Low root temperatures and nitrogenase activity in soybean

1984 ◽  
Vol 62 (5) ◽  
pp. 965-971 ◽  
Author(s):  
D. B. Layzell ◽  
P. Rochman ◽  
D. T. Canvin
Keyword(s):  
Gas Exchange ◽  
Relative Efficiency ◽  
Nitrogenase Activity ◽  
Temperature Drop ◽  
Relative Increase ◽  
Rhizobium Japonicum ◽  
Hydrogenase Activity ◽  
Symbiotic Association ◽  
Short Term ◽  
Gas Exchange System

A continuously flowing open gas exchange system was used to monitor the rates of CO2 evolution, C2H2 reduction, and H2 evolution from intact nodulated soybean ('Harosoy 63') roots, while root temperatures were dropped from the growing temperature (25 °C) to 10 °C at the rate of 5 °C/h. Four Rhizobium japonicum inoculants were used, three of which (type S (Nitragin Co.), USDA 16, USDA 35) displayed net H2 evolution while the fourth (USDA 110) did not evolve H2. Between 25 and 15 °C, values for Q10 in the H2-evolving symbioses ranged from 2.0 to 2.7 for CO2 evolution. 1.3 to 2.4 for C2H2 reduction, and 3.2 to 3.7 for H2 evolution. Nodulated roots of USDA 110 displayed the highest Q10 values for both CO2 evolution (Q10 = 2.9) and C2H2 reduction (Q10 = 15.2). The temperature profiles of these gas exchange measurements were used to calculate both the relative efficiency (RE = 1 − (H2 evolution/C2H2 reduction)) of N2 fixation and the ratio between CO2 evolution and C2H2 reduction at temperatures between 10 and 25 °C. The effect of short-term changes on the CO2/C2H2 ratio varied with symbiotic association. In the type-S symbiosis, long-term (96 h) treatments at low root temperature (9.5 °C) decreased the amount of CO2 evolved per C2H2 reduced to 35% of the value obtained at 25 °C. This study did not determine whether these observed changes were associated with N2 fixation or growth and maintenance of the nodulated root. In all H2-evolving symbioses, the RE increased from ca. 0.6 to 0.9 in response to a temperature drop from 25 to 10 °C. Studies of net H2 uptake and 3H2 exchange at 25 and 15 °C indicated that the observed changes in relative efficiency were due to variations in electron allocation by nitrogenase rather than a relative increase in uptake hydrogenase activity. The increase in RE above 0.75 suggested that lower temperatures may have altered the minimal nitrogenase electron allocation to less than one H2 per N2 fixed. This observed increase in RE with lower temperatures indicated that, in the symbioses studied, H2 evolution may have provided a buffer which permitted the maintenance of high levels of N2 fixation during short-term or diurnal fluctuations in soil temperature.

scholarly journals Chronicvs.Short-Term Acute O3Exposure Effects on Nocturnal Transpiration in Two Californian Oaks

2007 ◽  
Vol 7 ◽  
pp. 134-140 ◽  
Author(s):  
N. E. Grulke ◽  
E. Paoletti ◽  
R. L. Heath
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Exchange System ◽  
Short Term ◽  
Blue Oak ◽  
Unexposed Control ◽  
Nocturnal Transpiration ◽  
Gas Exchange System ◽  
Black Oak ◽  
Oak Seedlings

We tested the effect of daytime chronic moderate ozone (O3) exposure, short-term acute exposure, and both chronic and acute O3exposure combined on nocturnal transpiration in California black oak and blue oak seedlings. Chronic O3exposure (70 ppb for 8 h/day) was implemented in open-top chambers for either 1 month (California black oak) or 2 months (blue oak). Acute O3exposure (~1 h in duration during the day, 120–220 ppb) was implemented in a novel gas exchange system that supplied and maintained known O3concentrations to a leaf cuvette. When exposed to chronic daytime O3exposure, both oaks exhibited increased nocturnal transpiration (without concurrent O3exposure) relative to unexposed control leaves (1.8× and 1.6×, black and blue oak, respectively). Short-term acute and chronic O3exposure did not further increase nocturnal transpiration in either species. In blue oak previously unexposed to O3, short-term acute O3exposure significantly enhanced nocturnal transpiration (2.0×) relative to leaves unexposed to O3. California black oak was unresponsive to (only) short-term acute O3exposure. Daytime chronic and/or acute O3exposures can increase foliar water loss at night in deciduous oak seedlings.

