bluuebunny/crossref_metadata_2025 huggingface dataset:
VEGETATIVE ORCHARD FLOOR COVERS CAN REDUCE APPLE TREE ROOTING
Authors: Parker Michael L. , Warren Stuart L.
Published: April 2024

`Redchief Red Delicious'/MM.lll (Malus domestica Borkh.) apple trees were grown for 12 years in six vegetative covers: rye mulch (RM), bare soil (BS) maintained by herbicides, mechanical cultivation (MC), tall fescue (TF), Kentucky bluegrass (KB) and nimblewill (NW). Apple root distribution was determined using the trench profile method. A trench two meters long and one meter deep was dug perpendicular to the tree row, 80 cm from both sides of the tree. One meter square grids, sectioned into 10 cm squares, were placed on the profile walls and root diameter and number were recorded. Trees grown in RM had the highest number of roots, greater than all other covers, followed by BS. MC and NW had fewer roots than BS. However, MC and NW were higher than KB and TF. KB had fewer roots than all covers except TF. TF had the lowest number of roots.
COLD HARDINESS RESPONSE OF CABERNET SAUVIGNON AND CHARDONNAY GRAPEVINES TO WINTER PRUNING
Authors: Wample Robert L.
Published: April 2024

At approximately two week intervals starting in mid-December, sets of four vines were pruned either 24, 48, or 72 hours prior to sampling for low temperature exotherm (LTE) analysis of buds. Prepruned samples were compared with unpruned samples. Buds for cold hardiness were taken from the fourth to the sixth node positions from each of the four vines. A total of 30 buds from each of the treatments were used for LTE analysis. In addition to these samples, analysis of bud cold hardiness was also made of these prepruned vines after approximately 3, 6, and 9 weeks and compared to unpruned vines.

Despite the popular view that prepruning or pruning of grapevines during the winter reduces cold hardiness of the remaining buds, no differences were found between treatments during December, January, and February. Additional data on winter injury and budbreak will be presented.
COMPARISON OF TISSUE RESPONSES TO COLD HARDENING AND FREEZING IN LEAVES OF CABBAGE (BRASSICA OLERACEA VAR. CAPITATA)
Authors: Manley Reeser C. , Hummel Rita L.
Published: April 2024

When intact shoots and detached leaves of cold-hardened cabbage were frozen to -16°C the leaf lamina and leaf petiole were the limiting factors, respectively, in leaf survival. Hardened petiole tissues also had a greater ionic conductance than lamina tissues at all test temperatures. Vital staining of petiole sections with 2,3,5-triphenyltetrazolium chloride revealed that vascular bundle tissues survived lethal temperatures while ground parenchyma and collenchyma did not. In both controlled freezing tests with intact shoots and in the field when snow cover prevented soil freezing, petiole temperatures were consistently above air and leaf lamina temperatures. These observations point to a proposed dual mechanism of freeze protection in cabbage involving the innate freezing tolerance of the tissues and the protection of the more cold-sensitive petiole tissues by the presence of unfrozen water in the vascular tissues.
NITROGEN LEACHING FROM POTTED POINSETTIA WITH LEACHING FRACTIONS OF 0, 0.2, AND 0.4
Authors: Ku Catherine S.M. , Hershey David R.
Published: April 2024

Single-pinched `V-14 Glory' poinsettias in 15-cm diameter pots of growing medium received 200 mg/L N constant liquid fertigation from Hoagland solution with N sources of 100% NO3-N and 60% NO3-N:40% NH4-N, P concentrations of 8 and 23 mg/L, and leaching fractions (LFs) of 0, 0.2 and 0.4. There were 26 irrigations during the 13 week study. The total fertigation solution and N applied ranged from 6.5 L and 1.3 g at 0 LF to 14 L and 2.8 g at 0.4 LF. Leachate N concentration ranged from 170 to 850 mg/L. The percentage of applied N in the leachate of 100% NO3-N plants was 57% at 0.2 LF and 76% at 0.4 LF. For 60% NO3-N plants, these losses were 49% at 0.2 LF and 67% at 0.4 LF. For 100% NO3-N plants, the percentage of the applied N found in shoot tissues was 26% for 0 LF, 20% for 0.2 LF, and 15% for 0.4 LF. For 60% NO3-N plants these percentages were 35% for 0 LF, 27% for 0.2 LF and 22% for 0.4 LF. Averaged for both 60% and 100% NO3-N plants, the N in the shoot was partitioned as follows: 43% in leaves, 39% in bracts, and 18% in stems.
FERTILIZER RATE AND SCHEDULE CAN OPTIMIZE PLANT GROWTH AND MINIMIZE NITROGEN LEACHING
Authors: Conover C. A. , Poole R. T.
Published: April 2024

Codiaeum variegatum (L.) Blume `Petra' liners were transplanted into 15-cm pots and fertilized using 24N-3.4P-14.2K at a total of either 7.2 or 14.4 g N/pot over a 26-week growing period. Eight fertilizer treatments followed four application schedules at a low and high (double the low) rate. Schedules attempted to maximize fertilizer utilization with applications based on projected plant growth patterns. Irrigation was on an as-needed basis, and all leachate was collected from each pot. Weekly leachate per pot was analyzed for pH, electrical conductivity (EC), and NH4-N and NOx-N content. Plant and color grades, and height change were recorded and elemental tissue analyses done for each plant at experiment termination. Fertilizer rate and schedule affected height change, and pH and EC, as expected. Total mg NH4-N and NOx-N in the leachate increased with increased fertilizer rate. Fertilizer application schedule affected NH4-N content at the high fertilizer rate and NOx-N in the leachate at both fertilizer rates with the optimizing curve treatments leaching the least NOx-N for their respective fertilizer rates. Total mg N/pot (mg NH4-N + mg NOx-N) was significant for both fertilizer rate and schedule.
INHERITANCE OF COLD TOLERANCE IN CULTIVATED SPECIES OFOPUNTIA
Authors: Kuti J.O.
Published: April 2024

