bluuebunny/crossref_metadata_2025 huggingface dataset:
The Response of Three Ficus benjamina Clones to Stress Imposed by Complete Darkness or Reduced Frequency of Watering at Two Temperatures
Authors: Al-Khalifah N.S. , Alderson P.G.
Published: February 2019

Three clones of Ficus benjamina showed different responses to stress imposed by placing them in complete darkness for 2 weeks. `Natasha' was the most affected, showing 75% leaf abscission and a reduction of 25% of the chlorophyll content of the leaves. `Cleo' was the least affected. A general response of the three clones was the reduction in the quality of plants and in their shoot length. Withholding water for periods of 5, 9, and 14 days resulted in no stress response of the three clones at 22 ± 1C, and they only dropped their leaves at 30 ± 1C with the percentage of leaves abscising in∼creasing with longer periods between watering. `Natasha' was an exception, and showed an increase in shoot quality and leaf expansion under the high temperature and dropped only 4% of its leaves while the other two clones dropped 20% to 30% with watering at intervals of 9 days. `Cleo' dropped 90% of its leaves when watered at intervals of 14 days at 30C.
Inhibition of Root Formation in Cuttings from Flowering Stock Plants of Chrysanthemum
Authors: DeVier Carrie , Geneve Robert L.
Published: February 2019

The influence of flowers on root formation in mum cuttings was evaluated for stock plants grown under long (LD) or short (SD) days. SD plants showed visible flower buds after 20 days and color after 30 days. Cuttings were taken from LD or SD plants at 10-day intervals until flowers were fully open. Cuttings from LD plants rooted at 100% throughout the study, with 24 or more roots per cutting. Cuttings from SD plants showed a gradual reduction in rooting percentage and number as flower development increased. After 30 days, roots per cutting for SD plants was reduced by 85% compared to LD cuttings and only 30% of SD cuttings rooted. In a separate experiment, cuttings were taken from stock plants after 40 long or short days. Partial or all flower buds were removed from SD plants prior to sticking. SD cuttings (regardless of flower bud removal) rooted at <47%. LD cuttings rooted between 23.6 to 43.8, while SD cuttings rooted between 3.1 and 8.5 roots per rooted cutting. The data indicates that cuttings taken from flowering plants show reduced potential for rooting and that this effect was not influenced by removal of flowers prior to sticking cuttings.
Water Relations of a Semidomesticated Chile Ecotype (Capsicum frutescens L.) in a Semiarid Zone in Northwestern Mexico
Authors: Nieto-Garibay Alejandra , Troyo-Dieguez Enrique
Published: February 2019

Diurnal and seasonal water relations, soil humidity, transpiration, water demand, stomatal resistance, and fruit production, as well as some microclimatic parameters, were studied in a semidomesticated chile ecotype (Capsicum frutescens) under two treatments of plastic mulches, black and opaque, and compared with plants without a mulch in Baja California Sur, a Mexican semiarid state. Plants with opaque plastic mulch showed the highest chile production and total growth. The biggest transpiration rates from January to April was evidenced also by this treatment. The soil water content seemed to be determinant. Opaque plastic mulch plants had more soil moisture during the whole experiment. Plants without plastic mulch had the least chile production, with a lesser soil water content. These plants evidenced an osmotic adjustment under drought stress with low water potential, maintaining a partial turgor pressure, and stomatal regulation, in order to control the lost of water by transpiration.
A Model for Estimating the Yield of Coffee (Coffea arabica)
Authors: Loero Domingo R. , Kobayashi Kent D.
Published: February 2019

Nine years of historical yield, meteorological, and soil data were input into a soil water balance simulation model to generate a daily soil water status value. The values for the number of days and millimeters of deficit (duration and magnitude) were grouped into trimesters and used to estimate yield. The greatest frequency of days with plant moisture stress occurred during the January–March and the October–December periods. The greatest magnitude of stress occurred during the January–March period. Annual coffee yields were best estimated by the model that incorporated variables for the previous year including, April–June deficit magnitude duration, July–September deficit magnitude duration, and the previous year's yield. Model testing with data from nine cultivars over an 8-year period showed that the model estimated yields with a mean error of 17%. The use of this model permitted yield estimation 2 months before anthesis and 8 months before the start of harvest.
The Role of Osmotic Adjustment in Thuja occidentals' Response to Drought Stress
Authors: Edwards D.R. , Dixon M.A.
Published: February 2019

Six-year-old trees were repeatedly conditioned by withholding irrigation until Ψpd (predawn) thresholds of either –0.9 (“mild”) or –1.4 MPa (“moderate”) were attained. After conditioning, trees were exposed to severe drought (Ψpd –2.0 MPa) and then to 10 days of well-watered conditions. Throughout the investigation, osmotic potential (Ψπ), leaf RWC, transpiration, and total water potential (Ψx) were measured. Water stress was quantified by integrating Ψx. Conditioning caused a significant, but modest, degree of osmotic adjustment (0.08 to 0.28 MPa), which persisted after a brief relief from stress and transpiration rates were reduced 35% to 50%. Osmotic adjustment was not significantly enhanced by more than one stress exposure or conditioning beyond the mild threshold of stress. During severe drought, the moderate group maintained less negative Ψx and lower transpiration rates (38%). After prolonged stress relief, Ψx was similar among all treatments and daily transpiration rates and Ψx gradually recovered. Thuja occidentalis appears to rely on increased stomatal resistance more than osmotic adjustment to tolerate drought stress.
Onion Response to Water Stress
Authors: Shock Clinton C. , Feibert Erik B.G. , Saunders Lamont D.
Published: February 2019

