Jennifer Boldt

United States Department of Agriculture | USDA · Agricultural Research Service (ARS)

We previously showed that chronic warming plus elevated carbon dioxide (eCO2) causes extreme upward bending of leaflets and petioles (i.e., hyponasty) in tomato (Solanum lycopersicum), which reduces growth. In that study, only two levels of CO2 (400, 700 ppm) and temperature (30, 37 °C) were tested in young vegetative plants, and the underlying mec...

Silicon (Si) is known to protect plants from a variety of environmental and biological stressors. The mode of action for these Si responses is unclear. In this study, a family of 14 histidine-rich defensin genes (HRDs) in Nicotiana tabacum, previously described as Defensin 19-like were identified and induced following Si treatment. These genes form...

Supplemental lighting, temperature control, and CO 2 enrichment can improve the productivity of greenhouse crops, but operating costs for greenhouse control systems to maintain environmental parameters at desired setpoints can be expensive. To balance operating costs with productivity, growers need to be able to predict how a crop will perform as a...

Elevated CO2 (eCO2) and high temperatures are known to affect plant nitrogen (N) metabolism. Though the combined effects of eCO2 and chronic warming on plant N relations have been studied in some detail, a comprehensive statistical review on this topic is lacking. This meta-analysis examined the effects of eCO2 plus warming on shoot and root %N, ti...

The response of plant N relations to the combination of elevated CO2 (eCO2) and warming are poorly understood. To study this, tomato (Solanum lycopersicum) plants were grown at 400 or 700 ppm CO2 and 33/28 or 38/33 °C (day/night), and their soil was labeled with 15NO3− or 15NH4+. Plant dry mass, root N-uptake rate, root-to-shoot net N translocation...

Lower temperatures delayed development of systemic symptoms by Cauliflower mosaic virus (CaMV) in two different plant hosts. However, lower temperature exposure increased CaMV nucleic acid levels in leaves of systemically-infected turnips. Furthermore, lower temperature altered the formation of aggregates formed by the CaMV major inclusion body (IB...

Silicon (Si) is a plant-beneficial element that can alleviate the effects of abiotic and biotic stress. Plants are typically classified as Si accumulators based on foliar Si concentrations (≥1% Si on a dry weight basis for accumulators). By this definition, most greenhouse-grown ornamentals are low Si accumulators. However, plants that accumulate l...

The concentration of nitrogen (N) in vegetative tissues is largely dependent on the balance among growth, root N uptake, and N assimilation. Elevated CO2 (eCO2) plus warming is likely to affect the vegetative-tissue N and protein concentration of wheat by altering N metabolism, but this is poorly understood. To investigate this, spring wheat (Triti...

Plants treated with metals better fend off infection by pathogens. This activity is mediated, at least in part, by the activation of the salicylic acid (SA) signaling pathway. Previous work in our laboratory demonstrated that silicon (Si) could alleviate copper (Cu) toxicity stress in Nicotiana tabacum. However, how Si affected expression of genes...

During an infection, Cauliflower mosaic virus (CaMV) forms inclusion bodies (IBs) mainly composed of viral protein P6, where viral activities occur. Because viral processes occur in IBs, understanding the mechanisms by which they are formed is crucial. FL-P6 expressed in N. benthamiana leaves formed IBs of a variety of shapes and sizes. Small IBs w...

Premise: Atmospheric carbon dioxide (CO2 ) concentration is increasing, as is the frequency and duration of drought in some regions. Elevated CO2 can decrease the effects of drought by further decreasing stomatal opening and, hence, water loss from leaves. Both elevated CO2 and drought typically decrease plant nutrient concentration, but their int...

Adding green [G (500–600 nm)] radiation to blue [B (400–500 nm)] and red [R (600–700 nm)] radiation creates white radiation and improves crop inspection at indoor farms. Although G radiation can drive photosynthesis and elicit the shade-avoidance response, its effects on plant growth and morphology have been inconsistent. We postulated G radiation...

Environmental horticulture production (EHP) generates and employs approximately one-third of all specialty crop revenue and workforce, respectively. In recent years, however, EHP received only 12% of federal funds earmarked for specialty crops research from the USDA-Agricultural Research Service or the USDA-Specialty Crops Research Initiative. To i...

Silicon (Si) is beneficial for plant growth and aids in stress tolerance. In this study, the effects of Si on long-term copper (Cu) toxicity in the low Si accumulator Nicotiana tabacum were evaluated. Silicon supplementation alleviated growth inhibition in roots and shoots of N. tabacum exposed to Cu toxicity. Alleviation of Cu toxicity correlated...

Heating and supplemental lighting are often provided during spring greenhouse production of bedding plants, but energy inputs are a major production cost. Different energy-savings strategies can be utilized, but effects on plant growth and flowering must be considered. We evaluated the impact and timing of a two-week low-energy (reduced temperature...

High-quality young plant production in northern latitudes requires supplemental lighting (SL) to achieve a recommended daily light integral (DLI) of 10 to 12 mol·m ⁻² ·d ⁻¹ . High-pressure sodium (HPS) lamps have been the industry standard for providing SL in greenhouses. However, high-intensity light-emitting diode (LED) fixtures providing blue, w...

Limited evidence indicates that moderate leaf hyponasty can be induced by high temperatures or un‐naturally‐high CO2. Here we report that the combination of warming plus elevated CO2 (eCO2) induces severe leaf hyponasty in tomato (Solanum lycopersicum L.). To characterize this phenomenon, tomato plants were grown at two levels of CO2 (400 vs. 700 p...

