Abstract
In field tests conducted near Tifton, Georgia, soil fumigation with either a methyl bromide-chloropicrin mixture (67-33%, 480 kg/ha) or metham (748 liters/ha) decreased weed infestation and increased growth and marketable yields of pepper (Capsicum annuum L.) transplants, compared with pepper planted consecutively without fumigation. Alternate-year rotation of pepper with rye also reduced weed infestation and increased yield. Weed control accounted for 81% of marketable transplant yield. Xanthomonas vesicatoria (Doidge) Dows. overwintered in pepper debris incorporated fresh or dried. Bacterial spot occurred too erratically to permit any conclusions except that the methyl bromide-chloropicrin fumigation failed to provide any control.
immobilize a considerable amount of the N applied from fertilizers ( White, 2006 ). Some growers are using compost in addition to sawdust to provide additional nutrients and organic matter ( Gale et al., 2006 ; Larco et al., 2014 ). Municipal yard debris
Field conditions associated with commercial cranberry (Vaccinium macrocarpon Ait.) production were simulated in greenhouse studies to determine the effect of soil surface characteristics on dichlobenil activity. Sand was compared with organic matter, in the form of leaf litter, as the surface layer. A seedling bioassay using alfalfa (Medicago sativa L.), a dichlobenil-sensitive plant, was employed to determine root growth response on herbicide-treated soil. When the herbicide was applied to a sand surface, root growth was greater as time after application elapsed, indicating loss of herbicide activity. Conversely, the presence of organic matter on the surface prolonged the activity of the herbicide. Composition of the surface layer was more important than the depth of the layer in determining herbicide persistence. The influence of cultural practices, such as the application of sand or the removal of surface debris, on herbicide activity should be considered when planning weed management strategies for cranberry production. Chemical name used: 2,6-dichlorobenzonitrile (dichlobenil).
Abstract
The number of pollen grains in anthers of Phaseolus vulgaris L. was estimated using a Coulter Counter, an electrical particle-counting device. Nine green buds were collected randomly from 3 plants grown in a growth chamber. From each bud, one anther at a time was excised and placed in liquid Ν for 3 sec. Pollen grains were transferred from the anthers into a drop of 0.3 M NaCl on a glass slide. The saline-pollen grain mixture was cleaned of all debris, and pollen was washed into a beaker containing the same solution. This procedure was repeated for the remaining 9 anthers of each bud. The total number of pollen grains per bud was determined using a Coulter Counter.
This study evaluated the total and marketable yield of three peach cultivars [Prunus persica (L.) Batsch. `Autumnglo', `Harvester', and `Redhaven'] when mechanical pruning and harvesting systems were used and trees were grown under three irrigation regimes. All cultivars were trunk-shaken using an experimental inertial shaker on an over-the-row (OTR) shake–catch harvester. `Autumnglo' also was hand-harvested at all irrigation regimes. Fruit damage was not significantly affected by irrigation. A significant source of fruit damage was pruning debris that remained in the canopy after hedging and became lodged in the fruit-conveying system, resulting in cultivar effects on fruit damage. Total yield of firm-ripe fruit was similar among cultivars in 1987 and 1988. However, `Autumnglo' trees had a higher percentage of marketable fruit than `Redhaven' or `Harvester' in 1987 and 1991. Mechanical harvesting appeared to accelerate the decline of `Autumnglo' as shown by tree deaths and greater symptom expression of Prunus necrotic ringspot virus. The potential for a single mechanical harvest of peaches is limited because of the difficulty in managing the ripening window, the high potential for fruit damage, and the possibility of accelerated tree decline for disease-susceptible cultivars.
Industrial-scale cultivation of plant cells for valuable product recovery (e.g. natural pigments, pharmaceutical compounds) can only be considered commercially-feasible when a fully-automated, predictable bioprocess is achieved. Automation of cell selection, quantification, and sorting procedures, and pinpointing of optimal microenvironmental regimes can be approached via machine vision. Macroscopic staging of Ajuga reptans callus masses (ranging between 2-6 g FW) permitted simultaneous rapid capture of top and side views. Area data used in a linear regression model yielded a reliable, non-destructive estimate of fresh mass. Suspension culture images from the same cell line were microscopically imaged at 4x (with an inverted microscope). Using color machine vision, the HSI (hue-saturation-intensity) coordinates were used to successfully separate pigmented cells and aggregates from non-pigmented cells, aggregates, and background debris. Time-course sampling of a routine suspension culture consistently allowed pigmented cells to be detected, and intensity could be correlated with the degree of pigmentation as verified using spectrophotometer analysis of parallel samples.