Six soil water potential irrigation criteria (–12.5 to –100 kPa) were examined to determine levels for maximum onion yield and quality. Soil water potential at 0.2-m depth was measured by tensiometers and granular matrix sensors (Watermark Model 20055, Irrometer Co., Riverside, Calif.). Onions are highly sensitive to small soil water deficits. The crop needs frequent irrigations to maintain small negative soil water potentials for maximum yields. In each of 3 years, yield and bulb size increased with wetter treatments. In 1994, a relatively warm year, onion yield and bulb size were maximized at –12.5 kPa. In 1993, a relatively cool year, onion marketable yield peaked at –37.5 kPa due to a significant increase in rot during storage following the wetter treatments.
Effect of Two Levels of Deficit Irrigation on Photosynthesis, Canopy Light Interception, and Yields in Prune
Authors: Lampinen Bruce D. , Shackel Kenneth A.
Published: February 2019

Two levels of deficit irrigation were applied to mature French prune trees based on gradually declining midday stem water potentials decreasing to –1.5 MPa (moderate stress) and –2.5 MPa (severe stress) by harvest. The moderate and severe stress treatments resulted in 32% and 51% water savings, respectively, compared to the fully irrigated control. The average photosynthetic rate and dry fruit yield for the moderate stress treatment were not significantly lower than those for the fully irrigated control. The severe stress treatment had significantly lower photosynthetic rates from late morning until sunset on most days. However, this lower photosynthetic rate did not result in significantly lower dry fruit yields. There were no significant differences in light interception as measured diurnally or over the course of the season in the first year of the study. However, light interception and photosynthetic differences might be expected to be more pronounced in subsequent years, due to carryover effects.
Xylem Sap Abscisic Acid Concentrations and Stomatal Conductance in Mycorrhizal Cowpea
Authors: Ebel Robert C. , Duan Xiangrong , Augé Robert M.
Published: February 2019

Mycorrhizal colonization can alter stomatal behavior of host leaves before or during soil drying, but the mechanism of influence is not always clear. We examined the possibility that mycorrhizal symbiosis might result in either altered stomatal sensitivity to abscisic acid (ABA) moving from roots to shoots in xylem sap, or altered movement of ABA in xylem as a function of soil water content (θ). Mycorrhizal colonization of Vigna unguiculata did not change the relationship between stomatal conductance (gs) and xylem [ABA] during drying of whole root systems. Stomatal conductance was higher in mycorrhizal than in similarly sized and similarly nourished nonmycorrhizal plants when soil moisture was relatively high, perhaps related to lower xylem [ABA] in mycorrhizal plants at high soil θ. Neither gs nor xylem [ABA] was affected by mycorrhizae at low soil θ. Higher gs in mycorrhizal plants was evidently not related to a mycorrhizal effect on leaf water status, as neither gs/shoot Ψ nor shoot Ψ/soil θ relationships were altered by the symbiosis. Stomatal conductance was much more closely correlated with xylem [ABA] than with soil θ or shoot Ψ. Decreased xylem [ABA] may explain why mycorrhizal colonization sometimes increases gs of unstressed mycorrhizal plants in the absence of mycorrhizae-induced changes in host nutrition. This work was supported by USDA NRICGP grant 91-37100-6723 (R.M.A).
Water Use Efficiency, Nutrient Use, and Soil Shading Ability of Chemically Suppressed Ryegrass and Crimson Clover Living Mulches
Authors: Hadawi-Broeske Michelle , Harrison Helen C.
Published: February 2019

Renewed interest in soil conservation over the past decade has led to greater research efforts in the area of living mulch cropping systems. However, crop/mulch competition continues to present challenges. The objective of this study was to determine what effect two types of chemical growth suppressants (Mycogen 6121—an herbicidal soap, and Royal Slo-grow—a soil plant growth regulator) had on the water-use efficiency, nutrient use, and soil-shading ability of two annual living mulches, ryegrass (Lolium multiflorum) and crimson clover (Trifolium incarnatum). Two greenhouse experiments were performed in sand culture using a modified Hoagland's soap, one rate of growth regulator, and a mechanical treatment of mowing. Significant differences in nutrient use and soil-shading ability were obtained. The second experiment (69 days) replicated the ryegrass treatments less one rate of soap and included the legume crimson clover with one rate of soap and one rate of growth regulator. Results from both experiments will be discussed.
Inheritance of Resistance to Common Bacterial Blight in Tepary Beans
Authors: Dursun A. , Coyne D.P. , Mohamed M.F. , Jung G.
Published: February 2019

Common bacterial blight, incited by the bacterium Xanthomonas campestris pv. phaseoli (Xcp), is a serious disease of common beans [Phaseolus vulgaris (P. v.)]. Some tepary beans (P. acutifolius) are resistant (R) to Xcp and used to breed P. v. with R to Xcp. The objective was to determine the inheritance of the reaction to different strains of Xcp in crosses between susceptible (S) and R tepary lines. The parents, F2, and F3 populations from six tepary crosses involving 3 R × S, 1 R × moderately (M) R, and 2 R × R were inoculated with Xcp strains EK-11, LB-2, and SC-4A. Different single dominant genes controlled the reaction to different Xcp isolates in R × S crosses. Coupling linkage was detected between the genes controlling the reactions to each of the Xcp strains in the crosses NE #4B(s) × NE #19(R) and NE #4B(S) × CIAT-640005(R), except for NE #8A(MR) × NE #4B(S) with strains EK-11 and LB-2 and EK-11 and SC-4A. Transgressive segregation for S was observed in the F2 and F3 NE #8A × NE #8B(R), indicating that the parents possessed different genes for R. No segregation for reactions occurred n the F2 NE #8B × NE #19 and NE #19 × CIAT-640005, indicating that these parents possessed the same genes for R to the three strains.
Directional RAPD Marker Frequency Changes in Two Divergently Selected Beet Populations
Authors: Eagen K.A. , Goldman I.L.
Published: February 2019