Freezing temperatures limit areas in which prickly pears (Opuntis species) can be cultivated for their fruits and nopals. Inheritance of cold tolerance was investigated in three cultivated species ofOpuntia. Parental, F1, backcross and F2 populations from crosses between O. ficus-indica (accession #1271),O. lindheimeri (accession #1348) and O. robusta (accession #1241) were used. Plants were evaluated for cold tolerance by the conductivity method after 3 hrs in a growth chamber at temperatures ranging from 0° to -15°C and acclimation at 10°/5°C (day/night) for 14 days. Means of each genetic population were calculated and broad and narrow sense heritability estimates were determined. The heritability estimates were generally low with evidence of small additive effects and large environmental effects.
AN ECONOMICAL, EFFECTIVE ALTERNATIVE TO THE AIR-BLAST SPRAYER
Authors: Evert D.R. , Bertrand P.F. , Harrison K.A. , Mullinix B.G.
Published: April 2024

Five years of testing found equal damage on peaches from trees sprayed with an air-blast sprayer or with a PASS. A PASS is a modified boom sprayer mounted on the lower truss of a center-pivot. A PASS and an air-blast sprayer apply the same chemical formulations at the same rates per ha. Because a PASS injects no chemicals into the center-pivot, it is not chemigation. Unlike an air-blast sprayer that sprays out and up, a PASS sprays down, which should result in less spray drift. Because a PASS sprays over the tops of the trees, it places no restriction on row or tree spacing. Also, a PASS eliminates the pesticide exposure of a tractor driver spraying with an air-blast sprayer. Comparing capital costs of a PASS and an air-blast sprayer showed projected savings for the PASS of from $128/ha to over $248/ha as the orchard size increased from 7 ha to 29 ha. A PASS is much simpler than an air-blast sprayer which is pulled by a tractor, so the operating and maintenance costs for a PASS should be lower.
WATERMELON PRODUCTION SYSTEM INFLUENCES YIELD AND QUALITY
Authors: Schultheis Jonathan R. , Sanders Douglas C. , Monks David W.
Published: April 2024

The watermelon variety `Sangria', commonly grown in the eastern United States, has a tendency to produce off-shaped fruit. Certain watermelon varieties may require specific cultural practices to maximize both yield and quality. The objective of this study was to compare various production systems and varieties, and to evaluate their effects on fruit yield and quality. In 1991 and 1992, the effects of irrigation (overhead, drip or natural rainfall), with and without plastic on earliness, fruit quality and yield were evaluated on `Crimson Sweet', `Regency', `Royal Jubilee' and `Sangria'. In 1991, the best yield was obtained when black plastic mulch and drip irrigation were both used, while greater yields in 1992 were obtained when plastic was used with either overhead or drip irrigation. A higher percentage of melons were marketable with drip or overhead irrigation compared with non-irrigated plots. Less marketable melons were obtained with `Sangria' and `Crimson Sweet' in 1992. An earlier harvest was obtained with plastic mulch in 1992. `Royal Jubilee' was the best yielding variety.
TRIPLOID WATERMELON YIELD AND QUALITY COMPONENTS
Authors: Motsenbocker Carl E. , Picha David H.
Published: April 2024

Twenty-seven triploid watermelon cultivars and/or breeding lines were evaluated for yield and quality components. Total yield, rind thickness, mature and immature seed count, incidence of hollow heart, soluble solids, sugars, pH, titratable acidity, and internal color were measured for each cultivar/breeding line. Yields ranged from 32,000 to 66,000 kg per hectare. `Jack of Hearts' was the highest yielding cultivar. Hollow heart was moderate to severe in five of the genotypes. Except for two breeding lines, soluble solids were at least 11 per cent. Rind thickness ranged from 15.0 to 22.2 mm. Little or no mature seed was present in most of the genotypes. The cultivar `Millionaire' and the CLF breeding lines, with the exception of CLF 1016, contained the most mature seeds. A range of internal color and individual sugar content (fructose, glucose, sucrose) existed between genotypes.
NET CO2 ASSIMILATION RESPONSE OF APPLE TO TEMPERATURE UNDER FIELD CONDITIONS
Authors: Moran Renae E. , Rom Curt R. , Mauromoustakos Andy
Published: April 2024

Temperature is an important factor determining net CO2 assimilation (A). The reported optimum temperature for A in apple (Malus × domestic, Borkh.) under controlled conditions is between 16-30C. Response of A to temperature as it occurs in the field was measured with an open system IRGA for both spur and shoot leaves during 12 days from April through August of 1992. Trees studied were 11-year-old `Golden Delicious', `Spartan' and `Newred Jonathan' on M.7a trained to a three wire trellis. Response to temperature from 17-36C was quadratic for both spur and shoot leaves, but at each temperature A varied by about 10 μmol.m-2.s-1. Part of the variation was attributed to varying ambient [CO2] which varied from 321 to 396 ppm, depending on date of measurement. Covariate analysis using [CO2] as the covariate was conducted. Thus, the A model of temperature response takes into account [CO2]. The data will be discussed in view of interpreting plant response in the field and inherent problems with measuring A in situ.
CYCLES IN GAS EXCHANGE OF PEACH IN GREENHOUSE.
Authors: Yadava Umedi L.
Published: April 2024

