Polyamines (PAs) such as putrescine (PUT), spermidine (SPD), and spermine (SPM) are ubiquitous aliphatic amines involved in widely varying physiological behavior, but particularly they are actively involved in cell growth, division, and differentiation during reproductive events in plants. The contents of PUT, SPD, and SPM in infertile and fertile thalli of the red macroalga Grateloupia sp. were compared, and the results revealed a significant decrease in quantity from infertile to fertile status. At the enzymatic level, L-ornithine decarboxylase (ODC) was mainly detected, and L-arginine decarboxylase activity was not diminished by the inhibition of ODC. The maximum enzymatic activities, within the range of activities observed, correlated with the lower levels of polyamines in fertile thalli. In culture, SPM promoted the maturation of cystocarps to the eventual liberation of spores from aseptic fertile explants. PAs accumulated in cultivated explants as compared with noncultivated, but exogenous SPM addition further increased the endogenous SPM. The addition of berenyl, cordycepin, cyclohexylamine, dicyclohexylamine, and aurintricarboxylic acid blocked the synthesis in culture at the level of PUT, and partially at SPD and SPM synthesis, but the addition of SPM restored the levels of SPD and SPM as SPM accumulated, and they appeared to interconvert each other. The results obtained suggest that the culture in presence of SPM restored a deficient SPM situation in fertile explants, thus promoting sporulation.

Polyamines such as putrescine, spermidine and spermine are ubiquitous aliphatic amines involved in reproductive events in plants and algae, and first become evident through changes in endogenous levels during reproductive development. To examine whether the differences observed in polyamines, during carposporogenesis, in the red alga Grateloupia, followed a specific pattern as is seen in other organisms, infertile axes (i.e. not showing cystocarps) were excised from the same holdfast of female fertilized individuals (i.e. showing cystocarps in other axes), and cultivated until the cystocarps became visible. Changes in the endogenous levels of free putrescine, spermidine and spermine were monitored over the 8 days of culture. The activity of enzymes related to polyamine metabolism, such as L-ornithine decarboxylase (ODC), diamine oxidase and polyamine oxidase, was measured at the beginning and end of the experimental period. Up to 50% of the infertile axes became fertile and produced cystocarps at a density of 1.91 ± 0.1 cystocarps mm À2 after 8 days. The endogenous content of spermine increased markedly over the first 5 days of culture, then decreased to the initial level by day 8.Spermidine followed a similar pattern to spermine, whereas putrescine remained at high levels, until day 5 when it decreased abruptly. The activity of ODC was less on day 8 than on day 0, whereas the activities of diamine oxidase and polyamine oxidase increased. In parallel experiments with explants from infertile axes, exogenously added spermine (10 À6 M) increased the number of cystocarps, and reversed the effect of cyclohexylamine (CHA), which is known to inhibit polyamine synthesis in Grateloupia. Serial sectioning and microscopic observation of specimens from explants cultivated in 10 À6 M spermine indicated that cystocarp development was induced. The results suggest that, during transition from infertile to fertile spermine is accumulated, thus favouring the development of cystocarps, given the presumed role of spermine as an inducing agent.