In the past 20 years, betalain pigments found in red beet (Beta vulgaris L.) have been adopted for use as natural red food coloring. In an effort to develop red beet populations with elevated levels of betalain pigment, recurrent half-sib family selection for high pigment and both high and low solids was practiced for seven cycles, resulting in the development of a high pigment–high solids (HPHS) and a high pigment–low solids (HPLS) population. Thirty-one randomly selected decamer primers were chosen to assess RAPD marker frequencies on genomic DNA samples isolated from 47 randomly chosen individual plants in each of cycles 1, 3, and 6 in both HPHS and HPLS. A total of 161 RAPD markers were evaluated. Chi-square and regression analyses were performed to determine presence/absence of linear trends in marker frequencies during the selection scheme. Comparisons were made for individual cycles between HPHS and HPLS and among cycles within HPHS and HPLS. Significant linear trends were detected in both cases for key RAPD primers. Chi-square tests revealed a subset of the markers which exhibited significant frequency changes across cycles were associated with selection as opposed to genetic drift. These data demonstrate changes in RAPD marker frequencies with recurrent selection and suggest linkage of RAPD markers to genes controlling pigment and solids in red beet.
Inheritance of Resistance to Iron Deficiency in Cowpea
Authors: Cortinas-Escobar H.M. , Scheuring Douglas C. , Gerik Thomas J. , Miller J. Creighton
Published: February 2019

Cowpea [Vigna unguiculata (L.) Walp.] cultivars differ in their response to iron deficiency when grown on calcareous soils. This response is influenced by environmental factors such as soil pH, soil texture, presence of bicarbonates, and temperature. The objective of this study was to determine the genetic basis for resistance to iron deficiency in cowpea. Crosses of `Texas Pinkeye Purple Hull' (resistant) and `Pinkeye Purple Hull' (susceptible) were made in the greenhouse during Spring 1994, and F2 seeds were obtained in the summer. Reciprocal crosses were made in order to test for maternal effects. Seed of the parental, F1, and F2 generations were planted near Temple, Texas, during Fall 1994. The color (greenness) of 1031 F2 plants was measured using a chlorophyll meter (Minolta SPAD-502) 35 days after planting. Chi-square analysis showed a good fit to a 3:1 ratio of susceptible: resistant plants. These results suggest simple inheritance of the response to iron deficiency in cowpea. Similar segregation of the reciprocal crosses indicated absence of maternal inheritance.
Inheritance of Resistance to Iron Deficiency in Dry Beans
Authors: Cortinas-Escobar H.M. , Scheuring Douglas C. , Gerik Thomas J. , Miller J. Creighton
Published: February 2019

Dry bean (Phaseolus vulgaris L.) cultivars differ in their response to iron deficiency when grown on calcareous soils. This response is influenced by environmental factors such as soil pH, soil texture, presence of bicarbonates, organic matter, and temperature. The objective of this study was to investigate the genetic basis for resistance to iron deficiency in beans. Crosses between nine resistant and three susceptible cultivars/lines were made in the greenhouse during Spring 1994, and F2 seeds from 12 different crosses were obtained in the summer. Seed of the parental and F2 generations were planted near Temple, Texas, during Fall 1994. The color (greenness) of 1482 F2 plants was measured using a chlorophyll meter (Minolta SPAD-502) 35 days after planting. Chi-square analysis showed a good fit to a 15:1 ratio of resistant: susceptible plants. The F2 segregation suggests that two dominant genes are involved in the response to iron deficiency in dry beans, and when either dominant gene is present, resistance is expressed to some degree.
Root System of Plum Trees on Rootstocks of Pr. divaricata, Pr. tomentosa, and VVA
Authors: Devyatov A.S.
Published: February 2019

Root systems of 6-year-old trees of plum cultivar Edinburg on seedling rootstocks of Pr. divaricata(I), Pr. tomentosa (II), and clonal rootstock VVA (Pr. tomentosa × Pr. divaricata) (III) were studied with trench-monolith method, at a depth of 100 cm. Sodpodzolic loess soil had a A horizon (0–22 mm) with 2% humus. The area of cross-section on tree trunks on I, II, and III was 72, 44, and 18 cm2, respectively; yield efficiency was 0.22, 0.30, and 0.33 kg·cm–2, respectively. Specific length of scaffold roots of I and III was equal, but roots of I were deeper in the bed. Specific mass of scaffold roots of III was 35% less than I, but specific mass of fibrous roots of III was 84% more. All root indexes of II were many times smaller than I and III. Nearly 40% of total length of scaffold roots of all rootstocks was at the distance of 0.5–1.0 m from the trunk. Fibrous roots of II and III concentrated near the trunk. Specific mass of these roots of I at a distance of 2.0–2.5 m from the tree was twice those near the trunk.
Enhancing Branching of Apple Trees in the Nursery with Plant Growth Regulators
Authors: Jacyna Tadeusz
Published: February 2019

Nursery trees of new, promising apple selections [NY-75334-35 (A), NY-75414-1 (B), and NY-75413-30 (C)] from the Geneva breeding program exhibit a distinct apical dominant growth pattern characterized by poor lateral-shoot formation (feathering). To induce feathering, the trees were foliar-treated singly or sequentially with various concentrations of Promalin (1.8%w/w GA4+7 + 1.8%w/w 6BAP) and Accel (0.18% w/w GA4+7 + 1.8% w/w 6BAP), by themselves and in combination. Regardless of branching agent, concentration, and type of application, treated trees, as compared to the control, on average, induced 11.3 vs. 2.2, 6.6 vs. 0.4, and 6.6 vs. 2.0 feathers/tree for selections A, B, and C, respectively. In most instances, higher concentrations of both chemicals induced more feathers than lower concentrations. Tree height and caliper were less affected than lateral-shoot production.
Effect of Chemical Defoliation on the Budbreak of `Golden Delicious' Apple
Authors: Flores Aroldo Rumayor , Martinez C. Andres
Published: February 2019

