Alnusmaritima may have potential for use in home and commercial landscapes in northern Utah. This fast-growing, fall-blooming shrub is cold-hardy to USDA hardiness zone 3b and tolerant of nutrient-poor soils and full sun. Because this taxon is native to low-elevation wetlands, I seek to determine its response to the high desert soils and climate of northern Utah. My specific objective was to test germination and survival of plants from seed sowed in three diverse soil types typical of the Wasatch front in north-central Utah. Seeds were rinsed with distilled water and cold-stratified in darkness for 16 weeks between wet filter paper in sealed petri dishes. Stratified seeds were sowed in flats filled with soil from each of three sites at the Utah Botanical Center in Kaysville and held in a greenhouse. Seeds planted in flats filled with soilless germination mix served as controls. Flats with 60 seeds were experimental units, and each medium was replicated three times. Soils ranged from silty loam to loam, nitrate-N was 3.2 to 5.4 mg·kg-1, and there was 1.4% to 2.9% organic matter. Germination rates were highest in the soilless mix (50%). Of the three soil types, the highest germination rates (24%) occurred in a loamy soil high in organic matter (2.9%). Rates were similar (12.5% and 13%) in the other two soils. Seeds of A. maritima can germinate in soils typical of urban landscapes in northern Utah, so both the potential for invasiveness and the performance of plants in the landscape of northern Utah are being evaluated.
Taun Beddes and Heidi A. Kratsch
Seaside alder (Alnus maritima) is a rare species adapted for ornamental use. It can be produced easily by commercial growers, and when soil-inoculated in nursery containers, will form root nodules containing nitrogen (N)-fixing bacteria in the genus Frankia. It has been demonstrated that nodulation within this species can be controlled by the amount of N plants receive from a liquid source; however, granular controlled-release fertilizers (CRF) also are commonly used by commercial growers, and information is not available on CRF effects on nodulation. We sought to determine the application rate of CRF that will maximize nodulation of seaside alder while sustaining acceptable plant health and growth. Inoculated containerized plants were topdressed with CRF at eight application rates from 0 to 32.0 g per container. A control group of uninoculated plants received the manufacturer's prescribed rate of 6.0 g per 6-inch-diameter standard round pot. Regression analysis revealed that treatment with 2.0 g of CRF maximized root nodule formation (a mean of 26 nodules), while nodulation was inhibited at CRF rates ≥4.0 g. Plant growth parameters and leaf N content of inoculated plants treated with 2.0 g of CRF were similar to those of uninoculated plants receiving the prescribed rate of CRF (P < 0.05); nitrate-nitrogen leaching from pots containing 2.0-g CRF-treated plants was minimal. We conclude that vigorous nodulated plants of seaside alder can be produced, with minimal nitrate leaching, by providing CRF at lower than prescribed rates.
Heidi A. Kratsch and William R. Graves
Although many species of Alnus Miller grow in wet soils, none is as closely associated with low-oxygen, waterlogged soils as Alnus maritima (Marsh.) Muhl. ex Nutt. (seaside alder). An actinorhizal species with promise for use in horticultural landscapes, land reclamation, and sustainable systems, A. maritima associates with Frankia Brunchorst, thereby forming root nodules in which gaseous nitrogen is fixed. Our objective was to determine how root-zone moisture conditions influence the occurrence, location, and anatomy of nodules on A. maritima. Plants of Alnus maritima subsp. maritima Schrader and Graves were established in root zones with compatible Frankia and subjected to four moisture regimens (daily watered/drained, partially flooded, totally flooded, and totally flooded with argon bubbled through the flood water) for 8 weeks. Oxygen content of the root zone, number and location of nodules on root systems, and dry weight and nitrogen content of shoots were determined. Root-zone oxygen content ranged from 17.3 kPa for daily watered/drained plants to 0.9 kPa for argon-treated plants. Across all treatments, 87% of the nodules were within the upper one-third (4 cm) of the root zone. Although shoot dry weights of daily watered/drained and partially flooded plants were not different, daily watered/drained plants had more nitrogen in their leaves (2.53 vs. 2.21 mg·g-1). Nodulation occurred in all treatments, but nodules on totally flooded roots (with or without argon) were limited to a single lobe; in contrast, multilobed nodules were prevalent on partially flooded and daily watered/drained plants. Frankia infection within submerged nodule lobes was limited to one or two layers of cortical cells. Submerged nodules developed large air spaces between cortical cells, and phenolic-containing cells appeared to inhibit Frankia expansion within the nodule. These data suggest that access to root-zone oxygen is critical to the Frankia-A. maritima subsp. maritima symbiosis, and that plants of this subspecies in the drained soils of managed landscapes may benefit more than plants in native wetland habitats from nodulation and nitrogen fixation.
