Relationship Between Diurnal Changes of Net Photosynthetic Rate and Influencing Factors in Rice under Saline Sodic Stress

The net photosynthetic rate of flag leaves and influencing factors under saline sodic soil conditions were investigated at the full heading stage of rice. The net photosynthetic rate of rice leaves showed a double-peak curve in a day in both non-saline sodic and saline sodic soil treatments. The first peak of the net photosynthetic rate appeared at 9：00-10：00 and 9：00 in the saline sodic and non-saline sodic soil treatments, respectively, whereas the second peak both at 14：00. The midday depression of the net photosynthetic rate always appeared regardless of non-saline sodic or saline sodic soil conditions. In addition, the net photosynthetic rate significantly decreased in all day under saline sodic conditions compared with that under non-saline sodic conditions. Some differences were observed in correlation characters between the net photosynthetic rate and all influencing factors during 9：00-13：00. Under non-saline sodic conditions, the diurnal changes of the net photosynthetic rate in a day were mainly caused by stomatal conductance, and the limitation value and the stomatal factors served as determinants; whereas under saline sodic stress, the diurnal changes of the net photosynthetic rate in a day were mainly caused by non stomatal factors including light intensity and air temperature.

Effect of Different Norms of Under-Mulch-Drip Irrigation on Diurnal Changes of Photosynthesis and Chlorophyll Fluorescence Parameter in High Yield Cotton of Xinjiang

Under-mulch-drip irrigation is an advanced irrigation technique, which combines plastic-film-covered cultivation with drip irrigation. The influence of different norms of under-mulch-drip irrigation on diurnal changes of photosynthetic rates and chlorophyll fluorescence parameters of cotton was studied, in order to understand the physiological mechanisms of water-saving and high-yielding farming in Xinjiang. Results indicated that limited drip irrigation, which supplies 2/3 of 375 m3 ha-1, the widely-used irrigation norm in cotton cultivation in Xinjiang, caused a water deficit in cotton field. Compared with the proper drip irrigation, the leaf photosynthetic rate under limited drip irrigation decreased during 9:00 to 11:00 a. m. , and was significantly suppressed at midday, and then recovered afterwards. Using the chlorophyll fluorescence method, the absorption, transfer and transformation features of solar radiation by cotton leaf were investigated. Under limited drip irrigation, the variable fluorescence (Fv) and primary light transfer efficiency of PSII (Fv/Fm) in cotton leaves were reduced because of the high light intensities and high temperatures at noon, and the decrease in XinluzaoS was greater than that in Xinluzao6. Therefore, it could be concluded that Xinluzao6 has a higher drought-tolerance, and the Fv/Fm ratio could be used as a drought-resistance index for cotton.

Effect of diurnal changes on dichotic listening in younger adults with normal hearing

Background:Diurnal changes can be defined as the time of the day over an individual's performance level for different activities that involve physical and mental tasks.Objective:The current study aimed to evaluate the effect of diurnal changes in scores obtained for the Dichotic Consonant-Vowel paradigm by young adults with normal hearing sensitivity.Method:Based on the‘Morningness-Eveningness questionnaire’given by Horne&Ostberg,the subjects were divided into moderately-morning,intermediate and moderately-evening categories.The Dichotic Consonant-Vowel tests were performed during morning and evening,and the right ear,left ear and double correct scores were compared between morning and evening for each category.Results:There was significant diurnal changes noted for moderately morning and evening categories,where morning-type individuals performed better during morning and evening-type individuals performed better during the evening.The scores of intermediate individuals remained unchanged between morning and evening test results.Conclusion:Diurnal change is a phenomenon associated with an individual's biological clock mechanism.Hence,attention and inhibitory controls aid them in carrying out tasks that require sufficient physical and mental efforts.The current study suggests that clinicians and researchers consider diurnal changes as an extraneous variable that could affect the reliability of the Dichotic Consonant-Vowel test results.

