Common sugar maple (Acer saccharum Marshall) selections suffer from prolonged drought and constant wind on the southern Great Plains. Nonirrigated plants often have scorched and torn leaves as a result of these environmental stresses. In field studies, a sugar maple ecotype native to western Oklahoma (known as `Caddo' maple) has shown improved tolerance to drought and leaf tatter. A study to examine drought tolerance of seedling `Caddo' maple compared to typical seedling sugar maple was established at the John C. Pair Horticultural Center. One seedling of each type was planted in a single 38-L container. Containers were placed on a greenhouse bench, and once acclimated, irrigation was withheld until predawn leaf water potential indicated a substrate water potential of –1.5 MPa. Containers were weighed, and seedlings were maintained in a prolonged drought condition for 3 weeks by adding water each morning to return the container to the original weight. After 3 weeks, photosynthetic temperature response curves were generated for the drought-stressed and the irrigated control plants. Osmotic potential of expressed sap was also measured on rehydrated leaves. The main effects of species, irrigation, and temperature were all significant. `Caddo' maples were able to maintain a higher rate of net photosynthesis than the typical seedlings when drought stressed and as temperature increased. The optimum temperature for photosynthesis did not significantly differ among treatments (36 °C), whereas the maximum rate of photosynthesis was significantly greater for the `Caddo' maples (41 μmol·m-2·s-1) than the typical sugar maples (16 μmol·m-2·s-1).
Jason J. Griffin and F. Todd Lasseigne
The snowbells (Styrax L.) are a group of flowering shrubs and trees distributed throughout the warm-temperate regions of the northern hemisphere. In all, there are about 120 species, of which only Styrax japonicus Sieb. & Zucc. (Japanese snowbell) and its cultivars are currently of commercial significance. Other species may also posses desirable horticultural traits that could be valuable on their own merit, or used in plant improvement programs. Currently there is little information regarding asexual propagation of the lesser known species. The results herein show that propagation of a diverse collection of Styrax(15 taxa) is possible by stem cuttings. However, species and cultivars within a species do not respond to auxin treatment similarly. The percentage of rooting of many taxa was improved when cuttings were treated with 3000 or 8000 ppm (0.3% or 0.8%) of the potassium salt of indolebutyric acid (K-IBA). However, rooting was unaffected by K-IBA treatment in some taxa, while rooting was negatively affected by K-IBA in others. Additionally, the number of roots produced per rooted cutting were affected by K-IBA treatment. In some instances, K-IBA increased the number of roots per rooted cutting. However, in most of the taxa, root number was unaffected.
Jason J. Griffin, William R. Reid, and Dale J. Bremer
Establishment and growth of eastern redbud (Cercis canadensis L.) and pecan [Carya illinoinensis (Wangenh.) K. Koch] were studied where soil surfaces were either covered with each of three common turfgrass species or maintained free of vegetation by the use of an herbicide or an organic mulch layer. Turf species included two cool-season grasses, tall fescue (Festuca arundinacea Schreb.) and Kentucky bluegrass (Poa pratensis L.), and the warm-season bermudagrass [Cynodon dactylon (L.) Pers.]. After two growing seasons, tree caliper of both species was 100% greater in turf-free plots compared with trees in the cool-season grass plots. Root weight of pecans increased nearly 200% when turf was eliminated, and redbud root weight increased nearly 300%. Top weight of redbuds increased 300% and pecans increased 200% when turf was eliminated. Total leaf weight of both species was 300% greater in the turf-free plots, and leaf area increased 200% in both species. Net photosynthesis of redbud trees tended to be higher in the plots without turfgrass, and cool-season grasses inhibited photosynthesis to a greater extent than the warm-season grass. Foliar tissue analysis revealed that nitrogen (N) and potassium (K) were the only elements that increased in concentration when turf was eliminated. However, nutrient concentrations in all treatments were within recommended standard ranges. The results suggest that landscape tree establishment and growth are greatly inhibited by the presence of cool-season turfgrasses and that the inhibition may be more complicated than resource competition.
Sharon J.B. Knewtson, Jason J. Griffin, and Edward E. Carey
Microbial tea from a commercial source and a homemade manure tea were evaluated for 2 years under organic and conventional fertility regimens. Testing with different fertility regimens allowed broader assessment of tea efficacy. Collard green (Brassica oleracea L. var. acephala cv. Top Bunch) yield and soil microbial activity were measured after microbial tea applications were made in three fertility treatments (conventional, organic, or no fertilizer amendment) on a previously unfertilized sandy loam soil. Spinach (Spinacia oleracea L. cv. Hellcat) and collard green yields were determined after commercial microbial tea application to a silt loam soil previously managed with organic or conventional vegetable crops in open fields and under high tunnels. Results indicated that nutrient additions influenced crop yields, even doubling yield. This demonstrated that improved nutrient availability would affect yield at the chosen locations. However, microbial tea applications did not affect crop yield. These results did not support the hypothesis that microbial tea improves plant nutrient uptake. Additionally, soil microbial respiration and biomass were unaffected after two or three tea applications.
