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  • Author or Editor: William R. Graves x
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We quantified the growth and quality of ‘Arizona Sun’ blanket flower (Gaillardia ×grandiflora) grown in different bioplastic containers and characterized the interest of commercial perennial producers in using bioplastic-based biocontainers in their herbaceous perennial production schemes. Plants were grown in three types of #1 trade gallon (0.75 gal) containers at five commercial perennial producers in the upper-midwestern United States. Containers included one made of polylactic acid (PLA) and a proprietary bio-based filler derived from a coproduct of corn ethanol production, a commercially available recycled paper fiber container twice dip-coated with castor oil–based biopolyurethane and a petroleum-based plastic (control) container. Plant growth data were collected when most plants had open flowers, and plant shoots, roots, and containers were rated by commercial grower participants. Questionnaires were administered at the beginning and at the end of the experiment to characterize the perceptions and interest of growers in using these containers, their interest in different bioplastic-based container attributes, and their satisfaction from using the containers. Container type and grower interacted to affect growth index (GI), shoot dry weight (SDW), and container rating. Root rating was affected by container type or grower and shoot rating was unaffected by either. Our results indicate that commercial producers can adapt these bioplastic-based biocontainers to blanket flower production with few or no changes to their crop cultural practices.

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Our objectives were to quantify the growth and quality of herbaceous annuals grown in different types of bioplastic-based biocontainers in commercial greenhouses and quantify producer interest in using these types of biocontainers in their production systems. Seedlings of ‘Serena White’ angelonia (Angelonia angustifolia) and ‘Maverick Red’ zonal geranium (Pelargonium ×hortorum) that had been transplanted into nine different (4.5-inch diameter) container types [eight bioplastic-based biocontainers and a petroleum-based plastic (PP) (control)] were grown at six commercial greenhouses in the upper midwestern United States. Plants were grown alongside other bedding annuals in each commercial greenhouse, and producers employed their standard crop culture practices. Data were collected to characterize growth when most plants were flowering. Questionnaires to quantify producer perceptions and interest in using bioplastic-based biocontainers, interest in different container attributes, and satisfaction were administered at select times during the experiment. Container type interacted with greenhouse to affect angelonia growth index (GI) and shoot dry weight (SDW), as well as shoot, root, and container ratings. Container type or greenhouse affected geranium GI and shoot rating, and their interaction affected SDW, and root and container ratings. These results indicate that commercial producers can grow herbaceous annuals in a range of bioplastic-based biocontainers with few or no changes to their crop culture practices.

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Early nodulin genes, such as ENOD2, play a role in the first stages of nodulation. Although ENOD2 is conserved among nodulating legumes studied to date, its occurrence and activity have not been studied among woody legumes such as Maackia amurensis Rupr. & Maxim. Our objective was to localize MaENOD2 transcripts during nodule development and describe the anatomy of nodules formed on the roots of M. amurensis in relation to ENOD2 mRNA accumulation. Nodules (<1 mm, 1-2 mm, >2 mm in diameter, and mature) were prepared for light microscopy, sectioned, and stained with safranin and fast green for structural contrast or with the periodic acid Schiff's reaction for starch. The location of ENOD2 transcripts was determined by using in situ hybridization with DIG-labeled sense and antisense RNAs transcribed from a 602-bp fragment of the coding region of MaENOD2. Mature nodules from M. amurensis possessed peripheral tissues, a distal meristem, and a central infected region characteristic of indeterminant development. In situ hybridization showed that MaENOD2 transcripts accumulated in the distribution layer and uninfected cells of the central symbiotic region. Amyloplasts that contained starch grains were identified in these tissues and in the inner parenchyma of the nodule. Throughout nodule development, transcripts were restricted to areas with high levels of stored starch that surrounded cells actively fixing N2. Our results suggest that ENOD2 in M. amurensis may be a cell wall component of tissues that regulate nutrient flow to and from sinks, such as symbiotic regions of a nodule. These data may lead to a better understanding of the role of the ENOD2 gene family during nodulation.

