The Response of Transpiration Rate of Malus pumila cv.Goldspur to Illumination and Soil Moisture

We tested the transpiration rate ( Tr ) of seven\|year\|old field and two\|year\|old potted Malus pumila cv.Goldspur under different conditions of illumination and soil water. The results showed that the interrelationship between Tr of Malus pumila cv.Goldspur and illumination and soil water content ( SWC ) was quite remarkable. Tr increased with the increase of light intensity and SWC . However, when one of the environmental stresses of illumination and water existed, the improvement of the other condition couldn't make Tr rise greatly. Only when SWC was higher than 11%, which arrived at over 55% of the field content ( FC ), or the photosynthetic active radiation ( PAR ) higher than 400?μmol·s -1 m -2 , Tr could rise greatly with the increase of PAR or SWC . But when SWC was higher than 15%, which reached over 75% of FC or PAR higher than 1?000?μmol·s -1 ·m -2 , Tr would not change a lot with the change of PAR or SWC . That PAR and SWC influenced the magnitude of stomatic resistance( RS ) and leaf water potential ( Ψ l) was the basic reason for the Tr responded to them. Light stress reduced the open degree of stomas, so when severe light stress existed ( PAR <100?μmol·s -1 ·m -2 ), RS was larger ( RS >2 0?s·cm -1 ), which led to the decrease of Tr(Tr <5?μgH 2O·s -1 ·cm -2 ). When severe water stress existed( SWC <11% and<55% of FC and soil water potential Ψ ws <-1 15?MPa), RS was higher than 4 00?s·cm -1 and Ψ l lower than -2 10?MPa, which led to Tr lower than 11?μgH 2O·s -1 ·cm -2 . When soil water was adequate( SWC >15% amd over 75% of FC , and Ψ ws >-0 50?MPa), RS was lower than 2 00?s·cm -1 , Ψ l higher than -1 65?MPa and Tr would be higher than 15?μgH 2O·s -1 ·m -2 . The range of SWC , 11%～15%, which accounted for 55% to 75% of FC , and correspond RS (2 00～4 00?s·cm -1 ) were the turning area, where the variable curve of Tr transited from a variable trend to another variable one. It could be considered as the range to control soil water.

Phosphate Distribution and Movement in Soil－Root In－terface Zone：I． The Influence of Transpiration Rate

The experiments were conducted in the artificial climate laboratory using ￣(32)P labelled soil and soil-rootplane system to investigate phosphate distribution and its movement in the soil-root interface zone andtheir relations with phosphate uptake by plant as well as transpiration rate (atmosphere humidity). It wasfound that although the phosphate in the soilroot interface zone was of depletive distribution as a functionC/Co = ax￣b(C/Co is the relative content of fertilizer phosphate in a distance from the root surface x, aand b are the regression constants), and a relative accumulation zone of phosphate within 0.5 mm near theroot surface was often observed especially in the heavier texture soils because of root phosphate secretion.The depletion intensity of phosphate in the soil-root interface zone was in agreement with the phosphateuptake by plants under two humidities very well. However, the effects of air humidity on characteristics ofthe phosphate distribution near wheat or maize root surface were different. Wheat grew better under loweratmosphere humidity while maize, under higher humidity, which caused a more intensive uptake and thusa stronger depletion of phosphate in the rhizosphere. Moreover, the depletion intensity was greater by thebottom or the middle part of wheat roots and by the top or the middle part of maize roots. The depletivedistribution of phosphate in the rhizosphere soil and the relative contribution of phosphate diffusion to plant,which was more than 98% in the cultural experiments, indicated that diffusion was a major process forphosphorus supply to plants.