Jason J. Griffin, Houchang Khatamian, John C. Pair, and Mike Shelton
Jason J. Griffin, William R. Reid, and Dale Bremer
Successful establishment and growth of newly planted trees in the landscape is dependent on many factors. Weed pressure and water conservation are typically achieved with either organic mulches or chemical herbicides applied over the root ball of the newly planted tree. In the landscape, eliminating turfgrass from the root zone of trees may be more complicated than resource competition. Studies have shown that tall fescue (Festucaarundinaceae Schreb.) has allelopathic properties on pecan trees [Caryaillinoiensis (Wangenh.) K. Koch]. Well-manicured tall fescue turf in the landscape may have negative effects on the establishment and growth of landscape trees as well. A study was designed to examine the effects of popular turfgrasses on the growth of newly planted pecan and redbud (Cerciscanadensis L.). Results demonstrate that the presence of turfgrass over the root zone of trees negatively impacts tree growth. Through two growing seasons, every growth parameter measured on redbuds (caliper, height, shoot growth, shoot dry weight, root dry weight, leaf area, and leaf weight) was significantly reduced by the presence of turf. However, the warm season bermudagrass [Cynodondactylon (L.) Pers.] was less inhibitied than the cool season grasses. The affects of turfgrass on pecan growth was less significant; however, caliper, leaf area, and root dry weight were significantly reduced when grown with turf.
Jason J. Griffin, Thomas G. Ranney, and D. Mason Pharr
Net photosynthesis (Pn) of two ecotypes of redbud (Cercis canadensis L.) was studied following growth under high temperatures and increasing drought. Although mexican redbud [C. canadensis var. mexicana (Rose) M. Hopkins] exhibited greater Pn than eastern redbud (C. canadensis var. canadensis L.), Pn decreased at a similar rate under water deficit stress for both ecotypes. Mexican redbud also had greater instantaneous water use efficiency [net photosynthesis: transpiration (WUE)] than eastern redbud. Differences in both Pn and WUE might have been due to differences in leaf thickness. The optimum temperature for potential photosynthetic capacity (37 °C) was unaffected by irrigation or ecotype. Tissue osmotic potential at full turgor was more negative in eastern redbud, but was unaffected by drought stress in either ecotype. Soluble carbohydrate content was higher in eastern redbud, and in both ecotypes, d-pinitol was the major soluble carbohydrate and was considerably more abundant in the water-stressed plants. Total polyol content (myo-inositol + ononitol + pinitol) was also greater in the water-stressed plants. Both ecotypes were very tolerant of high temperatures and drought.
Jason J. Griffin, Thomas G. Ranney, and D. Mason Pharr
Tolerance to high solar irradiation is an important aspect of stress tolerance for landscape plants, particularly for species native to understory conditions. The objective of this study was to evaluate differential tolerance to high solar irradiation and underlying photosynthetic characteristics of diverse taxa of Illicium L. grown under full sun or 50% shade. Eleven commercially available taxa of Illicium were evaluated for light tolerance by measuring light-saturated photosynthetic capacity (Amax), dark-adapted quantum efficiency of photosystem II (Fv/Fm), and relative chlorophyll content using a SPAD chlorophyll meter. Comparisons of Amax indicated that three of the 11 taxa (I. anisatum L., I. parviflorum Michx. ex Vent., and I. parviflorum `Forest Green') maintained similar rates of light-saturated carbon assimilation when grown in either shade or full sun. All other taxa experienced a significant reduction in Amax when grown in full sun. Chlorophyll fluorescence analysis demonstrated that Fv/Fm was similar between sun and shade plants for the same three taxa that were able to maintain Amax. These taxa appeared to experience less photoinhibition than the others and maintained greater maximum photochemical efficiency of absorbed light. SPAD readings were not significantly reduced in these three taxa either, whereas most other taxa experienced a significant reduction. In fact, SPAD readings were significantly higher in I. parviflorum `Forest Green' when grown under full sun, which also maintained the highest Amax of all the taxa. These results suggest that there is considerable variation in light tolerance among these taxa, with I. parviflorum `Forest Green' demonstrating superior tolerance to high light among the plants compared. A more rigorous examination of I. parviflorum `Forest Green' (high light tolerance) and I. floridanum Ellis (low-light tolerance) demonstrated that I. parviflorum `Forest Green' had a considerably higher Amax, a higher light saturation point, greater potential photosynthetic capacity, reduced susceptibility to photoinhibition as indicated by superior PSII efficiency following light exposure, greater capacity for thermal de-excitation as indicated by a higher rate of nonphotochemical quenching (NPQ) under full sun, greater apparent electron transport rate (ETR) at mid-day, and higher concentrations of the free-radical scavenger myo-inositol. All of these factors contribute potentially to a greater capacity to use light energy for carbon fixation while minimizing photodamage.
