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Abstract

Flower bud ontogeny was similar in plants of high bush blueberry (Viccinium corymbosum Ait.) grown under normal conditions and under treatment with 5000 ppm succinic acid-2,2-dimethylhydrazide (daminozide) sprays.

Open Access

Cotyledons and hypocotyls of Fraser fir [Abies fraseri (Pursh) Poir.] were excised from seeds treated with H2 O2 for 9 days and placed on bud induction medium containing 10 mg BA/liter and 0.01 mg NAA/liter or medium without growth regulators. Although adventitious buds did not develop, cotyledons exposed to growth regulators responded differently than cotyledons placed on medium lacking growth regulators. Cotyledons and hypocotyls responded similarly to growth regulators during the initial phase in culture, but cell divisions ceased in cotyledons, thus preventing meristemoid and subsequent bud development. After 3 days on medium containing growth regulators cell divisions were localized in epidermal and subjacent layers of hypocotyls, whereas similar cell divisions were' not observed in hypocotyls placed on medium without growth regulators. Cell clusters consisting of two to five cells (promeristemoids) were present after 7 days on hypocotyls placed on bud induction medium. In hypocotyls placed on medium without growth regulators, stomata continued to develop and cells within the cortex became vacuolated during the first 2 weeks in culture. All explants were transferred to secondary medium after 3 weeks. Cell clusters continued to enlarge into meristemoids on hypocotyls initially placed on bud induction medium. Gradually, meristemoids developed into buds and cataphylls were observed covering bud meristems. Chemical names used: N -(phenylmethyl)-1 H -purine-6-amine (BA), 1-naphthaleneacetic acid (NAA).

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Abstract

The effects of the plant growth regulators (PGR) gibberellins A4+7 (GA4+7; 25, 50, and 150 mg·liter−1), BA (25 mg·liter−1), and GA4+7 + BA (Promalin; 25 mg·liter−1) on pedicel growth and fruit development of ‘McIntosh’ and ‘Spartan’ apple (Malus domestica Borkh.) trees previously treated with foliar- or soil-applied paclobutrazol (PBZ) were examined. By full bloom, pedicels had completed the elongation growth phase regardless of treatment. Pedicel length was very sensitive to PBZ treatment since it was reduced logarithmically in response to dose. No differences in pedicel diameters were found. PBZ decreased fruit fresh weight, dry weight, and fruit length and diameter in both ‘McIntosh’ and ‘Spartan’ trees. The adverse effects of PBZ carryover on fruit-quality factors such as size and pedicel length were not overcome with GA4+7 (25 or 50 mg·liter−1), BA, or Promalin (25 mg·liter−1) applied when the king-bloom was in full bloom. Reversal of PBZ-induced pedicel length inhibition was only observed with GA4+7 (150 mg·liter−1) applied prior to the main period of pedicel elongation. BA alone had no effect on any fruit growth parameters. PBZ reduced pedicel and fruit cell length, while GA4+7 (150 mg·liter−1) applied at 2 weeks before full bloom increased pedicel cell length. Chemical names used: β-[(4-chIorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazol-1-ethanol (paclobutrazol); N-(phenylmethyl)-1H-purine-6-amine (BA); (1α,2β4aα,4bβ,10β)-2,4a,7-trihydroxy-1-methyl-8-methylenegibb-3-ene-l,10-dicarboxylic acid l,4a-lactone (GA4+7).

Open Access

The skin of `Elegant Lady' peach [Prunus persica (L.) Batsch.] fruit turned black when exposed to 100 ppm ferrous sulfate solution. This color change appeared on the red and the yellow portions of the fruit. Microscopy of the skin showed blue-black pigment distribution in epidermal and hypodermal tissues. Some epidermal and hypodermal cells discolored immediately when exposed to ferrous solutions, but many cells turned black later. Some cells with anthocyanin pigments did not discolor. Chromic acid showed that tannic substances were distributed in the epidermal and hypodermal cells, and they likely are the main factor in black discoloration of peach fruit exposed to solutions containing Fe.

Free access

Hypocotyls of Fraser fir (Abies fraseri (Pursh) Poir.) were excised from seeds germination 9 days and placed on bud induction medium containing 10 mg/liter benzyladenine (BA) and 0.01 mg/liter naphthaleneacetic acid (NAA) or medium without growth regulators. After 3 days on medium containing growth regulators, cell divisions were localized in epidermal and subepidermal layers of the hypocotyl while similar cell divisions were not observed in control-treated hypocotyls. Cell clusters consisting of two to five cells were present after 7 days in hypocotyls placed on bud induction medium. In control-treated hypocotyls, stomata continued to develop and cells within the cortex became vacuolated during the first 2 weeks in culture. All hypocotyls were transferred to secondary medium after 3 weeks. Cell clusters continued to enlarge into meristemoids in hypocotyls initially placed on bud induction medium. Gradually, meristemoids developed into buds and cataphylls were observed covering bud meristems.

