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  • Author or Editor: C.R Roberts x
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Abstract

Seven mutant maize genotypes with sweet corn backgrounds and 4 commercially grown sweet corn cultivars were harvested from 18-45 days after pollination (DAP). The lipids were extracted with chloroform-methanol 2: 1 (v/v) and separated on a silicic acid column into neutral lipids, glycolipids and phospholipids. Mutant genotypes influenced lipid development while inbred lines seemed important in amount of oil synthesized by the kernel. Crude oil and neutral lipids increased from 18-45 DAP while phospholipid and glycolipid values (mg/10 g fresh weight basis) were higher 23-28 DAP which is the prime processing time. During the developmental period studied, neutral lipids, phospholipids and glycolipids amount to 63, 20, and 12% respectively of the crude oil extracted. About 5% of the crude oil was lost in the separation procedure.

Open Access

Abstract

Seven mutant maize genotypes with sweet corn backgrounds and 4 commercially grown sweet com cultivars were harvested from 18-45 days after pollination (DAP). The lipids were extracted, separated into major lipid fractions, transesterified and measured as methyl esters of palmitic (16:0), stearic (18:0), oleic (18:1), linoleic (18:2) and linolenic (18:3) acids by gas liquid chromatography (GLC). Neutral lipids had a low ratio of polyunsaturates to monounsaturates (1.7:1), i.e., linoleic and linolenic to oleic fatty acids. Glycolipids had the highest proportion of linoleic and linolenic acids. Phospholipids tended to be more saturated than other fractions because of their high proportion of palmitic acid. All fatty acids in the neutral lipid fraction increased on an absolute basis with advancing maturity. Fatty acids in the glycolipid and phospholipid fractions generally peaked at 28 DAP on a mg fatty acid/g corn wet weight basis and then decreased with increased maturity. The percentage of oleic acid in the glycolipid fraction doubled from 12-24 percent during the 18-45 DAP period. Experimental lines and commercial cultivars contained 18.4, 1.4, 21.5, 57.1 and 2.1 percent respectively of palmitic, stearic, oleic, linoleic and linolenic acid over the maturity ranges studied.

Open Access
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Abstract

Two-year-old containerized seedlings of American sycamore (Platanus occidentals L.) were treated with maleic hydrazide (MH) before, after, or in the absence of sulfur dioxide (S02) fumigation. Exposure to S02 did not reduce the effectiveness of MH in controlling regrowth of this species. A strong negative linear trend was observed between SO2 concentration and sprout growth, either with or without MH treatment. In all instances, exposure to 1.0 ppm S02 resulted in high levels of phytotoxicity.

Open Access

Abstract

Partial shading, as a means of preventing or decreasing flower development, was used to study the influence of flowering on leaf rootability. Reduced light intensity decreased the size of flowers and sugar levels in leaves. The rooting-potential of leaves from plants grown under 25 percent shade was reduced compared to full sunlight controls; but was increased in the ones from under 95 percent shade. Exogenous hormone application improved rooting of leaves from full sunlight and 25 percent shade treatments, but reduced rooting in those from 95 percent shade. It was suggested that the reduction or prevention of flowering improves rooting-potential because of less active competition for materials necessary in rooting.

Open Access

Abstract

Three cultivars of greenhouse-grown apple trees (Malus domestica, Borkh.) were fumigated for single, 4-hour exposures with ozone (O3) and/or sulfur dioxide (SO2) at 0.40 and 0.80 ppm. Fumigations were performed in a plexiglass chamber situated within a controlled environment walk-in growth chamber. All 3 cultivars responded to treatments in a similar manner. When applied separately both gases induced characteristic foliar injury. In general, apple trees were more sensitive to 0.40 ppm O3 than to 0.40 ppm SO2; but they responded similarly to 0.80 ppm O3 or SO2. Foliar injury, leaf abscission, and shoot growth reduction were greatest when 0.80 ppm O3 and 0.80 ppm SO2 were combined. The data showed a less-than additive response when the 2 pollutants were combined; a response due, in part, to the high amount of injury induced by single pollutants at these concentrations. All O3 and/or SO2 fumigations resulted in stomatal closure.

