Search Results

You are looking at 31 - 40 of 71 items for

  • Author or Editor: Paul E. Read x
Clear All Modify Search

Abstract

Three Typha species were micropropagated successfully using immature inflorescence segments as the explant. Plantlet production via organogenesis was optimum when the explants were first placed on LS medium + 5.0 mg°liter−1 2,4-D to initiate callus production, and after 9½ weeks the callus was recultured on LS + 1.0 mg°liter−1 benzyladenine (BA). Of three species tested, T. glauca produced callus and new shoots more readily than T. latifolia or T. angustifolia. As inflorescences matured, an increased level of an auxin-like plant growth regulator, picloram, was necessary for callus induction. Excision and separate culture of green “spots” or clumps that formed on the calli enhanced shoot regeneration from the callus. Chemical names used: (2,4-dichorophenoxy)acetic acid (2,4-D) and A-(phenylmethyl)-1H-purin-6-amine (BA).

Open Access

Abstract

Leaf explants from ‘Sugar Daddy’ and ‘Sugar Plum’ petunia (Petunia hybrida L.) were pretreated in solutions of 0, 200, 400, and 800 mg/liter 6-benzylamino purine (BA) and were placed in a cytokinin-free modified Murashige and Skoog (MS) medium, to which 0.05, 0.1, or 0.2 mg/liter naphthaleneacetic acid (NAA) were incorporated to test interaction. NAA at 0.05 or 0.1 mg/liter increased shoot number, fresh weight, and shoot quality rating for ‘Sugar Daddy’, while in ‘Sugar Plum’ addition of NAA increased shoot fresh weight and improved shoot quality rating without any effect on shoot number.

Open Access

Abstract

Yields of tomato cultivars ‘Heinz 1350’ and ‘Delaware 65S3-2’ (a mid-season processing variety) were increased by foliar sprays of succinic acid 2,2-dimethyl hydrazide (Alar) and 2-chloroethyl trimethylammonium chloride (Cycocel). The most effective treatments were those in which 2500 ppm Alar was applied at the first or fourth true leaf stage of growth or at both of these times. Concentration of harvest was improved and early yield was increased by subsequent application of 5000 ppm Alar as a flower “cut-off” spray after desired fruit set had been achieved. The latter treatment has desirable implications for mechanical harvesting, since it virtually eliminated green fruit “pick-out” and slowed vegetative growth, thus causing a more concentrated harvest because of more rapid fruit maturation.

The yield increases are attributed to a combination of effects including resistance to water and heat stresses, more flowers per cluster and thus more fruits per plant. Additional hormone-like effects of Alar and certain Alar analogs were observed.

Open Access

Abstract

Herbaceous cuttings dipped momentarily in solutions of several concentrations of B-Nine produced significantly greater weight and numbers of adventitious roots than did untreated cuttings. Concentrations of 1000 ppm and 5000 ppm were effective, with 2500 ppm optimum. Conversely, similar treatments of Cycocel caused a marked depression of adventitious root production. As rate of Cycocel was increased, production of adventitious roots diminished, suggesting corroboration of research proposing Cycocel’s behavior as being that of an “anti-auxin”.

Open Access

Abstract

Shoots harvested from the first and 2nd reculture of azalea (Rhododendron sp.) accession 800374 shoot tip cultures grown under 16 hr photoperiod from cool-white fluorescent light were taller and achieved higher quality ratings than shoots from 24 hr daily photoperiod. The number of shoots produced during the first reculture was the same for both 16 and 24 hr photoperiod, whereas significantly more shoots were harvested from cultures grown under 16 hr in the 2nd reculture. Similarly, 24 hr light inhibited elongation of shoots and decreased quality rating from in vitro-derived shoot cultures without any effect on the number of shoots per culture. Photosynthetic photon flux density (PPFD) of 30 and 75 μmol s−1m−2 (400–700 nm) increased number, length, and quality rating of shoots harvested from in vitro-derived shoot explants when compared to a 10 μmol s−1m−2 PPFD. However, recultured in vitro-derived shoot explants produced similar number and length of shoots under 10, 30, and 75 μmol s-1m-2, whereas the quality rating was reduced in cultures under 75 μmol s−1m−2. The highest percentage of rooting occurred in microcuttings harvested from cultures grown under 10 and the lowest under 75 μmol s−1m−2. Increasing the PPFD from 10 to 75 μmol s−1m−2 reduced shoot length and quality rating of rooted microcuttings, as well as root length and quality rating.

