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There Was Also a Metal

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There Was Also a Metal Respiration of Phycomyces by S.R. de Boer. INTRODUCTION. METHODS AND APPARATUS. the is of In following pages a description given experiments on the respiration of Phycomyces Blakesleeanus Burgeff. This fungus is wellknown under the name of Phycomyces but showed nitens Kunze, two years ago, Burgeff (16) that the latter name really belonged to another Phycomyces, so he called the former Phycomyces Blakesleeanus. In all the experiments transfers were used from a one culture of obtained from the spore a + strain, „Centraal- bureau voor Schimmelcultures” at Baarn, Holland. Two kinds of respiration apparatus were used, one of and the other of the closed the air current type space or Regnault type. Respiration, consisting in evolving carbon dioxide and measured. absorbing oxygen, is generally 1° the C0 off by determining 2 given 2° 0 taken in „ „ „ 2 3° both methods simultaneously. ,, using The first method has already been worked out by Pettenkofer (69); later on Pfeffer (70, 95) introduced it into plant-physiology. This socalled Pettenkofer-Pfeffer method consists in forcing or sucking a current ofair depriv- ed of carbondioxide through the respiration vessel. In leaving it the air has to pass a solution of bariumhydroxide in long horizontal glass tubes, called Pettenkofer-tubes. The of C0 off the can be deter- quantity 2 given by plant 118 mined from its absorption by the barytawater and sub- sequent titration. The air current can be led alternately into different tubes. Another absorber with barytawater behind the Pettenkofer-tubes will tell that all the C0 2 has been absorbed in the tube, if the solution in the absorber remains clear. This method is a very simple and handy one and can always be used when the only thing to be settled is the amount of the C0 off the It was in such 2, given by plant. cases that I made use of it, the air being sucked through of the kind the s ystem by an aspirator described by Fernandes Attached it (31). to was an open mano- with which enabled me check the meter mercury to sucking force of the aspirator. The respiration chamber was placed in a glass basin filled with water, kept at a constant temperature by elec- trical heating. Inside the glass basin there was also a metal had spiral tube through which the air to pass before entering the respiration vessel in order to take on the same tem- perature. Before entering the vessel the air was purified in different washing-bottles filled with solutions of sodium hydroxide, silver nitrate and strong sulphuric acid, potassium per- manganate. In leaving the respiration vessel the air passed a small absorbing flask with sulphuric acid. Without this precaution, the air, rich in watervapour given off by the respiring plant, would render the bariumhydroxidesolution less concentrated. The sulphuric acid should not be taken too strong, for in this case an absolutely dry air enters the Pettenkofer-tube and a humid one leaves it, also chan- ging the strength of the barytawater. Half Ad. determined a century ago Mayer (61, 96) the 0 - the decrease in a volume 2 absorption by measuring of air, which was shut off from the atmosphere by means 119 of alkaline solution all the mercury, a strong absorbing C0 evolved the plant 2 by the CO absorbed the alkaline By measuring a by solution, Godlewsky (35) determined the 0 taken in and the 2 C0 given off by the plant at the same time. 2 Bonnier and (11) examined the 0 absorbed Mangin 2 and the CO, given off by the plants by analysing samples of air. It is obvious that in both methods lack of a oxygen effect the in the last may respiration. Moreover, method, formed the a lot of C0 be in vessel, 2 may experimental the Besides the which may injure plants. this, more there is of C0 the more will be absorbed by the water and the 2, so the amount of C0 found will be too small. plants, 2 In zoo-physiology an apparatus is used without these drawbacks, the prototype of which was published by Regnault and Reiset (76). It has subsequently been modified and improved by Benedict (7) and by Fredericia In these of (33). apparatus a supply oxygen has the decrease in the to compensate oxygen pressure inside, so as to keep it as nearly as possible to the original Various devices are in use. Connected with the pressure. chamber a volume recorder is often arranged, which will certain close electric circuit and admit at a point an oxygen from a cylinder and reduction valve. In 