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- All Subjects: Plant sciences
- Creators: Park, Yujin
- Member of: Theses and Dissertations
Description
Chemical fertilizers are commonly used for controlled environment agriculture because they provide essential plant nutrient efficiently. However, rising fertilizer costs, global phosphorous shortage, and the negative impacts of producing and using chemical fertilizer are concerns for sustainable crop production. As sustainable alternatives to chemical fertilizers, there is a growing interest in using organic fertilizers with beneficial plant growth promoting microorganisms. The objectives of this research were to investigate how the application of plant growth promoting bacteria and arbuscular mycorrhizal fungi influences plant growth of lettuce (Lactuca sativa) and tomato (Solanum lycopersicum) seedlings in soilless media under organic fertilization. In the first study, the effects of Azosprillium brasilense and Rhizophagus intraradices inoculation on lettuce and tomato seedling growth were quantified under two different organic fertilizer types compared to under chemical fertilizer. The results showed that A. brasilense and R. intraradices had little to no effect on any growth parameter measured in either species regardless of fertilizer type. In the second study, an investigation of the co-inoculation of A. brasilense and R. intraradices or increasing the application frequency of A. brasilense or/and R. intraradices increased plant growth promoting effects in lettuce ‘Cherokee’ and ‘Rex’ grown under organic fertilization. An application frequency of every 2-days of the R. intraradices without or with A. brasilense increased shoot fresh weight in both lettuce cultivars by 51-58%, compared to un-inoculated control. In contrast, lettuce seedling growth were similar without or with applying R. intraradices weekly or A. brasilense regardless of frequency. Together, the results suggest that applying R. intraradices with a proper application frequency can enhance plant growth of lettuce under organic fertilization.
ContributorsMcClintic, Nicklas Charles (Author) / Park, Yujin (Thesis advisor) / Penton, Christopher R (Committee member) / Chen, Changbin (Committee member) / Arizona State University (Publisher)
Created2022
Description
The partitioning of photosynthates between their sites of production (source) and their sites of utilization (sink) is a major determinant of crop yield and the potential of regulating this translocation promises substantial opportunities for yield increases. Ubiquitous overexpression of the plant type I proton pyrophosphatase (H+-PPase) in crops improves several valuable traits including salt tolerance and drought resistance, nutrient and water use efficiencies, and increased root biomass and yield. Originally, type I H+-PPases were described as pyrophosphate (PPi)-dependent proton pumps localized exclusively in vacuoles of mesophyll and meristematic tissues. It has been proposed that in the meristematic tissues, the role of this enzyme would be hydrolyzing PPi originated in biosynthetic reactions and favoring sink strength. Interestingly, this enzyme has been also localized at the plasma membrane of companion cells in the phloem which load and transport photosynthates from source leaves to sinks. Of note, the plasma membrane-localized H+-PPase could only function as a PPi-synthase in these cells due to the steep proton gradient between the apoplast and cytosol. The generated PPi would favor active sucrose loading through the sucrose/proton symporter in the phloem by promoting sucrose hydrolysis through the Sucrose Synthase pathway and providing the ATP required to maintain the proton gradient. To better understand these two different roles of type I H+-PPases, a series of Arabidopsis thaliana transgenic plants were generated. By expressing soluble pyrophosphatases in companion cells of Col-0 ecotype and H+-PPase mutants, impaired photosynthates partitioning was observed, suggesting phloem-localized H+-PPase could generate the PPi required for sucrose loading. Col-0 plants expressed with either phloem- or meristem-specific AVP1 overexpression cassette and the cross between the two tissue specific lines (Cross) were generated. The results showed that the phloem-specific AVP1-overexpressing plants had increased root hair elongation under limited nutrient conditions and both phloem- and meristem-overexpression of AVP1 contributed to improved rhizosphere acidification and drought resistance. It was concluded that H+-PPases localized in both sink and source tissues regulate plant growth and performance under stress through its versatile enzymatic functions (PPi hydrolase and synthase).
ContributorsLi, Lin (Author) / Park, Yujin (Thesis advisor) / Mangone, Marco (Committee member) / Roberson, Robert (Committee member) / Vermaas, Willem (Committee member) / Arizona State University (Publisher)
Created2022