2024 PP Systems
Innovator’s Travel Award

Under our ultimate goal of improving profitability for controlled environment agriculture (CEA) by smarter lighting strategy, my research focuses on light quality of supplemental lighting.

There are many aspects of supplemental lighting that can be modified, for example, light intensity, photoperiod, and light quality. Optimized lighting strategy can help CEA growers reduce production costs, increase crop yield and quality, hasten or delay crop maturation time to meet market window, and overall increase profitability. Optimization of lighting strategy, however, requires an extensive understanding of spectral effects on photosynthesis and crop performance.

Part of my light quality research focuses on the benefit of green light on carbon fixation. Traditionally, green light is considered to be less photosynthetically active than red and blue light. However, green light can penetrate deeper into leaves and engage more cells for photosynthesis. Therefore it can be used more efficiently especially at high PPFD. To characterize the interactive effect of wavelength and intensity of growth lights on photosynthesis, I compared effects on photosynthesis of red, green and blue lights as well as red/green and blue/green mixtures at different ratios on ‘Green Tower’ lettuce (Lactuca sativa). At PPFD of 200 µmol m^-2 s^-1, red light and 80% red+20% green resulted in the highest photosynthetic rates, while blue, green and mixtures of these two yielded the lowest photosynthetic rates. At high PPFD (1000 mol m^-2 s^-1), red and green lights have comparably high photosynthetic rates, when blue light and its mixtures still have relatively low photosynthetic rates. Also, green light was efficient at up-regulating Rubisco activity.

In conclusion, green light is more effective at driving photosynthesis at high PPFD. This knowledge could lead to refined design of LED growing lights that will enhance the light use efficiency, cut back on energy consumption of CEA, help the industry increase profitability.

My research involves assessing the effects of Laurel wilt disease as it relates to the physiology of avocado cultivars and other related tree species. Laurel wilt is caused by Raffaelea lauricola, an aggressive fungal pathogen transmitted by bark beetles. Since its first report in 2002, laurel wilt has caused the death of millions of redbay and has become a major concern to Florida’s avocado industry. Florida’s avocado production is based in avocados from the West Indian race or West Indian hybrids, which have been proven to be far less tolerant to laurel wilt when compared with the Mexican and Guatemalan race. Infected trees with laurel wilt display a variety of internal and external disease symptoms including wilted and necrotic canopy and sapwood discoloration. After infection, some plants exhibited increased cell permeability, alterations in water use and photosynthesis as well as histological changes like the formation of gels, gums, and tyloses that occluded the xylem. For this reason, the overall goal of my research is to understand the relative physiological and anatomical differences among different avocado cultivars and forest trees to identify cultivars that are the most tolerant to laurel wilt infection as well as to understand the basis for this tolerance. Physiological measurements include periodic determinations of net CO₂ assimilation (photosynthesis), transpiration, stomatal conductance, chlorophyll fluorescence, leaf chlorophyll concentration, xylem sap flow, hydraulic conductance and stem anatomy among different seedling and clonal avocado. My last experiment involved the use of carbon isotopes to determine if the decrease in photosynthesis of plants with laurel wilt is caused by restricting CO₂ entry into the plant through the stomata or if there are other physiological factors involved. I will be presenting my findings at ASHS 2019.

Cultivated sunflower is the fourth most important oilseed crop globally and exhibits a wide phenotypic diversity across the germplasm. Using a core set of twelve inbred lines that capture approximately 50% of the allelic diversity across cultivated sunflower germplasm collections, the CIRAS-3 portable photosynthesis system was used to measure rapid A/C_i curves, generating key metrics of photosynthetic physiology like maximum rate of carboxylation, maximum rate of electron transport, maximum assimilation rate, and CO₂ compensation point. These measured photosynthetic traits will be used to ground-truth potential high-throughput proxies for these traits, including hyperspectral reflectance and chlorophyll fluorescence. We are currently assessing the utility of hyperspectral reflectance for predicting A/C_i curve-derived photosynthetic traits across a wider panel of sunflower germplasm. Given the contribution of photosynthetic performance to overall yield and growth, these proxies, if validated, would make for fast and easy tools for phenotyping photosynthesis with applications to molecular breeding. Finally, a high-density genetic map is currently being used to perform genome-wide association mapping to describe the genetic architecture of these descriptors of photosynthetic physiology in cultivated sunflower. I will be presenting my research at Botany 2019.

