Regulation of cadaverine and putrescine levels in different organs of chick‐pea seed and seedlings during germination

In chick‐pea (Cicer arietinum L.) seed germinated in the presence of 14C‐lysine, the latter is taken up and partly metabolised to cadaverine and TCA‐precipitable molecules. Labelled cadaverine is detectable in seedlings only after 3 days, on a labelled lysine‐containing medium, as confirmed also by the presence of lysine decarboxylase (LDC) activity, measured in the embryo axis and cotyledons of the seed and in the epicotyl, cotyledons, hypocotyl and roots of the seedling on the basis of 14CO2 evolution from the labelled precursor. Putrescine biosynthesis occurred only via arginine decarboxylase (ADC) activities in soaked seeds and via both ADC and ornithine decarboxylase (ODC) activities in seedlings. Both putrescine and cadaverine were present in soaked seed, and accumulated in very large amounts in the different portions of both 3‐ and 8‐day‐old seedlings, while spermidine and spermine titers were maintained at similar levels with respect to the seed. Diamine oxidase activity, measured by evaluating oxygen consumption in the presence of putrescine, was absent in ungerminated seed and appeared in 3‐ and 8‐day‐old seedlings. In order to clarify the metabolic relationships between cadaverine and the more common polyamines, gradients of biosynthesis, accumulation and degradation of putrescine and cadaverine along the seedling axis were compared, indicating that the two diamines behave similarly during seed germination and seedling development. Their conspicuous accumulation (up to 6 mM for putrescine) seems to be regulated mainly via oxidation rather than biosynthesis.