The pot experiment investigated an effect of varied phosphorus, potassium and magnesium fertilisation on the intensity of photosynthesis, transpiration, intercellular CO₂ concentration and stomatal conductance as well as some plant biometrics obtained from ‘Jaspis’, a traditional home cultivar pea, and from homozygotic isoline, ‘RRRbRb’, and yellow lupin; ‘Teo’, a traditional cultivar, and ‘Markiz’, a self-completing cultivar. A lowered phosphorus and potassium fertilisation decreased the intensity of photosynthesis in pea forms researched. The photosynthesis in the yellow lupin cultivars investigated was higher in the pod-filled stage than the intensity of the process in 3-7– true leaf phase. However the transpiration intensity was lower in the pod-filled stage. The research results showed that out of all the three applied macroelements only lowering of the magnesium dose decreased the weight of seed weight from plant both in the tested pea and in yellow lupin cultivars.