bluuebunny/crossref_metadata_2025 huggingface dataset:
174 Effect of Planting Method, Mulch, and Rowcover Combinations on Earliness, Yield, and Fruit Size of `Arriba' Watermelon
Authors: Bartolo Michael E. , Schweissing Frank C.
Published: February 2019

Colorado-grown watermelons command a premium price on the market based on their sweetness and overall flavor. Unfortunately, melon production is limited to mid-August through early September. This study was conducted to determine whether intensive production methods could enhance the traditional marketing period. The effects of different combinations of establishment methods, mulches, and rowcovers on `Arriba' (Hollar Seeds) watermelon growth and productivity were investigated in a field trial at the Arkansas Valley Research Center in Rocky Ford, Colo. In 1997, the combinations of transplanting, clear plastic mulch, and perforated or slitted rowcovers produced the earliest harvest and highest yield and fruit weight. The first harvest of the earliest treatments occurred on 4 July. Direct-seeding through clear plastic mulch, both with and without rowcovers, also enhanced earliness relative to the traditional marketing period. However, compared to transplanting, yield and fruit weight were less if the crop was direct-seeded. Intensive plasticulture techniques could substantially increase the earliness of Colorado-grown watermelons. The increased cost of production would be easily off-set by higher productivity and early season prices
175 Synthetic Mulches Increase Strawberry Yields Compared with Organic Mulches
Authors: Roe Nancy , Fojtik Toby , Schmidt Johnnie R.
Published: February 2019

Affluent “peri-urban” populations in some areas have created new markets for small specialized growers. Although intensive growing systems using drip irrigation and fertigation with new varieties can increase yields, there is also a desire to use systems that are viewed as more sustainable. One way to reduce the environmental impact of intensive systems is to use organic mulches that do not require disposal and can improve soil conditions. `Chandler' strawberry (Fragaria ×ananassa Duch.) transplants were set in raised beds on 28 Oct. 1997. All plots received pre-plant P at 73 kg/ha. Treatments were: hay mulch (HY); a commercial, pelleted, recycled paper mulch (PA); polyethylene mulch (PL); or a woven weed-blocking (WB) fabric, with or without dairy manure compost (22% moisture) at 22 t/ha tilled in before bedding. A total of 184 kg/ha N was applied through the irrigation system in weekly applications during the growing season. The first bloom set was killed by cold on 9 Mar. 1998. Yields from the two synthetic mulch systems (PL = 5502 and WB = 4996 kg/ha) were significantly higher than those from the organic mulches (HY = 2824 and PA = 1735 kg/ha). Mean fruit weight was also higher with synthetic (PL = 10.6 and WB = 10.4g) than organic (HY = 9.5 and PA = 9.0 g) mulches. Factors such as increased weed growth in organic mulches and warmer temperatures in synthetic mulches contributed to increased yields from synthetically mulched plots.
180 Cover Crops Improve Soil Quality in Strawberry Production
Authors: Summers Jillene R. , Nonnecke Gail R. , Cambardella Cynthia A. , Schultz Richard C. , Isenhart Thomas M.
Published: February 2019

Improving soil quality and suppressing weeds are two challenges facing strawberry growers. Cover crops, such as perennial ryegrass (Lolium perenne) and sorghum-sudangrass (Sorghum sudanense), have been used in rotation with strawberry in the Midwest. The objective of the field study was to investigate the effects of various cover crops on soil quality and weed populations for strawberry production. The experiment was established in 1996 at the Iowa State Univ. Horticulture Station, Ames, in plots that previously were planted continuously in strawberry for 10 years. Nine treatments were arranged in a randomized complete-block design with three replications. Treatments included cover crops of Indian grass (Sorghastrum avenaceum), switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), black-eyed susan (Rudbeckia hirta), marigold (Tagetes erecta `Crackerjack'), sorghum-sudangrass, perennial ryegrass, strawberry (Fragaria ×ananassa `Honeoye'), and bare soil (control). Data from 1998 showed that both annual and perennial cover crops were established more readily (higher treatment-plant populations and less weed populations) than in 1997. Water infiltration rates were highest in bare soil plots and lowest in P. virgatum plots. Bare soil plots and S. sudanense plots had the lowest percent soil moisture.
186 Effect of Primocane Topping Height and Lateral Length on Yield of `Navaho' Blackberry
Authors: Himelrick David G. , Ebel Robert C. , Woods Floyd M.
Published: February 2019

`Navaho' erect thornless blackberry plants were subjected to a combination of three primocane summer topping heights and two winter lateral length pruning treatments. Plants were topped at 91, 122, 152 cm tall, and laterals were shortened to either 30 or 61 cm in length. Treatment effects on yield and plant structure were examined for four growing seasons. Lateral length had little effect on yield and any pruning height. Yield generally increased with increasing plant height. The 122-cm height appeared to optimize yield while still allowing for manageable floricane architecture.
201 Growth and Flowering of Zephyra elegans D. Don Grown in Greenhouse or Growth Chamber
Authors: Kim Hyeon-Hye , Ohkawa Kiyoshi
Published: February 2019

As a new product in the floricultural market, Zephyra elegans D. Don, shows great potential. It is a new product, so there is little known about its physiology. In this study, the growth cycles and the effects of day/night temperatures on flowering control of this new product were investigated. Stems elongated gradually during the growing season but more slowly after flowering. Original corm fresh weight decreased with increasing daughter corm fresh weight. Druing the growing season, the original corm dies after producing usually one daughter corm. The high ambient temperature of summer adversely effected shoot emergence. The optimum day/night temperature regimes for shoot emergence was 15/10 °C and for growth and flowering it was 20/15 °C. Under these conditions, it is possible to produce Zephyra elegans D. Don year-round.
206 Risk Analysis of Adopting Zero Runoff Subirrigation Systems in Greenhouses Using Monte Carlo Simulation
Authors: Uva Wen-fei L. , Weiler Thomas C. , Albright Louis D. , Haith Douglas A.
Published: February 2019