Observations from the field experiments on peach (Prunus persica) over the past 7 years suggested a possibility of regular cycles in single leaf gas exchanges (SLGE). The purpose of this research was to study SLGE of peach under the controlled photosynthetic light using metal halide lamps in the greenhouse to determine if such cycle existed. Eighteen trees of Redhaven peach, 6 each on Lovell, Nemaguard, and Wildpeach rootstocks grown in 30 L plastic containers, which were arranged on 2 benches 6 feet below the metal halide lamps. Two leaves per tree were selected 5 feet below the individually controlled lamps. Lights were turned on 30 minutes prior to observations for PAR, leaf temperature, transpiration, stomatal conductance, and photosynthesis measurements. Using a portable (LI-6000) photosynthesis system, SLGE were recorded on the same leaves daily from 0900 to 1100 h for 3 weeks starting on 1 July 1992. Though fluctuating natural light caused minor variations in PAR, it was always above the saturation point. Light did not affect leaf temperature. No distinct cyclic pattern for any of the measured SLGE parameters was observed. Rootstock significantly affected photosynthesis; trees budded on Lovell had higher rate than on Wildpeach. It is concluded that the likely cycles in the SLGE data from field studies may not be real but have resulted from the environment.
INITIATING A STATEWIDE CERTIFICATION PROGRAM FOR LANDSCAPE PROFESSIONALS
Authors: Wade Gary L.
Published: April 2024

Other than short courses and one-day seminars offered by Universities and Technical schools, there has not been a vehicle in Georgia specifically designed to certify professional competence in the landscape industry. With a grant from the Georgia Green Industry Association a statewide certification program was developed. A 200-page study manual was developed along with a practical hands-on exam. The landscape certification exam requires seven hours to administer and involves four written components and nine practical components. The written components examine a participant's general knowledge, his ability to read and interpret a landscape plan, his ability to identify common landscape pests, and his ability to select plants properly for various site situations. The practical component of the exam, administered in an outdoor setting, requires a participant to demonstrate such skills as grading, pruning, sod installation, planting, staking trees, pesticide application, and equipment operation and maintenance. Two permanent testing sites, one in the northern part of the state and one in the southern part of the state, are presently being established. The exam is administered by the Landscape Division of the Georgia Green Industry Association.
LIMITED-SCOPE AUTOCAD® SELF INSTRUCTION FOR BASIC LANDSCAPE DESIGN
Authors: Swanberg Paul A. , Balbach Margaret
Published: April 2024

Many students in landscape design courses do not have experience in use of the computer for drafting designs. University and college situations, where computer laboratories may have only AutoCAD® installed on the computers, present an obstacle to horticulture students in that CAD courses are not ideally suited to their specific needs, and also require considerable time in doing the typical CAD assignments. Yet, if students could graduate with some basic experience in the application of AutoCAD® to landscape design drafting, they would be better equipped to meet employer needs for personnel prepared to handle computer drafting. A self-paced training manual with an embedded tutorial program has been developed with exercises that introduce the student to the basic commands and capabilities of AutoCAD®. This program takes the student through application of these commands to a landscape design layout. It contains a library of plant symbols and allows the student to design new symbols. The program also gives the student the ability to generate a materials and price report for every design generated.
MORPHOLOGICAL VARIATION IN A PETUNIA GERMPLASM COLLECTION
Authors: Krahl Kimberly H. , Randle William M.
Published: April 2024

In 1992 a petunia breeding program was initiated at the University of Georgia. The objective of this particular study was to screen an extensive collection of petunia germplasm for variability of numerous vegetative and floral characters in order to determine sources and extent of morphological variability existing in petunia.

One hundred twenty-two petunia cultivars and accessions including 83 current commercial F1 cultivars, 24 older cultivars, 3 accessions of the putative progenitor species of Petunia hybrida, 1 open-pollinated reseeding line, and 11 inbred lines were measured for 9 vegetative and floral characters. Genotypes include selections from all countries with major petunia breeding programs. Plants were grown in the greenhouse and measurements taken at time of first bloom.

Analysis of variance revealed highly significant variation among genotypes for each of the 9 characters measured. Cluster analysis was utilized to examine relationships among genotypes and to identify unique genotypes that may be useful in the UGA petunia breeding program.
DNA AMPLIFICATION FINGERPRINTING OF PETUNIA SPECIES
Authors: Cerny Teresa A. , Starman Terri W.
Published: April 2024

Earlier research suggests that P. axillaris, P. inflata, P. parodii, and P. violaceae may be part of the evolution of P. × hybrida. The precise probe and endonuclease combinations which would distinguish between these closely related species has not been found using other methods of DNA fingerprinting. Knowledge of the relationships among species within this genus could serve to advance breeding of P. × hybrida. The objectives of this project were to use DNA amplification fingerprinting (DAF) to fingerprint P. × hybrida and the four previously discussed species to show differences between them and to demonstrate the utility of DAF for floricultural crops. DAF does not require a precise probe; instead, it uses short arbitrary primers. Petunia seeds were obtained from foreign sources. Seedlings were grown in 0.4-liter plastic pots containing soilless medium under glass greenhouse conditions of 24/18°C. Tissue samples were collected, frozen with liquid nitrogen and stored in an ultra-low freezer. DNA was isolated and then amplified. Six different primers were used throughout the research. By using different primers, different segments of the DNA were amplified so more information about the relationships between species could be gained. Gels were both visually examined and quantitatively analyzed by a densitometer. Primer sequences GA-AAC-GCC and GT-TAC-GCC were found to be the most effective in showing amplification fragment length polymorphisms. Distinct differences were found between each of the species.
RECURRENT SELECTION FOR FLOWER COLOR IN THE DAVIS POPULATION OF GERBERA
Authors: Tourjee Kenneth R. , Harding James , Byrne Thomas G.
Published: April 2024

