Effects of Seedling Substrate and Hydroponic Versus Aquaponic Nutrient Solution on Growth, Nutrient Uptake, and Eco-Physiological Response of Lemon Basil (Ocimum × citriodorum)

Abstract

Lemon basil (Ocimum × citriodorum) is a highly valued aromatic plant renowned for its distinct citrus aroma. This study aimed to evaluate sustainable substrates and cultivation systems for its production. Two complementary and sequential experiments were conducted: an initial experiment designed to compare coconut fiber mixed in varying proportions with perlite to rock wool, evaluating their effectiveness during germination and early growth (experiment 1), and a subsequent experiment aimed at assessing plant performance in a decoupled aquaponic system relative to hydroponics utilizing the best-performing coconut fiber-perlite mixture from the first phase along with rock wool as substrates (experiment 2). The substrate with 70% coconut fiber and 30% perlite (F70:P30) significantly improved seed germination, leaf number, and total leaf area of seedlings. The decoupled aquaponic cultivation system resulted in a 52.5% increase in flavonoid content, accompanied by higher calcium and magnesium uptake in stems and roots compared to hydroponics. These findings clearly underscore the potential of coconut fiber substrates mixed with perlite as sustainable alternatives to rock wool, reducing environmental impact, disposal costs, and health risks. Similarly, aquaponic cultivation emerges as a valuable strategy for sustainable lemon basil (Ocimum × citriodorum) production, offering comparable yields to hydroponics while improving plant nutritional and phytochemical quality through beneficial plant-microbe interactions. These results provide practical evidence supporting the adoption of environmentally friendly substrates and cultivation practices, thus contributing significantly toward sustainable intensive vegetable production systems.

Keywords: aquaponics; coconut fiber; flavonoids; lemon basil (Ocimum × citriodorum); soilless cultivation.

Figure 1

Cluster heatmap analysis displaying the relationships among growth parameters of lemon basil (Ocimum × citriodorum) seedlings grown on four different substrates: coconut fiber mixed with perlite at three ratios (F50:P50, F70:P30, F90:P10) and 100% rock wool (RW), in controlled growth chamber conditions. Each row represents a specific growth parameter (e.g., germination percentage, leaf number, root length), while each column represents an individual substrate treatment. Colors represent standardized values (ln(x + 1) transformed): higher values in red indicate above-average performance, whereas lower values in blue represent below-average performance. Hierarchical clustering was performed using Euclidean distances and complete linkage to group similar treatments and parameters together.

Figure 2

Cluster heatmap analysis illustrating morpho-anatomical parameters of lemon basil (Ocimum × citriodorum) plants grown on two different substrates: 70% coconut fiber mixed with 30% perlite (F) and 100% rock wool (RW) and in two different cultivation systems, hydroponic (H) or aquaponic (A). Rows represent the measured parameters (e.g., leaf number, total leaf area, root length, flavonoid index), and columns represent each combination of substrate and cultivation system. Color intensity reflects standardized values (ln(x + 1) transformed), with red indicating higher-than-average values and blue indicating lower-than-average values. Hierarchical clustering was conducted using Euclidean distances and complete linkage.