Open Access

Abstract

Sphagnum peat (peat) media (adjusted to pH 4.0, 4.6, 5.5, 6.6, and 7.4 with ground dolomitic limestone) and unadulterated peat (pH 3.6) were tested for their effectiveness on rooting of hardy deciduous azalea (Rhododendron sp.) microcuttings in high-humidity chambers. Rooting of more than 90% occurred in media with pH 4.0, 4.6, and 5.5; however, a) shoot height and quality rating and b) root length and quality rating were superior at pH 4.0. Clonal differences in rooting percentages were found for 3 clones of azalea microcuttings rooted in 5 soilless mixtures. A mixture including equal parts (v/v) of peat and either sphagnum, vermiculite, or perlite, or a combination of 2 peat : 1 vermiculite : 1 perlite (by volume) increased rooting percentages over peat alone for all 3 azalea clones examined.

Open Access
Authors: and

Abstract

Developmental anatomy of interlocular cavitation (IC), defined as the formation of cavities in soft parenchymatous endocarp cells between seed locules, was studied in pods of several snap bean cultivars grown under various cultural and environmental conditions during the years 1969–1972. IC occurred in pods from the stages of rapid pod elongation (6–10 days after anthesis) until the time of pod senescence. Unbalanced swelling of endocarp tissues combined with decreased periclinal cell division and rapid cell elongation are concluded to be the causes of IC. In the most commonly observed form, IC also includes the separation of fused endodermal cells. Pod malformation is greater in pods with severe IC and such pods exhibited more quality defects after processing. Sequential development of this developmental and physiological disorder is illustrated.

Open Access

Abstract

Levels of root-promoting substances from Pelargonium hortorum Bailey were detected by the mung bean rooting bioassay. Fractionated ethanolic extracts from Pelargonium showed 1 major and 2 minor zones which promoted rooting of mung beans. The active fractions promoted rooting in the absence of indoleacetic acid (IAA), in contrast to results previously published. Levels of promoters fluctuated during the propagation period, decreasing to a low point just prior to root initiation. Active zones from extracts of Pelargonium treated with 2500 ppm succinic acid-2, 2-dimethylhydrazide (daminozide, SADH) did not differ from those of controls indicating that daminozide does not promote rooting by modification of the level of ethanolic extractable root promoters.

Open Access

Abstract

The propagation method and vegetative condition of ‘Northblue’ blueberry (Vaccinium corymbosum L.) stock plants influenced microshoot production in vitro and root formation on leaf-bud cuttings. In tissue culture (TC), explants from TC-derived stock plants produced longer shoots than explants from leaf-bud, standard- (ST-) derived stock on either Zimmerman’s (Zimm) medium at pH 4.8, Lloyd and McCown’s woody plant medium (WPM) at pH 4.8 or pH 5.2. Microshoots from explants of TC-stock plants also rooted more readily. Microshoot rootability decreased after 18 weeks on medium containing 68.6 μmol (12 mg/liter) 2iP. Microshoot production and rootability increased after 3 additional weeks on Zimm medium without 2iP present. Leaf-bud cuttings of ‘Northblue’ TC-stock plants treated with 5% and 10% concentrations of a commercial rooting compound (Dip-n-Grow) had a slightly higher rooting percentage and root rating than nontreated cuttings from ST-stock plants. However, cuttings from ST-stock plants of the same age showed larger increases in root formation and percentage of rooting in response to the same rooting compound treatments. Leaf-bud cuttings from vegetative TC-stock plants that developed shoots had more basal branches than those from floral ST-stock plants. Branch elongation was greatest and basal branches fewest on cuttings from floral ST stock plants. Successful propagation with cuttings and in vitro explants may be related to the condition of the stock plants, which have been altered by their own propagation methods and the plant growth regulators applied. Chemical names used: 1H-indole-3-acetic acid (IAA); 1H-indole-3-butanoic acid (IBA); 1-naphthaleneacetic acid (NAA); N-(3-methyl-2-butenyl)-2H-purin-6-amine (2iP).

Open Access

Abstract

N-phenyl-N′1,2,3-thiadiazol-5-ylurea (thidiazuron) and several substituted pyridyl phenylurea compounds have been demonstrated to stimulate in vitro meristem and shoot formation at unusually low concentrations. These compounds appear to have strong cytokinin-like effects on a wide range of species and on species that respond little to conventional cytokinins. Thidiazuron has been reported to stimulate shoot proliferation in several woody species (e.g., Acer and Malus). The addition of 0.5μm N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) to the culture medium caused dramatic shoot number increases in hardy dedicuous azaleas (Rhododendron sp.) cultured in vitro. In petunia (Petunia ×hybrida Hort. Vilm.-Andr.) leaf test systems both thidiazuron and CPPU caused greater proliferation when used as explant dips or in the medium than similar treatments with N-(phenylmethyl)-1H-purin-6-amine (BA). Further possible applications and roles for these compounds are discussed.

Open Access