Search Results
Abstract
Morphactins, mixed with non-phytotoxic paraffinic, low molecular weight oil, were applied as bark bands and tested for growth inhibition of trees growing under field conditions. Three species were tested: Monterey pine (Pinus radiata D. Don.), olive (Olea europaea L. cv. Manzanillo) and eucalyptus (Eucalyptus globulus Labill). Shoot elongation was inhibited in all three species, but sensitivity to the treatment varied.
Abstract
Watermelon [Citrullus lanatus (Schrad.) Matsum. & Nakai] seeds of the tetraploid ‘Alena’ and the diploid ‘Sugar Baby’ were subjected to one of several treatments prior to germination at 17°, 21°, and 25°C, including lateral splitting, soaking in H2O (aerated or nonaerated), GA4+7, or benzyladenine (BA) for 24 hr, or in KNO3 for 5 days, followed by drying. These treatments were successful in increasing germination percentage of ‘Alena’ seeds. Soaking treatments increased ‘Alena’ embryo length. ‘Alena’ seeds possessed thicker seed coats, larger seed cavities, and absorbed more water than those of their diploid counterpart, ‘Sugar Baby’.
Abstract
A new formulation of maleic hydrazide (Royal Slo-Gro), containing the surfactant polyoxyethylene trimethylnonyl ether (TMN-10), was superior to the maleic hydrazide formulation, containing polyoxyethylene nonyl surfactant (X-77) for inhibiting shoot elongation of Pinus radiata L., Xylosma congestum (Lour.) Merr., Viburnum japonicum (Thunb.) Spreng., and Coprosma repens A. Rich. The X-77 formulation was superior to the one containing TMN-10 for inhibiting growth of Juniperus sabina L. ‘Tamariscifolia’, Pyracantha coccinea (Roem.), and Callistemon citrinus (Curt.). There was little difference between the two formulations in tests with Cotoneaster pannosa (Franch.) and mixed results were obtained with Nerium oleander L. The greatest advantage of the TMN-10 formulation was manifested in Pinus where inhibition occurred without severe foliar discoloration, necrosis, or tip dieback which are characteristic of other maleic hydrazide formulations.
Abstract
Pea root tips were pre-incubated for 2 hr in the presence of Alar, Amo–1618, or Cycocel after which a quantity of 2-14C-mevalonic acid was added to the medium. The incorporation of mevalonic acid subsequent to decarboxylation into 3 gibberellic acid precursors, trans-geranylgeraniol, kauren-19-ol, and kauren-19-al was ascertained by paper and thin layer chromatography. The amount incorporated into a fourth acidic fraction containing kaurenoic acid was also estimated.
In the presence of Alar, the amount of radioactivity in trans-geranylgeraniol increased while that in kauren-19-al decreased simultaneously; the radioactivity in the acidic and kauren-19-ol fractions remained unchanged. Amo-1618 at 125 ppm induced an accumulation of radioactive acidic materials and concurrent decreases in the other 3 fractions. With Cycocel, the incorporation of 14C in kauren-19-ol and kauren-19-al remained unchanged while that in the acidic fraction increased and trans-geranylageraniol decreased. Amo-1618 was 100-fold more effective than Cycocel in altering the levels of GA precursors. The Alar concentration required to affect the biosynthesis of GA precursors was the same as that which inhibited epicotyl elongation of intact pea seedlings. The findings support the hypothesis that these growth retardants disrupt GA biosynthesis which in turn affects subapical meristematic activity, thereby inhibiting internodal elongation.
Abstract
Several field-established broadleaved and coniferous evergreen shrubs and 2 ground covers, Carpobrotus sp. and Hedera helix L., survived, and maintained adequate appearance with greatly restricted growth, without supplemental irrigation from May through September on deep soils at San Jose and Santa Ana, CA. Eugenia uniflora L. at Santa Ana required 1 irrigation (9.4 cm) in July to insure survival and both Coprosma baueri Endl. and Cotoneaster pannosa Franch. required 1 or 2 irrigations to insure adequate foliar density. At San Jose only Nerium oleander L. lost leaves or lost leaf color and turgidity in the non-irrigated plot. The plantings at both locations had viable roots down to 1 m and probably deeper. Non-irrigated and bimonthly irrigated soils were at or below the permanent wilting percentage down to 1 m. Leaf temp in the non-irrigated Xylosma congestum (Lour.) Merr. and Carpobrotus plots were 6 and 15° C, respectively, above ambient and yet no permanent foliar injury was observed. We suggest that leaf temp may be used to measure critical water stress in landscape plants. Our findings indicate that substantial savings in water costs and in controlling vegetative overgrowth can be realized by reducing irrigation frequency in established landscape plantings.
