Alterations in Chlorophyll a Fluorescence and Pigments Concentration in the Leaves of Cauliflower and Broccoli Transplants Subjected to Chilling

Abstract

Chlorophyll a fluorescence parameters and photosynthetic pigments content in leaves of broccoli (Brassica oleracea L. var.italica) cv. ‘Monaco’ F1 and cauliflower (Brassica oleracea L. var. botrytis) cv. ‘Bruce’ F1 transplants were analyzed to investigatethe effects of chilling temperatures (6 and 10 °C) and the exposure length (1 or 2 weeks) on the photosynthetic apparatuscondition in 3-year experiment. Data were compared to control plants exposed to 14 °C for 1 and 2 weeks. The lowest valuesof maximum quantum efficiency of photosystem II (Fv/Fm) and the performance index (PI) were observed in cauliflowerchilled at 6 °C for 2 weeks. This was not accompanied by any substantial reduction in chlorophylls concentration, however,significant correlations between Fv/Fm or PI and chlorophylls content in cauliflower leaves were found. There was no negativeeffects of chilling on photosynthetic activity and chlorophyll content in broccoli leaves, the amount of carotenoids significantlyincreased in the broccoli chilled for 2 weeks in 6 °C. The chlorophyll a fluorescence indices and accelerated carotenoidssynthesis showed that broccoli had less vulnerable photosynthetic apparatus to stress-induced temperatures and more efficientprotection mechanisms in comparison to cauliflower transplants.