Diurnal changes in bacterial communities in oxic surface and hypoxic middle seawater layers of the Changjiang River Estuary

The Changjiang River Estuary(CRE)in the East China Sea suffers from seasonal hypoxia in summer.The vertical distributions and seasonal changes of microbial communities in the CRE were well documented.However,little is known about the diurnal changes of bacterial communities in the hypoxic zone of the CRE.Here,16 S rRNA gene analysis was used to explore the changes of bacterial communities in the oxic surface and hypoxic middle seawater layers during 24 h in the CRE.Significant differences between the hypoxic and oxic layers were observed:the phyla Cyanobacteria,Bacteroidetes and Acidimicrobiia were enriched in the oxic layer,whereas the phylum SAR406 and the class Deltaproteobacteria were more abundant in the hypoxic layer.In addition,some subtle diurnal variations of the bacterial relative abundance were found in both two layers.The relative abundance of Synechococcus increased at night,and this change was more obvious in the hypoxic layer.The similar trend was also found in some phototrophic and several heterotrophic bacteria,such as Rhodobacteraceae,OM60 and Flavobacteriaceae.Their relative abundances peaked at 16:00 in the oxic layer,while the relative abundances peaked at around 7:00 and decreased until 13:00 in the hypoxic layer.Together,the results of the present study suggest that some photosynthetic bacteria and several heterotrophic bacteria have similar diurnal variations implying the light and physicochemical heterogeneity in the course of a day are important for bacterial diurnal changes in the CRE.

Diurnal Changes in the Transcription Profiles of Genes Encoding Starch Synthesis-related Enzymes in Wheat Grains under Field Conditions

[Objective] During the filling stage of plant growth and development, storage starch is diurnally synthesized and accumulated in the grains from cereal crops, but the underlying molecular mechanism is unclear. [Method] In this study, grains from the bread wheat cultivar Zhoumai 18 grown in fields were harvested at 15 d after anthesis, and quantitative real-time reverse transcription polymerase chain reaction(qPCR) was used to measure the transcriptional levels of 26 genes encoding starch synthesis-related enzymes at 2 h intervals throughout a diurnal cycle. [Result] Our findings indicated that storage starch was persistently synthesized in wheat grains throughout a 24 h period. The diurnal patterns of the transcriptional levels of 26 genes in wheat grains were classified into two groups. The 13 genes in Group 1 were temporally and highly expressed in wheat grains,and their encoded proteins could play crucial roles in starch synthesis. The other 13 genes in Group 2 were characterized by low or no transcription in wheat grains throughout a diurnal cycle, suggesting their function in the synthesis or degradation of transitory starches in wheat grains. [Conclusion] These results provide information on the molecular mechanism of storage starch synthesis in higher plants.

Diurnal changes in differential sensitivity and temporal resolution in morning-type and evening-type individuals with normal hearing

The present study attempts to determine diurnal changes by testing the differential sensitivity and temporal resolution in morning-type,evening-type,and intermediate-type individuals with normal hearing.Thirty participants with normal hearing were divided into morningtype,evening-type,and intermediate-type using“MorningnesseEveningness Questionnaire”.The tests of differential sensitivity and temporal resolution were administered to all the participants in the morning and evening,respectively.The differences in the test results between different timing across all the three groups were analyzed.The results of the study showed that there was a significant diurnal effect on psychoacoustic tests as morning-type individuals performed better when tested in morning and evening-type performed better when they were tested in evening.However,there was no diurnal effect found in intermediate group.The lack of inhibitory control and poor cognitive load in off peak time could have lead to poor scores.Thus,the variable of diurnal effects should be considered in further studies on psychoacoustic tests,especially in young adults.Furthermore,studies could be performed to explore diurnal effects on objective audiological tests in a larger group of population in the future.

Effects of Land-Sea Distribution, Topography and Diurnal Change on Summer Monsoon Modeling

The effects of the land-sea distribution, the topography and the diurnal change of the solar radiation on the summer monsoon modelings are studied by use of a coupled modeling system with a 5-layer primitive equation model of the atmosphere and a 2-layer soil or ocean thermodynamic model which are all solved in a zonal model domain between 60°S and 60°N. The results of numerical simulations show that the quasi-stationary patterns of the mean monsoon circulations are mainly affected by the land-sea distribution and the topography, the effect of the diurnal change is the secondary. However, the inclusion of the diurnal change into the model system may improve the intensity of the simulated monsoon circulation, it can influence the distributive pattern of precipitation to a larger extent,without the diurnal change precipitation in the interior of land would decrease and in the coastal regions it would increase.

