Search Results

You are looking at 1 - 10 of 28 items for

  • Author or Editor: M.J. Bukovac x
Clear All Modify Search
Authors: and

The effect of CPPU [forchlorfenuron; N-(2-chloro-4-pyridinyl)-N-phenylurea] on berry development of selected seedless and seeded grape cultivars was evaluated under field conditions. A concentration response curve was initially established by spraying clusters of `Himrod' at a mean berry diameter of 5 mm with 0, 5, 10, and 15 ppm CPPU. Berry enlargement was monitored (16, 30, 44, and 59 days after treatment) during development and cluster weight, berry number/cluster, weight, firmness and °Brix were determined at harvest. Berry size was dramatically (2.3 vs. about 3.6 g/berry) increased at harvest by all concentrations of CPPU; the response being linearly related to concentration (r 2 = 0.89). Cluster weight and compactness (rated) and berry firmness were significantly increased. There was no significant effect on berry number (79 to 86/cluster). °Brix and rachis necrosis (at harvest) as well as berry abscission after 30 days of refrigerated storage were significantly reduced. Effect of time of CPPU application (0, 5, and 10 ppm) was established by treatment of clusters at mean berry diameters of 4, 5, 7, and 9 mm. Response was indexed by following berry enlargement at 14, 28, 42, and 56 (maturity) days after treatment. Maximum berry enlargement for both 5 and 10 ppm was obtained from applications at 4 to 7 mm in diameter. Relative responsiveness of seedless and seeded cultivars was compared by application of CPPU at 0, 5, 10, and 15 ppm to clusters (4–6 mm berry diameter) of seedless `Himrod', `Vanessa' and `Lakemont' and seeded `Concord' and `Niagara'. Bioresponse was determined by a time course of berry enlargement and berry and cluster weight, number of berries/cluster and rating cluster compactness at maturity. CPPU at all concentrations increased seedless berry diameter significantly from the first measurement at 14 days through 56 days after maturity. Berry and cluster weight and cluster compactness were increased in the seedless cultivars, although `Lakemont' appeared less responsive than `Himrod' and `Vanessa'. CPPU did not change (`Lakemont') or decreased (`Himrod', `Vanessa') berries/cluster. In contrast, the only effect of CPPU on the seeded cultivars was an initial increase in berry diameter 14 days after application.

Free access
Authors: and

Abstract

S-ethyl dipropylthiocarbamate (EPTC, 2.24 kg×ha) inhibited epicuticular wax production on developing leaves of cabbage (Brassica oleracea L. Capitata group cv. Market Prize), resulting in an increase in cuticular permeability. This increased penetration of 14C-I-naphthaleneacetic acid (14C-NAA) and increased cuticular transpiration. EPTC-enhanced penetration was a consequence of increased diffusion across the cuticle, and not of active uptake. Application of EPTC increased penetration of NAA 200% in bean (Phaseolus vulgaris L.)and 121% in sugar beet (Beta vulgaris L.). For cabbage, the percent increase in penetration due to EPTC inhibition of cuticle development 7 days after treatment (141 %) was similar to that at 42 days (112%). The effect of EPTC declined until full leaf expansion (28 days after application). Silver nitrate was preferentially taken up by the cuticular ledges of guard cells and the anticlinal walls of epidermal cells, and was greater in leaves from EPTC-treated plants than in those from non-treated plants.

Open Access
Authors: and

Abstract

14C(2-chloroethhyl)phosphonic acid (ethephon) was readily absorbed by leaves of cherry (Prunus cerasus L. cv. Montmorency: Prunus avium L. cv. Windsor, Napoleon). Penetration was greater (20–25 ×) through the abaxial than the adaxial surface, in light than in dark, and for ‘Windsor’ and ‘Napoleon’ than for ‘Montmorency’. Penetration was temperature-dependent, increasing 55 × between 15–35°C. The addition of a surfactant (X-77) increased wetting and penetration (+ 65%). Radioassay of ethylene released after 14C-ethephon treatment indicated that most of the ethylene (>80%) was derived from ethephon and not endogenously produced. The significance of these findings in relationship to field application is discussed.

