Lecture 4 — 81 — Movement and Distribution 



plant, which were dependent upon the availability of 

 energy containing compounds or special organic units, 

 and of substances catalyzing or regulating metabolism, 

 for all of which photosynthesis is ultimately essential. 

 In these experiments not only the absorption of salt 

 but likewise its distribution between the root and the 

 shoot was largely independent of the quantity of water 

 absorbed and given off by the plant. Essentially, there- 

 fore, the salt absorption and movement was dependent 

 on the climatic factors that determined carbon fixa- 

 tion, respiration and other biochemical processes. _ 



It is possible to arrange other experimental con- 

 ditions which might seem to lead to a divergent con- 

 clusion but when the data are critically analyzed the 

 general view just outlined is supported rather than 

 contradicted. Barley plants were grown in a pre- 

 liminary growth period under two contrasted nutri- 

 tional environments. One set received frequent changes 

 of nutrient solution which produced a high-salt and 

 low-sugar status in the plants; the other set, as a 

 result of limitation in the nutrients supplied during 

 the preparatory growth period, attained a low-salt, 

 high-sugar status. Both sets of plants were then 

 subjected for a short time (about 24 hours) to sev- 

 eral conditions of illumination and humidity and the 

 absorption and upward movement of potassium and 

 bromide ions were studied. The roots received full 

 aeration in all cases. 



The importance of the initial status of the plant 

 on subsequent salt absorption and movement during 

 an experimental period was manifest. The influence 

 of aerial environmental conditions on the intake of 

 salt was much greater for the initially high-salt, low- 

 sugar plants than for the low-salt, high-sugar plants. 

 The former responded far more in increased salt ab- 

 sorption to conditions inducing increased transpira- 

 tion, but these conditions also modified the metabolic 

 status of the plants. Illuminated plants synthesized 



