摘要:

SUMMARYIn the laboratory flat forms of theLemna gibba/Lemna minorcomplex which are potentially gibbous, swell up in the presence of extremely low concentrations of ethylene (from 24 nl/l air upwards). In control cultures, where the ethylene concentration is 16 nl/l air or lower, the plants remain flat. In ditches in the Netherlands ethylene concentrations occur which are in the same range as the concentrations which induce gibbosity in the laboratory. These are further indications that ethylene is the gibbosity regulator of theLemna gibba/Lemna minorcomplex in natural waters.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01199.x

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe inner and outer integuments ofErythroxylum cocaare both of dermal derivation. The outer integument is initially 3 cells and later 3–5 cells thick. The inner integument is at first 3 cells thick to become multiplicative and ultimately about 20 cells thick and thus forming the greater part of the mass of the seed. The inner layer is developed as an endothelium. The nucellus is oblong by mitotic activity in the part beneath the embryo sac. The testa and tegmen are crushed with the exception of the fibrous exotegmen. The flattened cells of the inner layer contain tannin. The relationship between Erythroxylaceae and Linaceae is discusse

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01200.x

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe ultrastructure and histochemistry of the developing spinach ovule have been examined. The development and differentiation of the integuments, nucellus and female gametophyte results in an ortho‐amphitropous organisation of the ovule. In the nucellus four parts can be distinguished: the conductive part, the original chalazal part, the chalazal proliferating part and the laterial part. The cells of the various parts have common features as well as distinguishing characteristics related to their position and function. The inner and outer integuments show different features during their development. In the outer integument 3–5 cell layers develop, but the inner integument shows a development of two differing cell layers. Contact by plasmodesmata between the two cell layers diminishes and stops at maturity. The localization of different reserve substances (starch, other polysaccharides, proteins, lipids) have been studied in the developing ovules to determine the nutritional supply of the embryo sac and embryo. Extensive changes in the amount of reserve substances have been observed in the ovule right up to maturity of the embryo sac. In the outer integument storage of starch increases much up to maturity and after fertilization a gradual decrease occurs. The storage and transfer function of some cell types in relation to the nutrition of the embryo sac and embryo is discussed. The presence and location of polysaccharides during megasporogenesis and megagametogenesis is considered. Finally, the possible pathway of metabolites in spinach during different phases of the developing ovule is discus

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01201.x

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe papillar cells of the stigmas ofSecale cerealeandHordeum bulbosumshow characteristics suggesting specialisation for both external and internal secretion. Each papilla terminates in a reflexed pollen‐receptive tip bearing a proteinaceous surface pellicle overlying a thin mucilaginous layer, which in turn adjoins the markedly discontinuous cuticle. The basal part of each papilla contributes to the axis of a secondary stigma branch. A distinct layer of the papilla wall underlaying the cuticle is continuous with interstitial material in the axis of the branch. This material, which forms the pollen‐tube transmitting medium, is constituted principally of acidic pectic polysaccharides, but contains a protein component, seemingly an internal secretory product of the basal parts of the branch cells. The papillar cells are bounded by a further distinctive wall layer. This is PAS reactive, stains with phosphotungstic acid‐HCl, and also with the fluorescent polysaccharide stain, calcofluor white, which has been considered to have affinity with 1,4‐linked glucans. The layer shows no evidence of a microfibrillar structure, however, and is not birefringent.Dictyosomes are present during the final maturation of the stigma papillae, but they show no special evidence of secretory activity. On the other hand, paramural bodies are frequent in the papillar cells, and in the branch axes they are usually associated with vesicle swarms in the adjacent intercellular spaces. It seems likely that the paramural bodies form a granulocrine secretory system producing both the surface secretions of the papillae and the protein‐polysaccharide constituents of the intercellular spaces in the branch axes.The paper is the first of two; the second will be concerned with the responses of the stigma to po

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01202.x

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe interaction of crown gall provokingAgrobacterium tumefaciensstrains and Ti plasmids isolated from them, with pollen grains fromPetunia hybridaas well as other haploid cells from this plant have been investigated. Octopine and nopaline synthesis were used as indication of transformation. Tumours could be induced in all ploidy levels (2n, 3n, 4n) of vegetativeP. hybridatissue including haploid (n), but not in pollen grains.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01203.x

年代:1980

数据来源: WILEY

摘要:

SUMMARYThe vegetation history of S.W. Connemara was reconstructed on the basis of the available palynological and palaeobotanical data of the region. In the Pre‐Boreal Period birch forests replaced the late‐glacial tundra‐like vegetation. In the early Boreal Period hazel immigrated and the eutraphent water plant communities reached their optimum. After that thermophilous deciduous forests gradually crowded out the birch woods and reached their optimum in the Atlantic Period. The lakes were increasingly filled with peat, the eutraphent character of the marsh vegetation weakened and ombrogenous bog communities spread across the region. Shortly before the Sub‐Boreal Period the first indications of human interference in the forests were detectable. During the Sub‐Boreal and Sub‐Atlantic Periods the forest area was reduced gradually as a result of human activities and the spreading of the bogs. A more or less complete forest clearance took place in the last tho

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01204.x

年代:1980

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01205.x

年代:1980

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01206.x

年代:1980

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01207.x

年代:1980

数据来源: WILEY

摘要:

C.vandenHoekand H. M. Jahns:Algen. Einführung in die Phykologie. Georg Thieme Verlag, Stuttgart. 1978. X + 481 pp., 136 figures, 7 tables. Price DM 26.80

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1980.tb01209.x

年代:1980

数据来源: WILEY