摘要:

The various stages of female gametophyte development and embryogenesis inS. spiralisandS. aestivalisare described. In both species the reproductive cycle is sexual. Some peculiarities are present: the female gametophyte is usually 6-7-8-nucleate; after double fertilization a single endospermatic cell is formed; the proembryo appears differentiated and is made up of different cells in the chalazal and micropylar ends; a single basal cell in the proembryo acts as suspensor.

ISSN:0017-0070    

DOI:10.1080/11263508309427969

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The single integument of the anacampylotropous ovule ofPittosporum undulatumVent. (Pittosporaceae) has been investigated by light and electron microscopy. Three integumentary different regions have been detected: a peripheric layer, a parenchymatous outer region and an inner region. These may be distinguished in the medium antiraphe side on the basis of the cell shape, size and features. The cells of the peripheric layer facing the ovaric hollow appear different from the inner ones adjacent to the nucellar epidermis in their shape, for the thickness of their continuous cuticular layers and for the structure of the cell walls. The outer cells are also covered by an epicuticular layer and show the occurrence of plastids with starch grains, electron dense matrix and Light Stained Membranes. The same cells accumulate lipid bodies and a reserve of protein nature in cytoplasmic areas lacking ribosomes. The inner peripheric cells show thick inner periclinal walls characterized by a loose texture often containing flat sac-like structures. The outer integumentary region consists of parenchymatous cells with a high concentration of both carbohydrate and lipid bodies. On the other hand, the periclinally elongated cells which characterize the inner region show the ultrastructural features of scarcely differentiated cells. Such morphology of the tegumentary system has been also observed in anomalous ovules showing an arrested development of nucellus. They appear tenuinucellate and contain either a single megasporocyte or a linear tetrad of megaspores with an enlarged chalazal sporial cell.

ISSN:0017-0070    

DOI:10.1080/11263508309427970

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Different hydrolases were found to be present in the crude extract of dry de-embryonated wheat grains, including acid phosphatase. When the crude extract was chromatographed on a Wheat-Germ Agglutinin-Sepharose affinity column, an aliquot of acid phosphatase bound to the column and could be eluted specifically by N-acetyl-D-glucosamine solution. Some properties of the WGA-binding acid phosphatase (pH optimum, heat stability, Triton X-100 sensitivity, inhibition by some ions, molecular weight and Km) were studied. WGA appeared to have a stabilizing effect on the enzyme, while it was ineffective on the Km.

ISSN:0017-0070    

DOI:10.1080/11263508309427971

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Pisumseeds were soaked in water and in Cytochalasin B (CB) for 24 and 48 h, then left in the dark to germinate for 5 days. During this first phase of germination the ultrastructure of the cotyledonary cells was examined, seed respiration was measured, the contents of storage substances and acid phosphatase activity in the cotyledons and axes were separately evaluated. The ultrastructure of cotyledonary cells treated with CB appeared to be normal, thus indicating that the imbibition process was unaffected by CB. Respiration showed a similar pattern in all tested samples although its intensity was considerably lower in treated seeds. Treated axes and cotyledons, however, had a higher starch, soluble sugar and protein content but a lower acid phosphatase activity as compared to controls. These results suggest that the effects of CB on the rate of germination and cell wall extension, as reported in previous studies, may be due to an inhibitory effect of CB on mobilization and utilization of reserve substances.

ISSN:0017-0070    

DOI:10.1080/11263508309427972

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Qualitative and quantitative analysis of free and bound amino acids and amides during dormancy and the most important phases of the first cell cycle was carried out in tubers ofHelianthus tuberosus.

ISSN:0017-0070    

DOI:10.1080/11263508309427973

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The inhibition of growth by different concentration of eight heavy metals: Cd, Cr, Co, Cu, Hg, Ni, Se and Tl, in inorganic medium at pH 3 and 6.5, was studied in four green algae:Chlorella protothecoidesKrüger,Chlorella saccharophila(Krüger) Migula,Coenochlorissp. andStichococcus bacillarisNaegeli.

ISSN:0017-0070    

DOI:10.1080/11263508309427974

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The morphology of a new species ofPetalonemaBerk collected under a saxicolous habitat at 2900 m above sea level in the Singalila Range, Eastern Himalayas, during the Botanical Expedition of May 1974, was critically studied and named asPetalonema borziisp. nov. The same alga was collected again on 28 Nov. 1982 from the Singalila Range at an altitude of 2500 m above sea level.

ISSN:0017-0070    

DOI:10.1080/11263508309427975

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The distribution of macrophytic plant communities, defined by phytosociological numerical methods, in the irrigation system of the Lower river Po Plane was correlated with water characteristich. Water samples were collected periodically within phytocoena well-characterized from the phytosociological viewpoint. Nymphaeid-dominated communities (all.Nymphaeion) usually occur in deeper waters than elodeid- myriophyllid-, and ceratophyllid-dominated vegetation types (all.Potamogetonion). Hydrochemically, all of the studied waterbodies can be classified as rich in electrolytes and in bicarbonates. The distribution of phytocoena reflects a gradient in nutrient content: theNymphoidetum peltataecharacterizes waters moderately rich; theMyriophyllum spicatumcommunity and theTrapetum natantisfairly rich; thePotamogetonetum pectinatiand theCeratophyllum demersumcommunity very rich in nutrients.

ISSN:0017-0070    

DOI:10.1080/11263508309427976

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0017-0070    

DOI:10.1080/11263508309427977

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0017-0070    

DOI:10.1080/11263508309427968

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor