PRODUCTION OF SOLUTES IN GROWING EPIDERMAL CELLS

W. A. Beck
1941 Plant Physiology  
Growth by cell enlaroemiient, which is characteristic of plant cells, may be defined as the irreversible increment in the volume without appreciable increment in the mass of the protoplasm. Investigation of this kind of growth w-as oiven considerable impetus by URSPRUNG and BLUM (12) when they discovered that the turgor of young cells is minimum when the growth is maximum, and also by WENT (14) and his school wheni they proved that the growth-promotingr substanee which induces this kind of
more » ... s this kind of growth oririnates in the reoion of cell proliferation. Althougyh it appears evident that the growth-promotinog substance must exercise its effect on the living protoplasm (cf. 10) there is still some questioni about the effect produced directly or indirectly on the cell wall and the production of solute in the protoplasm which is osmotically active in the cell sap cavity. KLEBS (5) conieluded from his experiments that the protoplasm is directly responsible for cell enlargement, which is, of course, hardly tellable in view of the facts known to us at presenlt. HEGLER, SACHS, DEVRIES (3, 7, 13) and others assumed that cell enlargrement is directly due to the stretching of the wall, which itself is caused bv the turgor. This view was decidedly dispuited bv SCHWENDENER and KRABE (8), who contended that the wall grows actively by a process of intussusception with the cooperation of the protoplasmii. PFEFFER (6) explains how the growth of the wall may be the result of active and passive growth, with consequenit changes in the elastic conistanits of the wall. The fact which URSPRUNG an1d BLUm established beyond a doubt, that the turgor is minimum in the most activelv grow-ing cells (12) makes it certain that the turgor plays at most a seconidary role in the process of cell enlargement. It also makes it questionable if the soluLtes which are necessary to maintain the turgor are elaborated by the protoplasm to a degree which is commensurate with the growth of the cell. It is the purpose of the present investigation to determine the amount of soluite which is produced durinig the various stages of cell enlargemient. Material and methods The enlargemenit of the cells in different phases of development was first determined with the aid of an eve-piece micrometer. Theni the osmotic value at incipienit plasmolysis and the deoree of contractioni in passinlg fromi the niormal state to the state of incipienit plasmolysis were determined for 637 www.plantphysiol.org on August 31, 2017 -Published by Downloaded from
doi:10.1104/pp.16.3.637 pmid:16653726 fatcat:rsek2keccbcujdmtevcb7g7fxu