During 1993–94, in an area with a subtropical climate, 1500 m elevation, and 300 mm of precipitation, an experiment with `Golden Delicious' apples/MM.111 under irrigation was conducted with 11 treatments with three replications in a completely randomized complete-block design: T1, manual defoliation (27 Sept.); T2, 1% CuSO4 (15 Oct.); T3, 2% CuSO4 + Promesol (acido 2,3,4 trihydroxipentanodioico) (22 Oct.); T4, 1% CuSO4 + 0.1% Atlox; T5, 1% CuSO4 + 0.2% Atlox; T6, 1% CuSO4 + 0.1% Frigate; T7, 1% CuSO4 + 2% urea; T8, 2% sulfur; T9, 500 ppm tiadizuron + 1% carboxil; T4–T9, defoliation 12 Nov.; T10, control (natural defoliation on 3 Dec.); T11, 2% ZnSO4 + 0.07 carboxil (8 Nov.). All treatments received Atlox surfactant at 0.1%, except T4 and T5. On 11 Mar. 1994, trees received an application of 0.5% Dormex + 4% dormant oil. The percentage of terminal budbreak on 1-year-old wood was superior for T6, T9, and T11 compared with the control (11.7% budbreak on 2-year-old wood) for all treatments (except T1 and T3); all the treatments were superior to the control (47% budbreak), especially T2 (72.6%) and T9 (70.0%). The percentage of fruit set was similar in all treatments with the control (15.0%), except in T2 and T3, which set 7% more fruit.
The Management of Sod Proximity Increases Peach Productivity
Authors: Glenn D.M. , Welker W.V.
Published: February 2019

Mature peach trees were grown in six different-sized vegetation-free areas (VFA) (0.36 to 13 m2) with and without stage-III drip irrigation for 6 years. As the VFA increased, so did the trunk cross-sectional area, total yield/tree, large fruit yield/tree, and pruning weight/tree. The application of supplemental irrigation increased yield of large fruit and leaf N percentage in all VFAs. Winter hardiness was not affected by either size of the VFA or irrigation. The yield efficiency of total fruit and large fruit decreased, however, with the increasing size of VFAs. The smaller VFAs resulted in smaller, more-efficient trees. Managing the size of the VFA was an effective, low-cost approach to controlling peach tree size and, when combined with irrigated, high-density production, offers a potential for increased productivity.
Yield, Growth, and Weed Control in Four Strawberry Production Systems
Authors: Tedesco Angela K. , Nonnecke Gail R. , Christians Nick E. , Obrycki John J. , Gleason Mark L.
Published: February 2019

Field plots of four production systems of `Tristar' dayneutral and `Earliglow' June-bearing strawberry (Fragaria ×ananassa Duch.), established in 1993, included conventional practices (CONV), integrated crop management practices (ICM), organic practices using granulated corn gluten meal, a natural weed control product, (ORG-CGM), and organic practices using a natural turkey manure product (ORG-TM). `Earliglow' total yield from CONV plots in 1994 was similar to ICM and ORG-CGM, but greater than ORG-TM. Average berry weight and marketable yield were greater in the CONV system than both organic systems. CONV, ICM, and ORG-CGM plots had more runners and daughter plants than ORG-TM. Plots with CONV herbicide treatments were similar to ICM and ORG-CGM for percentage weed cover 1 month after renovation. `Tristar' crown number, crown and root dry weights, yield, and berry number were reduced when plants were grown under straw mulch in ORG-CGM and ORG-TM compared to CONV and ICM plots with polyethylene mulch.
Weed Management Methods Influence Growth of `Navaho' Blackberries
Authors: Whitworth Julia
Published: February 2019

In Sept.1993, `Navaho' blackberries were planted in raised beds in a converted bermudagrass hay meadow. Tall fescue was planted between the beds. There are three plants per plot and nine replications with 1.3 m between plants, 3 m between plots, and 5 m between rows. Each row is one replication. The plots are 3 m wide and 3.9 m long. Weed management treatments were applied in a randomized complete-block design, and included: alfalfa (Medicago sativa) cover crop, rye (Secale cereale) cover crop, herbicide (simazine and oryzalin) and hoeing, mowing volunteer vegetation, and hardwood sawdust mulch 8 to 10 cm deep. In Spring 1994 and 1995, data were taken on weed populations in each of the plots. In early 1995, the blackberry plants were measured. Data taken included cane number, cane length, and cane diameter. Early results indicate that the best blackberry plant growth occurred when rows were maintained with no mulch or vegetation by application of herbicides and hoeing. However, these plots sustained significant soil erosion, which may result in decreased plant productivity over time.
Effect of Irrigation and Fertilization on `Tifblue' Rabbiteye Blueberry
Authors: Spiers J.M. , Braswell J.H.
Published: February 2019

