摘要:

SUMMARYThe stomatal types of most Icacinaceous genera (28) outside Malesia are reported for a limited number of species. In addition to the stomatal types recognized in Malesian Icacinaceae in an earlier paper, complex cyclocytic stomata are recorded in some genera, notablyLeretia, for the first time. A fairly comprehensive survey of the genusCitronellaindicates some trends of differentiation between the Asiatic and Pacific species and the American and Australian species. The results are further discussed with reference to previous hypotheses on level of specialization and stomatal types.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00936.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYPollen tubes from germinatedPetuniapollen were prepared in different ways for electron microscopic investigation of their walls. The ultrastructural features of the tube walls depend strongly on the preparation methods used. The tube wall was found to be composed of two layers or appeared striated after fixation with KMnO4and OsO4, respectively. After freeze‐etching the tube wall is twice as thick as after chemical fixation and a fine striation is visible. Subsequent extractions dissolve the matrix substances and a network of microfibrils is left, which is not composed of lamella

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00937.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe residues of Golgi vesicles and tube walls from germinatingPetuniapollen were studied by application of the X‐ray diffraction technique after different chemical treatments. In the Golgi vesicles as well as in the tube walls the presence of a cellulose component was demonstrated. This result led to the assumption that the machinery for cellulose synthesis is already present in the Golgi vesicle

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00938.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe radially‐running intercellular spaces in ray parenchyma of adult xylem ofPicea abieswere studied with the light microscope and with the scanning electron microscope. Special attention was paid to radial continuity and dimensions of these channels, and also to the blind pits in the parenchymatous cell walls opposite these intercellular spaces. In locally very thick‐walled ray parenchyma, an aberrant type of blind pitting seems to oc

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00939.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYMeasurements were made at eighteen sites within a beechwood on a calm, uniformly overcast day in August, 1971. The sites varied in total incoming radiation (visible plus infra‐red), being placed at various points on a light gradient from a clearing to deep canopy shade. Readings of spectral intensity were recorded from 380 nm to 1100 nm both inside and outside the wood. Transmission curves were then plotted for all sites. These showed a relative increase in transmission in the green (550 nm) and far red/near infra‐red (beyond 700 nm) wavebands. When normalised, the transmission increment beyond 700 nm was shown to vary between sites, becoming less marked as total incoming radiation increa

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00940.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYTwo not previously recorded Belgian indigenes, viz.F. arnoldiiRuth. andF. monguilloniiThér., and one new Dutch one are reported. It is pointed out how these species can be distinguished from those species with which they are most likely to be confused. It is also indicated in what kind of habitat they are to be expected

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00941.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYTypological and ecological considerations point to the homology of the outer integument of the bitegmic chlamydospermous and angiospermous ovules with the single integument of the “lower” cycadophytic Gymnosperms. The inner integument either originatedde novoor developed out of an accessory organ of the ovule (for which the membranous extension of the macrosporangial = nucellar wall already forming the primary pollen chamber in pteridospermous presemina comes to mind). Arguments are adduced in favour of the second alternative, but either interpretation implies that the outer and the inner integuments are inhomolog

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00942.x

年代:1974

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00943.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYIn the present study a verification is undertaken of the research published so far on the formation of root nodules in alder plants (Alnus glutinosa(L.) Vill.) as a result of a symbiosis between the host plant and an endophyte, probably an actinomycete. After a brief discussion of the growth of the endophyte within the cortex of the host root and of the morphogenesis of root nodules, the hypothesis to the effect that a root nodule is a modified lateral root was tested. This possibility had to be rejected and the conclusion was drawn that root nodules appear adventitiously in‐between the normal points of lateral root production. As, from an anatomical point of view, a nodule shows a great deal of resemblance to a lateral root, the hypothesis was formulated that root nodules are adventitious lateral roots – induced by an endophyte – which develop into nodules following the penetration of their cortex by the endophyte. In order to imitate and study the reactions in the host plant set in motion by the endophyte, phytohormones were administered to whole plants as well as to explants of roots. Use was made of kinetin and the following auxins: indole‐3‐acetic acid (IAA), indole‐butyric acid (IBA), naphtalene‐acetic acid (NAA), and 2,4‐dichlorophenoxy‐acetic acid (2,4‐D). The auxins and the mixture of 2,4‐D and kinetin produced an induction of primordia; by means of IBA, moreover, a slight increase in the number of nodules in the inoculation experiments was obtained. Finally, some experiments with tetrazolium salts were undertaken in order to ascertain whether the reducing conditions which are essential for the reduction of atmospheric nitrogen are already present in young nodules. Seventeen days after the inoculation a reduction of tetrazolium could be obs

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00944.x

年代:1974

数据来源: WILEY

摘要:

SUMMARYTwo labelled amino acids (1 ml, 0.005 M), L‐α‐alanine and L‐α‐amino‐iso‐butyric acid were allowed to perfuse separately through isolated stem segments of about 12 cm length. After a rapidly increasing initial absorption a steady‐state absorption was established, from which for each amino acid the fractional rate of escape per unit stem length could be calculated (*K in mm−1). The values found could be confirmed by measuring the radioactivity in one‐cm pieces of the stem segment used. *K‐alanine was found to be about 8 × *K‐α‐amino‐iso‐butyric acid.Influences of transpiration and flow rate through the xylem vessels on the *K‐values could be demonstrated. A provisional model for amino acid absorption f

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1974.tb00945.x

年代:1974

数据来源: WILEY