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  • Author or Editor: Harry E. Sommer x
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Abstract

The acclimatization or hardening-off of in vitro-cultured sweetgum (Liquidambar styraciflua L.) plantlets was studied using scanning electron microscopy. Comparisons were made among leaves of plantlets differentiated in culture, plantlets acclimatized after transfer from in vitro conditions, greenhouse seedlings, and mature trees. Leaves of plantlets directly from tissue culture had superficial, circular stomata and epidermal cells with irregular, sinuous undulations in the anticlinal walls. Leaves from acclimatized plantlets had ellipsoid, depressed stomata and irregularly shaped epidermal cells. Seedling and field-grown leaves had depressed, ellipsoid stomata and well-defined isodiametric epidermal cells. Stomata in all cases were confined to the abaxial surface, with densities significantly greater in leaves of in vitro plantlets than in acclimatized plantlets or greenhouse-grown plants. Epicuticular wax was generally smooth and absent of waxy outgrowths in all conditions.

Open Access

Abstract

The anatomy of in vitro- and in vivo-developed leaves of sweetgum, Liquidambar styraciflua L., grown under three quantum fluxes (PPF), was evaluated using light and scanning electron microscopy. Leaf characteristics of both in vitro- and in vivo-developed plants were modified by light: high irradiance was associated with more compact mesophyll and larger cells than low irradiance. However, when compared to plants grown in vivo under corresponding irradiance levels, all plants grown in vitro had smaller, thinner leaves and smaller mesophyll cells lacking extensive vacuolar components. Leaves developed in vitro had larger, raised stomata regardless of light level and, except at the highest irradiance, exhibited significantly greater stomatal densities than in vivo-developed leaves.

Open Access

Abstract

Tissue cultures of pecan [Carya illinoensis (Wangenh.) C. Koch] were initiated from embryo explants collected weekly from 12 weeks post-pollination until fruit maturity. Three cultures derived from immature embryos collected 14 weeks postpollination produced primary somatic embryos within 1 month following transfer from modified woody plant medium (WPM) with 2.0 mgliter−1 2,4-D and 0.25 mg liter−1 BA in the light to hormone-free medium in the dark. Scanning electron microscopy documented the development of secondary embryos, which followed a globular, heartshaped, and torpedo-stage developmental sequence. Chemical names used: (2,4-di-chlorophenoxy) acetic acid (2,4-D), N-(phenylmethyl)-1H-purin-6-amine (BA), and 1H-indole-3-butanoic acid (IBA).

Open Access

Abstract

It is increasingly evident that the concentration and type of matrix used in nutrient media can profoundly influence the response of tissues cultured in vitro. Picea abies shoot cultures exhibited increased dry weight yields (4) and increased shoot growth (9) with decreasing agar concentrations. Singha (5) compared shoot proliferation of crabapple and pear in Phytagar concentrations ranging from 0% to 1.2%. Optimal proliferation and growth occurred in crabapple on 0.3% agar, with higher concentrations decreasing these growth characteristics. In pear, increasing agar concentration also decreased shoot growth, but shoot proliferation was greatest at 0.6% or higher agar concentrations. Rooting has been promoted without or with lower agar concentrations in grape (1), Norway spruce (9), and apple (10). However, vitrification (glassiness or waterlogging) has been shown to increase with lower agar concentrations (9) and limits the use of liquid culture in some species.

Open Access

Effects of autoclaving volume, gelling agent (Bactoagar, Gel-gro, Phytagar), and basal salts [Murashige and Skoog (MS); Woody Plant Medium (WPM); Gamborg B5 (GB)] on gel strength and pH of tissue culture media were tested. Gel strength was significantly affected by gelling agent and basal medium. MS media were generally softer than comparable WPM or GB media. As the vessel volume during autoclaving decreased, gel strength significantly decreased with Phytagar and Bactoagar gelling agents; Gel-gro had greater gel strength at the intermediate volume of medium autoclave. In all cases, autoclaving resulted in a pH decrease of 0.2 to 0.5 pH units. Lower pH values were associated with softer gels. The type of gelling agent did not greatly affect the postautoclave pH; mean values among gelling agents were within 0.05 pH units. Postautoclave pH of MS medium was lower than that of WPM or GB. This study verifies the need to observe uniform sterilization protocols to maintain consistency in the chemical and physical properties of media.

Free access