Although zero runoff subirrigation (ZRS) technology has great promise to manage fertilizer inputs while improving production efficiency in greenhouse operations, high initial investment costs and inadequate technical background are major impediments for initiating the change. In a world of uncertainty, greenhouse operators face the challenge of making an optimal investment decision to satisfy environmental compliance expectations and meet the companies' financial goals. Using Monte Carlo simulation, cost risk was analyzed to compare the relative risks of investing in alternative ZRS systems for greenhouse crop production. An investment model was defined for greenhouse production with alternative ZRS systems. Each cost variable was allowed to vary based on a probability distribution. Random numbers were generated to determine parameters for the probability distributions for the uncertain variables. The simulation process was repeated 300 times for each production model. Simulation results showed that among the four ZRS systems studied (ebb-and-flow benches, Dutch movable trays, flood floors, and trough benches), the Dutch movable tray system returned the highest average profit for small potted plant production and the flood floor system returned the highest average profit for large potted plant and bedding crop flat production. Risk of the production models were compared by the variability of simulation results. The Dutch movable tray system is the least risky for small potted plant production, and the flood floor system is the least risky for large potted plant and bedding crop flat production. Despite its low initial costs of adoption, the trough bench system was least competitive as a ZRS technology for a greenhouse operation because of the relative low profitability and high risk of production due to volatile profitability.
207 Tillage Methods Affect the Growth of Sweetpotato
Authors: Jett Lewis W.
Published: February 2019

Growth of the sweetpotato [Ipomoea batatas (L.) Lam.] is subject to environmental variation. High soil temperatures can restrict storage root initiation and development. Moreover, fluctuating soil moisture can have a pronounced effect on yield and quality. Cover crops, used in a conservation tillage system, could modify the soil environment. The objective of this research was to investigate the effects of conservation tillage on sweetpotato growth. A rye cover crop was broadcast seeded in Fall 1996, and sweetpotatoes were transplanted into the undisturbed residue the following spring. A fallow, unseeded plot represented the conventional method of sweetpotato culture. Plants were harvested at 14-day intervals commencing at 21 days after transplanting. Leaf area and dry weights of the storage roots and vines were recorded. Soil moisture was measured by taking soil cores at the depth of rooting (10 cm). The sweetpotatoes growing in the undisturbed rye residue had a significantly greater leaf area, vine weight, root set, and yield (particularly large grade class) relative to conventional-tilled sweetpotatoes. The rye residue was very effective in reducing soil evaporation.
212 Effects of Plant Density on Growth, Yield, and Quality of Fresh-market Sweet Corn
Authors: Hao Xiuming
Published: February 2019

In summer 1998, two sh2, fresh-market, sweet corn cultivars (`Candy Corner'—large plant size, and `Swifty'—small plant size) were grown at 5, 6.5, 8, and 9.5 plants/m2 to investigate the effects of plant density on growth, photosynthesis, biomass, yield, and quality. Biomass and leaf area per plant were not affected by plant density. Therefore, biomass and leaf area per unit area were increased with increasing plant density. Plant height, leaf chlorophyll, leaf photosynthesis, and transpiration (measured with the LI-COR 6400 portable photosynthesis system) were not affected by plant density. Total cob weight (husk off) and number of ears harvested from plants were increased with increasing plant density. However, marketable yield (number of marketable ears) was not affected by plant density and marketable cob weight (husk off) decreased with increasing plant density due to the reduction in ear size with high plant density. There was a significant increase in percentage of unmarketable ears at plant density higher than 6.5 plant/m2 with `Candy Corner'. Kernel sugar content (°Brix) in both cultivars increased with plant density. According to the results of this experiment, the optimum plant density for fresh-market sweet corn was 5 to 6 plants/m 2.
227 Response of Secondary Bloom of `Bartlett' Pear to Gibberellins, Ethephon, and Pruning
Authors: Moran R.E. , Southwick S.M. , Weis K.G. , Lampinen B.
Published: February 2019

Secondary or “rat-tail” bloom, a major site for fireblight infection of `Bartlett' pear, comprised 10% of the total bloom in 1997 and 20% in 1998. We are striving to find production practices that can be economically applied to reduce the number of “rat-tails.” Of the five known types of secondary clusters in pear, four occur on `Bartlett', the most numerous being types I and V. Type I rat-tails occur on the bourse at the base of normal clusters and bloom from 10 to 30 days after normal bloom. Type V rat-tails occur mostly at pruning sites and have one to three flowers per cluster, blooming 20 to 50 days after normal bloom. GA 3 or GA4+7 + BA were applied at 100 mg•L-1 in 1997 to reduce rat-tail bloom in 1998. In 1998, neither GA3 nor GA4+7 + BA had an effect on normal bloom or type I rattails. GA3 reduced type V rat-tails when applied at either 2 June, 2 July, or 15 Aug. but had no effect on type V clusters when applied at full bloom, petal fall, 16 June, or 15 July. GA4+7 + BA reduced the number of type V rat-tails when applied at either 2 June, 16 June, 2 July, and 15 July but had no effect when applied at full bloom, petal fall, or 15 Aug. Dormant pruning horizontal shoots resulted in as many rat-tails as vertical shoots, and heading cuts a similar number as stubbing cuts. Dormant pruning 1-year wood resulted in fewer rat-tails than 2-year wood. Summer pruning 21 or 49 days after bloom resulted in fewer rat-tails than pruning 10 days after harvest, but was similar to pruning 89 days after bloom. These and other results from ongoing work will be presented toward development of an integrated fire blight reduction strategy.
231 Effects of Stand Deficiencies and Timing of Replanting on Yields of `Athena' Muskmelon
Authors: Walters S. Alan , Schultheis Jonathan R.
Published: February 2019

