The specific nitrogen response in a Tokai hilly land element Drosera tokaiensis (Droseraceae) and its parental species

Abstract

The carnivorous plants of the genus Drosera grow on nitrogen-limited wetlands. Year-round measurements of nitrate concentrations at nine spots in the campus of Chubu University showed that nitrate concentration in the habitat of D. routundifolia (Dr) hardly exceeded 3 μM, whereas that of D. tokaiensis (Dt) ranged from 1 μM to 200 μM with the average being 50 μM, suggesting that Dt prefers (or tolerates) higher nitrate concentrations than Dr . Since Dt has been shown to originate from a natural cross between Dr and a closely related species Drosera spatulata (Ds), we compared the response of the three species to different nitrogen conditions in the greenhouse. In all three species, the shoot was burned by irrigation with 15 mM KNO₃ or 7.5 mM (NH₄)₂SO₄ but not with 15 mM KCl. At 5 mM of nitrate or ammonium, Dt and Ds could grow fine but Dr still showed growth inhibition. These results indicated 1) All the three Drosera species are sensitive to high nitrogen conditions; 2) Dr is more sensitive to nitrogen than Dt and Ds are; and 3) Dt inherited the tolerance against high nitrogen conditions from Ds.