Analysis of Net Photosynthetic Rate,Transpiration Rate Change and Its Influencing Factors of Saxifrage in Winter
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Comparison between diurnal variation of photosynthetic rate and transpiration rate,the influencing factors of cultivars and wild species of Saxifrage leaves in the Xiangxi winter was analyzed by Li-6400 portable photosynthesis system.The results showed that the net photosynthetic rate of Saxifrage showed a single peak in the winter,the net photosynthetic rate peaks of wild(14:30) was later than that of the cultivated species(13:00),and the average net photosynthetic rate of the wild species was significantly lower than that of cultivated species.Transpiration rate was not fully synchronized with net photosynthetic rate.The lowest value was at 10:00 by the air humidity.Correlation studies indicated that the photosynthetic active radiation and temperature were the major environmental factors to net photosynthetic rates.And the transpiration rate was affected by the humidity of the air.The internal physiological factors were non-stomatal factors that affected net photosynthetic rate and transpiration rate.Keywords:
Air humidity
Photosynthetically active radiation
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As an important species of plant used in urban landscape construction in China,Osmanthus fragrans is deployed in up to 98.88% in the greening of Shanghai residential areas.Present studies of Osmanthus fragrans are focused on its planting,cultivation and conservation,but that on photosynthesis and transpiration is sparse.Diurnal Variation of Net photosynthetic rate of Osmanthus fragrans under natural condition was measured by using LICOR-6400XT portable photosynthesis system in winter and in summer.And transpiration,intercellular CO2 concentration,stomatal conductance,air temperature,relative humidity,and photosynthetically active radiation were also measured at the same time.The paper analyzed the relation among net photosynthetic rate,physiological factors and environmental factors,and discussed the difference of net photosynthetic rate between in winter and in summer and the adaptive strategies to air temperature.The results were as follows.With the increased of T and GS,Pn increased gradually.And when it got the limitation of stomata regulation,Pn got the maximum and then deduced slightly.Efficiency of photosynthesis was lower in winter than in summer.By enlarging the adaptation range of light and fully using the optimum temperature and light at noon,Pn and fixed carbon content maintained at a high level.The hurt of High temperature and high light was avoided by Midday depression of photosynthesis and high transpiration in summer.The ability of carbon fixation had few differences between that in winter and in summer,and the water use efficiency in summer was much lower than that in winter.
Osmanthus fragrans
Photosynthetically active radiation
Stomatal Conductance
Diurnal temperature variation
Water Use Efficiency
Shading
Noon
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Photosynthetic characteristics were studied in mature leaves of Phalaris arundimacea using portable LI-6400 photosynthesis instrument(Licor,USA) in the field.The diurnal changes of net photosynthetic rate and its major affecting factors,including photosynthetically active radiation(Par),stomatal conductance(Cond),intercellar CO_2 concentration(Ci),leaves temperature(Tl),air temperature(Ta),transpiration rate(Tr),were measured.The results showed that the diurnal process of photosynthetic rate exhibited a double peak curve in which the main peak appeared around(10∶00),and the second around(15∶00).This may reflected an obvious phenomena of midday depression of photosynthesis caused by Non-stomatal limition.Diurnal variation of net photosynthetic rate is 5.86-20.64 μmol·m~(-2)·s~(-1),and transpiration rate is 2.8-6.22 mmol·m~(-2)·s~(-1).And the other parameters,light compensation point is 40 μmol·m~(-2)·s~(-1),light saturation point 2100 μmol·m~(-2)·s~(-1),apparent quantum yield 0.0565 mol·mol~(-1),dark(respiration) rate 2.26 μmol·m~(-2)·s~(-1),and water use efficiency is 2.31-3.65 μmol·mmol~(-1).The data showed that P.arundimacea was a kind of highly photosynthetic efficiency plant,(illumina-)ting for the exploitation of resources and maintaining the eco-stability of wetland ecosystem.