Seedling losses shortly after emergence in muskmelon (Cucumis melo L.) can be potentially devastating to growers. Muskmelon growers often have problems with obtaining adequate stands and need to understand the affects of replanting seed into poor stands. Field studies were conducted over 2 years to determine if replanting (at 1, 2, 3, or 4 weeks after the initial seeding) into stand deficiencies of 10%, 30%, and 50% affected `Athena' muskmelon size and yield. `Athena' muskmelon stand deficiencies up to 30% does not appear to reduce total or marketable numbers, but stand deficiencies of 50% or more will decrease total and marketable melon yields. Replanting into 10%, 30%, and 50% stand deficiencies will increase early season melon numbers regardless of the replant times used. For main-season and total-season harvests, there was no advantage of replanting into 10% deficient stands, and in most cases, replanting reduced total and marketable melon numbers. In the 1997 experiment, replanting into 30% and 50% stand deficiencies improved yields but this did not occur in the 1998 experiment. `Athena' muskmelon should be replanted only if a stand reduction of ≈50% or more occurs. Melon numbers were generally higher if replanted by 1 or 2 weeks compared to 3 or 4 weeks, but the timing of replanting does not appear to have significant influence on total or marketable melon numbers.
235 Seed Treatments for Inactivation of CGMMV in Gourd and Its Detection
Authors: Kim Du-Hyun , Lee Jung-Myung , Bae Jin-Ju
Published: February 2019

Cucumber green mottle mosaic virus (CGMMV) is a noxious disease in cucurbits, especially in Asia where grafting is commonly practiced. CGMMV can be easily transmitted by seed, hands, soil, or grafting. Seed companies are rigorously looking for effective and efficient means of CGMMV inactivation in infected seeds. Among the various treatments applied to the seeds, dry heat treatment (35° C 1 day + 50 °C 1 day + 75 °C 3 days) was found to be most suitable for complete inactivation. Various identification methods including high-density latex agglutination test (HDLPAT), ELISA, RT-PCR, and bioassay (Chenopodium amaranticolor) were compared for accurate diagnosis of the presence of virus in seeds. The results from HDLPAT showed the highest correlation with the bioassay results, suggesting that HDLPAT can be safely used for accurate means of virus detection. Details of dry heat treatment, various seed treatment, and other detection methods will be presented.
239 Evaluation of Spur-type Apple Cultivars on Dwarfing Rootstocks
Authors: Siswanto Usman , Matta Frank B.
Published: February 2019

The performance of spur-type apple cultivars was evaluated on MM.111, MM.106, M.7A, M.26, and Mark rootstocks. Shoot growth, leaf area, and total nonstructural carbohydrate (TNC) were affected by scion cultivar and rootstock. Empire on Mark stock had less shoot growth. Ultra Mac on M.7A produced smaller leaf area. `Braeburn' on Mark stock exhibited higher TNC content. Scion cultivar and stock influenced fruit weight and yield, L: D ratio, SSC, pH, and the content of N, P, K in leaves and fruit. `Braeburn' on M.7A, M.26, and MM.111 produced greater yield per tree. L: D ratio was higher in `Ultra Gold' on MM.106. `Ultra Gold' and `Jon-A-Red' had higher SSC on Mark. `Empire' and `Ultra Gold' on M.7A resulted in higher juice pH. `Empire' on MM.106 produced heavier fruit and higher N content in leaves and fruit. `Ultra Mac' on M.7A showed higher P and K content in the fruit.
245 Growth of Papaya Seedlings under Wind Load and Drought Stress
Authors: Clemente Hiphil S. , Marler Thomas E.
Published: February 2019

Two studies were conducted with `Known You 1' and `Sunrise' papaya seedlings to determine the combined influence of wind and drought stress on growth. For each study, 4-week-old nursery plants were transplanted into 2.6-L containers and placed in a protected site with rain exclusion provided by polypropylene cover. Industrial fans were used to provide unidirectional wind of ≈2 m/s for 12 hours per day to half of the plants; the remaining half of the plants received no wind. One half of the plants for each cultivar and wind combination were designated as well-watered and received daily irrigation. The remaining half of the plants were designated as drought-stressed and received 25% to 50% of the water applied to the well-watered plants. Plants were grown for 3 weeks under these experimental conditions. There were no interactions between the drought and wind main effects. The reduction in height, trunk cross-sectional area, total plant dry weight, and relative growth rate below that for control plants was similar for drought stress or wind stress. Wind stress reduced growth of `Sunrise' plants more than `Known You 1' plants in both studies. Although the main effects did not interact, the combination of drought and wind stress reduced growth of papaya seedlings more than did either main effect alone. The greatest wind load from trade winds occurs on Guam during the annual dry season. These data indicate that chronic wind stress during the dry season may be more detrimental to growth of papaya seedlings than during the rainy season or under sufficient irrigation practices.
251 The Effect of Simulated Stress on the Yield and Size of `Gala' and `Empire' Apple
Authors: Breitkreutz S.L. , Flore J.A.
Published: February 2019

