Can just one-second measurement of chlorophyll a fluorescence be used to predict sulphur deficiency in radish (Raphanus sativus L. sativus) plants?

Nutrients deficiency (ND) in plants is one of the main factors adversely affecting plant growth and yield of agricultural and horticultural production. Usually detection of NDs in plants is based on visible symptoms ordestructive chemical analysis. Recently chlorophyll a fluorescence is one of the most used approaches to in-vestigate photosynthesis light-dependent reactions. It is widely accepted that it can in form about structural and functional changes in photosynthetic apparatus, especially under abiotic stresses including NDs. The aim of thisresearch was to study the influence of sulphur deficiency on photosynthetic efficiency of two cultivars radish (Raphanus sativus L. sativus) - ‘Fluo HF1’ and ‘Suntella F1’, and to assess the potential of chlorophyll a fluorescence measurements in early detection of this stress. Our results showed the sulphur deficiency has decreasedthe electron transport rate, chlorophyll content, grana size, and, at some degree, net photosynthesis and stomatal conductance. The changes in photosynthetic machinery performance were observed earlier than the visible effects of sulphur deficiency. However, the photosynthetic apparatus of radish plants was not considerably affected by this stress. Some sensitive parameters of OJIP test were altered but we were not able to identify thesulphur deficiency stress based on the alteration of only o ne of these parameters. We conclude that the detectionof specific stress reactions of plants to sulphur deficiency should be based on integrative analysis of the response of the photosynthetic machinery. Such stress induced reactions can be detected by Principal Component Analysisof a large number of JIP-test parameters.