Transpiration Rate and Leaf Water Potential as Indices for Cassava Yield in Inland Valley Ecology

Differences in transpiration and leaf water potential （LWP） in relation to cassava yield were investigated along inland valley toposequence in a 4×4 Latin square design. The landrace with the highest transpiration rate and lowest LWP yielded the lowest, while TMS 91/02324 and TMS 91/02327 with intermediate rate and highest LWP yielded the highest, indicating that high transpiration rate associated with low LWP reduced yield. Transpiration was lower in the fringe with deeper water table than valley bottom at deep water table site, while at shallow water table, it was higher in the fringe than valley bottom, suggesting that drought and excess moisture reduced transpiration. LWP and water table depth correlated negatively indicating that shallow water table reduced transpiration by reducing LWP. Transpiration increased and LWP decreased as radiation, leaf temperature and vapour pressure deficit increased and differences in these microclimatic conditions caused differences in the two processes between sites, years and time of day. Under mild water stress, transpiration and LWP were higher in the afternoon than the morning, but the reverse occurred under severe stress. TMS 91/02324 and TMS 91/02327 had the highest LWP under severe stress, indicating their higher drought tolerance than the other cultivars.

Photosynthesis and Transpiration Characters of Alfalfa (Medicago sativa) and Their Relationship with Relevant Factors during Branching Stage

[ Objective] The paper presents the diumal changes of photosynthesis and transpiration of different alfalfa varieties and their relationship with the associated physiological and ecological factors during branching stage, so as to provide a basis for the development, utilization, and breed- ing of alfalfa. [ Method] Under natural conditions, the diurnal changes of net photosynthetic rate （Pn）, transpiration rate （Tr）, the relevant physio- logical factors including leaf temperature （TI）, stomatal conductance （Gs） and intemal COn concentration （Ci）, as well as the relevant physiologi- cal factors including photosynthetic available radiation （PAR）, CO2 concentration in field （Ca） and air temperature （Ta） were measured in four al- falfa varieties （Algonguin, WL323 HQ, WL414, and Millionaire）. The water use efficiency （WUE） and light use efficiency （LUE） were calculated, and the correlation among them was also analyzed. [Result] The Pn, Tr, PAR and Ta of the four varieties appeared to vary in a single-peak curve; the sequence of WUE was WL323 HQ ~ Algonguin ~ WL414 ~ Millionaire; there was no significant difference in LUE of the four alfalfa varieties; coef- ficient analysis showed that Pn was mainly affected by PAR, Gs, and Ci, while Tr by PAR and Ta. [ Conclusion] WL323 HQ is the variety with high Pn, high WUE and low Tr, and it has strong adaptability to drought. In four alfalfa varieties, PAR, Ta, Gs, and TI are the primary determining fac- tors while Ca and Ci the limiting factors of Tr; Gs is the primary determining factor while Ci the limiting factor of Pn.

Subtropical Modern Greenhouse Cucumber Canopy Transpiration Under Summer Climate Condition

Greenhouse canopy transpiration not only has effects on greenhouse air temperature and humidity, but also is important for determining the set-point of fertigation. In this study, Penman-Monteith equation was used to calculate the greenhouse cucumber canopy transpiration under summer climate condition. The effects of greenhouse environmental factors on canopy transpiration were analyzed based on the measurements of greenhouse microclimate factors and canopy transpiration. The results showed that Penman-Monteith equation was reliable and robust in estimating greenhouse cucumber canopy transpiration under summer climate condition. Greenhouse cucumber canopy transpiration rate increased linearly with the increase of net radiation and water vapor pressure deficit (VPD) above the canopy. But the maximum value of the canopy transpiration rate occurred at the same time as that of VPD whereas about two hours later than that of net radiation. Based on the results, it was concluded that in addition to radiation, air humidity should also be considered when determine the set-point of fertigation.

Study on Transpiration and Stomatal Conductance Characteristics of C3 and C4 Plant

The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper （Capsicum annuum Linn.） and two C4 plants, sorghum （Sorghum bicolor L.Moench） and maize （Zea mays Linn.）. Three species were irrigated with three different water treatment levels of 100%, 66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress. The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m. and 16.00 p.m. with measurements about each 1.5 h with an infrared gas analyzer. The results showed that Z. mays probably due to a higher leaf area had very low values and was significantly different （LSD pairwise comparison） from C. annuum and S. bicolor. The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results. However, the hypotheses that for the same species, the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.