Heidi A. Kratsch* and William R. Graves
Alnus maritima (Marsh.) Muhl. ex Nutt. is unique among alders in its degree of preference for low-oxygen soils of wetlands. An actinorhizal species with promise for use in sustainable horticulture, A. maritima develops a root-nodule symbiosis with nitrogen-fixing Frankia. Nodules of other actinorhizal species that are obligate wetland natives are adapted to low oxygen, and expression of hemoglobin is common to these taxa. Our objectives were to determine the range of oxygen tension under which Alnus maritima subsp. maritima fixes nitrogen and to investigate a potential role for hemoglobin in adaptation of nodules to low oxygen. Roots of plants, cultured aeroponically, were subjected to eight oxygen tensions from 0 to 32 kPa. After four weeks, plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate were measured. In addition, nodules were assayed spectrophotometrically for the presence of hemoglobin. A quadratic function best described the influence of oxygen on plant dry weight, nodule fresh weight, nitrogenase activity, and photosynthetic rate with maximal values above 20 kPa. Alnus serrulata (Ait.) Willd. is sympatric with A. maritima subsp. maritima but is not an obligate inhabitant of wetlands. In a separate experiment, we found higher nitrogenase activity in A. maritima subsp. maritima than in A. serrulata (0.74 vs. 0.26 μmol/h per plant) at hypoxic oxygen tensions. Further, optical absorption spectra of nodule extracts confirmed hemoglobin within nodules of A. maritima subsp. maritima. Our data suggest that hemoglobin contributes to oxygen regulation in nodules of A. maritima subsp. maritima.
Heidi A. Kratsch, Ruby Ward, Margaret Shao, and Larry A. Rupp
The green industry in Utah is a large and diverse group that ranges from nursery/greenhouse growers and retailers to landscape maintenance and design professionals to irrigation and turf industry professionals. Because of the size and diverse membership of the Utah green industry, extension faculty are challenged to gauge the needs and attitudes of the industry as a clientele group. In 2007, we conducted a mail survey of the Utah green industry to identify the learning preferences of industry members, to better understand the structure and extent of Utah green industry businesses, and to elicit industry perceptions about present and future challenges to success. We found that the service sector is a significant component of Utah's green industry, and that extension-based short courses can be used to provide more advanced and targeted education to specific industry groups. Drought/water issues and labor shortages were viewed as significant challenges to the future of the green industry, and these could be used as a foundation for building strategic alliances between extension and the green industry in Utah. Results of our survey will be useful to green industry professionals and extension educators that deal with green industry education, particularly in states with service- rather than production-oriented businesses.
Ji-Jhong Chen, Heidi Kratsch, Jeanette Norton, Youping Sun, and Larry Rupp
Shepherdia ×utahensis ‘Torrey’ (‘Torrey’ hybrid buffaloberry) is an actinorhizal plant that can fix atmospheric nitrogen (N2) in symbiotic root nodules with Frankia. Actinorhizal plants with N2-fixing capacity are valuable in sustainable nursery production and urban landscape use. However, whether nodule formation occurs in S. ×utahensis ‘Torrey’ and its interaction with nitrogen (N) fertilization remain largely unknown. Increased mineral N in fertilizer or nutrient solution might inhibit nodulation and lead to excessive N leaching. In this study, S. ×utahensis ‘Torrey’ plants inoculated with soils containing Frankia were irrigated with an N-free nutrient solution with or without added 2 mm ammonium nitrate (NH4NO3) or with 0.0 to 8.4 g·L−1 controlled-release fertilizer (CRF; 15N–3.9P–10K) to study nodulation and plant morphological and physiological responses. The performance of inoculated plants treated with various amounts of CRF was compared with uninoculated plants treated with the manufacturer’s prescribed rate. Plant growth, gas exchange parameters, and shoot N content increased quadratically or linearly along with increasing CRF application rates (all P < 0.01). No parameters increased significantly at CRF doses greater than 2.1 g·L−1. Furthermore, the number of nodules per plant decreased quadratically (P = 0.0001) with increasing CRF application rates and nodule formation were completely inhibited at 2.9 g·L−1 CRF or by NH4NO3 at 2 mm. According to our results, nodulation of S. ×utahensis ‘Torrey’ was sensitive to N in the nutrient solution or in increasing CRF levels. Furthermore, plant growth, number of shoots, leaf area, leaf dry weight, stem dry weight, root dry weight, and N content of shoots of inoculated S. ×utahensis ‘Torrey’ plants treated with 2.1 g·L−1 CRF were similar to those of uninoculated plants treated with the manufacturer’s prescribed rate. Our results show that S. ×utahensis ‘Torrey’ plants inoculated with soil containing Frankia need less CRF than the prescribed rate to maintain plant quality, promote nodulation for N2 fixation, and reduce N leaching.
