Abstract:
Tritiated water has been used as the aqueous medium for the germination of Sinapis alba (White mustard) seeds, A hitherto unknown metabolite, of great importance, labelled in this process has been identified as lactic acid. Another metabolite, tentatively identified by earlier workers as fructose, has been shown to be sucrose.
Studies on the metabolism of seeds, imbibing water under anaerobic conditions, have shown that Sinapis alba seeds do actively metabolise under these conditions. However, this metabolism does not lead to the formation of a seedling.
Moreover it has been found that the active metabolism of Sinapis alba seeds for 24 hours, under anaerobic conditions, does not lead to their death, since on restoration to air they do germinate, albeit much more slowly. It has also been shown that significant differences exist in the pattern of labelling under anaerobic conditions, from that under aerobic conditions. The notable difference found is that large amounts of lactic acid accumulate under anaerobic conditions, within the seed, but on transferring the seeds to an oxygen atmosphere this situation is reversed. As a working hypothesis it is proposed that the anaerobic metabolism leads to the accumulation of lactic acid which inhibits the metabolism leading to germination. Lactic acid has been shown to inhibit the germination of Sinapis alba seeds. It has also been found that while glutamic acid and aspartic acid are present under anaerobic conditions, these amino acids (in particular the former) do not become appreciably labelled, while under air they do. It is suggested that the lactic acid, accumulated under these conditions, possibly inhibits the enzymes involved in the utilisation of these very important amino acids, and hence inhibits the germination of the seed.
