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The Impact of seed size and varying N:P supply on seedling establishment of tropical plants

par Muthuthanthirige, Deshika
Promoteur Olde Venterink, H
Co-Promoteur Vandelook, Filip;POSCHLOD, Peter
Publication Non publié, 2022-08-30

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Résumé :

Nitrogen (N) and phosphorus (P) limitation and the ability of plant traits to obtain those nutrients actas ecological filters in terrestrial environments, shaping plant community composition. To ensuresuccessful early establishment, it is important to study how seedling traits respond to N and Pavailability, as well as how seed reserves allocate resources to seedlings. The aim of this study is toexamine how seed size affects seedling establishment under N and P limitation conditions. A shorttermgrowth experiment was conducted to examine how the relative availability of N and Pinfluences seedling traits and therefore to identify which of the nutrients (N or P) is in short supplyfor early establishment and whether this depends on seed mass. Seeds of eight tropical plant speciesbelonging to family Rubiaceae with varying seed sizes (masses) were selected. Seeds were grown for7 weeks at three N: P supply ratios: 1.7 (N limitation), 15 (balanced N and P), and 135 (P limitation),with two levels of supply (low and high) in the greenhouse. The variation of seedling traits; growthtraits (relative growth rate and total biomass); allocation traits (root mass ratio); tissue constructivetraits (specific toot length and specific leaf area) were measured in relation to varying N:P supplyratios and levels, and to seed mass. Seedling trait responses, notably growth traits for N and Plimitation, differ considerably between species. Seedlings raised from seeds with different seedmasses had a greater impact on seedling traits under different N: P ratios and supply levelsdemonstrating that larger seeds produce seedlings with higher biomass even when N and P werelimited. Despite the fact that P limitation affected RGR, seedlings did not respond to high nutrientsupply levels and instead relied on seed mass. Phosphorus limitation was more prominent than Nlimitation for the early growth and establishment of these tropical plant species especially on fastgerminating, small seeded species. Further, smaller seeds contain more N and P relative to theirtotal seed mass, resulting in a lower N: P ratio that facilitates for a higher relative growth rate. Thus,it is essential to understand seedling performance in N and P limited environments since itdetermines species composition in a plant community. This study may provide a betterunderstanding of why seed mass is critical to seedling establishment at an early stage when N and Pare limited.