Transpiration of the Tamarind Artificial Forest in the Arid-Hot Valleys of Jinshajiang River,Yunnan

The transpiration characteristics of the tamarind artificial forest in the arid-hot valleys of Jinshajiang River, Yunnan were investigated through the measurement of the transpiration rate, stomatal conductance of tamarind leaf and the related envi- ronmental factors. The results showed that the transpiration of the tamarind in the clear sky had the close positive correlations with photosynthetically active radiation and air temperature and negative correlation with atmosphere moisture in the whole growth period. The daily change tendency of the transpiration rate was the similar with stomatal conductance, and the transpiration had the positive correlation with stomatal conductance. The transpiration rate of tamarind was highest in the rainy season of June and July and was relatively low in the drought season of March and April. The transpiration water consumption in rainy season of June and July was obviously higher than that in drought season of March and April. It fully suggested that the tamarind showed very good drought resistance and adaptability to the arid-hot valleys of Yunnan .

Responses of the seedlings of five dominant tree species in Changbai Mountain to soil water stress

Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc., Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fisch.ex Turcz) from the broadleaved/Korean pine forest in Changbai Mountain. Leaf growth, water transpiration and photosynthesis were compared for each species under three soil moisture conditions: 85%-100% (high water, CK), 65%-85% (Medium water, MW) and 45%-65% (low water, LW) of 37.4% water-holding capacity in field. The results showed that the characteristic of typical drought-resistance of the leaves is significantly developed. The net photosynthetic rate and water use efficiency of Fraxinus mandshurica were higher in MW than those in CK. But for the other four species, the net photosynthetic rate and water use efficiency in CK were lower than those in MW and LW. The transpiration rate responding to soil moistures varied from species to species.

Effects of Different Vibration Intensities Harvesting on Photosynthesis System Parameters of Lycium barbarum L. Trees with Harvest Machine

The effects of different vibration intensities harvesting on photosynthesis system parameters of Lycium barbarum L. tree with harvest machine were researched. The result showed that the photosynthetic rate, transpiration rate, stomata conductance and intercellular CO2 concentration of L. barbarum tree＇s leaves under different treatment during different periods have no significant difference compared with contrast. It indicates that there is no significant effect on photosynthesis system parameters of L. barbarum tree＇s leaves with harvest machine.

Studies on Photosynthetic Characteristics of Tomato Leaves after Inoculation with Tomato Powdery Mildew (Oidium neolycopersici)

[ Objective ] The paper was to explore the pathogenic mechanism of tomato powdery mildew, and to study the effects of the disease on photosynthetic characteristics of tomato. [ Method ] With four tomato varieties as materials, the pathogen of tomato powdery mildew was artificially inoculated. After the varieties were infected, the parameters including net photosynthetic rate, stomatal conductance and transpiration rate of tomato leaf were measured by Li-6400 portable photo- synthesis detector under natural lighting conditions. [ Result] The net photosynthetic rate, stomatal conductance and transpiration rate of four tomato varieties all decreased after infection. However, the decrease extent of these parameters of four varieties was different. The parameters of seriously damaged Jinyangdajuxdng （ No. 4） and Xinsheng No. 1 （ No. 5 ） decreased greatly, while the parameters of slightly damaged Lujia （ No. 13 ） and improved 98-6 decreased lightly. [ Condu- sion] The results could provide theoretical basis for the study on pathogenic mechanism, new prevention way and resistance breeding of tomato powdery mildew.