The effects of varying rates of a complete fertilizer and trickle irrigation on the growth an fruit yield of `Tifblue' rabbiteye blueberries were determined in a 6-year field study. For the first 3 years, plants fertilized with the lowest rate (150 g/plant per year) had lower plant volume and fruit yield than plants receiving the higher rates (300, 600, and 1200). For the remainder of the study, fertilizer rates did not influence plant growth or fruit yields. The influence of irrigation rates (3 to 27 liters/plant per week) on growth and yields was less evident during the 1st and 2nd years, but became more pronounced in the 3rd and 4th years of the study. In general, plants receiving the lowest irrigation rate grew and yielded less than plants irrigated at the other rates. By the 6th year, however, there were no significant differences in fruit yield due to irrigation rates or fertilizer levels.
Effect of Hydrogen Cyanamide (Dormex) on Replacing Lack of Chilling in Kiwifruit (Actinidia deliciosa)
Authors: Powell Arlie A. , Tunnell Ed
Published: February 2019

It has been shown that the `Hayward' kiwifruit requires ≈1000 chilling hours for satisfactory production of female flowers, leading to full cropping in the southeastern United States. Part of the area along the Gulf Coast frequently suffers from inadequate winter chilling, resulting in poor cropping of `Hayward'. Studies were conducted over a 4-year period in a mature `Hayward' planting near the Gulf Coast to evaluate the efficacy of hydrogen cyanamide sprays in replacing lack of chilling and improving cropping. Rates of 2%, 3%, and 4% (v/v) of 50% Dormex significantly increased yield, with the highest rate providing the maximum yield. Fruit size and overall fruit quality from Dormex treatments were good. Dormex sprays performed quite well when only 600 to 700 chilling hours were received in the test area.
Evaluations of Organic Residues for the Production of Flowering Pot Plants
Authors: Gauthier Fabienne , Dansereau Blanche , Gagnon Serge
Published: February 2019

During Spring–Summer 1994, seedlings of Impatiens walleranc `Accent Coral' and Pelargonium × hortorum `Orbit Hot Pink' were grown in a commercial substrate (PRO-MIX BX) or in one of two substrates composed of six organic residues (composted water treated sludge, forestry compost, fresh or composted used peat extracted from a biofilter during treatment of municipal water, and fresh or composted paper sludge). These residues were incorporated with peatmoss and perlite at 5%, 10%, 25%, and 40% by volume to obtain the 24 substrate combinations. Plants were watered and fertilized by flooding ebb-and-flow benches. Growth measurements (growth index, top and root dry weight, number of flowers and buds, visual quality) varied considerably depending or the percentage of residue incorporated into the substrates. Moreover, substrates containing 40% of organic residues are not recommended for the production of impatiens and geraniums.
Effect of Humidity on the Transpiration of Greenhouse Tomato Crops
Authors: Trigui Maher , Gauthier Laurent , Barrington Suzelle
Published: February 2019

Experiments were conducted in four independently controlled greenhouses. The purpose of these experiments was to measure the effect of humidity on transpiration and yields. Four different humidity treatments were evaluated: 1) high night and high day humidity levels (vapor pressure deficits <0.4 kPa), 2) high night and low day humidity levels (VPD >0.8 kPa), 3) high night and low day humidity levels, and 4) variable greenhouse humidity to maintain a set hourly transpiration rate. Transpiration rates were measured in the four greenhouses at 15-min intervals from Nov. 1993 to May 1994. Results show that high humidity reduces the hourly and daily transpiration levels significantly and has an impact on crop yields. Results also show that it is possible to regulate crop transpiration by calculating the transpiration rate for a set of VPD and solar radiation levels.
Development of a Greenhouse IPM Program in Pennsylvania
Authors: Orzolek Michael D. , Thomas Cathy , Berghage Robert D. , Heller Paul R.
Published: February 2019

The dramatic reduction in available greenhouse insecticides and the potential for increased insect resistance has necessitated a change in insect control techniques. Because of the large acreage of greenhouse production in Pennsylvania and the need for a more environmentally effective method of controlling insects in greenhouses, an aggressive Integrated Pest Management research program was initiated and has been on-going since 1989. Our objectives were to develop a bibliography of major insect pests; to determine effectiveness of parasitoids on greenhouse and silverleaf whitefly, western flower thrip, and aphids; to reduce pesticide usage; and to comply with worker protection standards. The program was implemented by a joint venture among the Pennsylvania State Univ. faculty and technical staff, grower cooperators, the Pennsylvania Dept. of Agriculture, and the Pennsylvania Vegetable Growers Association. The IPM program was started with an active scouting and monitoring program in commercial houses to determine threshold levels. Control measures were implemented with biological controls, cultural management, and lastly chemical. In addition, the implementation of the results of this research to commercial growers has resulted in the formation of a Greenhouse Crop Management Association. Results of the 5-year research program are discussed.
Computer-based System for Dynamic Control of Greenhouse Tomato Grown in NFT System
Authors: Benmoussa Mohamed , Gauthier Laurent
Published: February 2019

To achieve high yield and better quality of soilless greenhouse tomato, it is necessary to keep the nutrient concentrations in the root environment at the target levels. Dynamic control of the nutrient solution composition can be used for this purpose. We developed a computer program that dynamically adjusts nutrient solution compositions based on various climatic and agronomic characteristics. The program integrates nutrient uptake and crop transpiration models and is part of a general-purpose greenhouse management and control software system developed at Laval University (GX). The architecture of the system and some simulation results comparing the effect of various control scenarios on the evolution of the composition of nutrient solutions are presented.
Low-temperature Tolerance in Vaccinium Angustifolium L.: Variation within Two Wild-managed Populations
Authors: Cappiello Paul E.
Published: February 2019

During the winters of 1993–94 and 1994–95, 54 clones of Vaccinium angustifolium were evaluated for low-temperature tolerance of inflorescence buds. During both seasons, clones were tested periodically, starting right after leaf drop, continuing through mid-winter, and finally through spring loss of low-temperature tolerance. Plants showed greatest variation in lowest survival temperature (LST) during fall and spring sampling dates, and the least variation on the mid-winter dates. In the 1993–94 study, clonal LSTs for November buds ranged from –5 to –27C; January buds showed LST variation of 6C. April buds showed a similar trend to that observed in late November. LST variation is discussed relative to clonal selection for ornamental and commercial use.
Controlled Freezing of Herbaceous Perennials
Authors: Perry Leonard P. , Herrick Todd
Published: February 2019

