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Open access

Jean-Pierre Privé, D. C. Elfving, and J. T.A. Proctor

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

R. E. Gough, V. G. Shutak, and R. L. Hauke

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.

Free access

D.S. Achor, L.G. Albrigo, and C.W. McCoy

Upper surface leaf lesions on `Sunburst' mandarin [(Citrus reticulata Blanco × (C. paradisi Macf. × C. reticulate)] associated with feeding by the citrus rust mite [Phyllocoptruta oleivora (Ashm.)] are more severe than those on other citrus cultivars. Development of leaf lesions on `Sunburst' mandarin and two other cultivars were examined by light and electron microscopy. Damaged leaves treated with a fungicide confirmed that the anatomical changes on `Sunburst' are an enhanced wound periderm response to feeding injury by rust mite and not the result of fungal invasion.

Free access

Alan W. Meerow and Timothy K. Broschat

Anatomical differences in leaves of queen palm [Syagrus romanzoffiana (Chamisso) Glassman] showing visible K, Mn, and Fe deficiency symptoms are described. Potassium-deficient leaves showed less organization in the mesophyll than healthy leaves. Adaxial fibers increased in diameter. Chloroplast frequency was reduced overall, but most severely in areas of the leaf showing gross symptoms of the deficiency. Manganese-deficient leaves had reduced chloroplast frequency, especially in tissue near necrotic areas, and thicker and more fibers per unit length. Iron-deficient leaves had few chloroplasts throughout the mesophyll, and also thicker and more fibers per unit length.

Free access

Ralph Scorzal, Lisa G. May, Beverly Purnell, and Bruce Upchurch

The growth in diameter of large-(`Loring' and `Suncrest') and small-fruited (`Bailey' and `Boone County') peaches [Prunus persica (L.) Batsch] was recorded at weekly intervals from 175 days prebloom to ripening. Samples collected at three dates prebloom, full bloom (FB), and four dates postbloom, including ripe fruit, were sectioned and stained. Total cell count and mean cell size were determined for prebloom ovaries and postbloom mesocarp tissue. Large-fruited cultivars had significantly more cells (up to 3.7 times) than small-fruited cultivars at all sampling dates. Cell sizes increased dramatically with fruit development, but were similar for all cultivars within each sampling date. These results suggest that mesocarp cell count is the major difference between small- and large-fruited peach cultivars and that this difference is determined early in the growth of the ovary.

Open access

R. G. Goldy, R. L. Andersen, and F. G. Dennis Jr.

Abstract

Eleven suspected somatic mutations, consisting of 7 trees and 4 individual branches of the ‘Montmorency’ cherry, were compared with standard ‘Montmorency’ for phenotypic traits including tree height, trunk circumference, leaf area, crotch angle, resistance of flowers to frost injury, pollen germination, fruit set, individual fruit weight, fruit removal force, and yield. Differences occurred between some variants and ‘Montmorency’ controls for all characters except fruit removal force. All variants were tetraploid (2n = 32), as is standard ‘Montmorency’, with no evidence of cytochimerism.

Open access

Mohamed Kouider, Safi S. Korban, Robert M. Skirvin, and M. C. Chu

Abstract

In vitro studies indicated that an isolated embryonic axis, or an intact embryo with all or part of its cotyledons, of a ‘Delicious’ apple (Malus Xdomestica Borkh.) produced only a single shoot and root. Adventitious shoot formation was observed when the embryonic axis was excised and the cotyledons were grown in vitro. The number of shoots formed increased as the length of the transverse cut surface was increased. More than 30 shoots per explant were obtained when both the proximal and distal one-third sections of the cotyledon (relative to the embryonic axis) were removed. An increase in shoot number per explant resulted in decreased shoot length. A polar phenomenon was observed in all excision treatments; adventitious shoot formation occurred only at the proximal cut end of the cotyledon.

Free access

Kalavathy Padmanabhan, Daniel J. Cantliffe, Roy C. Harrell, and Dennis B. McConnell

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.

Open access

Amul Purohit and J. B. Shanks

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.

Free access

Patrick J. Conner and Katherine L. Stevenson

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.