Seasonal and diurnal changes in β-carotene concentration in spinach plant grown hydroponically

Abstract

To produce spinach (Spinacea oleracea L.) plants with high quality and β-carotene, they were grown hydroponically in a glasshouse and analyzed at various times of the day and periodically during the growing season. Leaves weighing up to 2 g of fresh weight (FW), tended to be richer in β-carotene in March to April than September to October. In those weighing over 2 g FW, the β-carotene concentration did not differ significantly between seasons. The difference in FW of the leaf blade and petiole influenced β-carotene content of the whole leaf (Exp.1). β-carotene concentrations significantly decreased shortly after daybreak, then increased and remained relatively high until dusk. The high concentration during the day period reflects the accumulation of dry matter. The diurnal fluctuations at 15/10 °C and 20/15 °C were closely parallel (Exp.2). Based on these data, we recommend that spinach is not harvested when β-carotene level decreases in the morning.