Comparison of Gas Exchange Characteristic in Leaves of Soybean Varieties with Different Yield Levels

[Objective] The aim was to explore the gases exchange characteristic in leaves of soybean cultivars at different yield levels to provide a certain theories basis for high yield breeding and cultivation of soybean cultivars. [Method] Nine soybean cultivars divided into three yield levels were planted under the same environmental condition. At V4（seedling）,R2（blooming）,R4（pod-bearing）,R6（pod-filling） and R7（maturing） growth stages,the net photosynthetic rate （Pn）,stomatal conductance （Gs） and transpiration rate （Tr） in soybean leaves were measured with Li-6400 portable photosynthesis system. [Result] At all growth stages,the net photosynthetic rate,stomatal conductance in leaves of high yield soybean cultivars were significantly higher than low yield soybean cultivars. At V4,R2 and R4 stages,transpiration rate in leaves of high yield soybean cultivars was significantly higher than low yield soybean cultivars; there was no significant difference on transpiration rate in leaves of soybean cultivars at different yield levels at R6 and R7 stage. At V4 and R2 stage,water use efficiency （WUE） in leaves of soybean cultivars at different yield showed a trend of low yield cultivarsmiddle yield cultivarshigh yield cultivars,while it appeared high yield cultivarsmiddle yield cultivarslow yield cultivars at R4,R6 and R7 stage. [Conclusion] The gases exchange capacity in leaves of high yield soybean cultivars was significantly higher than low yield soybean cultivars,which had provided physiological basis of high yield. The net photosynthetic rate could be used as an selection index of high yield soybean.

Changes of Gas Exchanges in Leaves of Different Cultivars of Winter Wheat Released in Different Years

Three winter wheat cultivars ( Triticum aestivum L.), representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental condition, and their physiological features were investigated. Daily changes of net photosynthetic rate (P-n), transpiration (T-r) in different growth stages were measured in order to find the relationship between leaf photosynthesis and yield. Instantaneous water use efficiency (WUE) of leaf was calculated from P-n/T-r. It is suggested that relationship between photosynthetic rate and yield changed with the developing stages of wheat. High yield wheat cultivar Jingdong 8 (released in the 1990s) had a higher photosynthetic rate ( the maximal P-n increased by 77%) and transpiration rate (the maximal T-r increased by 69%), but a lower WUE than the low yield cultivar Yanda 1817 (released in the 1940s) during the day time at stem elongation stage. However; difference of P-n among the three cultivars changed with wheat growth process. Before 10 o'clock P-n in leaves of Jingdong 8 usually was the highest of the three cultivars, but P-n of Yanda 1817 was the highest after 10 o'clock. At dough ripe stage, P-n in leaves of Yanda. 1817 was the highest among the three cultivars during the whole day. The difference of changing trend of transpiration in three wheat cultivars was similar to P,, but WUE of Yanda 1817 was the highest in those three cultivars, indicating that the higher yield of Jingdong 8 was achieved via a greater consumption of water. Contrary to the cultivars released in the later period, midday depression of photosynthesis was small in Yanda 1817, which might suggest that Yanda 1817 was resistant to photoinhibition. It is possible that photosynthetic potential in leaves of wheat increased as wheat cultivars was improved over the past six decades. However, it became less resistant to photoinhibition.

Root distribution of three co-occurring desert shrubs and their physiological response to precipitation

Root distribution of three desert shrubs,Tamarix ramosissima Ledeb.,Haloxylon ammodendron(C.A.Mey.) Bunge and Reaumuria soongorica(Pall.) Maxim.was investigated under co-occurring conditions using a method for excavating the whole root system.Assimilation shoot water potential and transpiration rates were monitored during the wet-dry cycle.Leaf-specific apparent hydraulic conductance and the index of water stress impact for the three species were calculated from shoot water potential and transpiration rate.The results showed that,along the soil profile,the root system of T.ramosissima mainly distributed at 50 to 310 cm interval,with an average total absorbing root-surface area of 30,249.2 cm2 per plant;the root system of H.ammodendraom distributed at 0 to 250 cm interval with an average total absorbing root-surface area of 12,847.3 cm2 per plant;the root system of R.soongorica distributed at 0-80 cm interval,with an average total absorbing root-surface area of 361.8 cm2.The root distribution shows the following:T.ramosissima uses groundwater as its main water source;H.ammodendraom uses both groundwater and rainwater;and R.soongorica uses rainwater only.During the wet-dry cycle,the hydraulic parameters of T.ramosissima showed no responses to precipitation.R.soongorica responded most significantly,and the responses of H.ammodendraom were intermediate.In conclusion,the plant response to rain events is closely related to their root distribution and plant water-use strategy.