Open Access
Authors: and

Abstract

Production of epicuticular wax by expanding leaves of cabbage (Brassica oleracea L. var. capitata cv. Market Prize) was inhibited by S-ethyl dipropylthiocarbamate (EPTC) and trichloroacetic acid (TCA). Increasing the concentration of EPTC (0, 0.28, 0.56, 1.12 and 2.24 kg/ha) resulted in greater inhibition of epicuticular wax production. Both soil and foliar application of EPTC were effective. All leaves not fully expanded at time of application were affected, and no regeneration of epicuticular wax was evident after full leaf expansion. The difference between the amount of wax produced by the control and EPTC-treated plants gradually declined on those leaves which developed after EPTC application. This reduction was accompanied by an absence of wax bloom and a reduction of surface wax fine-structure.

Open Access

Abstract

Translocation of SADH was studied in young apple (Malus domestica Bork.) and peach (Prunus persica L.) trees using inhibition of shoot extension and distribution of 14C from foliar-applied 14C-SADH as indices of translocation. Two shoots were allowed to develop on each tree approximately 15 cm apart and orientated; in opposite directions. SADH (5000 ppm) inhibited elongation of the treated shoot but had not significant effect on elongation of the nontreated shoot. This response was independent of whether the upper or lower shoot was treated. In peaches, growth (dry wt) of the non treated shoot was greater than comparable shoots on control trees. These data suggest that SADH was not translocated into neighboring shoots. The absence of translocation of 14C from labeled SADH from treated to nontreated shoots was confirmed by radioautography.

Open Access
Authors: and

Abstract

Surface morphology and development of the cuticle of olive (Olea europaea L, cv. Manzanillo) leaves were studied in relation to some factors (wetting, retention) that influence absorption of foliar-applied substances. Cuticle deposition occurred at a uniform rate during leaf development, then ceased at full expansion. The total weight of the cuticular membrane per unit surface area remained constant during leaf expansion. The weight of the cuticular membrane of the adaxial epidermis was about 1.4 mg/cm2 and in μg/cm2 the principal constituents were: epicuticular wax, 243; cutin, 886; cuticular wax, 272. The thickness of the cuticle was greater on the adaxial (11.5 μm) than on the abaxial surface (4.5 μm), and both surfaces were covered with large (130 μm diameter) peltate trichomes, their number being greater on the abaxial surface (143/mm2 vs. 18/mm2). Stomata were present only on the abaxial surface (470/mm2). The large number of trichomes contributed significantly to the effective surface area of the leaf, which was about 3 times greater for the abaxial than for the adaxial surface. No epicuticular wax fine-structure was observed. Both surfaces were difficult to wet. The advancing contact angle formed by distilled water was 106° for the adaxial and 125° for the abaxial surface. Retention as indexed by dipping leaves in distilled water was 0.34 μl/cm2. When sprayed, maximum retention was 31.3 and 36.9 μl/cm2 by the adaxial and abaxial surfaces, respectively.

Open Access

Most growth regulators and crop protection chemicals are delivered to the plant as aqueous sprays. Spray droplet:plant surface interaction is central to establishing spray and, hence, dose retention by the plant. Further, the nature of chemical deposition from spray droplets plays an important role in determining the efficiency of the active ingredient (a.i.). Using scanning electron microscopy and dispersive x-ray analysis, we investigated chemical deposit formation of selected growth regulators (e.g. ethephon, 2,4, 5-TP, TIBA) on leaf surfaces differing in wettability and surface fine-structure. The a.i. frequently deposited in the form of an annulus on droplet drying, and the degree of spreading was related to surface tension of the spray solution, and wettability, fine-structure and morphology of the leaf surface. Marked differences were observed in spreading following impaction on veins vs. interveinal areas of leaves of Prunus and Pyrus sp. The epidermis over veins was more readily wetted leading to rapid lateral diffusion along veins. Surfactants (e.g. Tween 20, Regulaid) altered the deposition pattern, expanding the annulus and increasing spreading on the leaf surface.

