Accumulation of α-tocopherol in Capsicum annuum L. influenced by changes in water temperature

Abstract

A temperature below or above the optimum can reduce the rate of photosynthesis in higher plants, which in turn decreases metabolite precursor pools for the biosynthesis of secondary metabolites. The aim of this study was to determine the effects of seasonal changes in water temperature on α-tocopherol accumulation in pepper (Capsicum annuum L.) fruits from an aquaponic system. A portable dissolved oxygen meter was used to measure water temperature and high-performance liquid chromatography was used to determine the levels of α-tocopherol accumulation. Temperature of the fish water ranged from 8.3 °C to 13.8 °C in winter and from 20.2 °C to 25.8 °C in summer. Water temperature in winter was significantly different (p < 0.05) from that in summer. α-Tocopherol accumulation in pepper fruits differed significantly (p < 0.05) between winter (0.77 ± 0.13%) and summer (1.64 ± 0.21%). Changes in water temperature due to seasonality caused variations in α-tocopherol accumulation in pepper fruits, with fruits in the warmer season (summer) showing a higher accumulation of α-tocopherol. The warmer season is therefore a better period for α-tocopherol biosynthesis.

Significance:

This study evaluated whether variations in seasonal temperature in South Africa can affect α-tocopherol accumulation in pepper fruits grown in an aquaponic system. An aquaponic system could provide a sustainable solution for South Africa, with its diverse seasons and scarcity of fresh water. Determining the optimal temperature for increased α-tocopherol biosynthesis in higher plants improves our understanding of a favourable climate for a sustainable vitamin E source.