Previous research has shown high-quality annual bedding plant seedlings can be produced in controlled environments using light-emitting diode (LED) sole-source lighting (SSL). However, when only red and blue radiation are used, a delay in time to flower may be present when seedlings of some long-day species are subsequently finished in a greenhouse...

Silicon (Si) is a plant beneficial element associated with the mitigation of abiotic and biotic stresses. Most greenhouse-grown ornamentals are considered low Si accumulators based on foliar Si concentration. However, Si accumulates in all tissues, and there is little published data on the distribution of Si in plants. This knowledge may be critica...

Climate change will increase drought in many regions of the world. Besides decreasing productivity, drought also decreases the concentration (%) of nitrogen (N) and phosphorous (P) in plants. We investigated if decreases in nutrient status during drought are correlated with decreases in levels of nutrient-uptake proteins in roots, which has not bee...

Container nursery substrates in the central and eastern U.S. are composed primarily of pine bark with lesser percentages of other amendments, including sphagnum peatmoss. Peatmoss is often amended from 0% to 40% (by vol.) to increase the water holding capacity of the substrate. The objective of this research was to determine how a pine bark substra...

Energy inputs are a major production cost for greenhouse-grown plants, especially heating and supplemental lighting. A possible energy-efficient alternative is to optimize greenhouse conditions on days that have a low heating demand and reduce temperature and irradiance on days that have a high heating demand. The objectives of this study were to d...

Parboiled rice hulls (PBH) have been shown to be an effective mulch for weed control in container crops. As with other mulch products, there is concern that PBH mulch would interfere with nutrient delivery to the crop. The objective of this research was to determine the effect of PBH mulch on nutrient concentration of fertilized irrigation water as...

Atmospheric CO2 enrichment is expected to often benefit plant growth, despite causing global warming and nitrogen (N) dilution in plants. Most plants primarily procure N as inorganic nitrate (NO3−) or ammonium (NH4+), using membrane-localized transport proteins in roots, which are key targets for improving N use. Though interactive effects of eleva...

Multiple types of flesh browning can occur as storage disorders in ‘Honeycrisp’ apple (Malus × domestica Borkh.) fruit. Predicting its occurrence is hindered by differing definitions of the types of browning, incomplete understanding of their etiologies, and difficulty in assessing harvest maturity of ‘Honeycrisp’ fruit. In 2013, of ‘Honeycrisp’ fr...

Multilayer vertical production systems using sole-source (SS) lighting can be used for the production of microgreens; however, traditional SS lighting methods can consume large amounts of electrical energy. Light-emitting diodes (LEDs) offer many advantages over conventional light sources, including high photoelectric conversion efficiencies, narro...

Paclobutrazol is a plant growth retardant commonly used on greenhouse crops. Residues from paclobutrazol applications can accumulate in recirculated irrigation water. Given that paclobutrazol has a long half-life and potential biological activity in parts per billion concentrations, it would be desirable to measure paclobutrazol concentration in ca...

Dolomitic lime (DL) is the primary liming agent used for increasing pH in peatmoss-based substrates. Steel slag (SS) is a byproduct of the steel manufacturing industry that has been used to elevate field soil pH. The objective of this research was to determine the pH response of a peatmoss-based greenhouse substrate to varying rates of DL or SS. Tw...

Irradiance, CO2, and temperature are critical inputs for photosynthesis and crop growth. They are also environmental parameters which growers can control in protected horticulture production systems. We evaluated the photosynthetic response of 13 herbaceous ornamentals (Begonia × hiemalis, Begonia semperflorens, Catharanthus roseus, Cyclamen persic...

Anthocyanins, betalains, and carotenoids provide nongreen coloration in plants. In addition to adding aesthetic value to ornamental species, plant pigments play important roles in pollination, light harvesting, plant defense, protection against unfavorable environmental conditions, and human health. In leaves, anthocyanins are responsible for most...

Reducing greenhouse temperatures when ambient irradiance levels are low has long been a strategy to reduce energy costs and improve plant quality in greenhouse crop production. A question arose as to the impact of periodic temperature reductions paired with periodic ambient low irradiance in winter and early spring in the northern US on crop growth...

The impact of irradiance (25 to 800 μmol·m-2·s-1) and CO2 (100 to 1000 ppm) on photosynthesis of thirteen herbaceous ornamentals (Begonia x hiemalis Fotsch, B. semperflorens Hook. ‘Cocktail Vodka’, Catharanthus roseus G. Don. ‘Sunstorm Red’, Cyclamen persicum Mill., Euphorbia pulcherrima Wild. Ed Klotzsch ‘Prestige Early Red’, Gerbera jamesonii Adl...

Solenostemon scutellarioides (L.) Codd. (coleus) and Panicum virgatum L. (switchgrass) are two species cultivated for ornamental leaf color. We conducted experiments to determine how foliar anthocyanin content changes over time in response to changes in irradiance or temperature. Five S. scutellarioides cultivars [three anthocyanic: (‘Big Red Judy’...

A daminozide plus chlormequat chloride tank mix spray was applied to six Coleus cultivars or breeding lines at different times during propagation. For UF 03-8-10 and `Coco Loco', plants sprayed on day 7 or day 10 were shorter than control plants at transplant, but plants sprayed on day 13 were not. Other cultivars did not respond to single applicat...