Changes in the Free Amino Compounds in Young Tomato Plants in Light and Darkness with particular Reference to -Aminobutyric Acid

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Abstract
Tomato plants were grown to the five-leaf stage under uniform conditions in a growth room with a daily light period of 15 h. Plants were sampled at intervals through 24 h periods and the free ninhydrin-positive compounds determined in roots, bleeding sap, stems and shoots (mainly leaves), using ion-exchange column chromatography and a lithium-buffer separation system. The compounds present and their range of concentrations are given for two occasions: after illumination for 8 hand after 5 h of darkness. Data for γ-aminobutyric acid (GAB), glutamic acid, glutamine, alanine, aspartic acid and ammonia are summarized graphically for all occasions and for all parts of the plant; asparagine for sap only. The data were examined for correlations between these substances for both light and dark conditions. Relative amounts of free acids were: root glutamine> glutamic and GAB > aspartic > alanine; bleeding sap glutamine > asparagine > GAB > aspartic> alanine; stem glutamine > glutamic > GAB and aspartic > alanine; shoot (leaf) GAB and glutamine > aspartic > alanine and glutamic. Patterns of change were as follows: in the root GAB and glutamic were similar and unlike glutamine; alanine did not change;sap ammonia, GAB and alanine were parallel, glutamine was similar to these only in light; in the stem glutamine and glutamic tended to accumulate in parallel in light, but GAB did not; in the shoot (leaf) GAB and glutamine were similar except that the former accumulated more rapidly in the initial light period; glutamic acid and alanine were similar to each other but distinct from GAB and glutamine. The relatively large amounts of GAB in tomato plants and the magnitude of the changes occurring in light and darkness seem indicative of its importance as a temporary storage product for protein amino acids, but the factors controlling accumulation and utilization in different parts of the plant are unknown.

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