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Abstract
Dikegulac-sodium application markedly increased branch number and decreased branch length of Forsythia × intermedia Zab. plants, but salt application to the rooting medium decreased the effectiveness of this growth retardant. Ancymidol reduced branch length without increasing branch number, while daminozide did not affect branch length or number. Salt application did not affect plant response to ancymidol or daminozide.
Abstract
Foliar sprays of 0.05% to 0.4% dikegulac-sodium (Atrinal) reduced shoot elongation and promoted lateral branching of container-grown Euonymus fortunei (Turcz.) Hand.-Mazz. ‘Colorata’, purple wintercreeper during the first season of growth. The most effective treatment for chemical pruning was a singe foliar spray of 0.1% dikegulac which produced plants with the most shoot growth, optimum branching, and only initial leaf yellowing.
Abstract
An electrophoretic mobility technique utilizing molecular probes was employed to study the freezing patterns in apical stems of 2 azalea cultivars, Rhododendron yedoense var. poukhanense (Levi.) Nakai (unnamed clone termed ‘Poukhanense’ herein for convenience) and R. × ‘Maryann’ [R. indicum × (R. yedoense var. poukhanense × kaempferi)]. Excised twigs were frozen at 2°C per hr during which current and voltage were measured, and tissue resistance was calculated. As freezing occurred there was a dramatic increase in tissue resistance, indicating that ice quickly filled the extracellular space. This rapid ice formation is a nonequilibrium process independent of temperature change once nucleation has begun. Injury due to the rapid formation of extracellular ice, at temperatures well below the freezing point, may be a factor influencing winter survival.
Abstract
Specific injury symptoms were observed on 75 deciduous and coniferous species growing adjacent (8 to 40 m) to roadways and exposed to aerial drift of deicing salt Susceptible deciduous species (e.g. Cornus stolonifera Michx., Fagus gradifolia Ehrh.) exhibited twig dieback, evidence of previous dieback and inhibition of flowering while damage to conifers (e.g. Pinus strobus L., Thuja occidentalis L.) was evident as needle browning, premature needle abscission and twig dieback. Plants with resinous buds, submerged buds and needle cuticular wax seemed resistant to damage. A distinction between runoff of salty water and aerial salt spray is important when assessing plant damage.
Plug-rooted liners of cotoneaster (Cotoneaster dammeri C.K. Schneid. `Coral Beauty') were grown in 6-L nursery containers filled with three different media: 73 pine bark: 22 peat: 5 pea gravel (Medium 1); 60 pine bark: 25 peat: 15 compost (Medium 2); and 50 pine bark: 50 compost (Medium 3). Plants were fertilized with Polyon (Nutryon) 17–5–12 (17N–2P–5K) 6-month controlled-release fertilizer at various rates (0, 2.5, 4.5, 6.5, and 8.5 kg·m-3 incorporated or dibbled (placed under the liner at potting). Shoot dry weight of cotoneaster increased with increasing fertilizer rates in all three media, and was consistently higher with dibble (calculated maximum ranges, 269-362 g/plant at 6.1–7.5 kg·m-3) than with pre-incorporated (127-263 g/plant at 6.4-8.5 kg·m-3) fertilizer. Trends for root dry weight were similar with dibbled fertilizer but nonsignificant with incorporation, while those for shoot: root ratio were reversed to those for shoot dry weight. Positive correlations were observed between foliar contents of N, P, and K and shoot dry weight from both dibbled and incorporated treatments, as well as root dry weight from dibbled treatments. With incorporation, however, only foliar K was correlated with root dry weight.
Abstract
Two evergreen azalea clones, Rhododendron × ‘Maryann’ and R. poukhanense Levl., were studied in outdoor and controlled freezing experiments during 2 winters. Outdoor experiments revealed that 1) flower bud injury occurred in mid-winter, 2) flower buds of R. poukhanense were less hardy than those of R. ‘Maryann’, 3) splitting of apical stems often accompanied injury in R. poukhanense, and 4) a significant difference existed between the 2 clones in apical stem water percentage during December and January. In the laboratory freezing tests, initial injury occurred in the apical stem pith and at a higher temp than that which injured the flower bud. When twig water content of R. poukhanense was reduced prior to freezing, stem splitting was prevented and the twigs survived exposure to lower temp. Large ice masses were observed in the vascular tissue of R. poukhanense when the frozen twigs were sectioned. Water content and ice crystal development were the primary factors affecting survival of both clones.
Wastewaters from farm and composting operations are often rich in certain nutrients that can be reutilized in crop production. Liners of silverleaf dogwood (CornusalbaL. `Argenteo-marginata'), common ninebark [Physocarpusopulifolius(L.) Maxim.], and `Anthony Waterer' spirea (Spiraea×bumaldaBurvenich) were grown in 6-L containers filled with a medium consisting of 73% bark, 22% peat, and 5% pea gravel, by volume. Plants were fertigated daily via a computer-controlled multi-fertilizer injector with three recirculated fertilizer treatments: 1) a stock solution with macro- and micronutrients, electrical conductivity (EC) 2.2 dS·m-1; 2) wastewater from a mushroom farm; and 3) process wastewater from anaerobic digestion of municipal solid waste. The wastewaters used in both treatments 2 and 3 were diluted with tap water, and the computer was programmed to amend, dispense, and recirculate nutrients, based on the same target EC as in treatment 1. For comparison, there was a traditional controlled-release fertilizer treatment [Nutryon 17–5–12 (17N–2P–10K) plus micronutrients incorporated into the medium at a rate of 6.5 kg·m-1, nutrients not recirculated]. All three species responded similarly to the three recirculated fertilizer treatments. Growth in the recirculated treatments was similar and significantly higher than that obtained with controlled-release fertilizer. A similar trend in EC was observed in the media near harvest. Throughout the study, there was no sign of nutrient toxicity or deficiency with any of the species or treatment.