Amino-acid-transport mutant of Nicotiana tabacum L.

Abstract
The uptake rates of 16 amino acids were measured in leaf discs from Nicotiana tabacum L., cv. Xanthi (wild type) and from two valine-resistant mutants, Valr-1 and Valr-2. For all amino acids tested the uptake rates in Valr-1 were similar to those in the wild type. The Valr-2 mutant showed a reduced uptake of neutral and acidic amino acids, but uptake of the basic amino acids was only slightly lower than in the wild type. It is argued that two systems for amino-acid transport are present: one for neutral and acidic amino acids and the other for basic amino acids.