Pest damage to apple fruit is intolerable by our current standards. However, the effects of foliar damage on the plant's physiological status and fruit quality are not thoroughly understood. The objective of this work was to determine the time during the growing season when apple trees are most susceptible to foliar damage. Terbacil (50 ppm), an inhibitor of photosynthesis, was applied to 8-year-old `Gala'/Mark planted at 6 ×18-foot spacing or 14-year-old `Empire'/M106 planted at 18 × 20-foot spacing at 20- to 30-day intervals from petal fall until harvest to simulate environmental or biological stress. The work was conducted from 1995 through 1998. Photosynthesis was inhibited by 50% to 80% within 24 h of application of Terbacil but recovered to control levels 10 to 14 days after. The fruit were evaluated at harvest for total yield, size of fruit, and fruit number. Terbacil induced fruit abscission when applied at petal fall but not at later dates. The earlier the application, the greater the effect on current seasons yield and fruit size depending on crop load. For `Gala', there was a reduction in yield at petal fall of 30% to 70% over the control trees. Further detailed results will be presented.
262 Nursery Irrigation Effects on Postplanting Root Development of Two Mediterranean Species in Semi-arid Conditions
Authors: Franco J.A. , Bañón S. , Fernández J.A. , González A.
Published: February 2019

A study was conducted with Lotus creticus and Limonium cossonianum to analyze the influence of irrigation regime in nursery on the dynamics of root development after being transplanted with minimum management conditions. Plants were pot-grown in a greenhouse located at the southeastern Mediterranean coast of Spain (37°47′N, 0°54′W). Each plant was potted into 625-mL plastic pot filled with a 1 silica sand medium: 1 peat (v/v) mixture amended with osmocote plus (3.7 g•kg-1 substrate). Drip irrigation was used, with a 2-L•h-1 emitter per plant. Three irrigation treatments were utilized: T6, plants watered 6 days a week at the water-holding capacity (leaching ≈20% of the applied water); T3, plants watered 3 days a week; and T2, plants watered twice a week. T3 and T2 plants received amounts of water at ≈50% and ≈30%, respectively, of T6 plants troughout the nursery period (3 months for Lotus and 45 days for Limonium). After nursery period, plants were transplanted into transparent containers (round acrylic tubes 8 cm in diameter and 100 cm tall) filled with silt loam texture soil, and just one establishment irrigation was applied (30 mm). Containers were covered with a black plastic sheet and isolating material to prevent light influencing and becoming heated. There were three replications. Plant root and top growth were measured every 3 days for 1 month. Results indicate that those plants that were less watered in nursery showed a greater and faster root development especially where depth was concerned. Lotus plants root growth, for the top 20 cm of soil, were not significantly affected by irrigation treatments; between 20 and 40 cm deep, T2 plants at 12 days after transplanting (DAT) had 2.8- and 9.1-times greater root length (RL) than T3 and T6 plants, respectively. At 30 DAT, T2 plants had 1.7- and 6.2-times higher RL than T3 and T6, respectively. Under 40-cm deep (where infiltration of the establishment irrigation water was very limited), only T2 plants developed roots. There was no plant top growth throughout this period. Limonium plants exhibited notably lower root development (≈1/5) than Lotus plants. In the top 15 cm of soil, Limonium plants RL were not significantly affected by irrigation treatment; between 15 and 30 cm deep, T2 and T3 plants, at 10 DAT, had 2.2-times longer RL than T6 plants, and at 30 DAT, T2 plants had 1.4- and 2.1-times greater RL than T3 and T6 plants, respectively. Below 30 cm, only T2 plants developed roots and, even so, very few ones. For this period, a slight plant top growth was observed, there being no significant differences among irrigation treatments. Research suported by CICYT grant AGF-96-1136-C02-02.
266 Retractable Shading Reduces Summer Substrate Temperatures in Container-grown Nursery Crops
Authors: Svenson Sven E.
Published: February 2019

The influence of no shading; 30%, 47%, or 63% black polypropylene stationary shading; and white poly retractable shading (50% shade operated to provide morning “cold trapping”) on substrate temperature was studied for Coreopsis verticillata `Zagreb' and Forsythia `Lynwood' growing in 2.75-L black polycontainers filled with an unamended Douglas-fir bark substrate. The southwest region of the rootball had the highest daily substrate temperatures under all the shading systems. Substrate temperatures were highest under no shading or 30% shading (often >45 °C) and lowest under retractable shading (never >38 °C). Root death occurred on the southwest portion of the rootball on plants growing under all shading systems except under retractable shading. Coreopsis and Forsythia were taller when grown under 63% stationary shading compared to other shading systems but had more shoot dry weight when grown under retractable shading. Cooler substrate temperatures that prevent damage to the root system may help explain increased growth of some nursery crops when produced under retractable shading.
271 Unidirectional Wind Load Influences Growth, Morphology, and Physiology of Papaya
Authors: Clemente Hiphil S. , Marler Thomas E.
Published: February 2019

