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  • Author or Editor: B. W. Wood x
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Certain key experiments on the clonal propagation of pecan by stem and root cuttings are described. Juvenile cuttings of pecan cv. `Stuart' produced more roots and a larger percentage of rooted cuttings than adult cuttings when treated with 1% solution of (IBA) in Feb. and Aug. Successful propagation from `Stuart' stem cuttings was high from July to September. This study also fails to support the hypothesis that auxins are necessary to increase the level of rooting by pecan hardwood cuttings. Pecans were propagated using root cutting techniques and successfully transplanted to containers. Root cutting sections collected in either March or August from two-year-old `Curtis' seedling, responded yielding high rooting success and survival. The data also provides evidence that IBA could enhance the production of roots of root cuttings but BA (Benzyl Adenrine) offers no benefit. Girdling the sprout shoots from root cuttings with the use of IBA doubled the percentage of shoots producing roots and increasing root length.

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Polyphenols were analyzed in expanding buds and developing leaves of pecan [Carya illinoensis (Wangenh.) C. Koch] cultivars with varying responses to Cladosporium caryigenum (Ell. et Lang. Gottwald), the organism causing scab. Plant tissue extracts were examined by high-performance liquid chromatography using a water: methanol gradient to separate polyphenolic components on a C-18 reversed phase column. A diode-array detector was used to identify profile components by retention times and computer matching of ultraviolet spectra to standard compounds in a library. Concentrations of these polyphenols were compared throughout the growing season in leaves of pecan cultivars with low (`Elliott'), intermediate (`Stuart'), and high (`Wichita') susceptibility to scab; during susceptibility to infection by Cladosporium caryigenum from 16 cultivars; and in `Wichita' leaf discs with and without scab lesions. The major polyphenolic constituent of tissues for all cultivars was identified as hydrojuglone glucoside, which was detected in intact buds and leaves throughout the growing season. Hydrojuglone glucoside concentration increased concomitantly with leaf expansion and then declined slowly. Juglone was barely, if at all, detectable, regardless of leaf age. No correlation was found between cultivar susceptibility to pecan scab and the levels of either juglone or hydrojuglone glucoside in the healthy leaves of 16 cultivars. Leaf tissue with scab lesions had significantly higher juglone and hydrojuglone glucoside levels than leaf discs without scab lesions. Chemical names used: 4-8-dihydroxy-1-naphthyl b-d-glucopyranoside (hydrojuglone glucoside); 1,5-hydroxy-naphthoquinone (juglone).

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Polypeptides from pecan [Carya illinoensis (Wangenh.) C. .Koch] leaves were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and visualized by silver staining. Pecan leaf protein profiles were similar irrespective of cultivar (Desirable and Stuart), leaflet position, reproductive status of the allied shoot, or seasonal leaf age relative to fruit development. The large subunit of ribulose l,5-bisphosphate carboxylase and the majority of the other polypeptides were consistently present. However, the most striking change in the polypeptide composition was the seasonal decline of a polypeptide with an approximate molecular mass of 24.5 kDa. This leaf polypeptide was present in leaves collected in June and July, coinciding with the periods of initial fruit elongation and rapid increase in fruit volume. A detectable decrease occurred by mid-August, when kernel development was initiated. Changes in the abundance of this polypeptide relative to other polypeptides were observed over two growing seasons. Cells of young leaves collected early in the growing season contained more ribosomes and starch granules, but fewer vesicles and smaller electron-dense osmophilic granules than old leaves collected late in the growing season.

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Annual legume ground covers were evaluated in pecan (Carya illinoinensis) orchards to supply nitrogen and increase beneficial arthropods. Treatments were established at two sites, each with 5 ha of a `Dixie' crimson clover (Trifolium incarnatum) /hairy, vetch (Vicia villosa) mixture and 5 ha of grass sod. Data indicated that the legume mixture supplied over 100 kg·ha-1 N to the pecan trees. Beneficial arthropods were greater in orchards with legume ground covers than in orchards with a grass groundcover. Lady beetles and green lacewings were the most important spring predators, and green lacewings were the most important fall predator. The Species distribution on the ground covers differed from that in the canopy. Coleomegilla maculata lengi, Hippodamia convergens and Coccinella septempunctata were the most abundant lady beetle species in the legume ground covers, and Olla v-nigrum, Cycloneda munda, and Hippodamia convergens were the most abundant species in the pecan canopies. Beneficial arthropods appeared to suppress injurious pecan aphids.

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This study was conducted to determine fruit quality of Satsuma mandarin Citrus unshiu, Marc. `Owari' grown on the northern coast of the Gulf of Mexico. Soluble solids increased linearly and titratable acidity decreased quadratically during October and November for the four sampling years. There was no significant interaction between sampling date and year. There was a significant year effect for titratable acidity, but not soluble solids or their ratio. A 10:1 soluble solids to titratable acidity ratio was observed on 10 Nov. Variation in fruit weight corresponded with cropload. Fruit weight increased during the sampling period due to an increase in fruit length since there was no change in width. Peel color was yellow-orange by 10 Nov., with many fruit still exhibiting patches of green color. Because of some green color present in the peel, the fruit would have to be degreened for successful marketing in U.S. retail chain stores.

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Leaf water status, carbohydrate levels, net photosynthesis, stomatal conductance, ABA, dihydrozeatin riboside (DHZR), and trans-zeatin riboside (ZR) levels were determined in a greenhouse during rooting of stem cuttings of Acer rubrum L. `Red Sunset' taken on 3 Sept. 1987 and 28 May 1988. Leaf water status deteriorated before rooting and improved after root emergence. Leaf carbohydrate concentrations (glucose, sucrose, total soluble sugars, and total carbohydrates) increased until rooting and decreased after rooting, while changes in starch concentrations were trendless. ABA levels increased after insertion of cuttings into the rooting medium, but decreased before rooting. No correlation between timing of rooting and concentrations of the cytokinins ZR or DHZR was observed. Photosynthetic rates during rooting were higher for the Sept. 1987 cuttings and did not decrease to the compensation point as did those for May 1988 cuttings. Low photosynthetic rates and stomatal conductance of the cuttings during rooting were associated with water stress. The relationship between photosynthetic rates of such cuttings and cytokinin (CK) or ABA content was unclear. Chemical names used: [S-(Z,E]-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2, 4-pentadienoic acid (abscisic acid, ABA); 2-methyl-4-(1H-purin-6-ylamino)-2-buten-1-ol (zeatin, Z).

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