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Dianna L. Liu and Nick E. Christians

Corn gluten hydrolysate (CGH) was evaluated in the greenhouse for its herbicidal activity on 19 selected monocotyledonous and dicotyledonous species. Treatments included CGH at 0, 1, 2, 4, and 8 g·dm-2. Plant susceptibility was based on plant survival, shoot length, and root length. The germination and growth of all species were inhibited by the application of CGH at all rates. Black medic (Medicago lupulina L.), buckhorn plaintain (Plantago lanceolata L.), creeping bentgrass (Agrostis palustris Huds.), purslane (Portulaca oleracea L.), and redroot pigweed (Amaranthus retroflexus L.) were the most susceptible species, exhibiting more than 70% reduction in root length, 60% reduction in plant survival, and 52% reduction in shoot length with CGH at 1 g·dm-2. Common lambsquarters (Chenopodium album L.), curly dock (Rumex crispus L.), dandelion (Taraxacum officinale Weber), giant foxtail (Setaria faberi Herrm.), large crabgrass [Digitaria sanguinalis (L.) Scop.], and yellow foxtail [Setaria lutescens (Weigel) Hubb.] exhibited more than 50% reduction in root length and plant survival at 1 g·dm-2. Annual bluegrass (Poa annua L.), barnyardgrass [Echinochloa crusgali (L.) Beauv.], green foxtail [Setaria viridis (L.) Beauv.], orchardgrass (Dactylis glomerata L.), perennial ryegrass (Lolium perenne L.), quackgrass [Agropyron repens (L.) Beauv.], and velvetleaf (Abutilon theophrasti Medic.) survivial was reduced by 60% at 2 g·dm-2. Annual ryegrass (Lolium multiflorum Lam.) was the least susceptible species.

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Nick E. Christians and Dianna L. Liu

It has previously been reported that a byproduct of the corn (Zea mays L.) wet-milling process, corn gluten meal, has potential as a natural preemergence herbicide for use in turf and certain horticultural crops. In 1993, two additional patents were issued on the technology. The first is on the use of hydrolyzed proteins from corn and other grains that were shown to have higher levels of herbicidal activity than the corn gluten meal. These materials are water soluble and can be sprayed on the soils surface. The second patent was on 5 dipeptides extracted from the hydrolyzed corn gluten meal. These dipeptides were shown to have the same type of biological activity observed when the corn gluten meal and the hydrolyzed meal are applied to the soil. The possible use of the hydrolyzed grains and the dipeptides as natural preemergence herbicides in horticultural crops will be discussed.

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Nick E. Christians and Dianna L. Liu

Field and greenhouse studies on the use of a byproduct of the corn (Zea mays L.) wet-milling process, corn gluten meal, have shown that this high-protein fraction of corn grain contains an organic compound that inhibits root formation of a variety of monocotyledonous and dicotyledonous species. Seeds that germinate in a soil media to which corn gluten meal has been added form normal shoots, but no roots. The seedling quickly dies as the media drys. This inhibition of root formation can be timed to prevent the establishment of weeds in turf areas and other plant systems. Corn gluten meal also contains approximately 10% nitrogen and can be used as a natural fertilizer material. Repeated field trials have shown no detrimental effect of the corn gluten meal on mature grass plants. This combination of a natural fertilizer with a natural weed inhibiting compound may result in a `weed and feed' product for those who do not wish to use synthetic fertilizers and pesticides. A patent on the use of corn gluten meal as a weed control was issued in 1991.

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Tim J. O’Hare, Hung Hong Trieu, Bruce Topp, Dougal Russell, Sharon Pun, Caterina Torrisi and Dianna Liu

The kernel of the macadamia nut (Macadamia integrifolia and M. tetraphylla) is very high in oil, accounting for about three -quarters of their mass. In the current investigation, oil extracts from 20 breeding accessions and 14 cultivars had a range of 12.3% to 17.0% saturated fat, averaging 14.2%. Although all samples were found to be very high in “healthy” monounsaturated fats, the level of saturated fat slightly exceeds that of many other nuts that are able to make qualified health claims. The lowest saturated fat content (12.3%) corresponded to 4.6 g saturated fat/50 g kernels, which was slightly greater than the 4.0 g maximum. Despite this, potential exists to develop a reduced-saturated fat macadamia by combining characteristics found in different lines. The current trial indicates that lower total saturated fat was associated with a stronger ability to partition C16 and C18 fats to their monounsaturated fatty acids, or to elongate C16:0 to C18:0 and subsequently desaturate C18:0 to C18:1. It was also observed that the pollinizer parent is likely to have an influence on saturated fat content, although this would need to be confirmed in controlled pollination trials. Macadamia varieties generally outcross, and because the edible kernel (embryo) is formed from a pollinated ovule, it is likely any future reduced-saturated fat line would also require a reduced-saturated fat pollinizer parent.