Trade winds are a widespread horticultural consideration throughout the tropics. Growth and productivity of most horticultural crops are not optimal on sites that are exposed to these chronic, unidirectional winds. We conducted four container studies on an exposed site, using clear plastic or screening material to provide three levels of wind exposure: 0%, 36%, or 100%. Two studies were conducted with direct-seeding, such that seedling emergence and early growth were determined for 7 weeks. Two studies were conducted using 8-week-old nursery plants that had been grown in a protected nursery. These plants were transplanted to the experimental site and grown for 6 weeks. Cultivars were `Known You 1', `Sunrise', and `Tainung 2'. Full exposure to wind reduced height up to 32%, increased root: canopy ratio up to 36% and exhibited no influence or slightly reduced stem cross-sectional area when compared with full protection from wind. Net carbon dioxide assimilation (Pn) was measured on intervals of about 2 h throughout several 24-h periods. Although the daily pattern depended on cultivar and date, the general trend was for Pn to be unaffected by wind from early to mid-morning, and for Pn of the unprotected plants to decline below that of the protected plants throughout the rest of the day. The Pn of plants receiving intermediate protection was highly variable among the cultivars and dates in relation to the protected and unprotected plants. Moreover, dark respiration of the unprotected plants was greater than the protected plants throughout the entire nocturnal period. The primary influence of wind on growth of young papaya seedlings was a shift in biomass allocation in favor of the stem base and roots.
273 Reduction of Fruit Cracking by Automatic Application of Calcium Chloride
Authors: Reed Matt , Genter Brie , Flore J.A.
Published: February 2019

We have developed a system of automated intermittent salt application above the tree during a rain event that has shown very encouraging results (Washington State Hort Soc. Proc. 1995, Good Fruit Grower, vol. 47; pp. 23-24; Acta Hort. vol. 468 pp. 649 & 683) in Michigan and the Pacific Northwest. In 1998, we significantly reduced rain cracking with the system used in previous years. At the Southwest Michigan Research and Extension Center (SWMREC), on `Ulster', the control averaged 18% while the 0.5% calcium chloride had 6.7% cracks. Similar results were found for `Ulster', `Somerset', and `Rainer' at the Northwest Station. Cracking was greater in the upper part of the tree than the lower part for the control. The calcium chloride had less cracking on the upper part than the lower part indicating that calcium chloride applied from above the tree was not uniformly distributed to the lower part of the canopy in high enough concentrations. Multiple emitters per tree decreased this problem. We determined that there was an interaction with temperature. More fruit cracked at high temperature than low temperature. In the field more fruit cracked during the day than at night. We attribute this to the difference in day and night temperature. Using a bioassay system we able to determine the critical concentration of salt that must be on the fruit to inhibit water uptake and rain splitting up to a 4-h period. It ranged between 0.05% to 0.10 % depending on the variety and stage of development.
277 Transpiration and Membrane Competence in Fragaria Exhibit Genotype-specific Responses to ABA
Authors: Ringo J. Decker , Archbold Douglas D. , Clements Ann M.
Published: February 2019

Divergent physiological responses to drought between and among accessions within Fragaria chiloensis (FC) and F. virginiana (FV) may result from differing responses to ABA produced during the drought. Excised leaves from an accession of each species as well as F. ×ananassa (FXA) `Tribute' and their interspecific hybrids were fed ABA at 0, 1, 10, 100, and 1000 nM via the cut petiole for 24 h before measuring transpiration rate. Transpiration rates of the FV accession and FV by FXA hybrid were relatively less responsive to ABA than any of the others tested. Foliar membrane competence of the FC and FV accessions, measured by the gTi method using excised disks, was reduced by ABA treatment in both species with a relatively greater effect on FV. A drought episode before sampling affected gTi values of FV but not FC. ABA treatment had no additional effect on gTi values of a previously droughted FC accession, while gTi values of a previously droughted FV accession were increased with ABA treatment. Thus, transpiration of the FV accession was less responsive to increasing ABA concentration than the FC accession, while membrane competence of the FV accession was affected more by both drought and ABA treatment applied separately or in combination than the FC accession.
280 Botryosphaeria dothidea Causes Premature Breaking of Endodormancy and Reduces Cold Hardiness in Cercis canadensis
Authors: Shirazi A.M. , Jacobs K.A.
Published: February 2019

Near-lethal abiotic stresses, e.g., low or high temperatures, chemicals, etc., can break endodormancy prematurely and reduce cold hardiness in woody plants. It is not well-ducumented whether biotic stresses can cause the same effect. Botryosphaeria dothidea causes canker in redbud (Cercis canadensis) and many other woody plants and is one of the most limiting factors growing redbud in the landscape. Two-year-old seedlings were planted in a nursery in May 1998 at The Morton Arboretum. Trees were inoculated (n = 10/treatment) with the fungus in Sept. 1998 using the stem slit method (a slit was cut about 5 cm above the base of the trunk and the wound was covered with parafilm after treatment). The treatments were T1 = control (PDA, Potato Dextrose Agar),T2 = 1-mm mycelium plug, T3 = low spore suspension (25 μL), T4 = high spore suspension (25 μL). Stem cold hardiness was evaluated by artificial freezing tests in Nov. 1998. The mean LT50 (the temperature at which 50% of the tissues is killed) from ion leakage were T1 (Control) = -29.3 °C, T2 (mycelium): -24.05 °C, T3 (low spore) = -18.75 °C, and T4 (high) = -16.4 °C. T3 and T4, the low- and high-spore inoculation, significantly reduced cold hardiness in redbud stem tissues. The LST (lowest survival temperature) based on visual observation of the samples after 7 days indicated all Botryosphaeria dothidea-treated plants had lower cold hardiness compared to control. Endodormancy was broken in B. dothidea-treated plants after placing plants under 16 h of light and 23 /18 °C day/night temperature for 1 month after the treatment. The highest percent budbrealk was for T4 (high spore), followed by T3 (Low Spore) and T2 (Mycelium).
282 Shoot and Root Characteristics of Rudbeckia hirta L. at Different Clipping Heights in a Model Wildflower Sod Production System
Authors: Neigebauer Amy L. , Davis Greg L. , Horst Garald L. , Steinegger Donald H.
Published: February 2019

