The effectiveness of different combinations of hoaglands’s solution and azolla filiculoids on hydroponically cultivated beta vulgaris subsp. cycla ’Fordhook Giant'

Abstract

This study evaluated the effects of different combinations of Hoagland’s solution and Azolla filiculoides on Beta vulgaris subsp. cycla ‘FORDHOOK GIANT’ grown in different hydroponic nutrient solutions. These solutions were comprised of a full Hoagland’s solution and a Hoagland’s solution minus nitrogen solution and amalgamations of these with Azolla respectively. The objectives were to assess the effects of different combinations of Hoagland’s solution and A. filiculoides on uptake of nitrogen and other nutrients, photosynthesis, chlorophyll content, growth and development in B. vulgaris grown in hydroponic cultures. The treatments were made up of 1) Hoagland’s minus N solution (as the control), 2) A. filiculoides plus Hoagland’s minus N solution, 3) A. filiculoides plus a full Hoagland’s solution and 4) full Hoagland’s solution. Each treatment was replicated 4 times. Nutrient uptake was measured at 4 and 8 weeks into the experiment. Photosynthesis was measured by analysing the photosynthetic rate, stomatal conductance, intercellular CO2 concentration and the evapotranspiration rate of B. vulgaris on a weekly basis. Chlorophyll content was determined by analysing the samples at 4 and 8 weeks. Growth and development was determined by measuring plant height, leaf number, leaf colour, fresh weight and dry weight. Plant height, leaf number and leaf colour on a biweekly intervals, while fresh and dry weight were analysed at 4 and 8 weeks into the experiment. In this study, the most favourable results were attained by the full Hoagland’s solution. This treatment produced plants with the highest nutrient uptake, photosynthesis, chlorophyll content and best growth and development. Preceding this was the Azolla plus full Hoagland’s solution, followed by the Azolla plus Hoagland’s minus nitrogen solution. The poorest results were noted in the control (Hoagland’s minus nitrogen solution) as all the tested parameters in this treatment were the lowest. In this study, Azolla plus Hoagland's minus N solution treatment produced significant growth in B. vulgaris. Although nitrogen was not applied in this treatment, there was improved nitrogen content in B. vulgaris organs. It is postulated that, probably, Azolla released the fixed nitrogen in its surrounding environment making it available to B. vulgaris hence improving N uptake and growth. This implies that there was a synergistic effect from Azolla–Anabaena symbiosis. More studies to understand the mechanisms involved in improving the plant growth are recommended.