Flower color can be treated as a composite of three quantitative traits. The traits hue (H), chroma (C), and value (L), as described in the CIELAB (1976) color system, are continuous variables easily included into an index of a recurrent selection program. A Euclidian distance index was utilized to minimize the mean distance of a population to a color point (dark yellow). The index was: l= sqrt[0.5*(H-85)**2 + 0.25*(C-80)**2 + 0.25*(L-50)**2]

The index was applied to generation 15 of the Davis Pop. of gerbera, and two cycles of selection were performed (sel. intensity = 2.3 and 2.0 respectively). Crosses were made via a 6×6 factorial mating design. The mean index score in gen. 15 was 38.57. Two cycles of selection changed the mean to 15.08. The N.S. heritabilities for H, C, and L in gen. 15 were 0.6, 0.7, and 1.0. Selection reduced the heritabilities to 0.2, 0.0, and 0.1, respectively. The add. genetic corr. between H & C, H & L, and L & C were 0.1, 0.8, and -0.5, respectively. After selection, the correlations were 0.7, 0.9, and 0.2, respectively.
METHODS TO RECOVER TRIPLOID CITRUS HYBRIDS FOLLOWING 2x × 4x HYBRIDIZATION
Authors: Jia Y. , Gmitter F. G.
Published: April 2024

Methods for production of Citrus triploids were investigated. Ten diploid, strictly zygotic clones were used as seed parents. Two tetraploid somatic hybrids [`Key' lime (Citrus aurantifolia) with `Valencia' sweet orange (C. sinensis), and `Hamlin' sweet orange with `Flying Dragon' trifoliate orange (Poncirus trifoliata)] and two autotetraploids were used as the male parents. Embryos were excised from underdeveloped seeds 3-6 months after pollination and cultured. Murashige and Tucker's medium was supplemented with either malt extract (500 mg·L-1) and adenine sulfate (25 mg·L-1) (EMA), with gibberellic acid (1 mg·L-1) (EG1), or with malt extract (1500 mg·L-1) (MTG). Embryo proliferation was observed from 11.5% of all cultured embryos excised 3-4 months after pollination, but varied among crosses. Ploidy level was determined by flow cytometry. Most recovered plants were triploid, but tetraploids and diploids were also identified at frequencies that varied among crosses. The greatest frequency of 3× plant recovery per embryo rescued resulted when embryos were harvested 3 months post-pollination and cultured on EG1 medium.
GENETIC VARIATION IN CARICA PAPAYA GERMPLASM
Authors: Morshidi Maimunah , Manshardt Richard M. , Zee Francis
Published: April 2024

Genetic variation was examined by multivariate analysis among cultivated and wild Carica papaya from five Central American countries (Mexico, Belize, Guatemala, Honduras, and Costa Rica), together with cultivated materials from Malaysia, Thailand, Hawaii and South America (Venezuela and Peru) based on allele frequencies in each country. Five seedlings from each accession were analyzed for isozyme variability using starch gel electrophoresis. Aconitase (ACO), isocitrate dehydrogenase (IDH), malate dehydrogenase (MDH), phosphoglucoisomerase (PGI), phosphoglucomutase (PGM), triosephosphate isomerase (TPI) and alcohol dehydrogenase (ADH) gave consistent and polymorphic banding patterns. cluster and principal component analyses indicated that materials outside of Central America differed from those in Central American countries due to the presence of wild papaya accessions in Central America.
BLOSSOM THINNING OF `WENATCHEE' AND `TILTON' APRICOTS WITH AMMONIUM THIOSULPHATE
Authors: Looney Norman E. , Beulah Michael A.
Published: April 2024

A single spray of ammonium thiosulphate (ATS) fertilizer applied when the spur flowers are approaching full bloom and lateral flowers are at about 50% of full bloom effectively reduced hand-thinning time and substantially improved fruit size of apricot in experiments conducted over a four year period. When applied as a gun spray to solution run-off, 0.4% and 0.5% ATS reduced hand-thinning time by at least one-third, increased fruit size by about 20%, and did not reduce branch and tree yields compared to control trees hand-thinned at the normal time. Airblast sprays also proved effective but the amount of wetting appears to be very critical to success. With mature plantations, 1500 to 1800 L/ha of 3% ATS gave satisfactory results. Information concerning the relative susceptibility of spur and lateral flowers and beneficial effects on fruit color and internal quality will be presented and discussed.
EFFECTS OF NAPHTHALENEACETIC ACID (NAA) THINNING SPRAYS ON FRUIT SIZE OF REDCHIEF `DELICIOUS' APPLES
Authors: Black Brent L. , Bukovac Martin J. , Hull Jerome
Published: April 2024

