Location: Application Technology Research Unit
2013 Annual Report
Researchers continued to identify the effects of temperature, light, and carbon dioxide on photosynthesis of several ornamental crops. This year researchers focused on the effects of short-term 3 hour high-temperature stress on photosynthesis of heat tolerant and intolerant cultivars of three commercially significant ornamental crops. An experiment carried out to better understand the basis of heat tolerance in flowering and the impact of allowing greenhouse temperatures to rise in the afternoons in greenhouses on flowering. The experiments were conducted in growth chambers. Photosynthetic data were collected using a portable photosynthesis meter that has the capacity to alter irradiance, carbon dioxide. Plant temperature was altered using the growth chamber itself.
In a separate study researchers examined the role of leaf coloration, specifically anthocyanins, in protecting plants from adverse temperature effects on photosynthesis. Coleus and Panicum were used as model plants. In both cases, researchers studied the photosynthetic behavior of 2 cultivars of each – one with high and one with low levels of anthocyanin.
Researchers are also identifying combinations of plant growth regulators that result in synergistic or novel effects, and identifying alternative application strategies to maximize their efficacy. The goal is to reduce total plant growth regulator applied while maintaining the desirable effects of these compounds and reducing labor costs associated with their application. In addition, the novel effects of combinations we are finding offer new uses entirely for their application.
In other work, researchers are studying the basis for variation in disease resistance among geranium and fuchsia cultivars/varieties to Botrytis (major greenhouse disease). Susceptible and resistant cultivars/varieties were identified with industry representatives and were treated with growth regulators that impacted endogenous phytohormone levels to determine whether geranium susceptibility to Botrytis was impacted. Susceptibility was assessed using an assay we developed where a known quantity of Botrytis spores were applied to geranium leaves and disease proliferation in an environment conducive to disease infestation (growth chamber) was quantified after 3 days.
Scientists grew 40 ornamental/herb species under eight lighting treatments that varied in day length and irradiance to identify what conditions induced flowering. The experiment was replicated three times. Such information allows growers to schedule finishing of crops when they want them to and reduces potential inputs in overall crop production by reducing losses due to late finishing, or losses due to unsalable material because plants flowered at a size that is too small for sale.
Aside from this work, scientists continue to do work in identifying different ways to apply growth retardants to increase efficacy and reduce cost, and whether light quality can be altered to reduce growth retardant use and increase disease resistance to decrease pesticide use.
This project relates to two sub-objectives of the parent project. 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; and 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, and scheduling to meet premium market windows. Each 12-month milestone adds 6 to 8 new species, and this project will assist in meeting that goal. Additionally, features such as supplemental lighting, water use, nutrient use, can be added and improved, and additional model validation will be accomplished.