Specific leaf area, leaf nitrogen content, and photosynthetic acclimation of Trifolium repens L. seedlings grown at different irradiances and nitrogen concentrations

Abstract

Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO3-, i.e. N5 to N25) and two irradiances, I (200 and 400 μmol m-2 s-1 of photon flux density, i.e. I 200 and I 400). Net photosynthetic rate (P N), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (F v/Fm), and actual photochemical efficiency of photosystem 2 (PS2) (ΦPS2) increased from N5 to N15 and decreased with N15 to N25. P N, PNUE, and ΦPS2 were higher at I 400 than at I 200, but Fv/Fm and leaf Chl contents at I 400 were lower than at I 200. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (Nm) were similar, the SLA and Nm increased from N5 to N25 and they were higher at I 200 than at I 400. The nitrogen contents per unit area (Na) increased from N5 to N20, but decreased from N20 to N25. The Na was higher at I 200 than at I 400 when Trifolium repens grew at N 5 and N10, but it was higher at I 400 than at I 200 at N15 to N25. © 2008 Institute of Experimental Botany, ASCR.