Photosynthetically active radiation
Compensation point
Stomatal Conductance
Water Use Efficiency
Diurnal temperature variation
Respiration rate
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Photosynthetic diurnal variations of three materials of A.cristatum was determined by Li-6400 portable photosynthesis analyzer under dry conditions, which had been introduced and cultivated. The results showed that the diurnal variations of photosynthetic rates presented double peak, and the first peak of the materials were in 10:00, and the second were in 14:00, and the phenomenon on noon break were obvious, and especially the material from Shanxi had evident noon break phenomenon, while the net photosynthetic rate of the local A.cristatum was higher than the mean and the maximum of the two other materials; the diurnal variations of transpiration rate, stomatal conductance and leaf water pressure deficit were single peak, and the peak time were not inconsistent, and the mean or maximum of these parameters expressed as NMC3 HBC1 SXC2 by comprehensive comparison; chlorophyll a and chlorophyll b among three materials showed consistent trend; PAR and Ca had the greater effect on the diurnal dynamics of Pn, and its physiological factors were chlorophyll b and VPD, while RH and Ca had the greater effect on the diurnal dynamics of Tr, and its physiological factors were VPD and chlorophyll a. The materials from similar eco-geographical situations, which had been introduced and cultivated, had better photosynthetic Characteristic and strong compatibility.
Noon
Diurnal temperature variation
Stomatal Conductance
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CID-340Portable photosynthetic system was employed to measure the net photosynthetic rate,intercellular carbon dioxide concentration,photosynthetically active radiation,stomatal conductance,atmospheric temperature around the leaves,leaf temperature,and transpiration rate of Hydrocotylev ulgaris to study the photosynthetic characteristics in ecological ditch.The objective was to provide theoretic bases for ditch wetland restoration.The results were as follows:(1) The net photosynthetic rate of Hydrocotylev ulgaris changed in a double-peak curve with its peaks occurring separately at 11:00(16.21 μ mol.m-2.s-1) and 15:00(19.32 μ mol.m-2.s-1),which indicated a photosynthetic midday depressions at noon.(2) The regression equation of the diurnal variation of Pnand its major physi-ecological factors attained by the method of stepwise multiple-regression was as follows:Pn=-5.45613+0.006797PAR+0.050099Gs(multiple correlated coefficient 0.868).The results indicated that stomatal conductance(Gs) and transpiration rate(Tr) were the important factors that affected Pn.The analysis of partial correlation and path on Pnand factors showed that the diurnal variation of Pnhad significan impact with photosynthetically active radiation(PAR) and stomatal conductance(Gs),were the important factors which affected Pnand he order of effecting ability was GsPAR.
Photosynthetically active radiation
Stomatal Conductance
Diurnal temperature variation
Water Use Efficiency
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In order to discuss photosynthetic characteristics of Cyclamen persicum leaves and effects of environmental factors on photosynthetic rate , the experiments were conducted to study diurnal changes and seasonal fluctuation of the net photosynthetic rate and major environmental factors .The net photosynthetic rate reaches peaks at 10 :22 and 13 :42 respectively in dry-heat conditions .And it reaches also peaks on June and October in one year respectively .Hard photosynthetic photon flux , high air temperature and low relative humidity result in sleeping at noon for Cyclamen persicum leaves .The diurnal changes and seasonal fluctuation of net photosynthetic rate are affected by major factors , i .e .photosynthetic photon flux , air temperature , stomatal conductance , transpiration and relative humidity as well .The net photosynthetic rate , the light-saturating photosynthetic rate and the light compensation photosynthetic rate of middle-part leaf are higher than those of lowerpart leaf .Shading and spraying are contributed to improving the microclimate condition of Cyclamen persicum growth , increasing anti-high-temperature and efficiency for sloar energy utilization , decreasing sleeping in summer .
Microclimate
Shading
Stomatal Conductance
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In order to discuss the photosynthesis characters of mulberry in Yunnan laterite plateau,Nongsang 12 in Heqing Yunnan were used as experimental materials to analyze the diurnal variation of net photosynthetic rate,transpiration rate,other photosynthetic characteristic parameters and corresponding environmental factors.The results showed that the curves of daily variation of net photosynthetic rate displayed a bimodal curve and an obviously midday depression.The lower net photosynthetic rate at noon was mainly affected by non-stomatal limitation factors.The curves of daily variation of transpiration rate and stomatal conductance displayed bimodal curves,and showed significantly positive correlation.Diurnal variation of intercellular CO2 was reverse of that of net photosynthesis rate basically.The environmental factors affected the photosynthetic characteristic parameters of mulberry,and photosynthetic effective radiation played a decisive role on net photosynthetic rate.
