A kelp with integrity: Macrocystis pyrifera prioritises tissue maintenance in response to nitrogen fertilisation

摘要: Our understanding of the response vascular, terrestrial plants to nitrogen (N) addition is advanced and provides foundation for modern agriculture. In comparison, information on responses marine macroalgae increased far less developed. We investigated how in situ pulses nitrate (NO3 (-)) affected growth N physiology Macrocystis pyrifera by adding using potassium dissolution blocks during a period low seawater concentration. Multiple parameters (e.g. growth, pigments, soluble NO3 were measured distinct tissues throughout entire fronds (apical meristem, stipe, adult blade, mature sporophyll, holdfast). Unexpectedly, fertilisation did not enhance elongation rates within frond, but instead thickness (biomass per unit area) blades. Increased blade may have enhanced tissue integrity as fertilised kelp had lower erosion. Tissue chemistry also responded enrichment; pigmentation, (-), % N higher fronds. Labelled (15)N traced uptake translocation from sources canopy sinks holdfast, 10 m below. This first evidence long-distance (>1 m) transport macroalgae. Patterns physiological suggest that M. displays functional differentiation between basal aid nutrient-tolerance strategies, similar those seen unlike more simple algae (i.e. non-kelps). study highlights little we know about additions N-use strategies compared wealth literature available plants.