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Proteins obtained from seedling shoots and floral meristems of Sorghum bicolor (L.) Moench cv. NK 1210 induced mycelial growth in the smut fungus, Sporisorium reilianum in vitro. Proteins precipitated with trichloroacetic acid and ammonium sulfate were equally effective as inducers, although there were minor variations in the pattern of mycelial growth. Hydrolysis of the protein fraction with the proteolytic enzyme pronase E resulted in considerable reduction in the proteins' ability to induce mycelial growth. Digestion of the protein fraction with driselase, resulted in a slight enhancement of biological activity. The results suggest that amino sugar moieties in glycoproteins may act as inducers of mycelial growth in Sporisorium reilianum. [ABSTRACT FROM AUTHOR]

Sporisorium reilianum, the fungus that causes sorghum head smut, was grown with sucrose, lactose, trehalose or raffinose in liquid suspension or on a solid medium. Liquid culture media were analyzed for hydrolysis products of these carbohydrates to determine extracellular enzyme activity of the fungus. Increased amounts of glucose and fructose in the culture medium of S. reilianum grown with sucrose or raffinose indicated that invertase (β-fructofuranosidase, 3.2.1.26) activity was present. No evidence of extracellular galactosidase or trehalase activity was found. Enhanced sporidial colony formation on carbohydrates that can be hydrolyzed to hexoses, and specific forms of mycelial growth on lactose, trehalose or on a carbohydrate-deficient medium might suggest that mycelial growth is a way of foraging for food sources. However, the rapid and profuse mycelial growth on the host cell wall glycoprotein appears to be in response to abundant food supply (probably of a different type). Therefore availability of different kinds of carbon sources in the environment of the growing fungus might determine dimorphism and associated pathogenesis by S. reilianum. [ABSTRACT FROM AUTHOR]

Histologic examination of shoot-tip explants, 1 wk after culture initiation on Murashige and Skoog medium with 2.5 mg/liter 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.05 mg/liter kinetin, reveals active meristematic centers inside cultured tissue. Clusters of cells in these meristematic centers exhibit remarkable resemblance to the initial three divisions in the zygotic embryo. Several such meristematic groups of cells are observed in the cultured explant at this stage. Embryogenesis is obviously initiated very early in this tissue in the presence of 2,4-D. A well-defined, white globular embryogenic callus develops in culture in about 4 wk, and it consists of clusters of embryoids with large cells characterized by thick cell walls, numerous lipoidal vesicles, and localized areas of carbohydrate storage. These cells resemble the scutellar tissue of the embryo. However, there are cells within this tissue that themselves appear embryogenic. They undergo cell division giving rise to small clusters of cells. As long as 2,4-D is present in the medium, the cells apparently retain the capacity to proliferate and to produce more cells capable of embryogenesis. Embryogenesis seems to occur via two processes, initiation of somatic embryos early in culture and secondary embryogensis from the scutellar tissue that forms in vitro. [ABSTRACT FROM AUTHOR]

Shoot tip cultures from 2- to 3-d-old seedlings of Sorghum bicolor (L.) Moench cv. IS3620C develop highly embryogenic callus from which plants can be regenerated when transferred to plant growth regulator-free medium. Isolated shoot tips were cultured on Murashige and Skoog medium supplemented with 2.5 mg/liter 2,4-dichloro-phenoxyacetic acid and 0.05 mg/liter kinetin. Purple pigmentation characteristic of sorghum cultures on growth regulator-free medium is virtually eliminated with the shoot tip culture. Embryogenic callus is white and hard with an undulating appearance but can be separated into multiple bipolar structures by application of gentle pressure. The well-developed embryos have a cup-shaped scutellum. These germinate like zygotic embryos and develop root-shoot axis. Lack of vascular connections to the parent tissue and the synchronous development of the plumule and radicle suggest that these embryos may be of unicellular origin. In contrast, when the entire seedling serves as the explant, all meristematic centers in the shoot, including the coleoptile sheath close to the apical meristem respond to plant growth regulators in the medium by callus formation. Upon subsequent reculture onto growth regulator-free medium several modes of development occur. The differential response of these tissues to identical culture conditions indicate the presence of different population of cells that respond differently to exogenous plant growth regulators. [ABSTRACT FROM AUTHOR]

A method of clonal propagation via somatic embryogenesis of date palm, cultivar Barhee, which has potential for large scale commercial application as well as for developmental studies on embryos is described. Cultures were initiated from shoot tip and immature inflorescence explants, both of which were capable of development into embryogenic callus. When the embryogenic callus was cultured in liquid suspension on a rotary shaker, hundreds of embryos developed from milligram quantities of callus in a fairly synchronous manner. Scanning electron microscopy showed globular, heart-shaped and torpedo-shaped embryos. Green leaves emerged from a white cotyledonary sheath. [ABSTRACT FROM AUTHOR]