A portable, two-wavelength fluorometer based on recording chlorophyll fluorescence induction of agronomic plants is proposed. The effects of various fertilizers on fluorescence of soybean and rapeseed were studied. It was shown that the most effective fertilizer combinations were N15P15K15 for soybean and N75P60K75 for rapeseed. The effects of high-intensity solar radiation on chlorophyll fluorescence of bush bean can be explained by the process qE-quenching which depends on the presence of a proton gradient across the thylakoid membrane, and qI-quenching which occurs with excessive radiation; this type of quenching provokes photoinhibition. It is possible to suggest an effect of protein structural change in chlorophyll fluorescence quenching. Ultraviolet (especially UV-B) radiation predominantly damages DNA. The main molecular alteration in UV-B-irradiated DNA is the formation of dimer photoproducts – pyrimidine dimers of cyclobutane structure which are responsible for disrupting the genetic code and damaging the photosynthetic apparatus of bush bean. In detached leaves the water deficit develops faster and therefore it is accompanied with a decline of the fluorescence indices. The proposed portable fluorometer is characterised by compactness, an independent power supply, high sensitivity, and gives a non-destructive estimate of in vivo fluorescence parameters of agronomic plants.