A new automated stem CO2 efflux chamber based on industrial ultra-low-cost sensors

2019 ◽  
Author(s):  
Johannes Brändle ◽  
Norbert Kunert
Keyword(s):  
Gas Exchange ◽  
Low Cost ◽  
Climatic Conditions ◽  
Co2 Efflux ◽  
Diurnal Changes ◽  
Lowland Forest ◽  
Stem Respiration ◽  
Stem Co2 Efflux ◽  
Gas Exchange System ◽  
Controlling Processes

Abstract Tree autotrophic respiratory processes, especially stem respiration or stem CO2 efflux (Estem), are important components of the forest carbon budget. Despite the efforts to investigate the controlling processes of Estem in the last years a considerable lack in our knowledge remains on the abiotic and biotic drivers affecting Estem dynamics. It has been strongly advocated that long-term measurements would shed light into those processes. The expensive scientific instruments needed to measure gas exchange has prevented from applying Estem measurements on a larger temporal and spatial scale. Here, we present an automated closed dynamic chamber system based on inexpensive and industrially broadly applied CO2 sensors reducing the costs for the sensing system to a minimum. The CO2 sensor was cross-calibrated with a commonly used gas exchange system in the laboratory and in the field, and we found very good accordance of these sensors. We tested the system under harsh tropical climatic conditions, characterized by heavy tropical rainfall events, extreme humidity, and temperatures, in a moist lowland forest in Malaysia. We recorded Estem of three Dyera costulata trees with our prototype over various days. The variation of Estem was large among the three tree individuals and varied by 7.5-fold. However, clear diurnal changes in Estem were present in all three tree individuals. One tree showed high diurnal variation in Estem and the relationship between Estem and temperature was characterized by a strong hysteresis. The large variations found within one single tree species highlights the importance of continuous measurement to quantify ecosystem carbon fluxes.

scholarly journals Normal Cyclic Variation in CO2 Concentration in Indoor Chambers Decreases Leaf Gas Exchange and Plant Growth

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 663
Author(s):  
James Bunce
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Leaf Gas Exchange ◽  
Genetic Material ◽  
Co2 Concentration ◽  
Cyclic Variation ◽  
Indoor Exposure ◽  
Elevated Atmospheric Co2 ◽  
Gas Exchange System ◽  
Opening And Closing

Attempts to identify crop genetic material with larger growth stimulation at projected elevated atmospheric CO2 concentrations are becoming more common. The probability of reductions in photosynthesis and yield caused by short-term variation in CO2 concentration within elevated CO2 treatments in the free-air CO2 enrichment plots raises the question of whether similar effects occur in glasshouse or indoor chamber experiments. These experiments were designed to test whether even the normal, modest, cyclic variation in CO2 concentration typical of indoor exposure systems have persistent impacts on photosynthesis and growth, and to explore mechanisms underlying the responses observed. Wheat, cotton, soybeans, and rice were grown from seed in indoor chambers at a mean CO2 concentration of 560 μmol mol−1, with “triangular” cyclic variation with standard deviations of either 4.5 or 18.0 μmol mol−1 measured with 0.1 s sampling periods with an open path analyzer. Photosynthesis, stomatal conductance, and above ground biomass at 20 to 23 days were reduced in all four species by the larger variation in CO2 concentration. Tests of rates of stomatal opening and closing with step changes in light and CO2, and tests of responses to square-wave cycling of CO2 were also conducted on individual leaves of these and three other species, using a leaf gas exchange system. Reduced stomatal conductance due to larger amplitude cycling of CO2 during growth occurred even in soybeans and rice, which had equal rates of opening and closing in response to step changes in CO2. The gas exchange results further indicated that reduced mean stomatal conductance was not the only cause of reduced photosynthesis in variable CO2 conditions.

