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- Author or Editor: M. Sachs x
- Journal of the American Society for Horticultural Science x
Abstract
The postulation proposed by Reed and his colleagues (11, 12) that the mode of action of Alar was through hydrolysis of the growth retardant to unsymmetrical dimethylhydrazine, UDMH, which subsequently inhibits diamine oxidase from converting tryptamine to indoleacetaldehyde, was examined. In vitro tests showed that commercial proteolytic enzyme preparations as well as those prepared from Alar-sensitive plants were not capable of breaking the C-N (peptide) bond in Alar. Both UDMH and β-hydroxyethylhydrazine (BOH) reacted, with indoleacetaldehyde to yield several compounds which gave positive spot tests for indole and hydrazine. Likewise, UDMH reacted readily with constituents in the endosperm-nucellar tissues when injected into immature almond ovules. Experiments with Alar, UDMH and BOH showed that Alar was more effective as a growth retardant and as a promotor of floral initiation than the others at nearly equal molar concentrations. Injections of Alar and 2-14C mevalonic acid, together and separately, into immature peach ovules revealed that the synthesis of kauren-19-ol, a gibberellic acid precursor, was depressed in the presence of Alar. None of these results support the hypotheses that 1) the active portion of Alar is the UDMH moiety and 2) the primary effect of Alar is to inhibit IAA synthesis.
Abstract
In Coprosma baueri Endl. low response to foliar sprays of 1% daminozide (SADH; succinic acid 2,2 dimethyl hydrazide) was accounted for, in part, by low levels of endogenous SADH in the terminal shoot tissues. The same exogenous application rates to Xylosma congestum (Lour.) Merr. and Pyracantha coccinea Roem. caused greater inhibition of stem elongation and higher endogenous levels of SADH. However, the most significant results of this study were that a negligible relationship existed between level of SADH in tissues of elongating branches and the inhibition of stem elongation. Elongation did not increase in stems of Xylosma, Coprosma and Pyracantha after 60 to 90 days even though endogenous SADH concentration decreased sharply in this interval. We concluded, therefore, that only a portion of the SADH found in tissues was active in inhibiting stem elongation. Multiple applications of SADH, made after pruning but before branch elongation had begun, caused greater inhibition of elongation than was expected on the basis of endogenous levels of SADH. This response suggested that exogenous applications reached sites in axillary buds critical for inhibition of elongation more readily than endogenous SADH translocated from older leaves. The implications of these findings for interpreting comparative activity studies among analogs of growth retardants and among species is discussed.
Abstract
In ‘Bright Golden Anne’ chrysanthemums girdling below the treated leaves does not reduce, rather it may enhance, growth retarding activity of foliar applied ancymidol. Experimental evidence with 14C sucrose shows that the compound does not pass the girdle to enter the root system, and it is assumed that ancymidol transport is similarly restricted. Our results indicate that the major site of action of ancymidol is in the shoot tissues. One suggestion accounting for greater activity of soil, as compared to foliar, applications is that the chrysanthemum root system may absorb ancymidol more rapidly than the leaves.
Abstract
Ten compounds applied as foliar spray were screened for reducing and delaying bolting in fall-planted carrots (Daucus carota L.). Only butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) was effective; seedstalk height was reduced and root size was unaffected. Daminozide effectiveness was greatest in weak-bolting cultivars. Two sprays of 5000 ppm, 2 weeks apart at about 4 and 2 weeks prior to natural bolting were most effective, suggesting that daminozide does not interfere in the cold temperature induction process, but rather has a delaying and inhibitory effect on the initial seedstalk elongation. Two sprays of 500 liters/ha of daminozide solution of 5000 ppm gave promising results. Root quality was improved without influencing carrot yield or dry matter content. Although (2-chloroethyl)trimethymammonium chloride (chlormequat) suppressed bolting in some experiments, it was less effective than daminozide at comparable rates and higher rates decreased yield.
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.
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.