Abstract:
Indoor experiments were carried out to examine the effect of spirulina (Arthrospira platensis)
stimulant on growth performance and biochemical response of lettuce (Lactuca sativa) grown in
an aquaponic system. The lettuce plants, 10.45±0.12cm (Mean ± SD), were randomly distributed
and transplanted into four treatments consisting of 0 (control), 4.0, 8.0, and 12.0g spirulina/L of
water and replicated four times. The treatments were administered once every week in form of a
foliar spray for 5 weeks. The effect of spirulina stimulant on Leaf length, leaf width, leaf area,
dry matter, and antioxidants content of L. sativa in the aquaponic system was determined.
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Analysis with polynomial contrasts showed that the quadratic trend for the number of leaves
significantly (p <0.05) increased with a peak at 8 g of spirulina/L of water. The cubic trend for
final leaf length, width, and leaf area was significantly (p <0.05) increased with a peak at 8 g of
spirulina/L of water. The contrasts analysis showed a significant (p <0.05) linear increment for
dry weight with a peak at 12 g of spirulina/L of water. For antioxidant contents, the contrasts
analysis showed a linear increase for the FRAP, quadratic increase for the DPPH, cubic increase
for the ABTS, and quadratic increase for the Total phenols of L. sativa.
The results above show that the application of spirulina (A. platensis) foliar spray has a positive
effect on the growth performance and biochemical properties of lettuce (L. sativa) grown in an
aquaponic system.
Keywords: Antioxidants, Lactuca sativa, aquaponic system, spirulina
