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Carlos A. Lazcano, Fred T. Davies Jr., Andrés A. Estrada-Luna, Sharon A. Duray, and Victor Olalde-Portugal

Mature cladodes of prickly-pear cactus (Opuntia amyclaea Tenore. `Reina') were treated with five wounding methods and four concentrations of potassium salt indole-3-butyric acid (K-IBA) to stimulate adventitious root formation. The wounding method and K-IBA had highly significant effects on root number and root dry mass of cladodes. Interaction between K-IBA and wounding methods showed that greater root number was obtained at the higher auxin concentrations and with wounding methods that had the greatest cut surface area. K-IBA concentrations from 4,144 to 41,442 μm (1,000 to 10,000 mg·L-1) increased root dry mass. Only the wounding method affected rotting of cladodes. Treatments allowing suberization had a higher percentage of nonrotted cladodes. This research validates the commercial practice of allowing cladodes to suberize early in the propagation cycle. K-IBA altered rooting polarity and stimulated adventitious root formation along the wounded cladode surfaces. The vertical nonsuberized wounding methods and auxin treatments are an excellent classroom demonstration for manipulating rooting polarity. Auxin application and wounding could be of commercial benefit for enhanced rooting in the clonal regeneration of new selections for prickly-pear cactus orchards.

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William M. Walter Jr., Betsy Randall-Schadel, and William E. Schadel

Wound healing in cucumber fruit (Cucumis sativus L., cv. Calypso) was studied using histological and degradative techniques. A thick exudate appeared at the wounded surface shortly after wounding. This material retarded water loss and possibly aided in the formation of sclerified parenchyma observed 24 hours after wounding. The sclerified material was positive to a modified Weisner stain, indicating lignification was occurring. Wound periderm (cork) was initiated directly beneath the sclerified parenchyma cells within 48 hours after wounding. The cork layers were positive to Sudan IV stain, indicating suberin was being formed. The rate of phellem development decreased by 6 days after wounding. By day 7, younger phellem cells and sclerified parenchyma cells were stained by Sudan IV. Degradation of the wound tissue by chemical procedures demonstrated that relatively large amounts of lignin and suberin were deposited during healing. Fragments from the lignin degradation Indicated that lignin was composed mainly of gualacyl and p-hydroxyphenyl residues. Suberin was found to contain mainly 1,16-hexadecane and 1,18-osctadecene decarboxylic acids detected as the silylated diol derivatives.

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Vito S. Polito, Kirk D. Larson, and Katherine Pinney

Bronzing of strawberry (Fragaria ×ananassa Duchesne) fruit that is not the result of arthropod feeding or chemical spray application occurs frequently in California's central coast strawberry production region from late spring through midsummer, a period characterized by relatively high temperature, low relative humidity, and high solar irradiance. The cause of this phenomenon is not known, but in preliminary trials, intermittent, midday misting of plants and increased drip irrigation rate resulted in reduced incidence of fruit bronzing. To characterize the bronzing phenomenon and its development in strawberry fruit tissues, we conducted an anatomical and histochemical examination of bronzed fruit. Bronzed and nonbronzed fruit were sampled over a range of fruit maturities. Results show that bronzing derives from a lesion at the cortical surface early in the fruit's development. Epidermal cells become radially compressed and the cell contents coalesce into a densely staining mass. The cuticular layer becomes disrupted and discontinuous. As the fruit develops, densely staining materials, possibly phenolic precipitates, accumulate within subepidermal cells of bronzed fruit, subepidermal cell walls thicken, and intercellular spaces fill with pectic substances and other densely staining materials. Results are consistent with reports of sunscald injury from other fruit species, and raise the possibility that strawberry bronzing occurs in response to heat or solar radiation injury.

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Thanidchaya Puthmee, Kenji Takahashi, Midori Sugawara, Rieko Kawamata, Yoshie Motomura, Takashi Nishizawa, Toshiyuki Aikawa, and Wilawan Kumpoun

interconnect the vertical fissures as the fruit continues to mature ( Suzuki and Nonaka, 2004 ). Periderm tissues with waxy suberized cell wall layers heal these fissures or naturally occurring wounds. The network pattern formed by these healed fissures is

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Xiang Wang, Ramón A. Arancibia, Jeffrey L. Main, Mark W. Shankle, and Don R. LaBonte

and Lulai, 2002 ; Webster et al., 1973 ). The wound healing process is characterized by suberization/lignification of the exposed cells and developing of the new periderm beneath ( Lulai and Suttle, 2004 ; St. Amand and Randle, 1989 ). In addition

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Pedro Brás de Oliveira, Maria José Silva, Ricardo B. Ferreira, Cristina M. Oliveira, and António A. Monteiro

primocanes and leaves. Four random root samples were also taken at each pruning date × cane density treatment using a metal cylinder (15.5-cm diameter and 35.0-cm depth) and separated into fine roots (diameter <2 mm) and suberized roots (diameter >2 mm

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Gretchen B. North and Evan A. Baker

the shoot, ≈10 to 15 cm long, in which roots are mature with suberized (waxy) outermost cell layers but are of relatively small diameter (8 mm or less). With respect to chronological age, this region has been investigated in roots ranging from 5 months

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Yuliya A. Salanenka, Martin C. Goffinet, and Alan G. Taylor

). Stained with auramine O and examined under ultraviolet excitation. (F) Cross-section of the nucellar beak viewed with ultraviolet excitation shows the remnant of the pollen tube canal (C) and autofluorescent suberized cell walls (SCW). (G) The cuticle

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Kevin R. Kosola, Beth Ann A. Workmaster, James S. Busse, and Jeffrey H. Gilman

with suberized radial walls was most pronounced in striped maple, but this was also present in apple, river birch, and swamp white oak. Discussion Root damage was greater in the samples collected from the Minnesota site than in the apple roots

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Marie-Therese Charles, Alain Goulet, Francois Castaigne, and Joseph Arul

Hormic dose of ultraviolet light (3.7 kJ•m-2) induced disease resistance in tomato fruit. The biochemical nature of induced resistance by UV light was investigated by histochemical techniques. Ultraviolet light induced plasmolysis of the epicarp and few mesocarp cell layers, and collapse of these cell layers led to the formation of cell wall stacking zone (CWSZ). The treatment also stimulated the biosynthesis of phenolic compounds (Prussian blue reaction) in the epicarp and mesocarp cells. Biochemical reinforcement of the cell wall through lignification (Maule test) and suberization (berberine fluorescence) was also induced. These responses originating from the activation of phenylpropanoid path were principally localized in the CWSZ and were induced before inoculation by B. cinerea. The intensity of these responses was significantly increased in UV-treated tissue in response to infection. These responses were also induced in the inoculated control tissue but were either less substantial (phenolics, lignification, and suberization) or delayed.