Fifteen perennials were subjected to four to six (depending on species) levels of controlled freezing in chest freezers to determine killing temperatures. Average potting medium temperatures in six 1-liter pots of each species per freezing treatment were allowed to drop to target temperatures before plants were removed from freezers. Plants were held at 5 ± 2C for 3 months before freezing and for 24 hours after freezing before placing at 1 ± 2C. Two weeks after freezing, plant regrowth was rated on a scale of 1 to 5, 1 being dead, 3 being salable, 5 being normal (as controls of no freezing). Temperatures at which plants dropped below a 3 rating—not reliably hardy at that temperature—were –2C for Aster lateriflorus horizontalis and Tricyrtis formosana `Amethystina'; –6C for Caryopteris ×clandonensis `Longwood Blue', Phlox paniculata `David', Tiarella cordifolia collina `Oakleaf', Tricyrtis hirta `Miyazaki', and Veronica `Sunny Border Blue'; -9C for Astilbe `White Gloria', Hemerocallis `Joan Senior', Leucanthemum ×superburn `Alaska', and Tiarella c.c. `Dunvegan' and <13C for Monarda `Marshall's Delight', Phlox paniculata `White Admiral', Tiarella c. c. `Laird of Skye', and Achillea `Coronation Gold'.
Survival of Zoysiagrass Genotypes Following Low-temperature Exposure
Authors: Fuller Russell L. , Warmund Michele R. , Dunn John H. , Bughrara Suleiman S.
Published: February 2019

Zoysiagrass rhizomes were sampled at various intervals, from October through March, to determine their susceptibility to low-temperature injury. Five-node rhizome sections of the following genotypes were subjected to sub-freezing temperatures at each date: `Belair', `DAL 8507', `El Toro', `Emerald', `Korean Common', and `Meyer'. Rhizome sections of each cultivar were wrapped in moistened cheesecloth, enclosed in aluminum foil, and placed in a freezing chamber at –2C. After 2 h at –2C, samples then were cooled at 1C/h to temperatures estimated to result in tissue injury. Fifteen rhizomes of each genotype were removed from the chamber at each test temperature. After thawing for 12 h, rhizomes were planted and regrown in a growth chamber at 34C day/28C night for 4 weeks. In the freezing test conducted on 12 Oct. 1994, rhizomes of `Meyer' and `Emerald' had greater shoot regrowth than those of `El Toro' after exposure to –6C. The only rhizomes that produced shoot growth after exposure to –8C were those of `Korean common', `Meyer' and `Belair'.
Frost Tolerance of Black Spruce Seedlings (Picea Mariana) during Budbreak
Authors: Bigras Francine
Published: February 2019

Spring frosts frequently cause significant damage to conifer seedlings during bud flushing and shoot elongation in forestry nurseries. To ensure adequate protection, levels of frost sensitivity must be known during these stages of development. Eight-month-old, containerized, black spruce seedlings were submitted to freezing temperatures of 0, –4, –6, –8, and –10C for 1, 2, 3, 4, 5, and 6 h at the following stages: 1) nonswollen buds; 2) swollen buds; 3) bud scales bursting, needle tips emerging; and 4) shoot elongation, 1 to 5 cm. After the treatments, seedlings were grown for 90 days in a greenhouse. Seedling survival then was estimated; dead seedlings discarded; and damage to buds, needles, and roots and shoot increment and diameter were measured on the remaining seedlings. Results show that frost sensitivity increases with the developing bud and shoot. A decrease in seedling and bud survival was noted with an increase in time of exposure (stages 2, 3, 4); otherwise, time exposure has no effect. Damage to needles and roots increases and diameter decreases with decreasing temperatures at all stages. Shoot increment was influenced by decreasing temperatures at stages 2 and 3 only.
Cold Hardiness of Three Woody Plants
Authors: Duchesne Isabelle , Rioux Jacques-André
Published: February 2019

To examine injuries caused by freezing temperatures, three woody plants were placed under temperatures ranging from 0 to –20C. Control plants were placed at 0 or –2 C, depending on the field sampling period. Freezing tests were done three times during the fall: Sept., Oct. and Nov., 1993. Spiraea × bumalda `Flamingmount', Spiraea callosa `Alba', and Spiraea × bumalda `Crispa' were tested. After freezing tests were complete, all plants were stored at –2C for the remainder of winter. In May, plants were repotted into containers. Effects of freezing temperatures on plant growth were recorded at the end of the summer. Results indicated that the most sensitive species to cold temperatures is Spiraea × bumalda `Crispa'. Moreover, the response of plants to the September freezing test was too variable to give a valid statistical analysis. Regression analysis was used as a tool to determine the temperature at which there is a 25% reduction in growth of the stem and the root dry matter, respectively. Results obtained in October are as follows: Spiraea × bumalda `Crispa', –6 and –7.6C; Spiraea × bumalda `Flamingmount', –10 and –8.7C; and Spiraea callosa `Alba' –10.7 and –11.5C. Results obtained in November are as follows: Spiraea × bumalda `Crispa', –7.1 and –8C; Spiraea × bumalda `Flamingmount', –12.2 and –12.3C; and Spiraea callosa `Alba', –8.5 and –8.7C. The reduction in cold hardiness observed for Spiraea callosa `Alba' is caused by warmer conditions (20C) in which plants were placed 2 days before the freezing test.
Vegetative Growth and Gas Exchange of Apple at High Temperature
Authors: Moran Renae E. , Rom Curt R.
Published: February 2019

