The effects of potential organic apple fruit thinners on gas exchange and growth of model apple trees: A model plant study of transient photosynthetic inhibitors and their effect on physiology and growth

Few fruit thinners have been certified for organic fruit growers. Previous studies have shown that herbicides or shade are capable of reducing photosynthesis and are effective fruit-thinning techniques, although impractical. This project evaluated use of a model plant system of vegetative apple trees grown under controlled conditions to study photosynthetic inhibitors, which could be used as potential organic thinning agents. Various concentrations of osmotics, salts, and oils (lime-sulfur, potassium bisulfite, potassium bicarbonate, sodium chloride, soybean oil) were applied to actively growing apple trees and showed a reduced trend on the rate of apple tree photosynthetic assimilation (Pn), evapotranspiration (Et), and stomatal conductance (gs). From two studies, it was observed that treatments of 2% lime-sulfur (LS) + 2% soybean oil (SO), 4% SO, 8% LS, 5% potassium bicarbonate (KHCO3), and 5% potassium bisulfite (KHSO4) all significantly reduced Pn. The 4% LS + 2% SO, 4% LS + 4% SO, 0.5% sodium chloride (NaCl), and 2% NaCl did not significantly reduce Pn. The response of Et was significantly reduced by 2% LS + 2% SO, 5% KHCO3, and 4% SO. In a second study, trees had reduced Pn, Et, and gs after the application of 4% LS + 4% SO, 2% NaCl, 5% KHCO3, and 5% KHSO4. Stem weight, total plant weight, average leaf weight, and leaf surface area of the treated plants, although reduced, were not significantly so when compared to the control 20 d after treatment

Propagation of thornless blackberries utilizing adventitious shoots from root cuttings

Studies were conducted in early 2003 to determine the effect of root source and length on yield of adventitious shoots from root cuttings and on subsequent plant yield for University of Arkansasdeveloped thornless blackberries. In the first study, roots from ‘Arapaho’ and ‘Apache’ plants grown in an aboveground bed containing commercial potting soil were compared to field-grown roots. Bed-grown roots averaged 6.9 shoots per 15 cm root cutting while field grown roots averaged 3.4. ‘Apache’ produced more shoots/root cutting compared to Arapaho, (5.9 vs. 4.4 shoots/root cutting, respectively). In a comparison of 15- vs. 30-cm-long root cuttings of ‘Apache’, ‘Arapaho’, and ‘Ouachita’, shoot yield of 30-cm roots was higher than that of 15 cm roots, but total yield of shoots per root unit was not increased by the longer root cuttings. Rooting of adventitious shoots neared 100% in both studies, and resulting quality of plants from these shoots was very good. This minor modification to the traditional method of planting root pieces to yield individual plants could lead to a more efficient and productive yield of propagules. The use of adventitious shoots from root cuttings for blackberry plant propagation appears to be a viable method for nurserymen to consider

The effects of shade on primocane fruiting blackberries in the field

Primocane fruiting blackberry production in Arkansas is limited by heat during the flowering and early fruiting season. Shade could be used to delay flowering and fruiting to more favorable growth period. This study was designed to test three levels of shade (0% [control], 30% and 50% shading) applied at three times during the growing season that examined the growth, development, physiology of flowering, and fruiting of ‘Prime-Ark® 45’ blackberries. The seven treatments were as follows: 1) an untreated control (CK), 2) early shade 30% (ES30), mid shade 30% (MS30), 4) late shade 30% (LS30), 5) early shade 50% (ES50), 6) mid shade 50% (MS50), and 7) late shade 50% (LS50). The 30% and 50% treatments were implemented 16 June (ES) and left on for 95 days, 1 July (MS) and left on for 80 days, and 15 July (LS) and left on for 66 days. All shade was removed 19 Sept. 2014. Foliar gas exchange using CIRAS®-3 portable gas exchange monitor and estimated chlorophyll content (Minolta SPAD®) were measured weekly. Beginning at maturity, fruit was harvested biweekly to determine fruit yields per plot. Plant growth was measured destructively at the end of the study period. The cumulative berry weight was greatest for LS50 and LS30 which was not different from the CK or MS50, while ES30, MS30, and ES50 berry weights were significantly less. The cumulative marketable weights were greatest for LS30 and CK, while ES30 and MS30 were less than the CK. Shade altered flower and fruit production, but was not found to result in higher fruit quantities compared to the control. Some ES treatments reduced cropping compared to LS treatments

Potential For Population Regulation Of The Zebra Mussel By Finfish And The Blue Crab In North American Estuaries