NAA is commonly used for post-bloom apple thinning. However, occasionally with `Delicious', excessive small fruit (50 - 67 mm) may be produced, regardless of crop load. This effect has been associated with late and/or low volume applications, however the cause is not known. A preliminary study (1991; fruit diam., 11 mm; 15 mg·L-1 equivalent at 234 - 2104 L·ha-1) resulted in a high incidence (19 - 40 %) of small fruit. A later application (fruit diam., 20 mm, 701 L·ha-1) had a lower incidence and fruit size approached that of hand thinned controls. In 1992, NAA (15 mg·L-1,equiv.) was applied (fruit diam., 8 mm) at 250 - 2000 L·ha-1. Time of application was assessed by applying NAA (15 mg·L-1, high vol.) at 5 - 21 mm fruit diameter. At harvest, there was no significant amount of small fruit in any treatment. Fruit from NAA treatments were smaller than hand-thinned, but larger than non-thinned controls. Fruit size distribution showed no significant effect of spray volume or time of application. In a related study, a higher concentration (17 mg·L-1) of NAA induced small fruit. The possible involvement of seasonal/environmental factors will be discussed.
ETHEPHON HARVEST EFFECTIVENESS ON OLIVE: SOLUTION pH, TIME OF APPLICATION, AND ADDITION OF BA OR NAA
Authors: Denney James O. , Martin George C.
Published: April 2024

We studied the effect on fruit and leaf abscission of application of ethephon (ETP) at 600 mg liter-1 on excised fruit-bearing olive (Olea europaea L.) shoots held under controlled conditions of temperature and relative humidity analogous to field conditions during fall harvest. Fruit removal force (FRF) and percent leaf drop (%LD) were quantified. Raising solution pH did not improve harvest effectiveness. %LD was significantly higher than control at pH 5, but not at pH 3 or pH 7; FRF was not significantly affected by pH. %LD was not significantly higher than control in the time-of-application treatments (pH 3 only); FRF was significantly less than control when applied at 7AM or 12 noon, but not at 5PM or 10PM. Addition of NAA to the ETP solution raised FRF and lowered %LD; BA had the opposite effect. BA accelerated anthocyanin production on fruits. Regardless of treatment, FRF and %LD are highly but negatively correlated (r2 = 0.62). Harvest effectiveness of ETP use on olive can be defined as a convergence of decreasing FRF and increasing %LD. Mean values for all ETP treatments were FRF = 3.0 N and %LD = 15%, acceptable values for effective olive harvest. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon); naphthalene acetic acid (NAA); 6-benzylaminopurine (BA).
Response of cucumber and squash roots to chilling stress during early stages of seedling development.
Authors: Reyes Eleazar , Jennings Paul H.
Published: April 2024

4 day old squash and 3 days old cucumber seedlings germinated at 26°C were exposed to 2, 6, 10 and 15°C for 1, 2, 4, 6, and 8 days. Root growth at 2°C and 10°C was inhibited 70% and 35%, respectively, compared to the 15°C control in both species. Chilling at 2°C for 4 days or longer resulted in irreversible injury as determined by the ability of the seedlings to resume growth when placed at 26°C. Seedlings of both species chilled at 10°C were able to resume growth when transferred to 26°C. Root membrane permeability as measured by leakage of electrolytes and organic compounds increased with time of chilling at 2, 6 and 10°C. A comparison of the specific ions leaking from chilled roots will be presented.
EFFECT OF TIMING OF DROUGHT STRESS ON GROWTH, DEVELOPMENT, AND LEAF WATER STATUS IN NORHERN RED OAK (Quercus rubra L.) SEEDLINGS
Authors: Layne Desmond R. , Tomlinson Patricia T.
Published: April 2024

Northern red oak seeds planted in thoroughly watered peat:sand mix in 15 × 35 cm pots were grown through three flushes in environmentally controlled growth chambers (16h day, 27C, 600 μE m-2 s-1; 8h night, 21C). After planting, seedlings were: i. not watered (early); or watered 2X/week: ii. for 2 weeks (mid); iii. for 1 month (late); or iv. for the duration of the study (control). Plants from i-iii were not rewatered until severe water stress developed (as indicated by predawn leaf water potential, Ψ). Soil relative water content (RWC), determined by time domain reflectometry (TDK) was followed in conjunction with Ψ. RWC was calibrated to soil volumetric water content. As soil RWC decreased, Ψ became more negative. Saturated soil had RWC of 28%. Moderate and severe water stress occurred at RWC of 15 and 12%, respectively. Timing of onset of water stress affected developmental rate. Shoot:root ratio was higher for early-than late-stressed or control plants. Whole plant biomass decreased compared to control by 85, 71, and 39%, when water stress was imposed early, mid, or late, respectively. Water stress imposed early during seedling establishment was more detrimental than stress imposed later. Early water stress greatly reduced leaf area and root system which significantly limited flush growth that occurred after rewatering.
EVALUATION OF REMEDIAL DRAINAGE, AERATION, AND SOIL-LOOSENING TECHNIQUES ON TWO LANDSCAPE TREES IN COMPACTED SOILS
Authors: Day Susan D. , Bassuk Nina L.
Published: April 2024

Landscape trees are frequently planted in heavily compacted soils, such as around newly constructed buildings or in urban areas. Under such conditions, trees frequently die, or decline prematurely. Techniques for ameliorating these conditions were studied: vertical drainage mat panels, gravel-filled sumps, soil trenching and peat-amended backfill. Acer saccharum Marsh. `Seneca Chief, ` a species sensitive to compaction stresses, and the less sensitive Pyrus calleryana Decne. `Red Spire' were planted in a compacted clay loam. Shoot growth, root distribution and soil oxygen levels were measured over two growing seasons. Oxygen levels varied with treatment, but were not limiting to root growth. Shoot growth of pears was greatest for soil trenches. Except for the gravel-filled sumps, all other treatments also showed increased shoot growth compared to controls. Maple mortality was generally high and inversely correlated with field drainage.
DIURNAL VARIATIONS IN XYLEM FLUID CHEMISTRY OF LAGERSTROEMIA INDICA: AN ENDOGENOUS CIRCADIAN RHYTHM
Authors: Andersen Peter C. , Brodbeck Brent V. , Mizell Russell F.
Published: April 2024

