The photosynthetic apparatus of eukaryotic organisms posseses a remarkable ability to adapt to ever changing light conditions and other environmental cues. In the present study, the compositon of plant light harvesting complex I (LHCI), its association with photosystem I (PSI) and its dynamic changes upon iron deficiency as one environmental variable were investigated by means of qualitative and quantitative proteome analyses using Chlamydomonas reinhardtii and Lycopersicon esculentum as model organisms. With stable isotope labelling and mass spectrometry, C. reinhardtii LHCI was shown to be heterogeneously composed with a total number of between six and eight proteins. In a study comparing the photosynthetic apparatus under iron sufficient and iron deficient conditions, N-terminal processing of Lhca3 was shown to be a key event in the remodelling of PSI-LHCI into a dissipative conformation upon iron deficiency. The results show that the heterogeneity and plasicity of LHCI enable the photosynthetic apparatus to function optimally under varying environmental conditions.