INFLUENCES OF DIURNAL CHANGE OF SOLAR RADIATION ON SIMULATED PROPERTIES OF SUMMER MONSOON

Comparative experiments with and without the diurnal change of solar radiation are made in this paper by use of an air-sea coupled 7-layer primitive equation modeling system in a zonal domain between 60°S and 60°N.The results show that the quasi-stationary patterns of the mean monsoon circulations are not evidently affected by the diurnal change of solar radiation.The main influences may come from the land-sea distribution and the orography.However,the inclusion of the diurnal change of solar radiation into the model system may improve the intensities of the simulated monsoon circulations both at the high and the low levels.It can influence the distributive pattern of precipitation to a larger extent.Without the diurnal change,precipitation in the interior of land would decrease and in the coastal regions it would increase.The changes of the soil temperature and the soil moisture are fairly correspondent to that of precipitation.The areas with increasing precipitation and the areas with decreasing precipitation are distributed in the wave form.As to the influences on the monsoon development,the results indicate that the diurnal change of solar radiation can speed up the development of the monsoon in the early stage.Therefore,the inclusion of the diurnal change of solar radiation can make the model equilibrium state to reach earlier.

Analysis on Change Characteristics of Diurnal Temperature Range in Benxi County from 1958 to 2010

Based on annual mean maximum and minimum temperatures,diurnal temperature range,precipitation,sunshine,total cloud cover and water barometric pressure data in Benxi County from 1958 to 2010,using statistical analysis,the results show that the annual and seasonal diurnal temperature ranges present significant decreasing tendencies,and the reducing tendency is the most remarkable in winter. Autumn reducing tendency is stronger than that in spring,and it is the weakest in summer. Annual and seasonal average temperatures,average maximum and minimum temperatures all present the remarkable rising trends. Rising trend of the minimum temperature is more significant than that of the maximum temperature. The monthly mean diurnal temperature range also presents reducing tendency,and the most reducing scope appear in January and February. Annual and season diurnal temperature range changes are related to sunshine,mean minimum temperature,mean maximum temperature,precipitation,total cloud cover and water barometric pressure,but various essential factors are different in each season. Annual mean temperature,annual mean minimum temperature,annual mean maximum temperature and annual diurnal temperature range all have sudden changes,but the age is inconsistent.

Studies on Photosynthetic Characteristics of Plum Leaves

Many photosynthetic characteristics of three plum varieties were studied with a infrared CO2 analyzer. Results showed that plums belong to light - loving species, having a relative high light compensation point (75-80μmol· m-2·s-1). In natural light range from none to 1400μmol·m-2s-1PAR,the light response curve of plum as a hyperbo and the net photosynthetic rate(Pn) in leavs increased with PA elevation. Pn of plum tree was 20 to 22.50mg CO2·dm-1·h-1 at 1380μpol. m-2·s-1 PAN,indicating that plum was typi- cal C3-type fruit tree. Diurnal change in Pn was a bimoal curve with the highest photosynthetic rate arising at about 10:00 a. m. indicated the clear 'none - rest 'characteristic in plum leaves. Among three varieties. SuiLi3 had the shortest 'none - rest' time followed by JiLin6 and NuXinLi. Seasonal change in Pn was a bi- modal curve with the first period of high Pn in late June and the second in late August. Pn in leaves decreased visibly in period of drought in Spring and Summer.

Study of the Protective Effects in PEPC Transgenic Rice

The diurnal course of chlorophyll fluorescence parameter and active oxygen metabolism of flag leaves in PEPC transgenic and untransformed rice Kitaake were studied. The results showed that the photosynthetic rate under high light intensity has been increased by 50% and photoinhibition of photosynthesis in PEPC transgenic was alleviated after the introduction of PEPC gene from maize into rice. It was demonstrated that the increment of photosynthesis in PEPC transgenic was related to the introduction of PEPC gene using specific inhibitor of PEPC. Photoinhibition of photosynthesis in different genotypes exists at noon under natural condition. PEPC transgenic rice exhibited a less decrease in Fv/Fm, a less photoinhibition and a higher efficiency of light energy conversion to chemical energy and lower thermal energy dissipation. These results provided the physiological basis on the mechanism of tolerance to photoinhibition and rice breeding with high photosynthetic efficiency.