Diurnal Variation of Net Photosynthetic Rate and Influencing Environmental Factors of Hedera Nepalensis var. Sinensis Under Drought Stress
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The relation between diurnal variation of leaf net photosynthetic rate (Pn) and eco-physiological factors for three years old leaf of Hedera nepalensis var.sinensis under drought stress was analyzed using CIRAS-2 portable photosynthesis system.The diurnal variation of H.nepalensis var.sinensis photosynthesis and its midday depression phenomenon was explained clearly and its predominant environmental factors under drought stress were ascertained.Results showed that diurnal variation of H.nepalensis var.sinensis photosynthesis and its micro-environmental factors were connected with soil moisture nearly at the same time.With the aggravation of drought stress,the daily average and maximum Pn was decreased significantly.Compared with check treatment,the means of Pn in the drought stress of mild treatment,moderate treatment,and severe treatment were reduced by 15%,47%,and 70%,respectively.With the aggravation of drought stress,the diurnal variation of photosynthesis changed from a single peak curve to a double peak curve and the predominant cause of midday depression turned into non-stomatal limitation.By the methods of stepwise multi-regression and principal component analysis,there was an obvious difference in the environmental factors of impact Pn under different drought stresses.Under the condition of mild soil moisture,the causes of diurnal variation of Pn can be classified into two categories:one was air temperature,relative humidity and CO2 concentration and another was photosynthetic active radiation.The effects of photosynthetic active radiation,CO2 concentration,and relative humidity on Pn became more and more conspicuous with increase in drought stress and relative humidity was the dominant factor.Keywords:
Diurnal temperature variation
Drought stress
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In order to improve cultivation techniques of chestnut and enhance photosynthetic efficiency,diurnal variations of photosynthesis and some related factors were researched,taken Yanlong chestnut with 2 years as materials.The results showed that the curve of diurnal variations of net photosynthetic rate had 2 peaks,which were at 10:00 and 15:00 respectively,and midday depression was significant at 13:00-14:00;net photosynthetic rate was decreased after removing stamens;the trend of diurnal variations of stomata conductance was consistent with that of photosynthetic rate,but that of transpiration rate had only a peak which appeared at 13:00;intercellular CO2 concentration was high during midday depression.Air temperature,leave temperature and transpiration rate were increased with increasing of light intensity at noon,while stomata conductance and photosynthetic rate were decreased.
Noon
Diurnal temperature variation
Stomatal Conductance
Light intensity
Water Use Efficiency
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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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Comparative study on photosynthesis of medicinal plant Saposhnikovia divaricata in different periods
The diurnal changes in net photosynthetic rate(Pn)of Saposhnikovia divaricata(Turcz.)Schischk.and their relationships with photosynthetic active radiation(PAR),atmospheric CO2 concentration(Ca),ambient temperature(Ta),leaf temperature(Tl)and relative humidity(RH)were studied systematically in different periods.This knowledge is essential for formulating generalization regarding the cultivation of the species in Jilin Province.Results showed that the diurnal changes in Pn of the species in different periods were similar and could be expressed as two-hump curves,reflecting a significant middy depression.The decrease in Pn during midday was mainly resulted from non-stomatal limitation in July,but stomatal limitation occurred in August and September.High temperature and low relative humidity were critical factors constraining Pn in July.The non-synchronous change of Pn and E were the main reason leading the variations of WUE.PAR affected Pn,synthesis and transformation of organic matter,which restricted the production for S.divaricata.There was a significantly and positively correlation between the Pn and PAR(P0.05).The responses of S.divaricata leaves to the environmental factors were different during growing season,and the direct effects of environmental factors in three different months were of the order:TaPARTlCaRH in July,TlPARTaRHCa in August,TaPARTlCaRH in September.