Abstract
Concentrations of O2 greater than 21% stimulated germination rate of Capsicum annuum L. (sweet pepper) at 25°C but inhibited germination rate at 15°. At a 10% O2 concentration, germination rates were reduced at both temperatures. Gibberellins A4A7 (GA4+7) increased germination rates at 15° and 25° in air. At 25° in 100% O2, germination rates of GA-treated and nontreated seeds were the same. At 15° and 100% O2, germination rates were increased slightly by GA4+7 application; however, the rates were slower than in air. Total respiratory activity at 25° was higher in 100% O2 than in air. High O2 concentrations did not affect the proportion of respiration which was in the cyanide-sensitive and -resistant pathways. Cyanide-resistant respiration comprised only a small percentage of total respiratory activity. At 15°, total respiration and the cyanide-sensitive and -resistant components were similar regardless of O2 treatment. The addition of GA increased respiratory activity only after radicle emergence occurred. Thus, germination rate of pepper seed can be increased by increasing temperature, higher O2 concentrations at the higher temperature, and GA4+7 at normal and low temperatures. GA appears to affect germination through metabolic events which occur before radicle emergence and which do not include alteration of respiratory activity.
Abstract
Seed germination of sweet pepper (Capsicum annuum L.) is inhibited after the seed is coated. The inhibitory effect of pellet-coating of ‘Early Calwonder’ pepper seed was caused by the physical properties of the coating materials. Clay coating limited part of the oxygen (O2) from reaching the germinating seed and provided a mechanical barrier to protrusion of the radicle. Clay-coated pepper seed germinated satisfactorily on filter paper in a high O2 environment or with minimum moisture on agar. Pellet coating formulations which would provide more O2 to the imbibing seed would assure comparable germination of raw and coated sweet pepper seed.
Abstract
Germination rate of sand-coated pepper (Capsicum annum L.) seed (sand grain size < 75μm for an inner coat and 75–105 μm for an outer coat layer) was faster than clay-coated seed but was slower than raw seed. Part of the germination reduction in sand-coated seeds was caused by the water-soluble Gelvatol binder used. High oxygen (O2) levels promoted the germination of sand-coated seed to a rate comparable to that of raw seed. This suggests that even with a porous sand-coating material, O2 may be limiting for the germinating seed. When inorganic O2-releasing compounds (BaO2 or NaBO3) were incorporated into the sand material, the germination of pepper seed was further inhibited.
Exposure of dormant corms of Triteleia laxa `Queen Fabiola' to 20 ppm C2H4 for 7 days promoted flowering of small corms and resulted in increased apical meristem size, early sprouting, early flowering, more flowers per Inflorescence, and increased fresh weight of daughter corms and cormels. The respiration rate of the C&treated corms increased to four to five times that of the controls during the 7-day treatment, declined markedly after termination of the C2H4 treatment, but remained higher than that of the controls. The C2H4 effects were associated with increased growth rate and consequently a greater final size of the apical meristem (determined by scanning electron microscopy). Leaves produced by C2H4-treated corms were wider, longer, and weighed more than those of the controls.
Flowering of brodiaea (Triteleia laxa syn. Brodiaea laxa `Queen Fabiola') did not have an obligate requirement for manipulation of temperature or photoperiod. Vernalization of corms reduced the greenhouse forcing phase but did not alter the number of flowers per inflorescence or scape length. Long photoperiods hastened flowering but decreased flower quality and flowering percentage. Scape length, which was not affected by photoperiod or mother corm size, was increased when plants were grown at night temperatures < 10C. Diameter of the apical meristem in the dormant corm, flowering percentage, and flower quality were not affected by a 10-fold increase in corm size above a critical weight (0.6 g). In contrast, the weight and number of daughter corms were closely correlated with mother corm size. The optimum planting depth for brodiaea corms was 10 cm below the soil surface.