1923 Fernandes (30 and 31) introduced into plant-physiology an ingenious respiration apparatus on the The is obtained Regnault-Reiset principle. oxygen by a i.e. new method, by hydrolyzing a sodium hydroxidesol- ution. As much 0 as is taken the is formed 2 up by plant and led the vessel. So the of to respiration amount oxygen in the closed remains the The space always same. hydrogen formed at the other electrode is collected in an eudiometer. It is twice the of absorbed the equal to amount oxygen by A circulates the volume of air plant. pump constant through the system. By means of tubes filled with barytawater the 120 C0 can be absorbed. As both 0 and C0 are determined 2 2 2 the respiratory quotient is known. Fernandes did not pay much attention to the respir- determination of atory quotients. I made the the respir- of atory quotients an important part my investigations. I soon discovered that in order to be able to determine the quotients accurately, certain alterations had to be made. For a detailed description of the original apparatus I beg to refer the reader to Fernandes' publication. Here schematic of the I am only going to give a description appa- The ratus and its improvements as shown in fig. 1. closed volume of air is formed the space with the constant by H. H system A, B, etc... By means of the air is pumped in the direction indicated by the arrows. A is the respiration chamber, the air entering at the top and leaving the vessel Then the air has the at the bottom. to pass washing-bottle B filled with a solution of sulphuric acid of which the same be said 18. D and E Pettenkofer may as on p.l are tubes, long 2.1 filled with 80 barium- 35 c.m., diameter c.m., each can hydroxide solution, absorbing the C0 given off by the plant. 2 G is the control barytatube. The level in the right leg of the L would rise if formed in manometer oxygen was not the electrolyzing vessel M. The electrolyzing current can be regulated by means of a resistance. In the circuit I placed a milliamperemeter which was a great convenience as will be proved afterwards. It appears from the diagram that the most important improvement made is the compensating vessel K. In star- ting an experiment the vessels A and K are shut off from the atmosphere by closing the taps I and J. Changes in barometric have influence then. It stands pressure can no to reason that the electrolyzing vessel M must be shut off The tube left which the is formed too. glass at the in hydrogen and conducted to the eudiometer N is in connection with the atmosphere. O is a levelling device consisting of a glass 121 used. Apparatus Space Closed the of Scheme 1. Fig. 122 tube with water in connection with the lower end of the eudiometer N. During or at the end of each experiment O has to be raised or lowered till the pressure at the point * is the same as at the beginning of the experiment, which can be seen from the level in M being the same in the elec- trolyzing vessel and both its tubes. With the suction velocity employed, one Pettenkofer tube is sufficient. Two are the tube not necessary though upper has to absorb a small amount of C0 The use of only 2. 2 Pettenkofer tubes instead of 3 vertical absorptiontubes has The difference in is many advantages. pressure now only 3 c.m. water, whereas Fernandes had a difference of 35 c.m. This lessens the chance of leakage. The two tubes are attached to a frame. There is room enough for two of such sets of tubes. By means of the three-way- F taps C and these sets of tubes can be changed at time that any so any new experiment can go on without interruption. As far as possible the connections are of glass, the rest consisting of heavy vacuum-tube. As rubber will absorb C0 the section between A and Dis as short as 2 kept possible Behind E in the C0 cannot be lost (e.g. pump H) 2 by diffusion, because there is no more C0 2 present. When the apparatus is ventilated, purified air enters the vessel A and leaves the at F, passes system at C. I ven- tilated for instance when taking long experiments where measurements cannot continually be carried out. Except for O and N the whole apparatus is fixed in a glass basin with water, which is kept at a constant tempera- ture (± 0.03° C.) by electrical heating. The humidity in the respiration vessel during the experim- ents was always very high and nearly saturated for two 1° because the reasons, entering air was sucked through water and 2° because the respiring plant gives off water. It checked of was by means a hygrometer.
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