Effect of short-term exposure to high ambient temperatures on gas exchange and heat production in boars of different breeds

1998 ◽  
Vol 66 (2) ◽  
pp. 431-440 ◽  
Author(s):  
A.-H. Tauson ◽  
A. Chwalibog ◽  
J. Ludvigsen ◽  
K. Jakobsen ◽  
G. Thorbek
Keyword(s):  
Heat Stress ◽  
Gas Exchange ◽  
Heat Production ◽  
Live Weight ◽  
Mean Value ◽  
Short Term ◽  
Ambient Temperatures ◽  
Cooling Period ◽  
Basal Period ◽  
Short Term Exposure

AbstractThe effects of short-term exposure to high ambient temperatures on gas exchange, heat production (HE), respiration rate (RR) and rectal temperature were evaluated individually with boars of approximately 100 kg live weight. The boars were of different breeds with four of Yorkshire (YS), eight of Danish Landrace (DL), out of which three were found stress susceptible by the halothane test (DLH+), eight of Duroc (DR) and eight of Hampshire (HS) breeds. After 1 h rest in the respiration chamber at 17·0°C the gas exchange measurements started with al-h basal period at 17 °C, followed by 2h of heating during which temperature increased to 35·0 °C (period I) and then further to 39·7X1 (period II). Then cooling of the chamber started, and after 1 h (period III) temperature had decreased to 21·8°C, and after the 2nd h of cooling (period IV) temperature was 18·2 °C. The gas exchange was measured for each hour from 09.00 h (basal period) until 14.00 h (period IV). RR was recorded every 15 min. Rectal temperatures were measured when the animals were removed from the chamber. The gas exchange and HE increased slowly during period I but rapidly in period II, followed by decreasing values in the cooling periods. HS and DLH+ had considerably higher gas exchange and HE than other breeds in these two periods and the values remained high during period III. In period IV all breeds had gas exchange rates and HE below those of the basal period. RR increased slightly in period I and then a sharp increase followed during period II. Maximum RR was recorded in period III with an average of 183 breaths per min for all breeds. RR increased earlier and more steeply in HS and reached the highest mean value of 236 breaths per min. Four HS boars salivated heavily during heat stress and rectal temperatures of these animals were 39·7 °C when removed from the chamber compared with close to 39·0 °C for all other breeds. It was concluded that there were considerable breed differences in response to heat stress and that DLH+ and HS were more severely stressed than boars ofYS, DL and DR.

scholarly journals Photosynthetic Performance of Guaranazeiro Plants as Affected by Glyphosate Application

2020 ◽  
Vol 12 (10) ◽  
pp. 287
Author(s):  
Bruna N. Leite ◽  
Karla Gabrielle D. Pinto ◽  
Victor Alexandre H. F. dos Santos ◽  
Marciel J. Ferreira ◽  
Sônia Maria F. Albertino
Keyword(s):  
Gas Exchange ◽  
Chlorophyll Content ◽  
Photosynthetic Performance ◽  
Productive Performance ◽  
Weed Species ◽  
Short Term ◽  
Paullinia Cupana ◽  
Process Gas ◽  
Quantum Efficiency Of Psii ◽  
Relative Chlorophyll Content

The unsuitable use of herbicides damages many cultures. In cases of high infestations and presence of aggressive weed species in guarana (Paullinia cupana) culture, glyphosate application is advisable, but its impact on guarana physiology is unknown. Therefore, leaf photosynthetic characteristics were measured with the aim of identifying if the photosynthetic performance of guaranazeiro plants is affected in response to glyphosate application. Three glyphosate doses (0 (control); 324 and 432 g a.i. ha-1) were applied to two guaranazeiro cultivars (BRS-Andirá and BRS-Maués) selected on the basis of productive performance. An analysis was made of the effects of these doses on characteristics that represent the photosynthetic process: gas exchange, maximum quantum efficiency of PSII, performance index and chlorophyll content. The application of glyphosate did not affect the short-term responses relative chlorophyll content (SPAD index) and light use (chlorophyll a fluorescence). After 168 h, there were changes only in gas exchange variables. The effects of glyphosate doses on gas exchange was different between guaranazeiro cultivars. The photosynthetic performance of the guaranazeiro seems to be tolerant to the effects of short-term of glyphosate application.

scholarly journals PLANT RESPONSES TO A SHORT-TERM DAILY TEMPERATURE DROP AT DIFFERENT TIMES OF DAY AND NIGHT

2020 ◽  
pp. 60
Author(s):  
Татьяна Геннадиевна Шибаева ◽  
Елена Георгиевна Шерудило ◽  
Александр Федорович Титов ◽  
Tatyana Shibaeva ◽  
Elena Sherudilo ◽  
...  
Keyword(s):  
Temperature Drop ◽  
Daily Temperature ◽  
Plant Responses ◽  
Short Term
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