Microwave-assisted digestion of wetland plant tissue for TN and TP analysis

Can anyone tell me the most suitable set of methods for determining TN and TP in wetland plant tissue please? On a forthcoming trip abroad I shall have use of microwave-assisted digestion for the first time. I understand that most methods use acid (H2SO4?) and peroxide (H2O2) to complete the digest - but then how to proceed for TN and TP analysis (ICP spectroscopy?, are there standard methods for N and P?). Ideally I'm looking for a single digestion technique that allows for the simultaneous analysis of TN/TP, similar to those available for water analyses. The problem being that most water digestion techniques would not (in terms of achieving high enough temp and pressure) clear the digest of plant tissue (<1 g samples). The plant is a wetland emergent. Thank you very much indeed.