Location: Application Technology Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1: Evaluate plant nutritional requirements to optimize production and enhance quality. Sub-objective 1a: Elucidate the optimal tissue concentration of P and B in different light environments for major production species and how their susceptibility to foliar and root pathogens are influenced by nutrient status and light. Sub-objective 1b: Determine the uptake, accumulation, and potential benefit of silicon in ornamental crops and explore the potential for its use as a buffer to Cu toxicity and an alternative approach to pathogen control. Objective 2: Develop new and/or improved methods to detect, quantify, and manage biotic and abiotic stresses in ornamental crops grown in soilless and/or hydroponic greenhouse culture. Sub-objective 2a: Evaluate the use of existing non-destructive sensor technology and develop new molecular probes to measure and predict the impact of biotic and abiotic stresses on ornamental crops. Sub-objective 2b: Improve the Virtual Grower software model to enable growers to optimize their production systems by making more informed economic decisions about energy use, plant growth, pest management, and other production inputs. Objective 3: Evaluate existing and alternative growth medium amendments to determine the potential to deliver Si and buffer pH without negatively impacting beneficial microorganisms or crop growth.
1b. Approach (from AD-416)
Impatiens, geranium, vinca, and zinnia will be grown in media amended with different concentrations of phosphorus and boron under different light environments to determine optimum supply and tissue concentrations of these nutrients. Plants containing different amounts of these nutrients will then be inoculated with Pythium, Phytophthora, Botrytis, and powdery mildew to determine host susceptibility. These same plant species will also be grown with supplemental silicon in the fertilizer solution or incorporated into the substrate as rice hulls or Si-containing slags, and inoculated with the same pathogens or expose them to elevated Cu concentrations in the rootzone to determine if Si plays a role in a plant’s ability to withstand pathogen attack and Cu toxicity. Plants grown in different amounts of light and exposed to the aforementioned pathogens will be monitored with various sensors (e.g. digital cameras, infrared temperature probes, fluorometers, chlorophyll meters) and molecular tools to detect initial onset of stress symptoms. Finally, the production methods developed within these tests can be incorporated into the existing computer decision support software Virtual Grower to help growers make decisions in crop management.
3. Progress Report
Virtual Grower (VG) software improvements and additions were made and incorporated into the existing version (including the Spanish and French versions) and the next, completely revised version (3.0) was launched (Aug. 2011). VG 3.0 includes Mac compatibility as well as the addition of more crop growth models. Additional crop species were evaluated for silicon uptake and accumulation, including five species that will be used for lesion nematode/silicon interaction studies with an ARS collaborator. Roots and leaves/shoots are now routinely being analyzed separately as several species have shown differential accumulation in the roots which is possibly related to silicon transporters. Substrate amendment studies have focused on the utilization of wheat straw, which serves as a silicon source, in both floricultural crops and herbaceous perennials grown as a nursery crop and overwintered with stakeholder cooperation. Evaluation of by-products from biofuel generation (biochar) has been initiated to assess their potential as an additive to container media to moderate nutrient leaching. Significant progress has been made on identifying molecular tools to distinguish individual nutrient stresses and intellectual property considerations have been initiated with the cooperator toward development of plant stress test kits.
1. The effect of nitrogen deficiency on geranium and recovery. ARS researchers in Toledo, Ohio investigated the threshold beyond which a bedding plant crop that is recoverable from nitrogen (N) deficiency. Two experiments monitored chlorophyll content and growth of seedlings grown in hydroponic culture in which the N source was removed and then restored after differing lengths of time. Summarizing across both experiments, chlorophyll and foliar N levels were shown to rebound quickly after N depravation; however, growth was reduced after just four days compared to plants fed constantly. Geraniums grown without N for 4 to 12 days resulted in smaller, more compact plants, with lower shoot to root ratios. Experiments suggest that geraniums recover from reduced N when grown in hydroponic culture.
2. Geranium virus detected by molecular techniques. University of Toledo and ARS scientists conducted a viral protein-protein interactions project focused on two different viruses: Dahlia mosaic virus (DMV), and Pelargonium flower break virus (PFBV). Once viral protein-protein interactions are identified, they then become useful targets for interfering peptides that could block viral infections. DMV, an emerging problem in the floriculture industry, is related to the better-known Cauliflower mosaic virus (CaMV). The result of the research is we learned how the virus causes disease. When understood, we may learn how to prevent the effects of the virus. Data suggests that Silicon (Si) probably does not merely sequester Copper (Cu) in the cell wall, but also has an influence within the cell on genes involved in Cu metabolism. Joint research indicated that Si could alleviate Cu toxicity stress, but the degree of stress alleviation correlated with the amount of Si the plants acquired.
3. Possible diagnostic test for plant physiological disorders. University of Toledo and ARS researchers from Toledo, Ohio evaluated the use of non-destructive sensor technology to measure and predict the impact of biotic and abiotic stresses in ornamental crops. Antibodies were generated for Boron transport protein, BOR 1, active transport membrane protein, from the previous work on this project, has been characterized and used successfully in ELISA. A second antibody, Boron Nip5 is a facilitated-diffusion membrane protein. Both Boron antibodies will be necessary to differentiate among Boron deficiency, sufficiency, and toxicity. Similar work has progressed for iron metabolism and protein transport protein. Testing of these inventions will result in exploring the possibility of a patented plant stress test developed jointly by UT and ARS scientists that would be more efficient than grow out tests.
4. Mature dairy manure compost (DMC) substrates may allow considerable cost savings to root substrate formulators and container plant growers. The ARS study was conducted in collaboration with North Carolina State University and demonstrated that a water content of 30% in the DMC substrate provided for wettability equal to the peat moss-perlite substrate at 50% water content and a bulk density (Db) of 180g/L. Benefits include pH buffering, supply of pre-plant nutrients that qualify for organic certification, increased cation exchange capacity for greater nutrient retention and reduced leaching, reduction of peat moss consumption, and a substrate component with a cost advantage. The substrate formulation industry norm is to raise the water content of soilless substrates to 50% by weight prior to shipping to ensure a satisfactory level of water absorption for the recipient grower. The increase in weight of the DMC substrate at 30% water is only half that of this substrate at 50% water. These results allow for considerable savings in shipping cost which greatly fosters adoption of DMC substrates by plant production industry.
Davis, K., Niedziela, C.E., Reddy, M.R., Whipker, B.E., Frantz, J. 2011. Nutrient disorder symptomology and foliar concentrations of Clerodendrum thomsoniae. Journal of Plant Nutrition. 34:1079-1086.