Chalita Sriladda, Heidi A. Kratsch, Steven R. Larson, and Roger K. Kjelgren
The herbaceous perennial species in the genus Sphaeralcea have desirable drought tolerance and aesthetics with potential for low-water use landscapes in the Intermountain West. However, taxonomy of these species is ambiguous, which leads to decreased consumer confidence in the native plant nursery industry. The goal of this study was to test and clarify morphological and genetic differentiation among four putative Sphaeralcea species. Morphological characteristics of the type specimens were used as species references in canonical variate analysis to generate a classification model. This model was then used to assign putative species names to herbarium voucher specimens and to field-collected voucher specimens to clarify genetic variation among species. Field specimens were also classified using Bayesian cluster analyses of amplified fragment length polymorphism (AFLP) genotypes. Sphaeralcea coccinea (Nutt.) Rydb. and S. grossulariifolia (Hook. & Arn.) Rydb. formed a composite group morphologically and genetically distinct from the S. munroana (Douglas) Spach and S. parvifolia A. Nelson composite group. Each composite group displayed genetic isolation by geographic distance. Also, morphological traits of S. munroana and S. parvifolia correlated to geographic distance. Taken together these results suggest that our samples represent two sympatric yet reproductively isolated groups. Distinguishing between these two Sphaeralcea composite groups can create greater consumer confidence in plant material developed for use in Intermountain West low-water landscaping.
Heidi A. Kratsch, James A. Schrader, Kenneth G. McCabe, Gowrishankar Srinivasan, David Grewell, and William R. Graves
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.
Chalita Sriladda, Heidi A. Kratsch, Steven R. Larson, Thomas A. Monaco, FenAnn Shen, and Roger K. Kjelgren
Shepherdia rotundifolia Parry (roundleaf buffaloberry), a shrub endemic to the U.S. Colorado Plateau high desert, has aesthetic and drought tolerance qualities desirable for low-water urban landscapes. However, slow growth and too often fatal sensitivity to wet or disturbed soil stymies nursery production and urban landscape use. The goal of this study was to create an interspecific hybrid between the evergreen-xeric S. rotundifolia and its widely adapted, fast-growing, deciduous relative Shepherdia argentea (silver buffaloberry) distributed in western North America riparian habitats. Genetics and leaf morphology of the resulting S. argentea × S. rotundifolia hybrid are described and compared with the parents, as well as hybrid gas exchange as a reasonable proxy for growth rate and potential tolerance of poor soil. Hybrid genotypes were heterogenous, but contained an intermediate and equal contribution of alleles from genetically heterogenous parent populations. Leaf morphology traits were also intermediate between both parents. Aesthetic leaf qualities (silver-blue color and revolute margins) sought from S. rotundifolia were conserved in all offspring. However, gas exchange responses varied widely between the two surviving hybrids. Both hybrids showed greater tolerance of wet, fertile substrate—and promise for use in low-water landscapes—than S. rotundifolia. However, one hybrid conserved faster growth, and by inference possibly greater tolerance of wet or disturbed soil, from S. argentea, while the opposite was observed in the second hybrid. Following botanical nomenclature, we named this hybrid Shepherdia ×utahensis.
Ji-Jhong Chen, Jeanette Norton, Heidi Kratsch, Youping Sun, and Larry Rupp
Shepherdia ×utahensis ‘Torrey’ (hybrid buffaloberry) is an actinorhizal plant that can form symbiotic nodules with the actinobacterial genus Frankia. However, little research has been conducted to investigate the presence of Frankia in their nodules and the effects on plant growth. In this study, plants were grown in a Metro-Mix® 820 substrate and inoculated with soils collected from Mohave County, AZ, or in a low organic-matter substrate inoculated with soils from North Logan, UT. The presence of Frankia was quantified using PolF/PolR primers to amplify their nitrogenase (nifH) gene sequences. In the Metro-Mix 820 substrate, plants irrigated with nitrogen (N)-free Hoagland’s solution at pH 6.5 formed nodules at week 12 after experiment initiation, whereas those receiving the same solution with 2 mm ammonium nitrate (NH4NO3) appeared healthy, but no nodules formed. In the low organic-matter substrate, nodules formed in 5 weeks when plants were irrigated with N-free Hoagland’s solution at pH 7.5. Four 300-bp fragments of query sequences (SU1, SU2, SU3, and SU4) were obtained from nodules. When compared with nifH gene sequences reported in the literature using the Basic Local Alignment Search Tool (BLAST), more than 90% similarity to the nifH of Frankia spp. was obtained. The Frankia strains in the nodules shared nifH sequences similar to those of the same host-specific group of Shepherdia. Furthermore, Frankia strains with similar nifH genes have been reported in nodules of Shepherdia argentea (silver buffaloberry). Additionally, Frankia strains belonging to cluster 3 infective strains consisting of Elaeagnaceae and Rhamnaceae infective Frankia showed high similarity to the query sequences. This research demonstrates that nodulation of S. ×utahensis is inhibited at 2 mm NH4NO3. Apart from N, nodule formation may be associated with the substrate type and pH of the nutrient solution. Based on nifH gene sequence amplification, Frankia strains in the root nodules may have the potential to fix atmospheric nitrogen (N2). These Frankia strains have signature gene sequence characteristics of Elaeagnaceae-infective Frankia, suggesting that S. ×utahensis shares Frankia strains similar to its parents.