Our objective was to determine the potential for acclimation to high temperature in apple. `Imperial Gala'/Malling 26 EMLA and ungrafted Malling 26 EMLA tree were grown in growth chambers under four temperature regimes: 1) 25C for 42 days; 2) 35C for 42 days; 3) 25C for 21 days, followed by 21 days at 35C; and 4) 35C for 21 days, followed by 21 days at 25C. Response of net CO2 assimilation (A) to leaf temperature from 20 to 35C was measured at 21 and 42 days. Response to CO2 from 0 to 1000 ppm was measured at 42 days. Trees were separated into leaf, stem, and root fractions; dried; and weighed. High temperature increased the number of leaves per tree and reduced leaf size and leaf dry weight but did not affect leaf area, stem, and root dry weight. The apparent and minimal acclimation of A to high temperature is discussed.
Propagation of Cretan Silver Bush (Ebenus cretica L.), A Potential New Flower Crop
Authors: Vlahos J.C. , Dragassaki M.
Published: February 2019

Ebenus cretica, Leguminosae, is a characteristic endemic plant of the Mediterranean island of Crete. It is a perennial bush up to 1 m tall with composite pubescent leaves and pinky red or purple flowers on 5- to 20-cm-long racemes. The fruit is surrounded by the calyx and contains one seed. The plants grow on rocky hillsides in alkaline soils at an altitude of up to 600 m and flower from April to June. Ebenus has the potential for use as a container or landscape flowering plant, and this study was aimed at finding methods to propagate it either by seed or by shoot cuttings. Seed collected from native plants in late July/Aug. 1992 germinated well (70% to 90%) without scarification in a commercial potting mix. Fifty percent of the seed germinated in vitro between 13 and 25 days, depending on temperature and substrate used. Temperatures of 25 or 30C in light at a pH ≈6.0 favored germination. Removal of the dry calyx coating the seed enhanced germination and emergence. For rooting Ebenus cuttings, several concentrations of IAA, IBA, and NAA were used in combination with different types of cuttings (soft or hardwood, tip or basal, cultivated or wild). Best results were obtained by wounding the base and dipping shoot-tip cuttings (12 cm long) in 600 mg IBA/liter for 16 hours. Significant differences, however, were observed among germination and rooting percentages when seeds or cuttings were taken from different plants due to genetic diversity. Therefore, selection is required for optimal results.
Varietal Differences between Two Cultivars of Viola tricolor `Blue'
Authors: Shaw Sabrina L. , Hayslett William F. , Williams Eddie B.
Published: February 2019

Seeds of `Majestic Giant Blue Shade' and `Medallion Blue/Blotch' were initially begun in plug trays and later transplanted into flats of 32s. Observations included percent germination, rate of emergence, plant heights before treatment of plant growth regulators (PGR), plant fresh weight, plant dry weight, plant height after treatments, and visual appearance. PGR treatments included paclobutrazol at 16 and 25 ppm, uniconazole at 2 and 4 ppm, and B-Nine as the control. `Majestic Giant' had a higher percent germination rate and rate of emergence than `Medallion'. Overall growth of Medallion seemed to be behind by ≈5 days when compared to that of `Majestic Giant'. The `Medallion' group showed more of a response to PGR treatments than `Majestic Giant'.
Susceptibility in the Growth of Viola tricolor `Blue' to Plant Growth Regulators and Fish Emulsion
Authors: Shaw Sabrina L. , Hayslett William F. , Williams Eddie B.
Published: February 2019

A one-time application of fish emulsion 2 days before the application of plant growth regulators (PGR) showed an overriding effect on the growth of pansies. Blue/blotch shades of `Medallion' pansies were placed on a constant feed program of 100 ppm Peat Lite 20N–10P–20K, with half of the pansies receiving an additional one-time supplement of fish emulsion. PGRs and rates included B-Nine, 0.5% (used as the control); uniconazole, 2 and 4 ppm; and paclobutrazol, 16 and 25 ppm. Parameters taken included plant height, top fresh weight, top dry weight, days to anthesis, and visual appearance. Significant differences were noted in the plants receiving the supplement for plant dry weight, plant height, and visual appearance. Plants receiving fish emulsion grew taller and denser than those on constant feed alone despite the effects of the PGRs.
Peach Blossom Thinning with Armothin
Authors: Ga'ash Dan , David Israel , Cohen Malka
Published: February 2019

Blossom thinning trials with AKZO Co. surfactant Armothin were carried out on fruitful peach cultivars Early Grande and Babcock during 1993–94. Effective thinning occurred before “full bloom” (40% to 90% FB) at 3% Armothin, increasing between 2% and 4%. However, an improved fruit distribution of `Early Grande' was achieved by repeated application (35% + 75% FB) at 2%. A second spray at 3%, just after FB, thinned some late-blooming flowers on `Babcock' trees, but a temporary leach scorch occurred, as well as with 4% Armothin (single spray) on both cultivars. For a single spray, the optimal stage was found within 60% to 90% FB, at 3% Armothin. Flower biology studies showed susceptibility of the petals to increasing Armothin concentrations at all stages, but pollen tube penetration into the pistils and subsequent fertilization failed only after an earlier application, before anthesis or pollination of the stigma. Within this range of concentration and timing, no damage occurred to the vital fruit set and to commercial yield, provided that weather conditions were favorable during bloom (and spray). Some corrective hand-thinning (20% to 60%) should be applied to the fruitful trees 3 to 4 weeks later to achieve optimal fruit size at harvest. Blossom hand-thinning is still practical in Israel.
Thinning Ontario Apples with Accel
Authors: Tschanz Rodger , Murr Dennis , Wiley Len , Hustwit Kay
Published: February 2019