Diurnal temperature variation
Stomatal Conductance
Noon
Photosynthetically active radiation
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Diurnal changes of leaf net photosynthetic rates of two cultivars of Pueraria lobata were measured using the CIRAS-Ⅰ portable photosynthesis system(PP-Systems Co.,British),and the relationship among diurnal changes of net photosynthetic rates and those of environmental factors were analyzed.The results showed that diurnal changes in the net photosynthetic rates of both two cultivars could be interpreted as double-peak curves,i.e.they possessed obvious so-called midday depression phenomenon.Further analyses showed that the correlation between net photosynthetic rate and stomatal conductance was positive and extremely significant(P 0.01),the correlations between net photosynthetic rate and intercellular CO2 concentration as well as the transpiration rate were positive and significant(P 0.05),and the correlations between net photosynthetic rate and air temperature as well as leaf temperature were negative and significant(P 0.05).The results indicate that among the factors affecting photosynthetic characteristics,some of them could be grouped as stomatal restrictions,while the others could be grouped as non-stomatal restrictions.
Lobata
Stomatal Conductance
Diurnal temperature variation
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Under different cultivation density,net photosynthetic rate,transpiration rate and related physiological factors(leaf temperature,stomatec conductance,intercellular CO2 concentration) and ecological factors(PAR radiation,atmospheric CO2 concentrations,temperature and relative humidity of the atmosphere) of Ranunculus ternatus Thunb.during the fruiting stage were mea-sured and analyzed by using CI-340 portale photosynthesis system.The results showed that with the increase of the cultivation density,the net photosynthesis and stomatic conductance were increased slowly firstly,and then decreased significantly.While the transpiration rate showed a trend of high-low-high,internal CO2 concentration significantly increased with the increase of density.Coefficient analysis showed that the atmosphere relative humidity(RH),CO2 concentration in the field,stomatic conductance(Gs) and leaf temperature(Tl)were the main factors influencing the characteristics of photosynthesis and transpiration.Non-stoma-related factors affected net photosynthetic rate(Pn) changes under high-density conditions,while under low-density conditions stomatic factors affected net photosynthetic rate(Pn) changes.
Stoma (medicine)
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The Photosynthetic changes of trifolium L.were studied at the full light and light shaded conditions.The results showed that the net photosynthetic rates of the trifolium L under full light were higher than those under light shaded conditions.The daily patterns of net photosynthetic rate and transpiration rate appeared as double-peak curves.The stomatal limitation was the main factor of midday photosynthetic break.The trends of diurnal stomatal Conductance was similitudear to the diurnal net photosynthetic rates,and the intercellular CO2 concentration has a negative relationship to the net photosynthetic rate.The diurnal curves of Pn,Tr,Gs,Ci under light shaded conditions were different to full light conditions.
Stomatal Conductance
Diurnal temperature variation
Light intensity
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The leaf photosynthetic parameters of the introduced Macropanax rosthornii were measured by LI-6400 portable photosynthesis system and its photosynthetic and physiological characteristics were investigated so that the results can provide a scientific guidance for its introduction and landscape application. The results showed that the diurnal course curves of the net photosynthetic rate, photosynthetically active radiation, air temperature, transpiration rate and stomatal conductance had peaks without midday depression; The relativity analysis indicated that the key ecological factors of photosynthetically active radiation, air temperature, the physiological factors of stomatal conductance and transpiration rate played key roles in the net photosynthetic rate, the yearly course curve of the net photosynthetic rate had a single peak, in which the net photosynthetic rate was in the peak in June and July of summer season, and in the middle in either spring or autumn and at the bottom in winter; No strong light suppression was found on the photosynthetic light response curve of M. rosthornii; The maximum net photosynthetic rate, light saturation point, light compensation point, and dark respiration rate simulated by modified rectangular hyperbola were 6.902 μmol·m-2s-1,1013.163 μmol·m-2s-1,4.794 μmol·m-2s-1 and 0.290 μmol·m-2s-1 respectively, and thereby the findings suggested that M. rosthornii had a good shade-tolerance and adaptation to weak light, so it was advisable for growing under shading conditions.
Photosynthetically active radiation
Compensation point
Stomatal Conductance
Shading
Respiration rate
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