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M. G. STALFELT 



ment. Transpiration was then measured in the same way as earHer. Thus, 

 the root system was wrapped in aluminium foil. The plants were then placed 

 on a scale on which rapid readings could be made. They remained on the 

 scales during the whole experimental period, during which they were 

 exposed to illumination of about 1 5,000 m candles. The weight was read off 

 every 2 or 3 minutes. After 10-15 minutes, the stem was severed at the 

 base, the plants were weighed at once, and then every other minute for 6 

 minutes. Before the experiment, the plants were allowed to transpire with 

 or without a water supply for a varying period. This resulted in a water 

 deficit ranging from to 32%. 



In 28 such experiments, either an increase or a decrease in transpiration 

 occurred during the first 6 minutes after cutting. In 12 of these cases an 

 increase occurred, and in 16 cases a decrease. In another such experiment, 

 the value remained unchanged. As in the earlier measurements (1944), the 

 sum of the decrease in the individual experiments was about 10% greater 

 than the sum of the increase. 



The results are in agreement with the measurements made by Rutter 

 (1959) on Pimis sylvestris.Kuttet compared the transpiration of 3-year-old 

 plants which could be weighed intact in pots, and of detached branches, in 

 the 10 minutes following cutting. He found that the transpiration of the 

 detached branches was about 12% less than that of undamaged plants. 

 Similar results were obtained by Rawitscher (i955) in a study of Coffea 

 arahica, and by Parker (1957), who investigated Pinm strohus L. in the same 

 way. The latter author stated that transpiration of excised twigs or fascicles 

 'declined only shghtly after severing in the subsequent 6 minutes'. 



Consequently, the possible root damage that occurred in my earher 

 measurements (1944) cannot have had any appreciable effect on the results, 

 as was claimed by Allerup (i959)- The results do not, in any case, conflict 

 with Allerup's experiments and conclusions. This is because the spruce 

 plants used in my experiments lacked the ample water supply considered 

 by him to be a prerequisite for an increase in transpiration after cutting. 



Thus, according to the control measurements, the mean values for 

 transpiration given by the momentan method are not higher-but are rather 

 lower -than the transpiration immediately before the organ is severed. This 

 is provided that the measurements are Umited to the minutes directly after 

 cutting. It was for this reason that I chose the 'momentan method' for 

 measuring the transpiration of the 11 experimental trees. 



The needles from the last 5 years were used for the measurement. The 

 samples were taken at various levels of the crown, up to 6 m above the 

 ground, and from all sides of the trees. From 7-8 measurements were made 



