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  • Author or Editor: C.L. Taylor x
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Macrophylla-decline (MD)-affected citrus display apparent nutrient deficiencies in a sectorial pattern within the citrus tree canopy. The status of several elements (Ca, Cu, Fe, Mg, Mn, and Zn) was assessed in MD and healthy citrus selected from the same citrus orchards. Leaf and phloem tissues were sampled from mature, reproductive trees. Levels of Ca, Cu, Fe, Mg, and Mn were unaffected by the disorder in leaf or phloem tissues. Zinc was diminished in the leaves of MD citrus, and elevated in the whole phloem tissue (2.57-fold on a dry mass basis). Calcium and Cu were sufficient, while Mg, Fe, and Mn were slightly diminished in the leaf tissue, but phloem levels of these elements were not significantly different from that present in the phloem of healthy trees. Since Zn appeared to be redistributed to the phloem tissue from the leaves, the accumulation of the phloem specific, 5-kD Zn-binding protein (ZBP) was assessed in Macrophylla decline trees relative to healthy trees. The 5-kD ZBP was 4.77-fold greater in the phloem of MD citrus relative to healthy. This appears to account for the 2.4-fold greater level of Zn (on a fresh mass basis) found in the crude phloem extracts of the decline-affected citrus relative to healthy. In the purified ZBP fraction from decline-affected citrus, there was 4.73-fold greater Zn than in the ZBP purified from healthy. However, the ratios of Zn to ZBP were equivalent between MD citrus and healthy citrus, suggesting that phloem Zn accumulation in MD citrus is associated with the 5-kD ZBP.

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Management problems and information needs of Florida's approximately 12,000 citrus growers on 791,290 acres were identified by a statewide citrus management survey. During the summer of 1992, citrus county agents' mailing lists were compiled to create a master list of 2,964 addresses, from which a sample of 833 growers was selected by a stratified proportional sampling procedure. Three hundred ninety-eight useable questionnaires were returned from commercial citrus grove owners and managers in 23 citrus producing counties, representing 307,022 acres, 39% of the current acreage. Survey data on general management, young tree care, pest management, water management and cold protection was further analyzed by whether respondents' groves were bedded or unbedded. Information from this citrus survey and previous ones has been used to develop and evaluate comprehensive statewide citrus extension programs.

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Abstract

Seeds of tomato (Lycopersicon esculentum Mill.) and barley (Hordeum vulgare L.) on germination media were exposed to hydrogen chloride gas for 20 min. Seeds incubated and exposed on filter paper suffered developmental effects which were dependent on gas concentration. While germination rate was slightly reduced for sensitive seeds at the higher concentrations, suppression of seedling growth was evident at all levels of HCl tested. There was little effect on either germination or seedling length in seeds exposed and incubated on soil. Filter paper and soil adsorbed HCl during 20-minute exposures in proportion to gas concentration, but the soil apparently buffered most adverse reactions of the acid.

Open Access

Abstract

Extracts from Zn-accumulating phloem tissue of blight-affected trees had higher Zn-binding capacity than extracts from healthy trees. A 4-kDa, highly anionic, zinc-binding fraction was isolated from the phloem of predecline and decline stage ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] and ‘Marsh’ grapefruit (C. paradisi Macf.) trees grown on blight-susceptible rootstocks. Diethylaminoethyl (DEAE) Sephadex chromatography revealed the Zn-binding fraction contained at least four different anionic species. Two of the four species were present in healthy as well as predecline- and decline-stage trees. The other two species were found in only the predecline and decline trees. All Zn-binding factors were similar to the poly(γ-glutamyl-cysteinyl) glycine peptides in terms of size, anionic character, pH and temperature stability, capacity to bind other metals, and spectrophotometric properties.

Open Access

Six comprehensive surveys of the Florida citrus industry (345,645 ha), published from 1989 to 1993 as extension bulletins, provide information essential for long-range research and extension program planning and evaluation. These surveys documented changes in production practices, regional priorities for extension programming, marketing trends, and grower ranking of information sources. While formal, comprehensive surveys may be a valuable tool in long-range extension programming for large horticultural industries, more rapid, creative survey methods and educational programs may be needed for more timely programs and for specialized industry groups.

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Abstract

Several different split-root techniques, both horizontal zonation (1, 3, 6) and vertical zonation (2, 4, 7, 8), have been employed to study plant growth and water and nutrient uptake from differentially salinized root zones. High salinity level in one portion of the root zone may not affect overall plant performance if other portions of the root zone are relatively salt free (1, 3, 8). With uniform salinization, sodium chloride concentrations up to −0.8 MPa did not affect the 15N absorption rate in cotton, but osmotic pressures of −1.2 MPa substantially reduced it. However, water uptake and plant growth were affected to a greater extent than was 15N absorption (5).

Open Access

Citrus blight is an extremely complex decline disorder of unknown etiology, Zinc accumulates in the phloem of the tree 40-50 cm above the bud union 1-3 years prior to visible symptoms of blight (foliage wilt and twig dieback). This is accompanied by Zn deficits in the leaves. A Zn-binding peptide (ZBP) purified from citrus phloem tissue accounts for a symptomatic redistribution of Zn from the canopy to the trunk phloem. ZBP is found in blight and healthy trees and is therefore a normal component of cellular metabolism. To further understand ZBP's role in metabolism two citrus cell culture lines which were selected based on their susceptibility to blight have been characterized as to their growth under Zn treatments as well as Cu and Cd. In addition, their complement of metal-binding constituents is being determined.

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Planting cole crops and leafy greens in plastic mulch free of summer and winter annual broadleaf weeds is challenging. Because these crops are often grown as a second or third crop on mulch, weeds emerge in previously punched plant holes, tears in plastic, and row middles. Without the ability to use tillage and with limited herbicide options available for weed control, achieving a weed-free planting window is not often feasible. Additional herbicide options are needed, but their interaction with plastic mulch must be understood. Therefore, research has determined the persistence of preplant applications of 2,4-D tank-mixed with glyphosate applied over plastic mulch. Analytical laboratory analyses of plastic samples from field experiments, in conjunction with bioassays using broccoli (Brassica oleracea var. botrytis L.) and collard (Brassica oleracea var. viridis L.), evaluated herbicide dissipation. Analytical studies determined that 0.5 cm of irrigation after herbicide application and 1 day before planting removed 99% of 2,4-D, and 100% of glyphosate from the plastic mulch. Waiting an additional 14 days after application and irrigation further reduced the amount of 2,4-D on the plastic mulch 88% to 95%. For the field bioassay, preplant applications of 2,4-D tank-mixed with glyphosate resulted in 7% or less visual broccoli or collard injury without influencing crop growth, biomass, early season yield, or total yield as long as the mulch was washed with 0.5 cm of irrigation before planting. These studies also demonstrated there were no differences between the 1× and 2× use rates with respect to all response variables measured. Results suggest that 2,4-D and glyphosate can be effectively removed from the surface of plastic mulch with irrigation or rainfall before planting broccoli and collard.

Open Access

Abstract

‘Majestic’ peach {Prunus persica (L.) Batsch) was released by the Louisiana Agricultural Experiment Station to provide a large, excellent quality freestone fruit in the ripening sequence between ‘Harvester’ and ‘Red Globe’ or from June 22 to July 1 in north Louisiana (1).

Open Access

Abstract

‘Ouachita Gold’ peach (Prunus persica (L.) Batsch) was released by the Louisiana Agricultural Experiment Station to provide a high quality, large freestone fruit that ripens about 20 days after ‘Elberta’ or about August 5 in north Louisiana.

Open Access