The Effect of Different Nitrogen and Potassium Nutrient Levels Used in Hydroponic System on the Growth and Steviol Glycosides Production in Stevia Rebaudiana Bertoni

Ho, Zhi Wei (2022) The Effect of Different Nitrogen and Potassium Nutrient Levels Used in Hydroponic System on the Growth and Steviol Glycosides Production in Stevia Rebaudiana Bertoni. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Stevia rebaudiana Bertoni is a branched bushy shrub belonging to the Asteraceae family. Stevia rebaudiana contains various sweet-tasting diterpene glycosides in the leaves and has long been used as natural sweeteners. Stevioside and rebaudioside A are the two most abundant steviol glycosides and both are sweeter than sucrose. In recent years, stevia has become popularly used in the food and beverage industry. However, low biomass yield of the S. rebaudiana leaves which is dependent on the agricultural practices will lead to low yield of steviol glycosides extracted. Therefore, a study on the effect of different nitrogen (N) and potassium (K) levels on the growth and production of steviol glycosides, stevioside and rebaudioside A, of S. rebaudiana was undertaken. In this study, there were a total of seven treatments, which were 200% N, 150% N, 50% N, 200% K, 150% K, 50% K and 100% as control. There were 10 S. rebaudiana plants in each treatment, five plants per replicate, and two trials were done in Farm Box in a controlled environment with a hydroponic system, and also in a greenhouse, which was an uncontrolled environment at Tunku Abdul Rahman University College Johor branch campus. The growth parameters such as height, number of leaves, leaves area, and the chlorophyll content of the young leaves were measured for every 7 days from day 1 until day 35, the day of harvest. The soxhlet extraction was done after the drying of the S. rebaudiana leaves. The leaf extract was further analyzed by using HPLC for the qualitative analysis. From this study, the 150% N and 150% K had the best growth to the height: N (13.28 ± 3.72), K (17.29 ± 2.10), number of leaves: N (52.00 ± 17.73), K (97.50 ± 15.04), leaves area: N (5.66 ± 2.80), K (16.75 ± 5.99), chlorophyll content: N (31.35 ± 1.92), K (26.99 ± 1.77), biomass of leaves: N (2.59 ± 0.87), K (3.21 ± 1.08) of the S. rebaudiana that were planted in Farm Box with the controlled environment. Besides, the 200% N and 200% K had the best growth to the height: N (18.8 ± 7.53), K (8.86 ± 2.84), number of leaves: N (51.4 ± 7.73), K (32.00 ± 9.27), leaves area: N (4.36 ± 1.51), K (3.93 ± 1.15), chlorophyll content: N (16.48 ± 3.58), K (17.36 ± 1.71), biomass of leaves: N (0.52 ± 0.16), K (0.32 ± 0.09) of the S.rebaudiana that were planted with cocopeat in a greenhouse with the uncontrolled environment. With the qualitative analysis of HPLC, the stevioside and rebaudioside A were proved to have presence in the S. rebaudiana plant with the retention time of 10.83 min and 10.84 min.