Free access

Abstract

Hand thinning during late June drop increased fruit size and improved quality of ‘Stanley’ plum as indexed by soluble solids and color development. Crop load within the range of 200 to 990 g of mature fruit per cm2 trunk cross-sectional area was negatively correlated with fruit size, soluble solids and color. The percentage of mature fruits with cheek diameter less than 35 mm increased as crop load increased. Total flower buds and flowers per spur, and flowers per flower bud, were not significantly affected by fruit load in the range of 0.5 to 2.0 fruits per spur the previous season. However, a weak negative relationship was found between fruits per spur and flower buds produced per spur with a wider range (0 to 8 fruits/spur) in fruit load.

Open Access
Authors: and

Abstract

Surfactant toxicity was examined following application of octylphenol and linear alcohol surfactants to the adaxial surface of 10-day-old cowpea [Vigna unguiculata (L.) Walp. subsp. unguiculata ‘Dixielee’] leaves. Leaf damage first appeared as isolated discolored areas at the periphery of the droplet area, developed toward the center, and, when most severe, the entire droplet area was necrotic. Epidermal cells beneath the droplet area became discolored, lost structural integrity and collapsed. Similar changes were observed in the palisade layer and spongy parenchyma. In addition, walls of damaged cells were preferentially stained with Safranin O. For a given surfactant dose, phytotoxicity increased with increasing concentration, droplet volume, and temperature and decreased with increasing humidity. In general, phytotoxicity was inversely related to the length of the ethoxy (EO) chain for both the octylphenol (Triton X) and C12-15 linear alcohol (Neodol 25) surfactant series. Tissue did not recover after injury. Chemical names used: octylphenoxypoly(ethoxy)ethanol (Triton X-100), linear alcohol ethoxylate (Neodol 25-9).

Open Access

Abstract

Ethylene evolution induced by nonionic (Triton X-100, Triton X-405, Tween 20, Ortho X-77 and Regulaid), anionic (Aerosol OT and Dupanol ME), and cationic (Arquad C-50 and Arquad 2C-75) surfactants was characterized using cowpea [Vigna unguiculata (L.) Walp. supsb. unguiculata ‘Dixielee’] seedlings. Representative surfactants of each ionogenic class induced ethylene evolution. Time course studies revealed an increased rate of ethylene evolution during the first 6 to 12 hr after treatment, followed by a slow decrease for the next 12 to 36 hr, and a return to control levels within 48 hr. Ethylene production induced by Triton X-100 increased with increasing concentration, while Tween 20 did not induce ethylene at concentrations up to 1.0%. Surfactants that promoted ethylene evolution also generally induced visible phytotoxicity. Phytotoxicity symptoms increased with increasing time after treatment. Surfactant-induced ethylene production and phytotoxicity were observed with corn (Zea mays L. ‘B73 × MO17’), wheat (Triticum aestivum L. ‘Hillsdale’), soybean (Glycine max Merr. ‘McCall’), apple (Malus domestica Borkh. ‘Golden Delicious’), and sour cherry (Prunus cerasus L. ‘Montmorency’). Tween 20, nonactive on cowpea, induced ethylene and phytotoxicity when applied to the abaxial surface of sour cherry leaves. Chemical names used: octyl-phenoxypoly(ethoxy)ethanol (Triton X-100 and X-405), polyoxyethylene sorbitan monolaurate (Tween 20), alkylaryl polyoxyethylene glycols/free fatty acids/isopropanol (Ortho X-77), polyoxyethylenepolypropoxypropanol alkyl 2-ethoxyethanol/dihydroxy-propane (Regulaid), diocytl sodium sulfosuccinate (Aerosol OT), sodium lauryl sulfate (Dupanol ME), monococo trimethyl ammonium chloride (Arquad C-50), dicoco dimethyl ammonium chloride (Arquad 2C-75).

Open Access