Open Access

Ethrel sprays were applied at 50 or 100 ppm at approximately 40%, 70% leaf fall (10/16/89 or 10/24/89, respectively) or at both times on `Redhaven' and `Allgold' peaches. Bud hardiness was determined biweekly by differential thermal analysis (DTA). Stage and percentage of bloom open during the bloom period were subjectively estimated.

Spraying trees with 100ppm Ethrel at 50% leaf fall significantly increased bud hardiness at mid-winter compared to other treatments. After a mid-winter freeze (-21.7 C on 12/21/89), there was no significant difference between % bud survival of any treatments. But, trees treated with 50 or 100ppm Ethrel had 10-20% better bud survival than other treatments. Buds of the 2 cultivars had statistically similar hardiness although DTA analysis indicated that Redhaven had a .5-.8 C lower freezing point than Allgold in mid winter. This trend was reversed close to bloom with Allgold having .7 C lower freezing point than Redhaven. The time of full bloom was significantly delayed by treating trees with 100ppm at 40% leaf fall or 50ppm at both 40 and 70% leaf fall the previous autumn.

Free access

Abstract

Moisture retention data were collected for five porous materials: soil, phenolic foam, and three combinations of commonly used media components. Two mathematical functions were evaluated for their ability to describe the water content–soil moisture relationship. A cubic polynomial function with linear parameters previously used on container media was compared to a closed-form nonlinear parameter model developed to describe water conductivity in mineral soils. In most tests for precision, adequacy, accuracy, and validation, the nonlinear function was superior to the simpler power series. The nonlinear function provides an excellent tool for describing the water content for media with widely varying physical properties.

Open Access

Abstract

Handling and preparing growing media can have pronounced effects on the “intensity variables” bulk density and equilibrium volume wetness through changes in pore size distribution. These changes in turn affect the container “capacity variables”: the absolute amounts of medium, air, and water in a container. A nonlinear moisture retention function was combined with container geometry in an equilibrium capacity variable (ECV) model that provided accurate predictions of total porosity, container capacity, air space, unavailable water, available water, and solid fraction for several container-medium combinations.

Open Access

Abstract

Plants grown in small containers often show limited growth due to low levels of aeration and water holding capacity in the medium. These levels can be changed by management practices such as medium compaction, medium wetness at time of container filling, container height and volume, peat : vermiculite ratio, particle size, and the use of a wetting agent. A modified equilibrium capacity variable model was applied to an investigation of media-container interactions for short containers (<5 cm tall). Predicted volume percentages for total porosity (TP), container capacity (CC), air space (AS), unavailable water (UW), and available water (AW) were developed from measured moisture retention data and container geometry. AS increased with: 1) increased particle size, 2) increased media moisture at time of container filling, 3) decreased medium compaction, 4) increased wetting agent concentration, 5) decreased ratio of peat : vermiculite, and 6) increased container height. Increased percent AW resulted from smaller particle size, increased media moisture at time of container filling, decreased container compaction, decreased wetting agent concentration, increased ratio of peat : vermiculite and decreased container height.

Open Access

Abstract

A sand medium containing activated alumina was developed to provide a range of stable, reproducible P concentrations in plant cultures. The lowest P levels compare favorably to concentrations found in soils. Activated alumina was “loaded” by absorption of phosphate from 0.01 m NaCl solutions containing KH2PO4. Phosphorus concentrations in solutions expressed from sand-alumina mixtures were dependent upon the P concentrations used to absorb P onto the alumina. Increasing the density of a specifically loaded alumina did not affect the average solution P concentration in the cultures but did result in substantial increases in total dry weight yields of tomato (Lycopersicon esculentum Mill.) plants grown in the cultures. Thus, diffusion of P to root surfaces seems to be a prominent limiting factor in this system as in soils. The sand alumina culture technique shows promise for simulating plant responses to P at concentrations and under conditions comparable to those found in soils.

Open Access