Field-grown wildflower sod has been in production for several years, but as with any crop management system, the reasoning behind the methods is not always known. One characteristic of wildflower sod production that has been debated is the height at which the plant is maintained. The above-ground shoot growth is managed to reduce the damage to plants when undercut and to allow for ease of shipping. Growers typically use a height of 7.6 cm because this is the highest height allowed by many mowers. Also, root production is the key to forming a sod that will hold together well and withstand the rigors of undercutting, lifting, storage, and transplanting. The purpose of this study was to determine the influence of cutting height on the plant's ability to produce a sod. Rudbeckia hirta L. was used as a model wildflower species and was seeded into polyvinyl chloride (PVC) tubes 10.2 cm in diameter with a depth of 60 cm to simulate a field situation. To characterize shoot and root growth, during a period of 12 weeks plants either received no clipping or continuous clipping at heights of 5.1, 7.6, and 10.2 cm. Root dry weights were measured at depths of 0-2.54, 2.54-21.7, 21.7-40.8, and 40.8--60.0 cm. Leaf area measurements of the clippings were recorded to determine productivity. Results indicated that clipping the shoots of Rudbeckia hirta caused a decrease in root biomass.
296 Chemical Thinning of `Fuji' Apple with Ethephon, NAA, MCPB-ethyl, and Carbaryl
Authors: Guak Sunghee , Looney Norman E. , Fuchigami Leslie H.
Published: February 2019

We propose that return flowering of `Fuji' apple can be improved if sufficient flower clusters are removed during or shortly after bloom. In this study conducted at Corvallis, Ore., we evaluated two synthetic auxins, MCPB-ethyl and the Na salt of NAA, each at 0, 4, 8 and 16 ppm, as blossom cluster thinners. Each auxin treatment was applied alone or with 100 ppm ethephon as a tank mix. Six-year-old `Fuji'/M.26 trees were sprayed at full bloom of the king flowers (≈85% of whole-tree full bloom). A follow-up treatment of Sevin XLR (800 ppm carbaryl) was made at 11-mm fruit diameter to determine if carbaryl's known effectiveness as a fruitlet thinner was influenced by the bloom-time auxin or auxin + ethephon treatments. MCPB-ethyl proved ineffective as a bloom-time thinner, whereas the NAA effect on cluster removal was linear with concentration, 16 ppm NAA completely defruiting 33% of initial flower clusters. On control trees fewer than 12% of flowering clusters failed to set fruit. Ethephon alone defruited 25% of the clusters and NAA+ethephon defruited 51% of clusters. It is notable that the NAA and ethephon + NAA treatments did not reduce fruit set on the remaining clusters, resulting in considerable need for hand-thinning. Carbaryl effectively reduced total crop load by increasing the number of defruited clusters and reducing the incidence of doubles and triples. There was evidence to suggest that its effectiveness was compromised by the bloom-time NAA and/or ethephon sprays.
297 Effect of Gibberellic Acid on One-year Apple Rootstock Plant Growth in the Greenhouse
Authors: Pereira Jonny E. Scherwinski , de L. Fortes Gerson R. , da Silva João Baptista
Published: February 2019

Aiming to improve plant growth of the apple rootstock cultivar Marubakaido (Malus prunifolia) in greenhouse, 1-year-old plants were sprayed once, twice, and three times in a 7-day interval with gibberellic acid (GA3) in the following concentrations: 0, 50, 100, 200, 400, 800 and 1600 mg•L-1. The plant growth was evaluated every 2 weeks during 2 months. The internode length, bud number, and the dry weight of the aerial part were also evaluated at the end of the experiment. It was verified that GA3 sprayed at 800 mg•L-1 by three times consecutively was the best treatment presenting the largest rate of plants growth (912% against 114% of nontreated plants) in relation to their initial height, besides providing larger internode length and dry matter weight of the aerial parts. However, using this regulator did not affect the plant bud number. Plants sprayed once did not present significant response to GA3 for any of the studied variables. These results suggest that the use of GA3 in 1-year-old apple plants reactivates growth, although, the increase in the number of applications associated with higher doses is necessary to improve the efficiency of this product.
301 Bioregulators Affect Apple Yield and Quality Attributes
Authors: Ouma George , Matta Frank
Published: February 2019

Experiments were conducted in 1995 and 1996 to investigate the effect of Accel and Carbaryl sprayed 2 weeks postbloom on apple fruit yield and quality and to relate the degree of fruit set reduction to the yield of three apple cultivars (Empire, Jon-A-Red, and Braeburn). The treatments consisted of Accel 25 ppm, Accel 50 ppm, Accel 75 ppm, Carbaryl 0.05%, Carbaryl 0.1%, Carbaryl 0.2%, and an unsprayed control. Trials conducted over the 2 years indicated that Accel and Carbaryl reduced the fruit set of three apple cultivars as shown by the lower number of fruit per limb cross-sectional area on the sprayed trees compared to the unsprayed trees. Most effective concentrations in reducing the fruit set on apples were Accel 50 ppm, Accel 75 ppm, Carbary 0.01%, and Carbaryl 0.2%, with high yields and high fruit rates. Therefore, it was concluded that these are the best concentrations for thinning of apples. Other quality attributes, such as pH, sugar content, and percent fruit red were also increased by the treatments. The treatments did not influence the number of seeds in the fruit, fruit length, fruit diameter, and fruit length: diameter ratio.
315 Effect of Mycorrhizal Inoculation with Two Glomus spp. on Growth and Development of American Ginseng Plantlets in Greenhouse
Authors: Nadeau I. , Desilets H. , Gagne S. , Parent S. , Moutoglis P. , Robitaille D.
Published: February 2019

