摘要:

Floral buds of different sizes of the single-gene recessive mutant stamenless-2 (sl2/sl2) of tomato were treated with gibberellic acid (GA3) and the development of staminal features in each bud was followed. The results show that the application of GA3to buds with stamen primordia at the early stages of initiation (up to 0.1 mm in length) induced the formation of normal-looking stamens. However, with a progressive increase in stamen size, less and less of the normal stamen features were produced following the GA3treatment. Ultimately, buds with stamen primordia 0.8 mm long or longer failed to respond to GA3and produced all the mutant characteristics. These results are discussed in terms of Waddington's concept of “determination” and “canalisation” of development.

ISSN:0008-4026    

DOI:10.1139/b79-292

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Buds of intact plants ofVicia fabaL. are partially inhibited. Decapitation of the terminal bud of plants with four leaves leads to the reactivation of all the axillary buds, but to the growth of only the basal ones. The first events induced by the terminal bud excision do not occur at the level of the axillary buds, but affect rather the main axis.The kinetic study of the mitotic reactivation shows that the activation begins in cell layers of the cambial zone in the subapical internodes of the stem 1 h after decapitation and after 4 h in the more basal ones.The subapical axillary buds are first reactivated, but only temporarily, 8 h after the principal bud excision. The lower axillary buds are reactivated later, after 12 h, and their growth then becomes autonomous.These results are discussed with regard to the regulatory role of the main axis on axillary bud growth.

ISSN:0008-4026    

DOI:10.1139/b79-293

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Bothrodiscus obscura(Peck) comb.nov.,Hyalotiella americana(Speg.) comb.nov.,Mastigosporium graminum(Karst.) comb, nov., andPestalosphaeria austroamericanasp.nov. with aPestalotiopsisanamorph are described.

ISSN:0008-4026    

DOI:10.1139/b79-294

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Three pigmentation types (brown, red, and white) ofFusarium tricinctum(Corda) Sacc. were observed when an isolated mass culture from leaf spots on English ivy (Hedera helixL.) was single spored. Perithecia of the heterothallic fungusGibberella tricinctaEl-Gholl were produced at 20 and 27 °C on stem pieces ofCynodon dactylanPers. resting on water agar, under 12-h alternating light and dark when certain pigmentation types were paired. Pairing of red and brown pigmentation types yielded significantly (P < 0.05) more perithecia than red and white pairings at 20 and 27 °C. Perithecia were formed only in combinations of red with brown or white pigmentation types. In both sets of pairings, significantly (P < 0.05) more perithecia were produced at 27 than at 20 °C. No perithecia were formed in constant darkness. Occasionally, the red pigmentation type became white after subsequent transfers and never reverted to the red pigmentation on various media and failed to produce perithecia with any pigmentation type. Continuous darkness slightly favored red pigment formation over continuous light as detected by the Munsell color codes. Increasing temperatures from 20 to 32 °C decreased the colony growth diameter of the red-pigmented cultural type. At 32 °C a change in hue was noted with corresponding changes in color codes. Red mycelial pigmentation was intensified by the addition of copper, iron, manganese, and zinc to a basal medium. The addition of 0.1% yeast extract favored mycelial development and caused a more pronounced red mycelial pigmentation in the presence of heavy metals.

ISSN:0008-4026    

DOI:10.1139/b79-295

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Almost all ultrastructural studies of powdery-mildew fungi have been focused on the epiparasitic fungi. In this paper, one of the endoparasitic powdery-mildew fungi,Leveillula taurica(Lev.) Arn., on green pepper (Capsicum annuumL. var.angulosumMill.) leaves was investigated by light and electron microscopy. Most germinated conidia formed a lobed adhesion body (similar to the appressorium in morphology but different in function) before stomatal invasion. The track of the adhesion body on the leaf epidermis was depressed, and no cuticular perforations were observed in it. After stomatal invasion, infection hyphae grew extensively into the intercellular spaces of the leaves and formed haustoria in the spongy- and palisade-parenchyma cells. The haustorium was flask shaped with a neck arising from the intercellular hypha. The overall profiles of the haustorium resembled those of epiphytic powdery-mildew fungi of other authors; the haustorium was composed of a nucleate central body and many anucleate lobes, and the entire structure was bounded by an extrahaustorial membrane. Papillae consisting of three distinct regions formed against the outer cell walls at the site of penetration. The most obvious alteration in infected host cells was a marked increase in the number of large lipid bodies. Lipid bodies increased in number with time after haustorial formation. They appeared first in the host cytoplasm near the extrahaustorial membrane, then in the extrahaustorial matrix and haustorial body.

