Browsing by Author "BALBOA, O"

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    CHARACTERIZATION OF THE AMYLOLYTIC ACTIVITY OF ARAUCARIA-ARAUCANA (MOL) KOCH GERMINATING-SEEDS
    (1983) REINERO, A; BALBOA, O; CARDEMIL, L
    Starch is the main reserve in A. araucana (Mol.) Koch seeds. To understand the regulation of starch mobilization during seed germination, amylase activity was characterized and its levels were measured for the first 90 h after the start of seed imbibition. Amylase is present in the embryo and megagametophyte when seeds are quiescent. The enzyme activity of the embryo has 2 peaks during the 90 h, while amylase activity of the megagametophyte remains low and unchanged during this time. Analysis of the products released by the enzyme and thermostability experiments identify the amylase as .alpha.-amylase. Differential centrifugation of embryo homogenates under isoosmotic conditions shows that the enzyme is soluble. Quantification of the endogenous GA of the embryo shows a time correlation between the rise in amylase activity and the rise in specific GA levels during the 40 h after the start of imbibition. The growth retardant AMO-1618 [N,N,N-2-tetramethyl-5-(1-methylethyl)-4-[(1-piperidinylcarbonyl)oxy]-benzenaminium chloride] lowers enzyme activity to 37.3% of the control at this time. Activity is almost completely restored when the GA from embryonic tissue are added in physiological doses to the imbibition medium containing AMO-1618.
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    DISTRIBUTION OF GIBBERELLINS IN THE SEEDS OF 2 APPLE CULTIVARS
    (1980) BALBOA, O
    Inclusion of 4-hydroxy-5-isopropyl-2-methyl trimethylammonium chloride piperidine carboxylate (AMO-1618) in the stratification medium reduced germination in both ''McIntosh'' and ''Jonathan'' apple seeds from 94% to 17 and 30%, respectively, showing no effect on ''Golden Delicious''. Free and bound levels of gibberellins were also reduced in ''Jonathan'' after 30 days of chilling; this decrease suggests no interconversion of the free form into the bound form. In ''McIntosh'' after 30 days at 5.degree. C the seed coat accumulated the highest level of gibberellins (GAs) (5353 ng/g fresh weight) followed by embryonic axes (14.1 ng/g) and cotyledons (0.33 ng/g) but in ''Jonathan'' embryonic axes contained most of the gibberellins (130 ng/g).
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    FINE-STRUCTURE OF ACTINORHIZA OF THE RHAMNACEAE GROWING IN CHILE .1. TALGUENEA-QUINQUENERVIA (GILL-ET-HOOK)
    (1988) BALBOA, O; AVILA, G; ARCE, P
    Root nodules Talguenea quinquenervia Gill et Hook (Rhamnaceae) are restricted to the middle region of the root cortex. The root endophyte possesses hyphae which are septate and vesicles. The vesicles are spherical and are continuous with that of the hyphae. The endophyte fine structure is similar to other Frankia-induced root nodules.
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    SEASONALITY IN ROOTING OF PROSOPIS-CHILENSIS CUTTINGS AND INVITRO MICROPROPAGATION
    (1991) ARCE, P; BALBOA, O
    Seasonality in rooting of cuttings and its relationship with some environmental conditions and growth parameters of Prosopis chilensis (Mol. Stunz) were studied. It was observed that rooting could be induced in cuttings taken from field collections only during the dry season, the period corresponding to the highest vegetative growth and reproductive activity (September to March); however, percentages did not exceed 15%. The rooting response does not occur during the dormant period (May to September). When using cuttings from clonal material growing in the glasshouse, rootings exceeding 80% were obtained in liquid aerated media.
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    SEED DORMANCY IN 4 SPECIES IN A CHILEAN SAND-DUNE - A LABORATORY STUDY
    (1983) BALBOA, O
    Seeds of Neoporteria subgibbosa, Trichocereus litoralis, Plantago hispidula and Calandrinia arenaria were collected in 1979 from Mantagua dunes located 32.degree. 48''S and 72.degree. 30''W. The germination tests were carried out in the laboratory using continuous white, green, red, far red light (20 .mu.mol m-2 s-1) or darkness. N. subgibbosa and T. litoralis germinated under the 4 light regimes but darkness. White or red light gave the highest percent germination in both species. C. arenaria required scarification to start germination, which was low (35%); however, addition of GA3 (50 ppm) improved it reaching 75%. P. hispidula responded equally well to light and darkness. These seeds have the remarkable capacity to imbibe water up to 15-fold their fresh weight due mainly to the mucilaginous layer surrounding them. Thus, these species show different reproductive adaptations to cope with natural environmental conditions.