A diurnal increase in the concentration of amino acids (and N/C ratio) in xylem fluid of Lagerstroemia indica occurred from ca. 1230 to 2030 HR. Diurnal trends were similar for irrigated or non irrigated plants. Since the concentration of total organic nitrogen, total amino acids and most individual amino acids (but not organic acids or sugars) were also proportional to xylem tension (Xt) two experiments were performed to discern whether variations in chemistry were due to diurnal changes in moisture stress. First, L. indica when exposed to variable levels of moisture stress during midday manifested an increase in organic acids and a reduction in the N/C ratio. Second, chemical profiles of xylem fluid were collected at noon and midnight and were compared for plants exposed to a natural photoperiod, constant darkness, or continuous light. After 1 day the midday increase in concentrations of amino acids persisted for all treatments; the variation was greatest (10-fold) for plants in constant darkness where Xt varied from 0.20 to 0.25 MPa. Only plants exposed to continuous light lost this tendency after 3 days. Thus, the circadian rhythm was endogenous, terminated in continuous light and not mediated by changes in moisture stress. Glutamine accounted for most of the diurnal variation in total amino acids, organic nitrogen or N/C ratio in xylem fluid.
INHERITANCE OF FIELD REACTIONS TO GRAY MOLD, LEATHER ROT, AND ANTHRACNOSE OF STRAWBERRY
Authors: Olcott-Reid Brenda , Moore James N. , McNew Ronald W.
Published: April 2024

Inheritance of field reactions to three fruit rots of strawberry was studied in two complete diallele crosses between parents of varying rot susceptibility. Reaction to any of the three rots--gray mold, leather rot, and anthracnose--demonstrated a 0.61 to 0.67 correlation with reaction to total rots. Phenotypic and environmental correlations between incidences of the three rots were negligible, while a 0.43 genetic correlation was found for reactions to gray mold and leather rot. Overall broadsense heritabilities for rot reactions of individual progenies of crosses were 0.16 for gray mold, 0.51 for anthracnose, 0.27 for leather rot, and 0.39 for total rots. Analysis of general and specific combining abilities in both dialleles indicates mostly additive gene action for reaction to gray mold, leather rot and total rots, with strong non-additive gene action for reaction to anthracnose.

`Earliglow' as a parent significantly reduced gray mold incidence in its progeny by 7.6 and 5.0 percentage points in the two dialleles, and significantly reduced total rot by 12.9 and 6.8 percentage points. `Fairfax' as a parent significantly increased gray mold in its progeny by 3.2 percentage points, increased leather rot by 4.5 percentage points, and increased total rot by 8.7 percentage points.
RANDOMLY AMPLIFIED POLYMORPHIC DNA (RAPDs) IN OCTOPLOID FRAGARIA
Authors: Hancock James F. , Callow Peter W.
Published: April 2024

We have been screening Fragaria chiloensis, F. virginiana and elite breeding populations of F. × ananassa for polymorphisms using PCR and random 10 base sequences. Over 60% of the primers result in fragments that distinguish between the various genotypes. Many of them segregate as alleles at a single locus. This technology shows high promise as a means of distinguishing cultivars and developing a genetic map to aid in breeding.
SHOOT-TIP ENERGY BALANCE IN THE GREENHOUSE ENVIRONMENT
Authors: Faust James E. , Heins Royal D.
Published: April 2024

The shoot-tip energy balance of Vinca (Catheranthus roseus L.) plugs in the greenhouse environment was quantified. The components of the energy-balance model were measured for four stages of plug development. A pyranometer and a total-hemispherical radiometer were used to measure the radiation component of the energy balance. A hot-wire anemometer was used to measure air velocity and fine-wire thermocouples measured air and plant temperatures. Evapotranspiration was measured with thin-beam load cells and a dewpoint hygrometer was used to determine the vapor-pressure deficits. The vinca plugs were grown in a greenhouse with the air temperature maintained at 20C±l. Shoot-tip temperatures at night were usually 2 to 4C cooler than air temperatures due to radiant energy losses. Shoot-tip temperatures remained below air temperatures during the photoperiod whenever solar radiation was less than 150 W m-2. As the solar radiation increased above 150 W m-2, shoot-tip temperature increased with respect to air temperature. A model was then developed to predict shoot-tip temperature based on measured greenhouse conditions. Experimental results were validated in several commercial greenhouses.
PREDICTION AND CONTROL OF STEM ELONGATION IN POINSETTIA
Authors: Fisher Paul R. , Heins Royal D.
Published: April 2024

A stem elongation model is being developed for pinched poinsettia crops as part of a decision support computer program, the `Greenhouse CARE System'. Internode elongation is modelled as a function of DIF (day minus night temperature), plant density, and growth retardant applications. Average daily temperature and flower initiation date are used to determine internode number. Dose response curves are being developed to describe internode response to growth retardant applications, as affected by chemical type, concentration, time of application, and application method. The impact of plant density on growth and development is being modelled, and a spectroradiometer is being used to measure the effect of neighbouring plants on the light quality and quantity surrounding an individual plant. The model takes into account cultivar differences in their response to growth retardants and plant density. Output from the model is used to predict the short-term change in plant height under commercial greenhouse conditions. An interactive graphical interface to the model allows the comparison of alternative height control strategies.
USE OF A MODIFIED RICHARDS FUNCTION TO SIMULATE SHOOT ELONGATION IN CHRYSANTHEMUM.
Authors: Lieth J. Heinrich , Larsen Rolf U.
Published: April 2024