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Diurnal variation of net photosynthetic rate(Pn) of the leaves of Scutellaria baicalensis and its mutual relationship with environmental factors were studied.The results showed that net photosynthetic rate of S.baicalensis presented an atypical double-peak curve,with the peaks(19.33 and (15.45 μmol/(m~2·s)) respectively) appearing at 10:00 and 14:00.There appeared a slight phenomenon of photosynthesis midday depression,and the stomata factors caused the decrease of Pn.The diurnal variation of transpiration rate presented a one-peak curve in the leaves of S.baicalensis,and the peak of transpiration rate measured at 10:00 was mmol/(m~2·s);The diurnal variation of stomatal conductance presented a double-peak curve in the leaves of S.baicalensis,and the peaks of stomatal conductance measured at 10:00 and 14:00 were 381and 301 mmol/(m~2·s).The positive relationship between net photosynthetic rates and stomatal conductance of S.baicalensis was extremely significant(P0.01), the positive relationship between net photosynthetic rate and transpiration rate was significant(P(0.05).) The low atmospheric CO_2 concentration was the main environmental factor which influenced the Pn of S.baicalensis.
Stomatal Conductance
Diurnal temperature variation
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Using melon of Yujinxiang, the main melon cultivar on grave-mulched field in Ningxia, as the material to determine the diurnal variation of the net photosynthetic rate and the other influential factors such as air temperature, blade temperature, photosynthetic active radiation(PAR), transpiration rate(E), stomatal conductance(Cond), intercellular CO2concentration(Ci) and water use efficiency(WUE) in the periods of fruit-set and maturity. The results showed that in the two growing period, the photosynthetic diurnal variation tendency were different, the diurnal variation of photosynthetic rate in the fruit-set period had double peak curves and midday depression; while in maturity period it presented one peak curve. The stomatal limitation may be the main factor which influences the photosynthesis.
Diurnal temperature variation
Stomatal Conductance
Melon
Water Use Efficiency
Photosynthetically active radiation
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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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The CI-340 photosynthetic system was used to monitor the photosynthetic diurnal variation of Eupatorium adenophorum at the reproductive stage and determine the relationship between photosynthetic diurnal variation and environmental factors for providing the useful information for control E.adenophorum in natural condition.The results of this study indicated that the diurnal variation of net photosynthetic rate(Pn) presented a double-peak curve,peaking at 11:00 and 13:00,and this study also showed an obvious midday depression.The stomatal conductance(Gs) and transpiration rate(Tr) were positively consistent with Pn from 9:00 to 14:00,and then increased slightly,and they showed a three-peak curve.The intercellular CO2 concentration(Ci) was significantly negative correlation with stomatal limitation value(Ls)(R=-0.997 6**),presenting the single-peak curve.At the reproductive stage of E.adenophorum,Pn was mainly affected by Tr,Leaf Water Deficit and leaf temperature,and greatly regulated by photosynthetic active radiation(R=0.860 0**).This study suggested that the comprehensive control measures of E.adenophorum focused on choosing the more strongly photosynthesis replaced plants,herbicide,chemical control time.
Diurnal temperature variation
Stomatal Conductance
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The photosynthetic rate in leaves of grape is an important physiological index which can provide important reference basis for the adaptability research of grape. The study was performed by using Yaxin-1102 portable photosynthesis transpiration device to measure the diurnal variation of photosynthesis rate in leaves of‘jumeigui'during the fruit enlargement period,and to study the effect of environmental factors on diurnal variation of net photosynthesis rate through correlation analysis. The results showed that the diurnal variation of photosynthesis rate in leaves of‘Jumeigui'had two peaks,at 11: 00 and 17: 00 for peaks,and at 13: 00 for depression; The photosynthesis obviously existed‘midday depression'phenomenon,and the decline of net photosynthesis rate was regulated by non-stomatal limitation index; Pn could resume even exceed the previous level after‘midday depression'. The results indicated that‘Jumeigui'has a strong adaptability for adverse photosynthesis conditions.
Diurnal temperature variation
Adaptability
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[Objective] The research aimed to study the effects of water stress photosynthetic characteristics in L.fischeri [Method] The effect of water stress on diurnal variation of photosynthetic performance in one year old potted L.fischeri at the 12th day after the water stress and the natural condition treatment was investigated.[Result] The diurnal variation curves of Pn,Tr and WUE were double-peak types under the natural condition,but the curves of Pn、Tr and WUE turned to single-peak types with low peak values under severe stress.The decrease of net photosynthesis rate was caused by stomatal and non-stomatal inhibition.while under severe stress by the non-stomatal factors.[Conclusion] The photosynthesis of.L.fischeri exhibited a certain adaptability to water stresses except severe stress in city.
Water Stress
Adaptability
Water Use Efficiency
Drought stress
Diurnal temperature variation
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