Relationship between the dynamic changes in polyamine pool and related parameters and nitrogen supply in maize plants under field conditions

Polyamines are low-molecular-weight, amino group-containing compounds that have an essential role in plant growth and development. Although the relationship between polyamine metabolism and N assimilation, and, consequently, grain filling is becoming more obvious, the detailed metabolic connection is still unclear. Moreover, the dynamics of N supply-induced changes in polyamine metabolism have not yet been studied during maize plant development. This study demonstrated that changes in polyamine content and certain related parameters (nitrate and proline contents, the enzyme activities of diamine and polyamine oxidases) are N sensitive, and concentration-dependent tendencies were also observed. However, the N fertilisation induced well-characterised developmental stage-dependent changes in the polyamine and proline accumulation, and polyamine catabolism in both maize hybrids, differing in maturity and NUE potential. The metabolic shift during the vegetative to generative phase may be in relation to the grain filling-induced N remobilisation, for which polyamines are valuable sources. Changes in putrescine/spermidine and their relation with NO 3 content showed some temporal, genotype-dependent differences. The persistence of the correlation between putrescine and nitrate contents in the FAO 490 maize hybrid may suggest that the higher metabolic activity contributes to better N remobilisation and, in turn, higher yield upon NPK experiment. Based on the authors’ findings, the developmental stage determines the extent of nutrient responsiveness, which underscores the importance of synchronising nutrient management with crop developmental stages. Therefore, monitoring of polyamine metabolism-related parameters can be an indicator of better N assimilation rate in the early reproductive stage until the R1 stage. • PA metabolism is N supply responsive in a concentration-dependent manner • Metabolic shift in PA metabolism is induced during the vegetative to generative phase change • Correlation between PUT and NO 3 content may be in relation to higher yield • These results suggest that PAs have an important role in N remobilisation during grain filling