The Richards function has been shown to be a useful, flexible model for growth of plants and plant parts which follows a sigmoid pattern. Such a pattern is seen frequently in horticultural crops. The objective of this project was to explore the feasibility of using this model in conjunction with potted plant cropping systems to simulate shoot elongation. In this study, the experimental system consisted of potted chrysanthemum (Dendranthema ×grandiflora) grown under various light and temperature regimes and subjected to growth regulator (daminozide) treatments. Shoot length was measured several times weekly while electronically logging environmental data continually. One or more daminozide applications were made in some treatments. The results indicate that very precise shoot length prediction is possible using this model. The differential equation on which this model is based was modified for use in a simulation model. The fits were very good, particularly for the growth regulator effect. Once validated for accurate representation of temperature and light, this model will have applicability as a production management tool for potted chrysanthemum.
EFFECT OF SEASON ON GROWTH OF LETTUCE IN A COLD FRAME
Authors: Gent Martin P.N.
Published: April 2024

In a cold frame, the growth rate of lettuce varies with season. At regular intervals in fall, winter and spring, two-week-old lettuce seedlings were transferred to a cold frame. The leaf area and dry weight were measured at the time of transfer, after 5 to 10 days, and after 10 to 20 days in the cold frame. The relative growth rate, RGR, leaf area ratio, LAR, and net assimilation rate, NAR, were calculated and regressed against averages for temperature and light for each growth interval. RGR varied from 0.07 day-1 in midwinter to about 0.30 day-1 in late spring. Leaf area RGR depended on temperature and dry matter RGR depended on light. However light and temperature were correlated, R2 = 0.62. Temperature extremes decreased RGR if the maximum exceeded 25C or if minimum fell below 0C. LAR increased with temperature, primarily, but also decreased with light. NAR depended on light to the second order, with a half maximum response at 4 Mj.m-2.d-l total irradiance, and increased linearly with temperature. The dependence on solar insolation for warmth decreased growth rates in midwinter to about half that expected in a heated greenhouse.
PROVIDING ACCESS TO UNIVERSITY EDUCATION IN HORTICULTURE: PARTNERSHIPS THROUGH TECHNOLOGY
Authors: Caldwell Judith D.
Published: April 2024

Clemson University and Horry-Georgetown Technical College are using communications technology and non-traditional strategies to offer university horticulture education opportunities to a much larger and more diverse student clientele than is currently served by the traditional campus. This pilot project focuses on delivery of a complete Clemson horticulture/turfgrass science baccalaureate degree program through the technical campus. This partnership was selected for the pilot project, in part, because of the strong commitment to turfgrass related educational programs at each school. Faculties and administrators worked together to remove “campus-bound education” barriers and develop alternate degree pathways. A critical component of this pathway is the offering of select courses through Clemson TELECAMPUS, which delivers live, interactive instruction throughout South Carolina via the South Carolina Educational Television system. The Clemson University Forestry and Agriculture Network (CUFAN) will be used to further enhance interactive opportunities between students and instructors, and to access university support facilities. Additional campus services and resources will be focused to provide an innovative and enriched distance learning opportunity.
USING PROBLEM-SOLVING OPPORTUNITIES TO IMPROVE HORTICULTURAL EDUCATION
Authors: McKenney C. B.
Published: April 2024

Historically horticulture students have received excellent scientific and technical training through their degree programs but they must rely on internships to develop the implementation skills and “hands-on” experiences necessary to be successful. With the use of creative term projects, many problem solving opportunities can be integrated into the curriculum enhancing synthesis level decision making. At Texas Tech this is accomplished by identifying a campus interiorscape requiring renovation. Interior Plants students are then asked to develop a design solution which utilizes existing plant materials. The designs are evaluated and the best one is selected. The class then installs the design providing them the chance to select estimate and source materials within a limited budget, work with clients, comply with state operating procedures, and coordinate with various campus work units. The project provides the students with the transition experience from lecture to implementation while instilling self-confidence.
CONSTRUCTION AND APPLICATION OF A GENETIC LINKAGE MAP IN CUCUMBER
Authors: Kennard Wayne C. , Havey Michael J.
Published: April 2024

Genetic linkage maps have been proposed as tools for crop improvement. We constructed a genetic linkage map of cucumber including RFLP, RAPD, isozyme, and disease resistance markers. The map was used to determine the number, magnitude of effects, and action of genes conditioning quantitatively inherited fruit-quality traits, including length, diameter, seed cavity size, and color. Traits were evaluated in a replicated field trial over 2 years. A mating design was employed to confirm putative trait loci across generations and estimate overall genetic variances for the quality traits. For some traits, gene number estimates were similar to previously published reports employing biometrical methods.
INDO-US CUCUMIS GERMPLASM EXPEDITION
Authors: McCreight James D. , Staub Jack E. , Koppar N. M. , Srivastava U. Ch.
Published: April 2024

Fruits and seeds of cucumber (Cucumis sativus L.), melon (Cucumis melo L.), 11 other cucurbit species and five non-cucurbit species were collected in the states of Rajasthan, Madhya Pradesh, and Uttar Pradesh in October and November, 1992. Seeds were collected from cultivated and noncultivated areas, vegetable markets (subji mundi), and from seed dealers. Though many samples were collected as fruit, we were not always able to observe the plants or the growing areas. The origin, description, and use of the collections were noted at the collection site whenever possible. Cucumber landraces were scarce whereas melon landraces were abundant. Of the 681 collections, there were approximately 186 cucumbers and 447 melons. Exact numbers will be known after discrepancies in the records have been resolved. These seeds will be available after they have been increased and documented in the U.S. Germplasm Resources Information Network (GRIN) database. To that end, 1993 plans call for increase, and morphological and biochemical evaluations of a significant portion of the cucumber and melon collections in the U.S., and a substantial parallel increase and morphological evaluation of the collections in India.
TRADITIONAL SWEETPOTATO AND POTATO STAND ESTABLISHMENT CONSIDERATIONS
Authors: Henninger Melvin R.
Published: April 2024

Less attention is paid to the stand establishment of transplanted or seedpiece propagated crops because of the large amount of plant material used compared to a small vegetable seed; however, many crop failures have resulted from this lack of concern by growers and researchers.