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Authors: and

Shoot regeneration in carnation (Dianthus catyophyllus L.) was influenced by genotype, explant source, and plant growth regulator balance. Plants were regenerated from petals, calyxes, nodes, internodes, and leaves, but only petals, calyxes, and nodes were regenerative from all three cultivars examined (`Scania', `Improved White Sire', `Sandra'). Maximum proliferation was achieved with petals on Murashige and Skoog medium supplemented with 0.05 μm TDZ and 0.5 μm NAA. Shoot initiation originated from cells near vascular regions and perhaps from epidermal cells in petals and via organogenic callus from other explants. There was no evidence of chimeral separation from petals or callus, but somaclonal variants (3.3%) were observed involving petal hue and plant dwarfness. Unstable color patterns were observed in tissue-cultured regenerants of `Scania' and `Improved White Sire' similar in type and frequency to propagules derived from cuttings; none were observed for tissue-cultured or cutting-derived plants of `Sandra'. Chemical names used: N-pheny1-N′-l,2,3 -thiadiazol-5-ylurea [thidiazuron (TDZ)]; 1-napthaleneacetic acid (NM).

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To facilitate the breeding of scab-resistant pecan [Carya illinoinensis (Wangenh.) C. Koch] cultivars, more information is needed about the pathogenic variation of the causal organism, Cladosporium caryigenum (Ell. et Lang.) Gottwald (1982). This study examined the virulence patterns resulting from the field inoculations of 19 pecan cultivars with 12 monoconidial isolates from 8 pecan cultivars at 7 locations. The virulence pattern was different for each of the fungal isolates. Each isolate was virulent on some cultivars and avirulent on others. Most isolates were most virulent on the cultivar of their origin and one or a few other cultivars. Several cultivars were resistant to most of the tested isolates. The results indicate a large pool of differential and ephemeral resistance to scab resides in the pecan germplasm. Microscopic examination of developing lesions suggests that resistance is mediated by the speed of plant cell wall modifications that limit the growth of subcuticular hyphae. This information will be useful in the selection of cultivars with functionally different resistance genes for use in designing cultivar mixtures or in breeding programs.

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Authors: and

Abstract

UBI-P293 (2-3-dihydro-5,6-diphenyl-l,4 oxathiin) applied to stem tips of Chrysanthemum X morifolium ‘Paragon’ inhibited stem elongation and promoted formation of lateral branches without apex removal. Treated shoot apexes were inhibited temporarily in their development and in endogenous auxin activity as indicated by bioassay. There was a negative growth response of bean sections treated with extracts from tips for 4 days after treatment with UBI-P293 at 0.02 m, and this concentration led to a disruption of normal organization within the apex.

Open Access

A comparison of external morphology captured via a computer vision system and a study of internal anatomy of sweetpotato somatic embryos identified five different major morphological variants among torpedo and cotyledonary stage embryos. These included 1) Perfect Type, 2) Near Perfect Type, 3) Limited/No Meristematic Activity Type, 4) Disrupted Internal Anatomy Type, 5) Proliferating Type. Perfect and Near Perfect types of somatic embryos were categorized as competent, while Limited/No Meristematic activity, Disrupted Internal Anatomy, and Proliferating types were categorized as noncompetent with respect to their conversion ability. Lack of organized shoot development in somatic embryos of sweetpotato was attributed to the following abnormalities: 1) lack of an organized apical meristem, 2) sparsity of dividing cells in the apical region, 3) flattened apical meristem, 4) multiple meristemoids and/or diffuse meristematic activity throughout the embryo. A morphological fate map of most of the torpedo and cotyledonary embryo variants was identified, which will be beneficial in synthetic seeding and transgenic research and development of sweetpotato.

Free access

Seedlessness is an important trait in the evaluation of commercial mandarin for fresh consumption. However, in the last decade, the presence of seeds in fruit of cultivars considered as seedless has become a problem in different citrus-growing areas because the commercial value is depreciated. Seeds have appeared concomitantly with the introduction of new cultivars that appear to be cross-compatible. To overcome this problem, different strategies have been explored, but a definitive answer is still elusive. The search for alternatives contrasts with how little is known about the basis of the problem: the pollen-pistil incompatibility reaction in mandarin, and the intercompatibility relationship between different cultivars. In this work, we characterized the pollen-pistil incompatibility in the two commonly grown mandarin cultivars Fortune and Nova, and evaluated the intercompatibility relationship between six cultivars with different genetic origins; these cultivars included Fortune (Citrus clementina Hort. ex Tan. × Citrus reticulata Blanco), Nova [(Citrus paradisi Macf. × C. reticulata) × C. clementina), Comune Clementine (C. clementina), Avana apireno (C. reticulata), Primosole (Citrus unshiu Marcov. × C. reticulata), and Simeto (C. unshiu × Citrus deliciosa Ten.). Following the controlled hand pollination in the field, we evaluated pollen tube performance after self- and cross-pollination, as well as intercultivar compatibility by observing pollen tube growth. The results show the self-incompatibility of these cultivars with the pollen tube having been arrested in the style, which explains their seedless condition when planted in solid blocks. The study of intercompatibility indicates a different pollen tube behavior depending on the genotype, as well as on the cross combinations. These results provide a basis to evaluate self- and intercompatibility in citrus, and the effect of close planting of some cultivars.

Free access