American ginseng (Panax quinquefolius) is a native plant of the deciduous forests of eastern North America. This highly valuable medicinal plant has been grown commercially for nearly a century in the field, under artificial shade sources, or in forests under mature trees. Wood-grown ginseng roots are highly similar to the wild ones, which increases their value. However, the time required to produce a marketable root is two to three times longer in the forest than in the field. In an attempt to reduce this time, a new technique has been developed to produce ginseng transplants destined for forest culture. Ginseng seedlings pre-treated with giberellic acid were sown in forest plots in a peat base culture medium ammended with an inoculum of the arbuscular fungi Glomus intraradices or G. etunicatum. The plantlets were grown for 18 weeks in greenhouse under shade cloth. The two Glomus spp. suceeded in colonizing the ginseng rootlets, developing the `Paris' mycorrhizal type, as previously reported for this plant. In addition, plantlets inoculated with G. etunicatum weighed 15% more than the control and were significantly more branched. The amount of P, K, and Mg in the roots was significantly higher in mycorrhizal ginseng plantlets.
316 Effects of Planting Density and Short-term Changes in Photoperiod on the Growth and Photosynthesis of Two Cultivars of Bean (Phaseolus vulgaris L.)
Authors: Yorio N.C. , Stutte G.W. , Goins G.D. , de Villiers D.S. , Wheeler R.M.
Published: February 2019

The effects of planting density and short-term changes in photoperiod on the growth and photosynthesis of bean (Phaseolus vulgaris L.) was investigated. Two cultivars of bean (cv. Etna, a dry bean variety; cv. Hystyle, a snap bean variety) were grown using nutrient film technique hydroponics in a walk-in growth chamber with a 12 h/12 h (light/dark) photoperiod and a corresponding thermoperiod of 28/24 °C (light/dark) and constant 65% relative humidity. Lighting for the chamber consisted of VHO fluorescent lamps and irradiance at canopy level was 400 μmol·m-2·s-1 PPF. For each cultivar, plants were grown at densities of 16 or 32 plants/m2. Short-term photoperiod changes were imposed during vegetative growth (21-29 DAP) and pod-fill (42-57 DAP). From the base 12 h/12h (light/dark) photoperiod, lighting in the chamber was cycled to provide 18 h/06 h (light/dark) or 24 h/0 h(continuous light) for 48 h. Diurnal single leaf net photosynthetic rates (Pn) and net assimilation vs. internal CO2 (Aci) measurements were taken during the short-term photoperiod adjustments. Results showed that there was no difference between cultivars or planting density with regard to total biomass or single leaf photosynthetic rates, but cv. Etna produced 35% more edible biomass than cv. Hystyle. Additionally, there was no effect of short-term photoperiod adjustment on single leaf Pn or Aci.
317 Photosynthetic Characteristics of Two Cycas micronesica Leaf Cohorts
Authors: Marler Thomas E.
Published: February 2019

Cycas micronesica is an arborescent cycad with sclerophyllous, long-lived compound leaves that are produced in synchronized pulses. The photosynthetic characteristics of leaves in two sequential cohorts of ≈2 and ≈11 months after leaf expansion were determined in this study. Fluorescence yield following 30-min of light exclusion or from leaves engaged in photosynthesis under ambient light was measured throughout several 24-h periods to determine maximum quantum efficiency of PSII photochemistry and quantum efficiency under ambient light. Maximum quantum efficiency was similar for the two cohorts throughout the nocturnal period. Maximum quantum efficiency and quantum efficiency under ambient light declined following exposure to daily direct sun but recovered quickly each afternoon. This daily decline was greater for the older cohort than the younger cohort. Net carbon dioxide assimilation (Pn) was also determined using gas exchange, and light saturated Pn of the older cohort was 75% to 85% of that for the younger cohort during the daily maximum at late morning. Pn of the older cohort increased more slowly in the morning and declined more rapidly in the afternoon than did Pn of the younger cohort. Apparent quantum yield determined by gas exchange was similar for the two cohorts in the absence of extended sun exposure. However, this characteristic declined during midday, and the decline was greater for the older cohort. These results indicate that photosynthetic capacity of older C. micronesica leaf cohorts remains high, and these older leaves may substantially contribute to the plant's overall carbon economy. However, the number of hours during the day in which these older leaves reach their photosynthetic capacity is less than for the younger leaves.
321 Morphological Shoot Apex Changes During Inflorescence Development in Heliconia rostrata Ruiz & Pavon
Authors: Maciel Norberto , Criley Richard
Published: February 2019