Variable hydrological effects of herbs and shrubs in the arid northeastern Qinghai-Tibet Plateau,China

This study aims to assess the hydrological effects of four herbs and four shrubs planted in a selfestablished test area in Xining Basin of northeastern Qinghai-Tibet Plateau, China. The RainfallIntercepting Capability(RIC) of the herbs and shrubs was evaluated in rainfall interception experiment at the end of the third, fourth and fifth month of the growth period in 2007. The leaf transpiration rate and the effects of roots on promoting soil moisture evaporation in these plants were also assessed in transpiration experiment and root-soil composite system evaporation experiment in the five month's growth period. It is found that the RIC of the fourstudied herbs follows the order of E. repens, E. dahuricus, A. trachycaulum and L. secalinus; the RIC of the four shrubs follows the order of A. canescens, Z. xanthoxylon, C. korshinskii and N. tangutorum. The RIC of all the herbs is related linearly to their mean height and canopy area(R^2 ≥ 0.9160). The RIC of all the shrubs bears a logarithmic relationship with their mean height(R^2 ≥ 0.9164), but a linear one with their canopy area(R^2 ≥ 0.9356). Moreover, different species show different transpiration rates. Of the four herbs, E. repens has the highest transpiration rate of 1.07 mg/(m^2·s), and of the four shrubs, A. canescens has the highest transpiration rate(0.74 mg/(m^2·s)). The roots of all the herbs and shrubs can promote soil moisture evaporation. Of the four herbs, the evaporation rate of E. repens root-soil composite system is the highest(2.14%), and of the four shrubs,the root-soil composite system of A. canescens has the highest evaporation rate(1.41%). The evaporation rate of the root-soil composite system of E. dahuricus and Z. xanthoxylon bears a second-power linear relationship with evaporation time(R^2 ≥ 0.9924). The moisture content of all the eight root-soil composite systems decreases exponentially with evaporation time(R^2 ≥ 0.8434). The evaporation rate and moisture content of all the plants' root-soil composite systems increases logarithmically(R^2 ≥ 0.9606) and linearly(R^2 ≥ 0.9777) with root volume density. The findings of this study indicate that among the four herbs and four shrubs, E. repens and A. canescens possess the most effective hydrological effects in reducing the soil erosion and shallow landslide in this region.

Effects of Drought Stress on Photosynthetic Characteristics of Kentucky Bluegrass

Drought stress is one of the major constraints on turf growth and performance in northern China. Based on previous assessments of drought tolerance levels, four varieties of Kentucky bluegrass （Poa pratensis L.） representing different types （＇Baron＇, BVMG type; ＇Blackstone＇, Cheri type; ＇Kenblue＇, Midwest type; and ＇Bluemoon＇, Midnight type） were chosen for this study. Grass materials were established in a glasshouse, and the changes in their photosynthetic and metabolic characteristics were analyzed during a period of imposed drought stress. Drought stress led to decrease in chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate in all four cultivars, but the relative changes in each characteristic varied among varieties. The results also showed that changes in the photosynthetic and metabolic characteristics of different varieties under drought stress were related to the morphological characteristics of the plants. Varieties with longer narrow leaves, longer roots, higher root-to-shoot ratios, and higher chlorophyll contents showed greater rates of photosynthesis and stomatal conductance, and lower transpiration rates.