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Research examining biocontainers for container-crop production has demonstrated that bioplastics made from soybean [Glycine max (L.) Merr.] can supply mineral nutrients to plants. Using soybean-based bioplastics and biochar (BC), we created pelletized fertilizer designed to be incorporated into soilless substrate. We evaluated the growth of ‘Honeycomb’ marigold (Tagetes patula L.), ‘Montego White’ snapdragon (Antirrhinum majus L.), and ‘Laser Synchro Scarlet’ cyclamen (Cyclamen persicum Mill.) grown with pelletized soy-based bioplastic fertilizers [soy-bioplastic polymer (SP.A) compounded with poly(lactic) acid (PLA) or polyhydroxyalkanoates (PHA), containing 15% or 25% BC] or a synthetic controlled-release fertilizer (CRF). Our objectives were to evaluate the effectiveness of prototype SP.A-based fertilizers and compare their performance to that of a traditional CRF for growing common greenhouse crops. In our first experiment, treatments of 0, 346, or 691 g nitrogen (N)/m3 of substrate from different fertilizer types were applied to marigold in containers with 15.2-cm top diameter, and in our second experiment, 0, 211, 423, 819, or 1638 g N/m3 were applied to marigold, snapdragon, and cyclamen in containers with 11.4-cm top diameter. Marigolds grown in larger containers accumulated more shoot dry mass (SDM) when supplied with 346 or 691 g N/m3 from each type of the SP.A-based fertilizers than did plants in the nonfertilized control group. Plants supplied with synthetic CRF accumulated similar or greater SDM than plants supplied with the same rate of N from SP.A-based fertilizers. In smaller containers, marigold and cyclamen provided with 211 or 423 g N/m3 from SP.A-based fertilizers accumulated more SDM than nonfertilized plants. Snapdragon provided with SP.A-based fertilizer grew poorly, and plants of this species died before the end of 5 weeks when provided the high and heavy rates of SP.A-based fertilizers. Plants fertilized with CRF had the largest SDM across the three species at most fertilizer concentrations. Tissue N concentration and N uptake were greater for plants provided with SP.A-based fertilizers at most N rates (211, 423, 819 g N/m3) or synthetic CRF (all four rates) than for nonfertilized plants. The effectiveness of prototype SP.A-based fertilizers was better at common application rates (211 and 423 g N/m3), but showed a diminishing return at high and heavy rates of application (819 and 1638 g N/m3). The SP.A-based fertilizers made with PLA copolymer were more effective than those made with PHA. Our results serve as proof-of-concept that pelletized soy-based bioplastic fertilizers can be effective for meeting the nutrient needs of plants during containerized-crop production, but formulations require further development to improve their properties for use with a broad range of species and application rates.

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Various types of emerging bioplastic containers present a range of physical and chemical properties and can perform differently from one another in production environments. Container performance may be affected by substrate moisture content. We quantified the effects of bioplastic container type and substrate volumetric water content (VWC) on the aesthetic and mechanical strength properties of bioplastic containers and on plant growth. Seedlings of ‘Divine Cherry Red’ new guinea impatiens (Impatiens hawkeri W. Bull) and ‘Pinot Premium Deep Red’ zonal geranium (Pelargonium ×hortorum L.H. Bailey) were transplanted into five types of 11.4-cm–diameter containers, four types made from bioplastics and one type made from petroleum-based plastic and used as a control. Plants were watered to container capacity at transplant, allowed to dry down to VWC thresholds of 0.20 or 0.40 m3·m−3, and subsequently maintained at desired set points by using a precision irrigation system controlled by soil moisture sensors. Total volume of water applied per plant to new guinea impatiens was affected by VWC and not container type, whereas irrigation volume was affected by both for geranium. Growth index and shoot dry mass (SDM) of new guinea impatiens and geranium were affected by VWC. Container type affected growth index and SDM of geranium only. Water use efficiency (WUE) of both species was similar regardless of container type and VWC. Aesthetic quality varied based on VWC for only one container type, which was made from a blend that included soy-based bioplastic. Containers manufactured with polyhydroxyalkanoates (PHA) and dried distiller’s grains and solubles (DDGS) or polylactic acid (PLA), soy polymer with adipic anhydride (SP.A), and a proprietary bio-based filler (BR) derived from modified DDGS were stronger when maintained at a lower VWC, 0.20 m3·m−3. Our findings indicate that restricting irrigation to the minimum needed to achieve the desired crop growth is a viable strategy for sustaining aesthetic quality and strength of bioplastic containers manufactured with plant protein–based fillers such as SP.A and BR. Other bioplastic containers, such as those made of PLA–lignin biocomposite, show durability equal to that of petroleum-based plastic containers and maintain pristine appearance regardless of substrate VWC during production.

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The container-crops industry relies heavily on single-use plant containers made from petroleum-based plastics, most of which contribute to the solid waste stream in landfills. Plant containers made from biorenewable materials have potential to be more sustainable, but most commercially available biocontainers are either not durable enough for common production cycles or do not effectively biodegrade in soil after use. In 2012 and 2013, we evaluated 28 novel biocontainers (injection-molded prototypes) for their performance during plant production and their biodegradation in soil at two sites with dissimilar soil and climate in Iowa and Nevada, and we compared their performance to that of commercially available biocontainers. Prototype containers made of blends or composites of polylactic acid (PLA) or polyhydroxyalkanoates (PHA) performed well during crop production, and many showed an effective rate of biodegradation in soil. Their rates of biodegradation in Nevada were either similar or lower than they were in Iowa, but the highest rated containers were acceptable for use in both locations. Adding biobased fibers of distiller’s dried grains with solubles or corn stover to form composite materials improved biodegradation over that of the base polymers (PLA or PHA) and had little effect on container performance under greenhouse conditions. Many of the injection-molded prototypes performed as well as the petroleum control containers during crop production, yet biodegraded at similar or faster rates than commercially available fiber containers.

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