Acquisition and allocation of resources in two waterlogging-tolerant grasses

This study focuses on the following questions: (i) whether reductions in ro ot:shoot ratio have a cost in terms of nutrient balance of the plant, and ( ii) whether changes in resource-allocation patterns are proportional among different resources. Our approach was to analyse the variations in the allo cation pattern induced by soil waterlogging. A pot experiment was conducted to analyse the effects of waterlogging on biomass, phosphorus (P) and nitr ogen (N) accumulation of Paspalum dilatatum and Danthonia montevidensis, tw o waterlogging-tolerant grasses. When changing from oxic to anoxic conditio ns, a common response of these and other waterlogging-tolerant grasses is a reduction in allocation to below-ground resources. It was observed that (i ) the reduction in root:shoot ratio caused by waterlogging did not have a c ost in terms of capacity for nutrient uptake; (ii) resource partitioning wi thin aerial parts was less sensitive to treatments than partitioning betwee n roots and shoots; and (iii) biomass does not appear to be a useful curren cy for evaluating nutrient-allocation patterns, as the allocation of P and N was inadequately represented by biomass. The results presented here indic ate that the existence of compensation mechanisms reduces the predictive va lue of the partition of resources for the capacity of plants to acquire res ources. Data on the allocation of nutrients in relation to biomass suggest that the assumptions of independence in the allocation pattern between biom ass and limiting nutrients under the effects of environmental factors can b e extended.