Skip to Main Content
 

Global Search Box

 
 
 
 

ETD Abstract Container

Abstract Header

Improving Lettuce Productivity while Suppressing Biofilm Growth and Comparing Bacterial Profiles of Root Area and Nutrient Solutions in Windowfarm Systems

Abstract Details

2014, Master of Science, Ohio State University, Food Science and Technology.
Hydroponic systems have gained worldwide popularity and are increasingly used in various purposes in different geographic areas. To improve and produce more hydroponic crops, a variety of hydroponic systems have been developed, such as: wick, drip, ebb-flow, water culture, nutrient film technique, aeroponic, and windowfarm systems. Numerous studies show that hydroponics have many advantages over culture systems; i.e., reuse of water, ease in controlling external factors, and reduction of traditional farming practices (e.g., cultivating, weeding, watering, and tilling). However, limitations include: high setup cost, rapid pathogen spread, and specialized management. The purpose of this Review (Chapter 1), `Introduction to Hydroponic Systems’ are to: 1) characterize the trends, advantages, and limitations of different systems; 2) introduce different types and methods of operation; and 3) discuss research being conducted in plant diseases and the role of beneficial bacteria. The Review (Chapter 1) provides a better understanding of hydroponics and newly applied systems and discusses their optimization to enhance food quality and quantity, and reduce plant diseases. In Chapter 2, the windowfarm is described, when plants are often prone to infections by phytopathogens that slow plant growth and reduce crop productivity and excessive biofilm build-up due to high concentration of nutrients in the system. The major items discussed in Chapter 2 are: 1) development of a new windowfarm system that uses minimal water; 2) presentation of methods that promote plant health by making plants more resistant to phytopathogen infection and enhance growth using biosurfactant-producing Pseudomonas chlororaphis around plant roots; and 3) demonstration of methods that minimize biofilm build-up, such as UV irradiation, thereby extending the usable lifespan of the whole hydroponic system. To examine these items, Romaine lettuce was cultivated for 11 weeks in a windowfarm system. P. chlororaphis was inoculated near the roots, subsequently producing pyoverdine (yellow-green fluorescent pigments). For enhancing bacterial colonization, glass beads or clay granules were added. The water reservoir was treated once a week for 5 min with low pressure ultraviolet (UV) irradiation to minimize biofilm build-up in the system while maintaining the colonized beneficial microbial flora around the roots. Food productivity was measured by the number of leaves and length and weight of the lettuce; quality was measured by lettuce color. Pythium ultimum, a plant pathogen, was inoculated on the root areas to examine the protective effects of P. chlororaphis against P. ultimum. The results show that P. chlororaphis-treated lettuce grew significantly better than non-treated lettuce as indicated by enhancement of color, weight, length, and number of leaves per head (p < 0.05). The death rate of the lettuce was also reduced by half when the lettuce was treated with P. chlororaphis. UV irradiation reduced the concentration of bacteria (4 log reduction) and algae (4 log reduction) in the water reservoirs and water tubing systems. In summary, the results suggest that introduction of P. chlororaphis into a windowfarm system promotes plant growth and reduces damage caused by plant pathogens. Additionally, UV irradiation of the water reservoir results in reduction of algal and biofilm growth and extends the lifespan of the system. In Chapter 3, how the use of beneficial bacteria, addition of beads around roots and UV treatments affect bacterial diversity and community in hydroponic systems were examined. . The objectives of this study were to: 1) examine bacterial diversity and community in hydroponic systems; 2) compare the effect of three different treatments (beads, P. chlororaphis, and UV irradiation) in root areas using the PCR-DGGE method; and 3) identify bacteria in root areas and water in a windowfarm system. Bacterial profiles were compared under three different treatments (bead and P. chlororaphis treatments in root area, and UV irradiation of reservoir water) using PCR-DGGE and banding pattern analysis. After cultivation of lettuce in windowfarm systems, clay, bead and water samples were collected and bacterial community DNA was extracted for analysis. The DGGE bands were analyzed and interesting bands were selected for bacterial identification. The results demonstrated that 1) P. chlororaphis had positive effects on lettuce’s growth and root development; 2) the bacterial community of the root area was affected significantly by beads (clay pelltes versus glass beads with clay pelltes) and P. chlororaphis treatments; 3) Beads and P. chlororaphis treatments did not make the change of bacterial diversity around root area in the windowfarm system. Bacteria that are beneficial for plant growth were found in the windowfarm sytem (Variovorax paradoxus, Pseudomonas fluorescens, Pseudomonas thivervalensis, and Pseudomonas brassicacearum). In conclusion, the results suggest that 1) P. chlororaphis-treated lettuce grew significantly better than non-treated lettuce as indicated by a 50% reduction in the death rate and enhancement of color, weight, and number of leaves per head (p < 0.05); 2) UV irradiation reduced the biofilm growth in water tubing systems and extended the lifespan of the system; 3) the bacterial profile provides a better understanding of bacterial activities in the root area and water in hydroponic systems and how plants and microorganisms interact.
Jiyoung Lee (Advisor)
Ahmed Yousef (Committee Member)
Luis Rodriguez-Saona (Committee Member)
122 p.

Recommended Citations

Citations

  • Lee, S. (2014). Improving Lettuce Productivity while Suppressing Biofilm Growth and Comparing Bacterial Profiles of Root Area and Nutrient Solutions in Windowfarm Systems [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1398988586

    APA Style (7th edition)

  • Lee, Seungjun. Improving Lettuce Productivity while Suppressing Biofilm Growth and Comparing Bacterial Profiles of Root Area and Nutrient Solutions in Windowfarm Systems. 2014. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1398988586.

    MLA Style (8th edition)

  • Lee, Seungjun. "Improving Lettuce Productivity while Suppressing Biofilm Growth and Comparing Bacterial Profiles of Root Area and Nutrient Solutions in Windowfarm Systems." Master's thesis, Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1398988586

    Chicago Manual of Style (17th edition)