My thesis research focuses on promoting the use of native plants for a water-efficient landscape. Developing sustainable horticultural practices for growing native plants in low-water-use landscapes will assist in water conservation and enhance environmental stewardship. I will use symbiotic bacteria to improve the adaptability and performance of two native plants [Ceanothus velutinus (snowbrush ceanothus) and Shepherdia rotundifolia (roundleaf buffaloberry)] in an urban landscape. These plants are actinorhizal plants and do not perform well in an urban landscape, which might be caused by the ineffective development of actinorhizal symbiosis with nitrogen-fixing actinobacteria (frankia). Frankia strains will be isolated from the soil and root samples of roundleaf buffaloberry and snowbrush ceanothus. The isolated frankia strains will inoculate roundleaf buffaloberry and snowbrush ceanothus plants that are propagated via cuttings and seeds with the hope to enhance their performance. Plant photosynthesis of inoculated plants in greenhouse or field environment will be investigated.

Additionally, I have investigated the salt tolerance of three common landscape plants [Hibiscus syriacus (rose of sharon), Physocarpus opulifolius (ninebark), and Spiraea japonica (japanese spirea)] using a near-continuous gradient dosing (NCGD) system. The innovative NCGD system allows researchers to evaluate a large number of plants for salt tolerance with multiple treatments, more flexibility, and reduced efforts of irrigation. The NCGD system delivered saline solutions at electrical conductivity (EC) levels ranging from 0.8 dS·m^-1 to 6.4 dS·m^-1. The salt stress negatively impacted plant growth and photosynthesis as EC levels increased. The salinity threshold defined as 50% loss of shoot dry weight was 5.4 and 4.6 dS·m^-1, respectively, for ninebark and japanese spirea, however not determined for rose of Sharon which is the most salt tolerant species in the study. I am looking forward to presenting the detailed results of my research at the American Society for Horticultural Science 2019 annual conference in July 2019.

Turfgrasses are a vital part of human lives since they provide several services including recreational, aesthetic and environmental services. The turfgrass industry is one of the fastest growing segments of U.S. agriculture with an annual economic value of $35 billion (Huang et al., 2014). However, drought is one of the major constraints to turfgrass production that causes severe damage each year (Dai, 2013). There is a need to improve understanding of turfgrass drought tolerance mechanisms for its sustainable production. The objective of our study was to enhance understanding of turfgrass drought tolerance mechanisms and identify drought tolerant turfgrass cultivars using physiological and molecular approaches. Fifteen genotypes of seashore paspalum were grown under two different water treatments: well-watered and water-stressed for 20 days. They were assessed using morpho-physiological parameters including gas exchange parameters measured using CIRAS 3 to identify drought tolerant and sensitive genotypes. Identified drought tolerant genotypes had greater photosynthetic rates, osmotic adjustments and leaf water use efficiencies compared to sensitive genotypes after drought stress treatment application. However, transpiration rates and stomatal conductance were lower in tolerant genotypes compared to sensitive ones indicating better ability of tolerant genotypes to conserve water by stomatal regulation under drought stress. Identified drought tolerant and sensitive genotypes will be further grown under fully watered and water stressed condition for proteomic and metabolomic analysis in the future. Leaf and root samples will be used to extract proteins and metabolites and extracted proteins and metabolites will be identified using mass spectrometry coupled with protein and metabolite databases. Identified proteins and metabolites will be compared to determine their differential expression pattern among seashore paspalum genotypes. Greatly expressed proteins and metabolites might have involved in improving drought tolerance mechanisms of drought-tolerant seashore paspalum genotypes.

I will be presenting my research at the 2019 annual Crop Science Society of America meeting.