Acta Scientifica Malaysia (ASM)

The present study was aimed to determine the effects of seasonal changes in pH, water temperature (WT), and electrical conductivity (EC) on β-carotene biosynthesis in green spinach (GRSP) and green lettuce (GRLE) leaves from an aquaponic greenhouse. The pH values of the fish water tap (FWTP) and deep-water culture tank (DWCT) were measured with a portable electrode pH meter. The WT and EC of the FWTP and DWCT were measured using a portable dissolved oxygen meter and multi-parameter water quality meter, respectively. The biosynthesis of β-carotene in the GRSP and GRLE was determined using HPLC-Shimadzu Prominence. This research was conducted over four consecutive seasons (winter, spring, autumn, and summer). The pH values of the FWTP and DWCT ranged from 6.39±0.33–7.43±0.43. The pH levels were significantly differed among some seasons. The maximum and minimum pH values were detected in the winter and autumn, respectively. The WT values of these components (FWTP and DWCT) ranged from 12.12±1.34–25.21±0.95 °C. The EC levels ranged from 0.55±0.05–0.65±0.55 mS cm-1. The WT and EC values differed significantly across four seasons. The highest and lowest WT and EC levels were observed in the summer and winter, respectively. The biosynthesis of β-carotene in the GRSP and GRLE leaves ranged from 3.63±0.27–25.80±6.67%. A significant difference in β-carotene biosynthesis was detected among some periods. The highest level of β-carotene biosynthesis in both leafy vegetables occurred in the summer. The results of this study revealed that the seasonal dynamics of pH, WT, and EC induced variations in β-carotene biosynthesis in the studied leafy plants. Therefore, the results of this work could be used to understand better climate and growing conditions for sustainable food production.