With commercial sweetpotato production, the whole root is planted in a bed to produce the transplant. The preconditioning of the roots and the care of the bed are both very important to the production of good transplants. Field establishment is equally as critical.

With commercial white potato production in the developed world, seedpiece propagation is used to establish the crop. Seedpiece size and pre-conditioning, as well as soil conditions, at and after planting are the most important considerations.

Research studies on the size and pre-conditioning of the seedpiece and the plant population of these species as they relate to size and quality of the saleable product will be discussed. Grower observations of tillage practices which have produced the good stands will also be included.
SEXUALLY PROPAGATING POTATOES
Authors: Pallais Noel
Published: April 2024

The importance of sowing vigorous seed is particularly well recognized by commercial growers of small-seeded sexually propagated crops. The possibility of producing clean potato seed tubers with true potato seed (TPS) has existed in many developing countries since the seventies. In China, about 15,000 ha of potatoes are grown with seed tubers originally derived from TPS. The possibility to establish a fast field-stand and to produce a commercial crop of potatoes within 90 days after transplanting TPS seedlings has only been recently realized. This paper outlines the methodology used and the results obtained during 10 years of study focusing on the most critical factors involved in the production and preservation of high-quality TPS. Seed dormancy accounts for the most important difference between the undomesticated TPS and other related crops such as the tomato.
USE OF SYNTHETIC SEED TECHNOLOGY AND OTHER NONCONVENTIONAL PROPAGATION METHODS
Authors: Gray D. J. , Compton M. E.
Published: April 2024

For certain crops, the high cost of stand establishment and/or maintenance has stimulated the search for alternative propagation systems. This presentation discusses the possible applications of these systems to high value crops. Germplasm conservation of vegetatively propagated or recalcitrant seeded crops is difficult due to the high cost of stand maintenance. Utilization of synthetic seed technology (i.e., somatic embryos) would allow clonal germplasm to be economically conserved in seed repositories. Many ornamental crops with high per-plant values are now laboriously micropropagated via organ culture. Substitution of synthetic seed technology for propagation of such crops would decrease production costs by reducing labor. Similarly, field establishment of seedless watermelon can cost $0.40 or more per plant, whereas synthetic seed cost has been calculated (for alfalfa) at $0.04 per plant; approximately 10% less than that of conventional seed. In seedless watermelon variety development, simple micropropagation can be used to reduce the time required for commercial seed increase of new tetraploid parental lines from ten years to less than one year.
MICROWAVE-POWERED LAMPS: A NEW SOURCE OF HIGH INTENSITY LIGHTING
Authors: Krizek Donald T. , Britz Steven J. , Mirecki Roman M.
Published: April 2024

Although microwave-powered systems have been used for nearly two decades as UV sources for annealing and other industrial processes, recent discoveries indicate that these systems may also have application in providing a source of high intensity lighting. The spectral characteristics of newly developed microwave-powered lamps will be described in comparison to sunlight and a mixture of high pressure sodium and metal halide lamps. The responses of plants grown under these sources will be compared.
TEACHING PLANT PHYSIOLOGY AND MORE WITH WISCONSIN FAST PLANTS®
Authors: Jourdan Pablo
Published: April 2024

Budgetary, logistical and time constraints frequently limit the extent of hands-on activities included in introductory courses in horticulture. Model organisms can facilitate the demonstration of broad-based principles and enhance learning. The Wisconsin Fast Plants®, rapid cycling forms of Brassica rapa, represent such a model organism with diverse and useful applications in horticultural instruction. These organisms offer not only a practical advantage for teaching, but also facilitate learning at higher levels of thinking because they permit integration of concepts at the molecular, organismal, and population levels. A large collection of educational activities is currently available with these plants that can be used to enhance understanding of basic botanical principles; many aspects of plant physiology; broad principles of crop production; genetics and plant breeding; and molecular manipulations. The educational strategy afforded by these plants will be described.
FLOWERING PLANTS AS RESOURCES FOR NATURAL ENEMIES OF APPLE PESTS IN ORCHARDS
Authors: Matthews-Gehringer D. , Lachowski E. , Schettini T. , Bugg R.L.
Published: April 2024

To obtain preliminary information on what flowering plant species are suitable to provide pollen, nectar and shelter for natural enemies of apple pests, six plant species were evaluated in a one-acre orchard in PA for their habitat potential. Sweepnet samples revealed that peak arthropod population densities were collected during peak bloom periods which varied for each plant species. The highest densities of Parasitic Hymenoptera and Insidious Flower Bugs (natural enemies) were found on Buckwheat, Mustard and Queen Anne's Lace, and lower densities on Anthemis, Black-Eyed Susan and Showy Goldenrod. Tarnished Plant Bug (apple pest) population trends were similar. Management of flowering ground covers for orchards should balance providing optimum resources for natural enemies without encouraging apple pest populations.