Intra-specific variations of two Leymus chinensis divergence populations in Songnen Plain, Northeast China

Population demography, seed production, biomass allocation, net photosynthesis and transpiration of two Leymus chinensis divergent populations and between two years in Songnen plain, northeast China were compared. Strong differences between the dry 1997 and moist 1998 occurred in vegetative shoot and sexual shoot densities, sexual differentiation and tiller densities, as well as in the lengths of inflorescence, seed numbers per inflorescence, seed weights and biomass allocation in each population respectively ( P < 0.01). While strong differences between the two populations occurred in vegetative shoot densities, sexual shoot densities, sexual differentiation and seed weights in each year ( P < 0.01). The differences between the two populations in tiller densities and in biomass allocation to sexual shoots were significant ( P <0.05). But there were no significant differences between the two populations in the lengths of inflorescence, seed numbers per inflorescence and biomass allocation to rhizomes and vegetative shoots ( P >0.05). Excepting the transpiration rate in the early June, the differences between the two populations in net photosynthesis and transpiration rate of vegetative shoots and sexual shoots were strongly significant in the early June and July respectively ( P <0.01). Relative stable variations in population demography and physiological traits between the two populations indicated that they are divergently in the Songnen Plain.

Cotton stomatal closure under varying temperature and vapor pressure deficit,correlation with the hydraulic conductance trait

Background:Cotton(Gossypium hirsutum L.)is often grown in locations characterized by high atmospheric evaporative demand.It has been hypothesized that plants which resist hydraulic flow under this condition will limit water use and conserve soil water.Therefore,in a series of controlled environment experiments ten cotton cultivars were exposed to two different temperature and vapor pressure deficit(VPD)conditions(i.e.,38℃,>3 kPa and 32℃,1∼1.5 kPa)as well as a progressive soil drying.Then,individual differences in shoot hydraulic conductance(K_(shoot))was measured using a hydraulic conductance flow meter(HCFM).Physiological parameters were reported included leaf area,dry leaf weight,stomatal conductance(g_(s)),and water use efficiency coefficient(WUE_(k)).Results:Differences were observed in K_(shoot) among cultivars under the 38℃,>3 kPa but not the 32℃,1∼1.5 kPa environment.Under the 38℃,>3 kPa environment,correlations were found between K_(shoot),stomatal conductance(gs),VPD breakpoint,WUEk,total leaf area,dry leaf weight,fraction transpirable soil water(FTSW)threshold,and slope of TR decline after FTSW threshold.Conclusion:Results show that the ability of some cotton cultivars to restrict water loss under high evaporative demand through early stomatal closure is associated with the cultivars’K_(shoot).The K_(shoot) is influential in the limitation of TR trait under high temperature and VPD.

Effects of regulated deficit irrigation on soil salinity,physiological processes and fruit quality of gray jujube under desert conditions

Regulated deficit irrigation(RDI)was applied to gray jujube trees in an oasis region,to determine the effects of this irrigation system on soil salinity,gray jujube physiological processes,fruit yield,and fruit quality.Treatments consisted of severe,moderate and low deficit irrigation(irrigated with 85%,70%and 55%of CK,respectively)at the flowering stage to fruit set stage.During the other growth stages,all treatments were irrigated with 80%of pan evaporation,which was the same as that in control.The results indicated that soil salinity was enhanced during the periods of water stress,but the high value of soil salinity declined by 3.48%-37.27%,at each depth,after irrigation was resumed.RDI caused a decline in the photosynthetic rate,transpiration rate,and stomatal conductance,but enhanced the water use efficiency of the leaves.However,the leaf photosynthetic rate was effectively enhanced after the recovery of irrigation,especially in the moderate deficit irrigation treatment,which exceeded the control.This led to an improved fruit yield,which was 9.57%higher than that of the control.The deficit treatments caused a significant increase in the soluble solid content,soluble sugar content,single fruit weight and sugar/acid ratio.Enhanced vitamin C content,resulting from deficit treatments,has also been observed in the gray jujube.Therefore,this research shows that RDI provides some benefits in the production of gray jujube trees in desert conditions.