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Abstract

Somatic embryos were induced from the primary callus of celery (Apium graveolens L. cv. Utah Improved #15) arising from leaf blade explants placed on Murashige and Skoog (MS) salts and vitamins medium supplemented with 9 μM 2,4-D for 4 weeks and then subcultured to 2,4-D-free MS medium. The histological origin of somatic embryos was from single cells along the surface of callus clumps. Embryos proceeded in a standard developmental pattern through the globular-, heart-, and torpedo-shaped stages. Secondary somatic embryos occurred on the cotyledons and hypocotyls of primary embryos. Chemical names used: 2,4-dichlorophenoxyacetic acid (2,4-D).

Open Access

The action of foliar-applied uniconazole, paclobutrazol, dikegulac-sodium, ancymidol, 6-BA, GA4+7, and 6-BA + GA4+7 On container–grown Photinia × fraseri was studied over a one year period. Vegetative growth habit was evaluated at three month intervals. Shoot dry weight and histological examination of stern anatomy in the apical meristematic region was conducted at experiment termination.

Several plant growth regulators, primarily uniconazole, 6-BA, 6-BA + GA4+7, and dikegulac-sodium, stimulated lateral branching. Linear increases in lateral branching occurred as application rates increased. High application rates of uniconazole and paclobutrazol created an asymmetrical growth habit and decreased dry weight accumulation.

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We thank Dr. T. Niki, Associate Professor, Takushoku Univ., Tokyo, for his valuable advise on the method of histological observation for thin sections. We also thank Dr. B. Leckett, Quanta Vision, Canada, and Mr. J. Lawn, Macquarie Univ

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Authors: and

the Hawaiian Anthurium Industry Assn. We thank D.G. Fisher for histological advice. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked

Free access

Abstract

Various histological criteria were employed in studying the chronological and morphological development of the apex of field-grown plants of Brassica oleracea var. italica, cv. ‘Coastal’. Time of differentiation was based on changes in the size and configuration of the apex. The earliest evidence of reproductive differentiation was 5 weeks after sowing or at the time of macroscopic appearance and unfolding of the eighth true leaf. First order floral stalks began to appear at 7 weeks or at the time of macroscopic appearance of the 14th true leaf. Thus, the time interval for the transition from a vegetative to a reproductive apex appears to be approximately 2 weeks, under field conditions. By 9 weeks after sowing, or after the macroscopic appearance of the 22nd true leaf, second order floral stalk initiation and hence inflorescent head formation predominated.

Open Access

Abstract

Bush type snap beans (Phaseolus vulgaris L.) with resistance to the root-knot nematode, Meloidogyne incognita (cotton strain) are being developed by using PI-165426 as the resistant parent. PI-165426 (resistant), ‘Black Valentine’ (susceptible) and F5 breeding line B3864 (resistant) were inoculated with second-stage larvae. There were no significant differences in larval penetration of roots. Root tips showed slight swellings at infection loci of resistant and susceptible plants. Necrosis was evident in the resistant lines 4 days after inoculation. Histological studies of early infections showed that resistance was due to absence of adequate giant cell development and to hypersensitive reaction within the infected portion of the root. When soil temperature was changed from 16 to 28°C, galling, female development, and egg mass production in the resistant plants were increased.

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Authors: and

Abstract

Tomato seedlings of a selection from the plant introduction PI 244956 and the cultivar, ‘Floralou’, were grown for 5 weeks following cotyledon expansion under 2 different temperatures regimes, i.e., 42 to 56°F, and 68 to 80° and subsequently grown in the greenhouse at 68 to 80°. Plants of the PI selection grown at the 42 to 56° range as seedling bore more deformed fruits on the first and second clusters than those grown at 68 to 80°. The PI plants produced more deformed fruits in both temperature regimes than did ‘Floralou’ plants. Most fruits from ‘Floralou’ plants appeared normal regardless of seedling temperature. Flower buds from the first and second clusters of both warm and cold-treated plants were studied histologically. Buds with abnormal ovary development exhibited breakdown of tissue at the stylar base. Ovaries of such buds developed into abnormal fruits that were not marketable.

Open Access

Two studies were conducted to test the effects of various tissue culture media on somatic embryogenesis from cotyledon tissue of cucumber (Cucumis sativus L.). The two best media for embryo initiation were Murashige and Skoog (MS) salts and vitamins containing either 1 or 2 mg 2,4-D/liter and 0.5 mg kinetin/liter. In the second study, embryos developed more normally. More plantlets developed when tissue was removed from the initiation medium after 3 weeks and transferred to MS containing 1 mg NAA/liter and 0.5 mg kinetin/liter for 3 weeks, rather than leaving the embryos on a medium containing 2,4-D. Histological evidence indicated that the embryos were multicellular in origin. Charcoal in the maturation medium inhibited embryo development. Chemical names used: (2,4-dichlorophenoxy) -acetic acid (2,4-D); N-(2-furanylmethyl)-lH-purine-6-amine (kinetin); 1-naphthaleneacetic acid (NAA).

Free access

Abstract

Callus tissue of ‘Seyval’ (Seyve-Villard 5-276) (Vitis sp.), a French hybrid grape, formed adventitious embryos when transferred from a medium with 2,4-dichlorophenoxyacetic acid (2,4-D) to a medium containing 1-napthaleneacetic acid (NAA). Embryos began to turn green and develop into apparently normal vines when placed on a medium free of hormones and vitamins in the light. Histological evidence indicated that plants derived from callus originated from embryo-like structures and not from plantlets or excised buds. Secondary embryoids formed on primary embryoids, and tertiary embryoids occasionally formed on secondary embryoids. More than 50 vines and several hundred adventitious embryoids were obtained from approximately one cubic centimeter of callus.

Open Access

Abstract

Continuous gamma irradiation during polyembryogenesis was tested to determine if the number of embryos could be reduced in ‘Marukinkan’ (Fortunella japonica Swingle), a polyembryonic Citrus relative, and effectively increase the number of F1 hybrids in crosses. The number of embryos in untreated plants was 10.9, and this number was reduced with increasing exposure rate to 2.4 at 500R/day. The percentage of monoembryonic seeds in untreated plants was 1.1, and this was raised with increasing exposure rate to 34.0% at 500R/day. Cytological and histological observations of polyembryogenesis showed that early adventive embryonic cell divisions were retarded severely by gamma-rays (500R/day), and most of them could not develop beyond the stage of small globular proembryos consisting of 1 to 4 cells. These proembryos finally disappeared, but the fertilized embryo generally survived, probably because of a division earlier than those of adventive embryos and a vigor afforded to fertilized cells.

Open Access