ISSN:0008-4026    

DOI:10.1139/b79-296

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Meiosis was examined in plasmodia of the protistPlasmodiophora brassicaewithin artificially inoculated cabbage roots, using light and electron microscopy. Meiotic nuclear divisions occur following the cessation of vegetative growth of the Plasmodium. Synaptonemal complexes develop in nuclei of the “akaryote stage,” which represents prophase I. Meiosis I and II take place concurrently with cleavage of the Plasmodium into resting sporangia. Previous reports of synaptonemal complexes and sporangiogenic meiosis in the Plasmodiophorales are thus corroborated. Centrioles are paired and bipolar until the end of meiosis I; then they separate and migrate to opposite poles, without replicating, between prophase II and metaphase II. Centrioles elongate considerably between prophase I and the end of meiosis II, then appear to disintegrate as uninucleate resting sporangia are formed and are absent from mature sporangia.

ISSN:0008-4026    

DOI:10.1139/b79-297

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Frequency and length of stomata of field-grown plants of 21Populusclones were studied. All clones except one were amphistomatous, and all clones had the greatest number of stomata per unit of leaf area on the abaxial surface. Variation in stomatal frequency, length, and relative distribution of stomata between abaxial and adaxial leaf surfaces among clones was found. Although differences in stomatal frequency and length were observed in some cases between early and late leaves of a clone, pore area differences were small because of the tendency for leaves with fewer stomata to have larger stomata. Cluster analysis utilizing abaxial and adaxial stomatal frequency and length as independent variables indicated that stomatal characteristics were related to parentage. Relationships between clonal stomatal characteristics and preliminary shoot dry weight data were not significant.

ISSN:0008-4026    

DOI:10.1139/b79-298

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

In anther culture ofSolatium surattense, the Murashige and Skoog's medium supplemented with 2,4-dichlorophenoxyacetic acid (2.2 mg/L), indoleacetic acid or naphthaleneacetic acid (1.9 mg/L), and kinetin (2.2 mg/L) served as “callus-producing medium.” Histological and cytological observations indicated that the callus originated from the pollen grains. Synergistic action of kinetin (5.0 mg/L) and coconut milk (15%) in basal medium was able to induce differentiation of shoot buds either from the anthers directly or from the callus. Directly differentiating buds were formed by whole shoot bud morphogenesis of pollen. They were produced at a low frequency and showed presence of well-developed radicular and plumular regions. But the buds originating from callus lacked radicular ends. Root initiation in such buds was achieved by transferring them to basal medium. Cytological examination of the androgenic plantlets revealed a chromosomal series ranging from the haploid to the hexaploid with a few aneuploids.

ISSN:0008-4026    

DOI:10.1139/b79-299

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Clubroot galls taken from 40-day-oldBrassica rapaL. var.glabraKitamura, grown in soil infested withPlasmodiophora brassicaeWor. were examined by scanning (SEM) and transmission (TEM) microscopy. SEM materials were prepared by freeze fracturing followed by ion etching. A thin layer enveloped the mass of sporangia which in etched specimens appeared to be embedded in a fibrillar net deposited among the sporangia. Both SEM and TEM micrographs revealed a circular germ pore (ca. 1 μm in diameter) with a thickened plug-like region in the pore orifice. The wall of the mature resting sporangium consisted of three layers W1, W2, and W3.

ISSN:0008-4026    

DOI:10.1139/b79-300

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Teliospore initials ofPuccinia podophyllidevelop from binucleate sporogenous cells lining the base of the telium. The teliospores are formed in basically the same fashion as those of other rusts that have been examined at the ultrastructural level. The long, straight or slightly curved spines present on mature teliospores initially develop as slight bulges or protrusions on the spore surface. The spore wall in such a region then evaginates to form a slender spine that is initially filled with cytoplasm. The cytoplasmic material is then progressively excluded from the tip of the spine as a result of the thickening of the spine wall. Mature teliospores ofP. podophyllipossess a wall consisting of a thick, outer, electron-dense layer in which stratification is only rarely visible and an inner thinner, less electron-dense layer.

ISSN:0008-4026    

DOI:10.1139/b79-301

出版商:NRC Research Press    

年代:1979

数据来源: NRC