146 



TRANSLOCATION IN PLANTS 



defoliated tree or in the stump and roots of a felled tree. 



In this the cell at the top of the 

 diagram is omitted and water 

 entering T would tend to bleed 

 from the cut stump or be forced 

 toward the defoliated twigs. (3) 

 Transport in a complete normal 

 plant as indicated in the diagram 

 here presented. He also gives dia- 

 grams indicating transport to fruits. 

 Miinch claims the system will work 

 under any conditions of water sup- 

 ply; for, even if water is deficient, 

 reducing the turgor in the leaf 

 or supplying cell, P, he claims that 

 to an equal extent there would 

 be an increase in the tension of the 

 cohesive xylem water in T, and this 

 would be transferred to the cam- 

 bium, so that the sum of the suction 

 and turgor pressures of the receiv- 

 ing and supplying cells, which are 

 responsible for the pressure gradient 

 and circulation of sap, is as great 

 as before a reduction of turgor took 

 "^° place and is equal to the osmotic 



ri(j. 10. — Diagrammatic ^ . r xi, i • 1 f 



representation of transport by Concentration 01 the Supplying leai 

 an osmotic flow as proposed ^^^j^ jy^^^.^ exactly, the pressure 



difference would be equal to the 

 difference between the osmotic 

 concentration of the supplying and 

 receiving cells and would not be 

 equal to the osmotic concentration 

 of the leaf. In the fundamental 

 scheme diagrammed in Fig. 9, the 

 pressure gradient would depend on 



the difference between the concentrations in membranes 



A and B. 



by Munch. Diagram adapt- 

 ed from Miinch with slight 

 alterations. T, xylem tube; 

 P, leaf parenchyma; <S, sieve 

 tube; C, cambium; Z, sugar; 

 E, endodermis of root. Sim- 

 ple arrows indicate direction 

 of movement of water, single- 

 feathered arrows direction of 

 carbon dioxide movement, 

 double-feathered arrows direc- 

 tion of movement of sugar 

 solutions. 