The colorful and pendulous inflorescence of Heliconia rostrata Ruiz & Pavon terminates an erect and herbaceous-musoid axis of a sympodial rhizome system. Each hapoxanthic axis bears a variable number of leaves (5 to 10) subtending the inflorescence. The number depends on the time between shoot emergence and flowering stimulus. Inflorescence initiation and development occurs without external evidence of this process until the inflorescence emerges from the pseudostem. The morphological changes occurring at the terminal shoot apex of the H. rostrata as it changes from vegetative to the flowering stage are described and illustrated by photomicrographs in this paper. The anatomical sections reveal that the apex on vegetative phase is domed, and a maximum of four furled leaves including one leaf primordium can be observed surrounding it. The growth of the leaf primordium is highly synchronized with growth of the most recently formed leaves. With the transition to inflorescence development, more primordia are observed on the apex, which ultimately give rise to the bracts. Except for the first sterile bract, a cincinnus primordium (flower cluster) is detectable in the axil when the next bract begins to develop. Flower differentiation on the cincinnus begins when many bracts are well-developed. The increase of longitudinal height on the internodes is among the first detectable morphological changes in the apex. Under inductive conditions, the transition to the reproductive stage is achieved early in plants with three or more unfurled leaves. The reproductive plant status is easier to detect under the microscope when the inflorescence has at least three bracts.
327 High Root-zone Temperature Effects on Floral Initiation in `Allstar' June-bearing Strawberry
Authors: Biela Melita M. , Nonnecke Gail R. , Graves William R. , Horner Harry T.
Published: February 2019

Temperature, as a potential environmental stressor, interacts with photoperiod in floral initiation of June-bearing strawberries (Fragaria ×ananassa), such that high-temperature exposure can result in poor floral initiation. Our objectives were to examine the effects of various durations of high root-zone temperature on floral initiation and development and on vegetative growth and development. In a 1998 greenhouse experiment, hydroponically grown `Allstar' June-bearing strawberry plants were subjected day/night temperatures of 31/21 °C in the root zone for one, two, or three continuous periods (of ≈7 days), followed by exposure to 17 °C for the duration of the experiment. Control plants were raised at 17 °C in the root zone throughout the experiment. An additional temperature treatment was exposure to 31/21 °C in the root zone for two periods, each followed by a period at 17 °C. Plants were arranged in a randomized complete-block design with factorial treatments of duration of high root-zone temperature and harvest time. At the end of each period, plants were harvested and the apical meristems dissected for microscopic evaluation of vegetative and floral meristems and the stage of development of the primary flower. We observed floral initiation in all treatments after photoperiodic induction. However, exposure to 31/21 °C in the root zone during key periods of floral initiation in June-bearing strawberry may alter floral development.
331 Late Planting Reduces Annual Artichoke Productivity
Authors: Drost D.T. , Philips N. , Thomsen N.
Published: February 2019

Artichoke, a cool-season, frost-tolerant, but freeze-sensitive, crop, was investigated for annual production in Utah. The objectives were to assess the effects of alternative cropping methods on growth and productivity. Artichoke (`Imperial Star') was seeded in January or February and grown for 3 months before transplanting to the field. Plants were planted in bare soil, through plastic mulch or through plastic with floating rowcovers in April or May. Plant growth (leaf area), environmental conditions, and yield (number, weight, and quality) were monitored throughout the year. Planting date and mulching treatments had a significant effect on plant growth and productivity. Leaf area was greatest at all measurement dates as temperature adjacent to the plant increased (plastic with cover > plastic > bare soil). Early planting had greater yield than late planting regardless of mulching treatment. There was no difference in final yield between the plastic mulch and plastic plus cover at early plantings, although yields were higher than in bare soil. However, late planting through plastic with rowcovers significantly reduced bud yields compared to bare soil or black plastic only. While higher temperatures associated with plastic and rowcovers increased plant growth, increased temperatures under covers after the May planting date devernalized artichoke seedlings, which contributed to the lower yields late in the season.
333 Evaluation of New Elms from China for Stress Tolerance
Authors: Shirazi A.M. , Ware G.H.
Published: February 2019

The high resistance of Chinese elms to Dutch elm disease and elm leaf beetles makes them excellent trees for the urban landscape. There are many new Chinese elms being developed through the tree breeding program at The Morton Arboretum. Many new elms are already on the market or will be available soon from nurseries. There is little known about the stress tolerance, e.g., cold, heat, drought, etc., of new elms from China. The objectives of this study were 1) to determine the midwinter cold hardiness of new Chinese elms and 2) to determine the leaf heat tolerance and stem cold hardiness of new elms from the nursery. The stem cold hardiness of nine new elms from China was evaluated in Feb. 1998 and 1999 from the elm breeding program at The Morton Arboretum by using an artificial freezing test. The LT50 (the temperature at which 50% of the tissues were killed) of the most to least hardy genuses for Feb. 1998 were Ulmus macrocarpa (> -36 °C), U. wilsoniana # 673 (-34 °C), U. parvifolia R-89-120 (-34 °C), U. wilsoniana # 669 (-34 °C), U. wilsoniana # 997 (-33.8 °C), U. szechuanica (-30 °C), U. gaussenii R-94-85D (-30.7 °C), U. bergmanniana var. lasiophylla R-9422SD (-27.7 °C), and U. castaneifolia #R-9411-11-SD (-25.9 °C). Four new elms from Schmidt Nursery, Boring, Ore., were also evaluated for leaf heat tolerance in August and cold hardiness in Dec. 1998 and Feb. 1999. The LT50 of cold hardiness of stem tissues of cultivars in December were U. parvifolia `Emer 1' P.P. 7551, Athena® elm (-23.5 °C), U. parvifolia `Emer 1' P.P. 7552 Allee® (-26.5 °C), U. Accolade™ (-33.5 °C), and U. Danada Charm™ elm (-31 °C). The LT50 of the most to least heat-tolerant cultivars were U. parvifolia `Emer 1' P.P. 7551, Athena® elm (53.8 °C), U. parvifolia `Emer 1' P.P. 7552 Allee® (52.1 °C), U. Accolade™ (50.8 °C), and U. Danada Charm™ elm (50.6 °C). Growth, dormancy development, spring budbreak, and performance of these cultivars will be compared.