904 ADVEXTURES IN RADIOISOTOPE RESEARCH 



formed their experiments on roots of young seedlings, viz. 2—4 days 

 old. According to these experimentors, the process of exudation of 

 nucleotides from the root is a characteristic feature of the still growing 

 parts; the lower 5—10 mm of the roots exude per unit dry weight 3 — 4 

 times as much nucleotide as roots of 30—40 mm length. The nucleotides 

 are assumed to participate in the building up of cellulose fibres which 

 constitute the cell wall. In the course of development of the cells, the 

 nucleotides are gradually liberated and the exuded molecules are not 

 renewed in ageing cells. The frequency of nucleotides diminishes con- 

 sequently and the growth slackens. Thus, the exudation of nucleotides 

 can be expected to diminish with increasing age of the seedlings. 



Summary 



Wheat seedlings with parted roots are grown. One part of the roots is placed 

 in an inactive nutrient solution, the other part in a nutrient solution containing 

 labelled phosphate. The radio-phosphorus is found to migrate through the plant 

 from the active into the inactive nutrient solution. 



When the nutrient solution contains 0.4 millimol. P per hter, for 6 phosphate 

 atoms taken up by the plant about 1 is found to migrate from the roots into the 

 nutrient solution. 



An increase in the phosphate concentration of the nutrient solution was found 

 to increase the amount of labelled phosphate given off by the roots, and vice 

 versa. Such a result is to be expected if we are mainly faced with an interchange 

 between the phosphate ions of the roots and the phosphate ions of the nutrient 

 solution. 



Roots placed in distilled water for 1 hour give off more labelled phosphate 

 than roots placed in a nutrient solution free from P. DistiUed water influences 

 thus the root cells of wheat seedlings. 



Beside labelled phosphate, roots of wheat seedlings give off a minor amount 

 of labelled nucletoids when placed in distilled water. This observation supports 

 the results obtained by Lundegardh and his collaborators. 



Comment on papers 89 — 92 



The first application of radioactive tracers in life-sciences was the investigation 

 of the uptake of lead by plants using ThB as an indicator of lead (paper 89, pub- 

 lished in 1923). The first apphcation of an artificially produced radioactive isotope, 

 that of 32P, in botanical studies was the investigation with Linderstr0m-Lang 

 and Olsen of the uptake of 32P by the maize plants (paper 90, published in 1936) 

 and by the sunflower and germinated maize and pea seeds (paper 91). The 

 extrusion of phosphorus compounds from the roots of labelled plants was studied 

 later (paper 92). These modest beginnings were followed by a spectacular deve- 

 lopment in the field of Botanies, Agriculture and Forestry. The present position 

 and future trends of this development are stated among others by the European 

 Productivity Agency Of The Organisation For European Economic Co-operation. 

 Paris 1958 and 1959. 