We conducted a series of descriptive and manipulative experiments aimed at quantifying the abundance, natural mortality, and effectiveness of predators in controlling the zebra mussel, Dreissena polymorpha, in the Hudson River Estuary. First, we measured distribution, abundance, and mortality rates of a zebra mussel population in the middle portion of the Hudson River Estuary, NY. Rocks were collected along a depth gradient in the field and sampled for the density and size structure of the resident mussels over the growth season. Next, we either allowed access (controls) or denied access (predator exclusion) to predators in field experiments with rocks harboring a known number of zebra mussels to estimate natural mortality. Finally, we conducted manipulative field experiments to test the effectiveness of the blue crab, Callinectes sapidus, at consuming zebra mussels by presenting similar rocks to crabs in field enclosures. Field sampling in June, July, and August 1993 indicated a dense (similar to 30,000 mussels/m(2)) population composed of a single cohort of 1 + year-class mussels. Sampling in August 1994 indicated a decline in D. polymorpha density. Mussel density increased dramatically with depth less than 2 m below the spring low tide mark. in cage experiments, blue crabs caused mortality rates that were an order of magnitude higher than those measured for the local predator guild, which was primarily composed of finfish. Localized extinctions of zebra mussels within one growth season were predicted in areas where blue crab densities approach 0.1 crabs/m(2)

Nuclear powered air cushion vehicles for transoceanic commerce

Characteristics and cost analysis of nuclear powered air cushion vehicles for oceanic commercial operation

Symmetry breaking perturbations and strange attractors

The asymmetrically forced, damped Duffing oscillator is introduced as a prototype model for analyzing the homoclinic tangle of symmetric dissipative systems with \textit{symmetry breaking} disturbances. Even a slight fixed asymmetry in the perturbation may cause a substantial change in the asymptotic behavior of the system, e.g. transitions from two sided to one sided strange attractors as the other parameters are varied. Moreover, slight asymmetries may cause substantial asymmetries in the relative size of the basins of attraction of the unforced nearly symmetric attracting regions. These changes seems to be associated with homoclinic bifurcations. Numerical evidence indicates that \textit{strange attractors} appear near curves corresponding to specific secondary homoclinic bifurcations. These curves are found using analytical perturbational tools

Impacts of a multi-trap line on benthic habitat containing emergent epifauna within the Mid-Atlantic Bight

Alteration and degradation of benthic structure by fishing gear can impede efforts to manage fish stock sustainably. Although the impacts of mobile gear are well known, effects of passive gear (e.g. fish traps) upon structure have been little studied. We modified commercial traps for American lobster Homarus americanus and black sea bass Centropristis striata by attaching GoPro (R) cameras to ascertain the degree and nature of impacts to seafloor habitats. Customized traps were included within a line of 20 traps, deployed and retrieved according to standard commercial fishing practice. Less than 5% of traps landed directly on bedforms when deployed. However, during retrieval traps dragged along the ocean floor, increasing trap-habitat contact rate to 50%, and causing traps to collide with corals, bryozoans, and other epifauna. Drag time of traps depended on the position in the trap line. Experimentally extending the trap line reduced drag time during retrieval for traps near the distal end of the line. Our results show that impacts of commercial trap fishing can be substantial during trap retrieval, and that the impact depends on their location on a trap line. Fishing practices should be developed that minimize effects of trap retrieval on structural benthic habitat

Propagation of thornless Arkansas blackberries by hardwood cuttings

Effects of auxin application and cutting location on canes on adventitious root development in hardwood cuttings of three Arkansas thornless blackberry cultivars were studied. Dormant canes were collected from one-year-old plants of ‘Apache’, ‘Arapaho’, and ‘Navaho’ and stored in a cold room until February. Two- or three-node cuttings were taken from the canes at apical, mid, and basal locations along the cane and were placed under intermittent mist in a perlite-filled greenhouse bed. Cuttings were either untreated or treated with auxin indole-3-butyric acid (IBA), applied as a liquid quick dip at 0.3%. In general, cutting diameter was greatest for basal and smallest for apical cuttings. Significant interactions were observed for cultivar and cutting location and for cultivar and auxin treatment for rooting. ‘Apache’ with auxin treatment had the highest rooting percentage, and ‘Arapaho’ and ‘Navaho’ with auxin the lowest. For cuttings that rooted, auxin treatment increased the root rating, representing root system development, for ‘Apache’ and ‘Navaho’ but had no affect on ‘Arapaho’

Density-Dependent Liquid Nitromethane Decomposition: Molecular Dynamics Simulations Based on ReaxFF

The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C–N bond cleavage is the dominant route, producing CH_3 and NO_2 fragments. As density and pressure rise approaching the Chapman–Jouget detonation conditions (~30% compression, >2500 K) the dominant mechanism switches to the formation of the CH_(3)NO fragment via H-transfer and/or N–O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods