Regulation of Amino Acid Uptake into Oat Mesophyll Cells: A Comparison between Protoplasts and Leaf Segments

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Abstract
The uptake of α-aminoisobutyric acid (AIB) into protoplasts and into 1 cm sections of leaves from 7 d old light-grown oats (Avena sativa L. cv. ‘Garry’) was studied. Both protoplasts and leaf sections with cuticle and epidermis removed accumulated AIB against a concentration gradient although the rate of uptake into protoplasts was one-third to one-sixth that into leaf sections. AIB uptake into both protoplasts and leaf cells in situ was stimulated by ‘aging,’ and low pH, and inhibited by osmotic shock, respiratory poisons, and KCl concentrations above 1 mM. It was concluded that the rate of uptake of AIB and its accumulation ratio could be accounted for by the energy inherent in the proton-motive force, the proton-motive force being the sum of the pH gradient and potential difference across the plasma membrane. The similarities between oat mesophyll protoplasts and leaf cells in situ suggest that these protoplasts are suitable material for the study of certain membrane-regulated events.