Fertiliser application positively affects plants performance but reduces seed viability in seashore mallow (Kosteletzkya pentacarpos): implication for biomass production and species conservation

Kosteletzkya pentacarpos seashore mallow, is recognised as an important plant species for several industrial applications, especially in North America and Asia. In Europe, seashore mallow is highly threatened and subject of conservation actions (e.g. reintroduction). In order to define appropriate multipurpose cultivation protocols, suitable for biomass production and for conservation purposes, we investigated the effect of varying levels of soil salt content and nutrient availability on seashore mallow. As expected, seashore mallow had the best performance in terms of growth rate, flowering and fruit production when fertiliser was applied, while salt had only limited effects. Interestingly, seeds produced by fertilised plants showed a lower germination performance and higher mortality than seeds developed from non-fertilised plants. Our results highlight a trade-off between parental plant growth and seed performance, the former being enhanced and the latter being reduced by fertiliser application. The causes of this trade-off are related to a transgenerational maternal effect of fertiliser application that has important implications for seashore mallow cultivation. Biomass production benefits from fertiliser application but if the quality of seeds and the fitness of the next generation are major objectives (e.g. seed production and species conservation), fertiliser application is not recommended.