Ionic Relations and Ultrastructure in Ulva Lactuca

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Abstract
Measurements have been made of fluxes of potassium and sodium in U. lactuca. As far as K exchange is concerned, the non-free space acts as a single component; the rate of exchange of the 350 u-equiv/g of K is apparently limited by the plasmalemma where the flux is about 100 [mu]-equiv/g fresh wt./hr. In the dark the flux drops by about 50%, and can be further reduced by inhibitors of oxidative phosphorylation. Na exchange is characterized by 2 components in the non-free space; it is suggested that the flux at the plasmalemma is about 100 [mu]i-equiv/g fresh wt./hr and that the flux at the tonoplast is only 1-3 [mu]-equiv/g fresh wt./hr. A study of the structure of cells by electron microscopy showed the distribution of cytoplasm and chloroplast in these cells. A feature of particular interest was the well-developed golgi complex close to the nucleus.

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