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Respiratory Rates and Glycosidase Activities of Juice Vesicles

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Respiratory Rates and Glycosidase Activities of Juice Vesicles 8 WAT again showed significantly reduced fertilization and mowing height effects on ten- Evaluation of herbicides on ccntipedegrass. Ark. root numbers. sile strength of bermudagrass sod. Agron. J. Farm Res. 23(6):10. In general, the effects of herbicides on root 71:1061-1062. Turgeon, A.J. 1972. Preemerge herbicides and their length were similar to their effects on root Shearman, R. C., E.J. Kinbacher, and D.H. Stein- effects on the turfgrass ecosystem. Proc. North igger. 1979. Herbicide effects on sod transplant Central Weed Cont. Conf. 27:62. number. In 1986, at 2 WAT, root lengths rooting of three Kentucky bluegrass cultivars. Turgeon, A. J., J.B. Beard, D.P. Martin, and W.F. were reduced by bensulide, imazapyr, na- -1 HortScience 14:282-283. Meggitt. 1974. Effects of successive applica- propamide at 4.5 kg·ha , and sulfometuron Troutman, B.C. and J.A. Jagschitz. 1971. Effects tions of preemergence herbicides on turf. Weed treatments (Table 4). By 4 WAT, only ben- of preemergent herbicides on development and Sci. 22:349-352. sulide, imazapyr, and napropamide at 4.5 rooting of Kentucky bluegrass sod. Agron. Abstr. Turner, D.L. and R. Dickens. 1987. Atrazine ef- kg·ha -1 continued to reduce root length; sul- p. 50. fects on tensile strength of centipedegrass sod. fometuron-treated sod no longer had reduced Troutman, B. C., R.E. Frans, and J.W. King. 1974. Agron. J. 79:3942. root length. At 8 WAT, napropamide at 4.5 kg·ha-1 had ceased to affect root length, but bensulide and imazapyr continued to sup- press root elongation. In 1987, bensulide, imazapyr, and napro- HORTSCIENCE 25(5):544-546. 1990. pamide at 2.2 kg·ha-1, and sulfometuron at 0.03 and 0.07 kg·ha-1 had reduced root length by 2 WAT. At 4 WAT, none of the herbicide Respiratory Rates and Glycosidase treatments could be shown to reduce root length, possibly due to the large variation Activities of Juice Vesicles Associated among the samples (CV = 36%). At 8 WAT, bensulide and imazapyr were the only her- with Section-drying in Citrus bicide treatments that still reduced root length of the sod. Jacqueline K. Burns The results indicate that neither mature nor Citrus Research and Education Center, IFAS, Department of Fruit immature sod will exhibit visible effects from any of the herbicides at 8 WAT, except im- Crops, University of Florida, 700 Experiment Station Road, Lake Alfred, azapyr, which had killed the aerial portion FL 33850 of the sod completely by that time. None of Additional index words. cell wall, Citrus paradisi, Citrus reticulate, granulation, the herbicides reduced tensile strength of oxygen uptake, tangelo, tangerine, grapefruit mature centipedegrass sod, and only ima- zapyr and bensulide affected strength of im- Abstract. Oxygen uptake and glycosidase activities were examined in normal and mature sod when applied after spring growth granulated juice vesicles of several citrus fruit. Oxygen uptake was low in normal juice was well under way. However, results might vesicles isolated from freshly harvested ‘Lee’ tangelos [Citrus reticulate Blanco CV. Cle- be quite different if the same herbicides were mentine × (Citrus paradisi Macf. CV. Duncan × Citrus reticulate Blanco CV. Dancy)] and applied in early spring, before centipede- stored ‘Dancy’ tangerine (C. reticulate Blanco) and ‘Marsh’ grapefruit (Citrus paradisi grass has fully recovered from winter dor- Macf.) (35.7, 17.9, and 11.6 µl O2/hr per g fresh weight, respectively), but was 2- to mancy. 3-fold higher in granulated juice vesicles. As severity of granulation increased in grape. Although many of the herbicides causing fruit, O2 uptake increased. Oxygen uptake in normal and disordered juice vesicles of reduced root length and/or number also vis- all citrus fruit examined was reduced to nondetectable levels with 0.1 mM KCN and ibly injured the turfgrass, the degree of in- was insensitive to salicylhydroxamic acid. a - and b -galactosidase and a- and b -gluco- jury was not consistent with respect to the sidase activities were present in extracts of normal grapefruit juice vesicles (123, 214, degree of damage to rooting or tensile 51, and 25 nmol·hr-1·g-1 fresh weight, respectively) and was 2- to 3-fold higher in strength. However, since salability of sod extracts of granulated tissue. a- and b -mannosidase activities, nondetectable in normal is affected materially by the aesthetic quality juice vesicle extracts, were present in extracts from granulated tissue. The results of the top growth, visible injury may make suggest that increased metabolic activity occurs in granulated juice vesicles and the certain herbicides unacceptable for use in sod energy produced may be used to support cell wall synthesis and modification. Increases production. Imazapyr and bensulide caused in O2 uptake and glycosidase activities correlate well with