A CONTRIBUTION TO THE STUDY OF DORMANCY IN SEEDS: LACTUCA SATIVA L.

1948 ◽  
Vol 26c (2) ◽  
pp. 194-217 ◽  
Author(s):  
C. W. Leggatt
Keyword(s):  
Carbon Dioxide ◽  
Blue Light ◽  
Seed Coat ◽  
Respiratory Metabolism ◽  
Carbon Dioxide Output ◽  
Lettuce Seeds ◽  
Inhibiting Factors ◽  
Lactuca Sativa L ◽  
Other Substances ◽  
Light Effects

The ease with which lettuce seeds may be made dormant by placing them under germinating conditions in blue light suggested that this kind of seed would provide satisfactory material for a study of certain aspects of dormancy in seeds. Studies have been made of the behavior of lettuce seeds under varied conditions of moisture, atmosphere, color of light, and integrity of the testa. Measurements of the absolute respiration have provided curves of the drift with time of carbon dioxide output, oxygen uptake, and of respiratory quotient. Experiments with substances that might induce dormancy and light-sensitiveness similar to that induced by blue light have been made. The bearing of the results obtained upon possible metabolic changes in the seed are discussed.The possibility that the observed effects of light upon seed germination are due to changes in the permeability of the seed coat induced by light is considered as untenable, but this does not exclude the fact that the seed coat is a restrictive agency to the free passage of oxygen, carbon dioxide, and other substances. Indeed, in any description of the probable metabolic state, this must certainly be considered. While it has not been possible to formulate a definite biochemical scheme to account for blue light effects, the experimental evidence suggests that 'carbon dioxide zymasis' may be promoted by blue light and that carbon dioxide may be one of the inhibiting factors. The blue light dormant condition is characterized by depressed respiration but without more disturbance of the equilibrium of the pre- and postglycolytic phases of respiratory metabolism than is found to be characteristic of uninhibited seeds as reported by other workers.The results of this research suggest that further elucidation of the phenomenon of dormancy should be sought in the direction of more extended studies of the respiration of dormant and non-dormant seeds.

scholarly journals The duration of the recovery period following strenuous muscular exercise

1933 ◽  
Vol 113 (783) ◽  
pp. 327-344 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Normal Values ◽  
Recovery Period ◽  
Oxygen Intake ◽  
Respiratory Metabolism ◽  
Carbon Dioxide Output ◽  
Steady Level ◽  
Made In

There are a variety of ways in which the duration of the recovery period after exercise can be determined. The method most frequently employed depends upon observations of the respiratory metabolism. This method has been chosen because the respiratory changes due to exercise can be followed with reasonable ease and accuracy, and because these changes are among the last of the more obvious effects of the exercise to disappear during recovery. In addition, interesting data concerning the effects of exercise on respiratory metabolism can be collected during the determination of the duration of the recovery period when this method is used. In determining the duration of the recovery period by observation of the respiratory metabolism, it is necessary to decide when the carbon dioxide output and oxygen intake have returned to their normal values and are no longer affected by the process of recovery from the exercise. This decision has been made in a variety of ways by different investigators. Some have made one or more pre-exercise determinations of the subject's basal oxygen intake and carbon dioxide output. Recovery was said to be complete when the carbon dioxide output and oxygen consumption returned to these values after exercise. Others found that the oxygen consumption did not return to the pre-exercise level within a reasonable length of time, but remained above normal for several hours. They considered that recovery was complete when the carbon dioxide output and oxygen intake returned to a steady level after exercise, even if the level was not the same as that before exercise.

PHYSIOLOGICAL AND BIOCHEMICAL STUDIES IN PLANT METABOLISM: III. THE EFFECTS OF STARVATION AND MECHANICAL STIMULATION ON THE RESPIRATORY METABOLISM OF THE FIRST LEAF OF THE WHEAT PLANT

1951 ◽  
Vol 29 (4) ◽  
pp. 383-402 ◽  
Author(s):  
D. W. A. Roberts
Keyword(s):  
Carbon Dioxide ◽  
Wheat Plant ◽  
Carbon Dioxide Tension ◽  
Temporary Increase ◽  
Respiratory Metabolism ◽  
Protein Nitrogen ◽  
Carbon Dioxide Output ◽  
A Value ◽  
Biochemical Studies ◽  
Physiological And Biochemical

The oxygen uptake and carbon dioxide output records of detached starving first leaves of wheat have been investigated. Small changes in the oxygen tension or carbon dioxide tension of the surrounding air do not make any difference in the records. The data obtained with the Barcroft method agree with those obtained by the Pettenkofer method. The form of the starvation air line is described. It is generally similar in the four quarters of the leaf but the senescent hump of the basal quarter is much flatter and its peak much lower than in the other three quarters. The total senescent hump carbon dioxide is shown to be proportional to the protein nitrogen in each of the four quarters. The effect on the air lines of rubbing and quartering the leaves is described. There is a great temporary increase in carbon dioxide output as a result of rubbing. This quickly subsides and the respiration rate after the rubbing settles down to a value slightly in excess of that prior to the rubbing. Rubbing and quartering have no effect on the R.Q. of the starving leaves.

