from leaf-colored gradient populations,and further determining the differentiation of Leymus chinensis from leaf-colored gradient populations.It is of great significance to cultivate high quality Leymus chinensis varieties.The main findings are as follows:1.Comparison of diurnal variations of photosynthesis of Leymus chinensis from leaf-colored gradient populations.The diurnal variations of the net photosynthetic rate?Pn?and transpiration rate?Tr?of Leymus chinensis from leaf-colored gradient populations showed double peaks curves,and the peaks appeared at 8:00 and 14:00respectively.There was a clear"photosynthetic lunch break"phenomenon.Pn was higher in the morning than the afternoon.The diurnal variations of the stomatal conductance?Cond?showed a single peak curve,the peak appeared at 8:00.The intercellular CO₂ concentration?Ci?was higher in the early morning and late evening.The daily average value of net photosynthetic rate,transpiration rate and stomatal conductance of three leaf-colored Leymus chinensis were gray-green Leymus chinensis>transgenic Leymus chinensis>yellow-green Leymus chinensis;the daily average value of water use efficiency?WUE?was yellow-green leaves>transgenic leaves>grey-green leaves.Correlation analysis showed that the main factors affecting the net photosynthetic rate of Leymus chinensis from leaf-colored gradient populations were Cond,Tr,PAR and Ta.2.Comparison of photosynthetic response curves to light intensity in Leymus chinensis from leaf-colored gradient populations.The maximum net photosynthetic rates?Pnmax?were grey-green Leymus chinensis>transgenic Leymus chinensis>yellow-green Leymus chinensis,and the light compensation points?LCP?were transgenic Leymus chinensis>grey-green Leymus chinensis>yellow-green Leymus chinensis,the light saturation points?LSP?were grey-green Leymus chinensis>transgenic Leymus chinensis>green-yellow Leymus chinensis,dark respiration rates?R_d?were transgenic Leymus chinensis>grey-green Leymus chinensis>yellow-green Leymus chinensis,the apparent quantum efficiencies?AQE?were grey-green Leymus chinensis>yellow-greenLeymuschinensis>transgenicLeymuschinensis.The maximum net photosynthetic rate?Pnmax?and the apparent quantum efficiency?AQE?of the grey-green Leymus chinensis were the highest,indicating that the light energy efficiency of the grey-green Leymus chinensis was the highest.Compared with the transgenic Leymus chinensis,the light compensation point was lower and the light saturation point higher of the grey-green Leymus chinensis,indicating that the grey-yellow Leymus chinensis had a stronger ability to adapt to the light environment.The light response parameters of the yellow-green Leymus chinensis were relatively low,and the ability to use weak light was stronger.3.Comparison of leaf photosynthetic ability in different leaves positions of Leymus chinensis from leaf-colored gradient populations.The net photosynthetic rate,stomatal conductance,and transpiration rate of different leaves positions of Leymus chinensis indicated a trend of“low-high-low”with the increase of leaf position,whose maximum value emerged at 2rd-4rd leaves.Pn and Cond were significantly positively correlated;intercellular CO₂ concentration increased slowly with the increase of leaf position,and the maximum value appeared in the lower leaf position.The water use efficiency of the middle and upper leaves were higher than that of the lower leaves.Differences in leaf traits at different leaves positions in Leymus chinensis from leaf-colored gradient populations.The leaf dry matter contents?LDMC?gradually increased,leaf water contents and specific leaf areas?SLA?gradually decreased with the increase of leaf position.Pn and leaf water contents and SLA significant or very significant positive Correlation,and LDMC significantly or extremely negatively correlated.The chlorophyll a,chlorophyll b,total chlorophyll and carotenoid contents firstly increased and then decreased with the increase of leaf position,Pn and photosynthesis pigment contents were extremely or significantly positively correlated of the yellow-green Leymus chinensis.The net photosynthetic rates,stomatal conductances,transpiration rates,and photosynthetic pigment contents in same leaves positions of the three leaf-colored L.chinensis were the highest in the grey-green Leymus chinensis,followed by the transgenic Leymus chinensis,and the lowest in the yellow-green Leymus chinensis.