Ross C. Braun, Jack D. Fry, Megan M. Kennelly, Dale J. Bremer, and Jason J. Griffin
In the transitional climates, warm-season turfgrasses are more heat and drought resistant and require fewer pesticide and fertilizer inputs than cool-season turfgrasses, but an extended winter dormancy period in warm-season turfgrasses makes them less attractive. Our objective was to evaluate color intensity and persistence of colorants applied at two volumes, once or sequentially, on buffalograss (Buchloe dactyloides) maintained at 2.5 inches and zoysiagrass (Zoysia japonica) maintained at 0.5 inch. Field studies were conducted in Manhattan, KS, and Haysville, KS, from Oct. 2013 to May 2014 on dormant ‘Sharpshooter’ and ‘Cody’ buffalograss and ‘Meyer’ zoysiagrass. The colorants Green Lawnger, Endurant, and Wintergreen Plus were applied at 100 or 160 gal/acre in autumn (single application) or autumn plus midwinter (sequential application). Every 2 weeks, visual turf color was rated on a 1 to 9 scale (9 = best) with ratings based on the intensity of the color, not the color (hue) of green. Few differences in color persistence occurred among colorants, but color persisted longer at the higher spray volume. In general, buffalograss receiving a single autumn colorant application had acceptable color (i.e., a visual rating ≥6) for 55–70 days at 100 gal/acre or 55–88 days at 160 gal/acre. Zoysiagrass receiving a single autumn colorant application had acceptable color for 56–97 days at 100 gal/acre or 97–101 days at 160 gal/acre. Across all sites, a sequential midwinter application applied at 160 gal/acre on buffalograss and both application volumes on zoysiagrass provided acceptable green turf color from that point until spring green-up. Most buffalograss plots receiving the sequential midwinter application at 100 gal/acre had acceptable color from that point until spring green-up. Winter color of buffalograss and zoysiagrass can be enhanced by colorant application, and a longer period of acceptable color can be achieved by applying at a higher volume or by including a sequential midwinter treatment.
Zachary N. Hoppenstedt, Jason J. Griffin, Eleni D. Pliakoni, and Cary L. Rivard
Sweetpotatoes (Ipomoea batatas) are nutritious, easily stored, and well adapted to a variety of organic farming operations. This widely consumed root crop is propagated through the use of cuttings, known as slips. Slips are commercially grown primarily in the southeastern United States, and growers in the central United States still have limited access to sweetpotato planting material. Production of organic slips in high tunnels (HTs) could be a profitable enterprise for growers in the central United States given the season extension afforded by controlled-environment agriculture, which could allow growers to diversify their operations and facilitate crop rotation. In trials conducted in 2016 and 2017 at two research stations in northeast and south central Kansas, a systems comparison was used to evaluate the yield and performance of organic sweetpotato slips grown in HT as compared with the open field (OF), with four to six replications at each location. Propagation beds planted with ‘Beauregard’ seed roots in 2016 and ‘Orleans’ in 2017 were established in HT and OF under similar cultural methods and planting schedules. Slips were harvested from both treatment groups and transplanted to field plots to investigate the impact of production system on transplant establishment and storage root production. Slip yield from HT was greater than OF at both locations in 2016 (P ≤ 0.001), but this trend was inconsistent in 2017. Slips grown in HT were on average 12% less compact (slip dry weight per centimeter length) with fewer nodes than their OF counterparts in 2016. Nonetheless, mean comparisons for vine length, stem diameter, and total marketable storage root yield were not significant between HT and OF treatments (1.7 and 2.1 lb/plant, respectively). Similarly, the number of marketable storage roots for HT and OF groups was comparable (3.4 and 3.8 storage roots/plant, respectively). Although more research is needed to evaluate the feasibility of slips grown in HT and to determine recommendations for seed root planting densities, results from this study suggest that HT organic sweetpotato slip production could be a viable alternative to OF production as it relates to slip performance. According to this study, HT production could be a useful mechanism for growing sweetpotato slips, which could provide regional growers more control over planting material. Furthermore, HT slip production could promote the adoption of an underused vegetable crop that can be grown throughout many parts of the United States.