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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).
Abstract
Naphthaleneacetic acid (NAA) applied to young ‘Washington’ navel orange trees [Citrus sinensis (L.) Osbeck] as a 1% sodium salt or ethyl ester formulation was translocated from the treatment site and inhibited growth of the untreated portion of the tree. The Na salt formulation translocated farther than the ethyl ester formulation.
Abstract
Ripening is a dramatic event in the development of many fleshy fruits. Tomato ripening involves a number of chemical and physical changes which convert the fruit from a relatively inedible state to one of optimal quality (2, 19). These changes appear to be highly synchronized, as evidenced by the fact that respiratory patterns, rate of ethylene production, carotene development, and flavor and textural changes normally associated with the ripening process, occur in close succession during the relatively short period in which the fruit ripens (2, 22). The association of these changes with seed maturation supports the popular view that ripening is of adaptive significance in seed dispersal by rendering fruit attractive to animals responsible for dispersal.
Abstract
Spray applications of naphthaleneacetic acid (NAA) at concentrations of 0.25 to 1.5% delayed bud break of sweet orange (Citrus sinensis (L.) Osbeck) seedlings for up to 177 days. Untreated buds on the same plants exhibited delayed growth initiation of up to 150 days due to translocated NAA. Length of time of bud break inhibition was dependent on NAA concentration, and the Na salt of NAA produced a more pronounced inhibitory effect than the ethyl ester formulation.
Abstract
The outer pericarp thickness of fruit of tomato (Lycopersicon esculentum Mill) ripened off the vine depended upon the maturity of the fruit when harvested. Immature fruit has thinner outer pericarps than fully mature green fruit. Similar results were obtained with 4 cultivars and 3 fruit sizes. The pericarp thickness did not change during a 6-day ripening period for any maturity. There was no difference in number of cells in the outer pericarp due to maturity or fruit size.
Abstract
Seedlings of ‘Mexican lime’ (Citrus aurantifolia Swing.), planted 3 per container attained budding caliper of 0.6 cm stem diameter in 4.5 months from transplanting at wide spacing in the greenhouse, whereas plants in closely spaced containers had not reached caliper after more than a year. Closely-spaced plants were more variable in stem diameter when they reached budding caliper than were widely spaced plants. Retention of basal leaves was directly proportional to spacing and ranged from 77% for the widest spacing to 6% for the closest spacing.
Abstract
Naphthaleneacetic acid (NAA) formulated as a sodium salt and as the ethyl ester applied in the spring of 1975 and 1976 to unpruned trunks of Pyracantha coccinea (Roem.) cv. Rosedale effectively controlled sprout growth. The 1% concentration of each formulation reduced growth 4 cm more than the 0.5% concentration. The control averaged 49 sprouts and treated plants ranged from 2 to 4 sprouts.
Abstract
Application of 6-benzylamino purine (BA) and 6-(benzylamino)-9-(2-tetrahydropy-ranyl-)-9H-purine (PBA) at several concentrations enhanced forcing of newly inserted fall buds of ‘Washington’ navel orange (Citrus sinensis [L.] Osbeck) on Troyer citrange (Poncirus trifoliata Raf. × C. sinensis). Growth of fall-inserted buds was more influenced by an extended day length than greenhouse temperature.
Abstract
Juice made from carrots stored at 20, 25, 30 or 35°C for 0,2,4 or 8 days contained negligible amounts of nitrite when sampled immediately. The bacterial populations were higher in juice made from carrots stored for longer periods and at the higher temperatures. Juices incubated at 35°C for 4 hours accumulated nitrite in amounts that tended to correspond to the bacterial populations in the fresh juices.
Off-site movement of sediment, nutrient and agricultural chemicals from plasticulture production of green-pack tomatoes on water quality is a serious environmental concern, particularly for the clam aquaculture industry of eastern Virginia. Thus, the development of ecologically sound, economically sustainable cultural management strategies for tomato (Lycopersicon esculentum Mill.) production is needed. Two plantings were made within each of the three tomato harvest seasons [summer, bridge (late summer) and fall] in 1998 and 1999 (one summer crop in 1999). Between-bed treatments included clean culture or pearl millet [Pennisetum glaucum(L.) R. Br.] sown at bed establishment. On-bed treatments included standard plasticulture with fumigation on a 76-cm-wide bed (std), plasticulture without fumigation on a 76-cm-wide bed (std-fum), plasticulture on a 61-cmbed with fumigation (narrow) and organic mulch [wheat straw (Triticum aestivum L.) in 1998; desiccated hairy vetch (Vicia villosa Roth.) in 1999]. Total and marketable yields for the three plasticulture on-bed treatments (std, std-fum and narrow) were similar in 1998 and 1999. Yield was suppressed for the organic mulch on-bed treatments in all but the bridge plantings in 1999. Improved yield with plasticulture treatments and high market price for the summer crop in 1998 resulted in elevated crop value and return to land and management (return) compared to that of organic mulch. The return for later plantings was low, but positive. Return was negative for both bridge and the first fall crops in organic mulch in 1998. Low yields in all treatments and low prices in 1999 resulted in negative to negligible return for on-bed treatments in all but the summer planting using plasticulture. Return was consistently lower with organic mulch compared to plasticulture for the high value summer crop in Virginia with between-bed millet in 1998 and with or without millet in 1999. The use of organic mulch on the beds in this study was not economically feasible for the high value summer crops. Adjustments (desiccation of cover, control of weeds) in cultural management of the between-bed management strategy are needed before large-scale commercial implementation will occur.