observed symptoms of sec- visible injury and/or reduced rooting enough’ tion-drying in citrus. to preclude their use on centipedegrass sod within 8 weeks before expected harvest. Section-drying is a late-harvest physiolog- but becomes more severe during storage of ical disorder of citrus fruit, such as ‘Valen- late-harvest fruit. Some cultivars, such as Literature Cited cia’ orange (Bartholomew et al., 1941) and ‘Lee’ tangelos, can often show symptoms of Coats, G. E., 1975. Effect of preemergence her- many tangerine and grapefruit cultivars (Na- section-drying before optimum maturity is bicides on centipedegrass establishment. Proc. kajima, 1976; Burns and Achor, 1989). The attained. Southern Weed Sci. 28:81. disorder is characterized by the hardening, Anatomical investigations have shown ex- Cope, J. T., C.E. Evans, and H.C. Williams. 1980. or granulation, of the juice vesicles at the tensive cell wall thickening and scattered Soil test fertilizer recommendations for Ala- stem and/or the stylar end of the fruit seg- secondary wall formation in internal paren- bama crops. Ala. Agr. Expt. Sta. Cir. 251. ment. In grapefruit, affected vesicles even- chyma and epidermal cells of granulated juice Jagschitz, J.A. 1977. Development and rooting of tually discolor and collapse. In some cases, vesicles isolated from late-harvest citrus fruit Kentucky bluegrass sod as affected by herbi- vesicles may collapse without undergoing (Burns and Achor, 1989; Shomer et al., cides. Proc. 3rd Intl. Turf. Conf. p. 227–235. granulation. Section-drying can occur in fruit 1989). Lignin deposition within cells of Johnson, B.J. 1973. Establishment of centipede- that remain on the tree late in the season, granulated vesicles has also been detected grass and St. Augustinegrass with the aid of chemicals. Agron. J. 65:959-962. histochemically in grapefruit (Burns and Achor, 1989), as well as chemically in pum- Johnson, B.J. 1975. Herbicides for weed control Received for publication 28 Aug. 1989. Florida during establishment of warm season turf- Agricultural Experiment Station Journal Series no. melo (Shomer et al., 1989). Loss of soluble grasses. Coop. Ext. Serv. Univ. Ga. Leafit. 177. R-00146. The cost of publishing this paper was sugars and acidity occurs in juice vesicles Johnson, B.J. 1987. Turfgrass species response to defrayed in part by the payment of page charges. associated with granulation (Bartholomew et herbicides applied postemergence. Weed Tech- Under postal regulations, this paper therefore must al., 1941; Sinclair and Jolliffe, 1961; Gil- nol. 1:305-311. be hereby marked advertisement solely to indicate fillan and Stevenson, 1977; El-Zeftawi, 1978; Mitchell, C. H., and R. Dickens. 1979. Nitrogen this fact. Shomer et al., 1989). A decrease in the 544 HORTSCIENCE, VOL. 25(5), MAY 1990 Table 1. Oxygen uptake in normal and granulated juice vesicles of grapefruit, tangerine, and tangelo used per cultivar. Oxygen uptake in juice fruit. Data presented are the means (±SE ). vesicles was expressed in microliters O2/hour per gram fresh weight. Glycosidase extraction. Glycosidases were extracted from normal and granulated juice vesicles of grapefruit by the method of Pres- sey (1983), with some modification. Juice vesicles were homogenized in cold distilled H2O (100 g tissue :150 ml H2O). All sub- sequent steps were carried out at 4C. The homogenate was stirred for 30 rein, then brought to 1 M salt by addition of solid NaCl. After the pH was adjusted to 6.0 with 1 N HCl, the homogenate was stirred for an ad- ditional hour. The homogenate was clarified zNormal, granulated, and granulated-collapsed (grapefruit) different for each citrus fruit, paired t test, by centrifugation at 10,000× g for 20 min. P < 0.005. Solid (NH4)2SO4 was added to the superna- tant to » 65% saturation over 2 hr. The pre- cipitant was collected by centrifugation and then dialyzed overnight against two changes of 0.1 M NaCl. Insoluble material, formed during dialysis, was removed by centrifu- gation. The supernatant was lyophilized and stored at – 15C. When needed, lyophilized powder was resuspended in 0.05 M sodium acetate buffer, pH 5.0 (10 mg powder/ml), and centrifuged. The resulting supernatant was considered the enzyme solution and as- sayed for activity. Enzyme assays. Glycosidase activities were assessed by the use of the appropriate p-ni- trophenyl glycoside substrate (Pressey, 1983) (Sigma). For example, the reaction mixture for determination of b -galactosidase (EC Fig. 1. Glycosidase activities present in extracts of normal and granulated juice vesicles of ‘Marsh’ 3.2.1.23) activity contained 1.0 ml of 0.05 grapefruit. Data plotted are the means + SD. a -gal, b -gal, a -glc, b -glc, a -man, and b -man are a- M sodium acetate buffer (pH 5.0), 0.1 ml of galactosidase, b -galactosidase, a -glucosidase, b -ducosidase, a -mannosidase, and b -mannosidase. enzyme solution, and 0.4 ml of 3.5 mM p- respectively. nd = None detected. nitrophenyl- b -galactoside (final concentra- tion).
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