Global carbon dioxide output of volcanic lakes in the Azores archipelago, Portugal

2021 ◽  
pp. 106835
Author(s):  
César Andrade ◽  
Fátima Viveiros ◽  
J. Virgílio Cruz ◽  
Rui Coutinho
Keyword(s):  
Carbon Dioxide ◽  
Azores Archipelago ◽  
Carbon Dioxide Output ◽  
Volcanic Lakes ◽  
Global Carbon

Breathing in brief exercise

1960 ◽  
Vol 15 (4) ◽  
pp. 583-588 ◽  
Author(s):  
F. N. Craig ◽  
E. G. Cummings
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Respiratory Exchange Ratio ◽  
Metabolic Cost ◽  
Carbon Dioxide Tension ◽  
Minute Volume ◽  
Carbon Dioxide Output ◽  
Respiratory Minute Volume ◽  
Before And After

Two men ran for 20 or 60 seconds while inhaling air, oxygen or 4% carbon dioxide. Inspired respiratory minute volume was determined for each breath. Ventilation increased suddenly in the first breath with minimal changes in end-expiratory carbon dioxide tension and respiratory exchange ratio to a rate that remained constant for 20 seconds before increasing further. The rate of carbon dioxide output was uniform during the first 20 seconds. A 12% grade did not increase ventilation or oxygen uptake during runs of 20 seconds, but in the first minute of recovery, ventilation was 64% greater than after level runs. Inhalation of oxygen inhibited ventilation by 24% in the 20-second periods before and after the end of a 60-second run. Inhalation of carbon dioxide begun at rest produced increments in ventilation and end-expiratory carbon dioxide tension that varied little during running and recovery. In the 20-second runs ventilation varied with speed but appeared independent of ultimate metabolic cost. Submitted on January 21, 1960

scholarly journals Preventing thermoinhibition in a thermosensitive lettuce genotype by seed imbibition at low temperature

2003 ◽  
Vol 60 (3) ◽  
pp. 477-480 ◽  
Author(s):  
Warley Marcos Nascimento
Keyword(s):  
Seed Germination ◽  
Low Temperature ◽  
High Temperatures ◽  
Lactuca Sativa ◽  
Lettuce Seed ◽  
Temperature Dependent ◽  
Lettuce Seeds ◽  
Lactuca Sativa L ◽  
Lettuce Seed Germination ◽  
Dark Green

Lettuce (Lactuca sativa L.) seed germination is strongly temperature dependent and under high temperatures, germination of most of genotypes can be erratic or completely inhibited. Lettuce seeds of 'Dark Green Boston' (DGB) were incubated at temperatures ranging from 15° to 35°C at light and dark conditions. Other seeds were imbibed in dark at 20°; 25°; 30°; and 35°C for 8 and 16 hours and then transferred to 20 or 35°C, in dark. Seeds were also incubated at constant temperature of 20° and 35 °C, in the dark, as control. In another treatment, seeds were primed for 3 days at 15°C with constant light. DGB lettuce seeds required light to germinate adequately at temperatures above 25°C. Seeds incubated at 20°C had 97% germination, whereas seeds incubated at 35°C did not germinate. Seeds imbibed at 20°C for 8 and 16 hours had germination. At 35°C, seeds imbibed initially at 20°C for 8 and 16 hours, had 89 and 97% germination, respectively. Seeds imbibed at 25°C for 16 hours, germinated satisfactory at 35°C. High temperatures of imbibition led to no germination. Primed and non-primed seeds had 100% germination at 20°C. Primed seeds had 100% germination at 35°C, whereas non-primed seeds germinate only 4%. The first hours of imbibition are very critical for lettuce seed germination at high temperatures.

Use of respiratory quotients in assessment of aerobic work capacity

1962 ◽  
Vol 17 (1) ◽  
pp. 47-50 ◽  
Author(s):  
B. Issekutz ◽  
N. C. Birkhead ◽  
K. Rodahl
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Work Load ◽  
Work Capacity ◽  
Bicycle Ergometer ◽  
Carbon Dioxide Output ◽  
Ergometer Test ◽  
Aerobic Work Capacity ◽  
Bicycle Ergometer Test ◽  
Better Than

Oxygen uptake and carbon dioxide output were measured in 32 untrained subjects during exercise on the bicycle ergometer. It was shown that the work respiratory quotient (RQ) under standardized conditions can be used as a measure of physical fitness. ΔRQ (work RQ minus 0.75) increases logarithmically with the work load and maximal O2 uptake is reached at a ΔRQ value of 0.40. This observation offered the possibility of predicting the maximal O2 uptake of a person, based on the measurement of RQ during a single bicycle ergometer test at a submaximal load. For each work RQ between 0.95 and 1.15 a factor was presented, together with the aid of a simple equation, which gave a good approximation (generally better than ±10%) of the maximal O2 uptake.

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