The use of chemical thinners is an essential component of commercial apple production in Ontario. As chemical thinning options decrease, due to environmental concerns, newer and less toxic alternatives must be found. Benzyladenine (BA), available in the United States as Accel, shows promise as a thinning agent. During the 1994 growing season, Accel was applied under commercial conditions to seven apple cultivars—`McIntosh' (spur), Delicious `Starkrimson', `Empire', `Jonagold', `Golden Delicious', `Jonamac', and Gala `Royal Gala'. Application concentrations ranged from 50 to 75 ppm (a.i. BA), depending on cultivar. Mean king fruitlet diameter at time of application ranged from 9 to 12 mm. The thinning response of Accel was compared with that of traditional chemical (e.g., carbaryl, NAA, or both) or mechanical thinning treatments. At the concentrations used in this experiment, thinning with Accel was comparable or better than traditional methods in the case of `Gala', `Jonagold', `Empire', and `Golden Delicious'. In those cultivar trials displaying an acceptable Accel thinning response, a significant fruit size increase also was observed.
Floral Response of Lime (Citrus latifolia Tan. cv. Tahiti) to Foliar Sprays of Hydrogen Cyanamide
Authors: Rojias Eybar
Published: February 2019

Flowering of `Tahiti' lime/C. volkameriana Pasq. was studied in response to several levels of hydrogen cyanamide sprayed on isolated terminal twigs of 3- year-old plants growing under field conditions. The study was performed in the central region of Venezuela at 180-m altitude (lat. 9°43'N). Hydrogen cyanamide had significant effects on floral and total activity, and on generative, mixed, floral, and total shoot flux density, as well as on defoliation of sprayed twigs. Conversely, it did not show any significant effect on vegetative development, either as activity or shoot flux density.
Plant Growth Regulators and Yields of Seed Potatoes
Authors: Bandara Manjula S. , Tanino Karen K. , Waterer Doug R.
Published: February 2019

Seed potato growers seek to maximize yields of desirable sized tubers. This study examined how foliar applications of plant growth regulators influence yields of drop or single-cut seed tubers under field conditions. In 1993, paclobutrazol (PTZ; 300, 450, and 600 mg·liter–1), kinetin (KIN; 10 and 20 mg·liter–1), and methyl jasmonate (MJ; 10–7, 10–6, 10–5, and 10–4 M) were applied to `Norland' (NOR) and `Russet Burbank' (RB) potatoes. In 1994, PTZ (300 mg·liter–1), KIN (both rates), and MJ (10–7 and 10–6 M) treatments were eliminated, and GA3 at 250 mg·liter–1 or KIN at 20 mg·liter–1 was applied to some of PTZ treatments. In 1994, the cultivar Shepody (SH) also was included. Plants were treated at two growth stages; NOR (1993), RB (1993 and 1994), and SH (1994) were treated when tubers were <10 mm or <20 mm in diameter. NOR (1994) was treated at stolon initiation (no tubers) or early tuber initiation (<8 mm in diameter). PTZ had no effect on seed tuber (25–50 mm in diameter) yield in NOR in either season. PTZ increased seed tuber number (STN) in RB by 29% to 40% and in SH by 57% to 70% over the controls. KIN had no effect on STN in any cultivar. MJ had no effect on STN in NOR (1993) or in RB in either season or in SH in 1994. In 1994, the highest rate of MJ (10–4 M) increased STN in NOR by 40% over the controls. GA3 had no beneficial effect on STN when applied after PTZ. This study suggests that, under field conditions, PTZ can increase seed tuber production in RB and SH while MJ was effective in NOR potatoes.
Apical and Distal Pieces of Aged Potato Tubers Respond Differently to Paclobutrazol
Authors: Timm George H. , Mikitzel Loretta J.
Published: February 2019

The influence of paclobutrazol, an inhibitor of GA synthesis, on kindertuber formation was studied using 13.5-month-old `Russet Burbank' potato (Solanum tuberosum) tubers. Suberized apical and distal tuber pieces of equal weight were sprayed daily with distilled water (control), 0.001 and 0.01 mg paclobutrazol/liter with or without 2.5 mg kinetin/liter, and 2.5 mg kinetin/liter alone. The tuber pieces were held in the dark (20C) and harvested 8, 16, and 22 days after the first treatment. Only sprouts developed from control apical piece eyes after 22 days. There was an average of 3.6 sprouts/eye, which, in total, weighed 735 mg. Sprouts (2.4/eye) from treated apical piece eyes averaged 46 mg. By 22 days, 0.001 mg paclobutrazol/liter plus kinetin applied to apical pieces resulted in the most kindertubers, 1.9/eye. The largest kindertubers (1.2 g) were produced from apical pieces treated with 0.001 mg paclobutrazol/liter. At each harvest and regardless of treatment, distal tuber pieces produced larger sprouts and more sprouts per eye than apical pieces. Kindertubers developed from distal piece eyes only with the paclobutrazol plus kinetin treatments. Distal eyes produced half as many kindertubers as apical eyes treated similarly. Apical pieces treated with kinetin alone produced fewer sprouts than control pieces, and fewer tubers than paclobutrazol-treated pieces. Sprout weight per eye of kinetin-treated apical pieces was one-third that produced by control pieces and 5.1-fold greater than that of paclobutrazol-treated pieces. A similar trend was observed with sprout weight from distal eyes. Results suggest lowered GA levels are involved in kindertuber formation on aged potato tubers, and GA content or metabolism of distal pieces is unlike that of apical pieces. Distal tuber pieces do not form kindertubers as readily as apical pieces.