A scale-up process of lettuce (Lactuca sativa L.) suspension culture in a 2-liter bioreactor was investigated. Factors that influenced cell growth and differentiation, including foaming, the wall effect (inoculum adhering onto the vessel wall above the medium level), aeration, and dissolved oxygen (DO), were tested. The wall effect resulted in severe inoculum loss (10%) in 24 hours. Inoculum loss significantly decreased shoot regeneration. The wall effect was caused by two factors: 1) foaming caused by the interaction between air bubbles and inoculum, and 2) the bubbles produced by aeration. Foaming could be prevented by sieving the inoculum through a 400-pm screen filter and then rinsing the inoculum thoroughly with distilled water to remove single cells, cell debris, and the contents of broken cells. The wall effect caused by air bubbles could be prevented by putting a 150-μm screen column in the center of the bioreactor to isolate the aeration area from the inoculum. After the wall effect was removed, shoot regeneration in the bioreactor increased significantly to a level similar to that in 125-ml flasks at an aeration rate of 1 to 2 vvm (liters air/liters medium per rein). DO for this shoot regeneration level was ≈ 70% to 80%of saturation at the end of bioreactor culture.
The effect of high-pressure washing (HPW) on the surface morphology and physiology of citrus fruit was examined. Mature white (Citrus paradisi Macf. `Marsh') and red (Citrus paradisi Macf. `Ruby Red') grapefruit, oranges (Citrus sinensis L. `Hamlin'), and tangelos (Citrus reticulata Blanco × Citrus paradisi Macf. `Orlando') were washed on a roller brush bed and under a water spraying system for which water pressure was varied. Washing white grapefruit and oranges for 10 seconds under conventional low water pressure (345 kPa at cone nozzle) had little effect on peel wax fine structure. Washing fruit for 10 seconds under high water pressure (1380 or 2760 kPa at veejet nozzle) removed most epicuticular wax platelets from the surface as well as other surface debris such as sand grains. Despite the removal of epicuticular wax, HPW did not affect whole fruit mass loss or exchange of water, O2, or CO2 at the midsection of the fruit. Analysis of the effect of nozzle pressure (345, 1380, or 2760 kPa), period of exposure (10 or 60 seconds), and wax application on internal gas concentrations 18 hours after washing showed that increasing nozzle pressure increased internal CO2 concentrations while waxing increased internal ethylene and CO2 concentrations and decreased O2 concentrations. An apparent wound ethylene response was often elicited from fruit washed under high pressures (≥2070 kPa) or for long exposure times (≥30 seconds).
The frequency of tropical cyclones is a major factor affecting the vegetation of the Mariana Islands, where these storms are called typhoons. An average of about one typhoon per year has passed within ≈100 km of Guam during the past 50 years. The physiognomy of Guam's natural and urban forests is largely determined by these typhoons. The impact of each typhoon is determined by a long list of interacting factors such as species characteristics; environmental and horticultural conditions preceding the typhoon; the intensity, direction, and duration of winds; the amount of rainfall associated with the typhoon; and the environmental and horticultural conditions following the disturbance. Many species survive typhoons by reducing aerodynamic drag of the canopy by abscising inexpensive leaves or breakage of small stems which results in an intact major structural framework. Speed of recovery for nonlethal damage following disturbance depends on nonlimiting conditions during recovery. Thus, the most destructive typhoons are those that occur in sequence with other environmental stresses. The most common of these may be heat and high-light stress, associated with subsequent high pressure systems, and severe drought conditions. For example, the 230–298 km·h–1 winds of Typhoon Paka in Dec. 1997 were followed by the driest year on record for Guam. Typhoon debris and drought generated 1400 forest and grassland fires from Jan. through May 1998. Sequential typhoons are also severely damaging. For example, Guam experienced three direct eye passages and two more typhoons within 113 km during the months Aug. to Nov. 1992. Damage susceptibility and recovery dynamics will be discussed in relation to these and other physical, chemical, biological, and human-induced factors.
Depending on the materials used to produce a compost, it will contain lower or higher levels of nutrients and metals. If composts have been appropriately matured, nutrients are in plant-available forms for crop production, and the compost pH will be near neutral. After 25 years of research and development of regulations and advice for biosolids and compost utilization, pretreatment of industrial wastes allows biosolids composts, and composts prepared from biosolids mixed with municipal solid wastes or yard debris to contain levels of microelements needed for plant nutrition but not high levels that could cause phytotoxicity. Composts can supply N, P, K, Ca, Mg, Fe, Zn, Cu, Mn, B, Mo, and Se required by plants or animals. When used in potting media, supplemental N fertilization is usually required, depending on crop requirements. Use of compost can replace other forms of microelements used as fertilizers in media or fields. Detailed evaluation of potential food chain transfer of Cd, Pb, and other elements in composts clearly shows that consumption of 60% of garden foods produced on pH 5.5 soils with 1000 t compost/ha would not comprise risk over a lifetime of consumption, nor would ingesting the composts at 200 mg/day for 5 years. Potentially toxic organic compounds are either destroyed during composting, or bound very strongly by the compost so that plant uptake is trivial. Compost use can be a safe and wise choice for both home and commercial use to replace peat or uncomposted manures, etc. Many states have developed regulatory controls to assure that pathogenic organisms are killed during composting, and that product quality standards are attained that allow marketing for general use in the community.