摘要:

AbstractBRIGGS, HOPE and ROBERTSON (1961) consider the uptake of electrolytes to be a combination of active and passive processes, causing simultaneous influx and efflux of salt ions.In this publication it has been shown, that inVallisnerialeaves the peripheral plasma membrane is non‐permeable to electrolytes. The continuation of this non‐permeability is essential for the efficiency of the active uptake process. The permeability of the membrane is increased by manipulation of the leaves and by changes in the ionic composition of the external solution. A consequence of the non‐permeability of the plasma membrane to electrolytes is the active uptake of ion pairs. Ion exchange between plasma and external medium is not involved in active uptake processes of resistant plants. The validity of these principles for active uptake of cations as well as for anions is treated in the discu

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00137.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00138.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractTo study the immigration and spreading of the beech(Fagus sylvaticaL.) in the Netherlands during the young Holocene, three peat bogs were palynologically investigated in the eastern Netherlands and in the adjacent German area. For this purpose peat samples have been collected in the Korenburgerveen near Winterswijk, in a peat bog near Burlo (Germany) and in the Aamsveen south‐east of Enschede. The analysis of the peat‐samples proved, that extensive beech‐forests existed in subatlantic times in the subcentreuropean flora district of the Netherlands. This is shown in the comparatively high Fagus‐percentages in the pollen

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00139.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractAlter young inflorescent stalks of intact, actively transpiringYucca flaccidaHaw. plants were wounded an exudate was obtained. Its flow continued for several weeks provided there was regular re‐wounding.The exudate had a pH of 8.0–8.2 and contained about 18 per cent of total solids. Of these, sucrose constituted about 80–90 per cent. Glucose and fructose were minor constituents. The amino acid concentration was as high as 0.07 molar. Glutamine appeared to be the main nitrogenous constituent.The exudate only contained small amounts of inorganic solutes of which potassium was the main kation. The calcium content was relatively low.There appeared to be a great similarity between this phenomenon of bleeding and the composition of the exudate and that observed by one of the authors (P.M.L.T.) in previous years in several palm species.Various arguments are adduced in favour of the view that the exudate has a phloem o

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00140.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractFollowing the feeding of 14C02to a mature leaf ofYucca flaccida Haw. a number of exudate fractions were collected from a bleeding inflorescence Stalk.The maximum amount of activity was collected on the third day after the application of the 14C02. In all the exudate fractions sucrose contained about 90 per cent of the radioactivity present.The 14C‐content of the exudate exhibited a pronounced daily rhythm. The fractions which exuded during the night contained concentrations about four times those of the exudates collected during the hours of daylight. In contrast, the total dry substances and total sugar contents only showed slight daily variations. Apparently the various leaves or other parts of the plant contribute with slightly different rhythms to the solutes of the exudat

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00141.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract1Roots ofVicia faba, on the horizontal clinostat revolving at velocities of 1 revolution per hour and 1 revolution per 2 hours, grew faster than vertical roots.2When roots were placed in a horizontal position at rest the upper side grew faster than vertical roots during the first hour. The growth rate of the lower side was not significantly different from the growth of vertical roots during the first hour. After that period the growth of the lower side decreased markedly.3It is suggested that the growth‐increase of roots on the horizontal clinostat is caused by the fact that each root cell is at the upper side for a sufficiently long time to react with accelerated growth, but that this period is too short to inhibit the growth of the root cells when these are at the lower sid

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00142.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract1The ovules of all gymnospermous groups are essentially bitegmic.2The two integuments of the angiospermous ovule are the homologues of the two ovular coats of a gymnospermous prototype.3The cupule, a characteristic organ of pteridospermous and lower cycadopsid groups, is also represented by homologous structures in bennettitalean, chlamydospermous and angiospermous forms.4In the Higher Cycadopsida (including the Angiosperms) the homologue of the cupule is almost invariably one‐ovuled, which is the result of a progressive oligomerisation of the number of ovules during its evolution from a primitive pluri‐ovulate pteridospermous archetype.5Derivatives of the cupule in the Higher Cycadopsida include the interovular scales of cycadeoid groups, the chlamys of gnetalean forms and the true aril of the angiospermous ovule, but more important from a phylogenetic point of view is that in a number of angiospermous taxa the cupule homologue constitutes the outer wall (or at least a substantial part of the outer wall) of the ovuliferous gynoecial structure,i.e., of a pistil or ‘ovary’, or of an element of a phalangiate gynoecium.6The homology of some traditional angiospermous ‘pistils’ with a cupulate (chlamydote, arillate) ovule sheds light on the phylogenetic relationships between plants at a gymnospermous (chlamydospermous‐bennettitalean) evolutionary level and a number of angiospermous forms, thus indicating that Angiosperms with carpellate gynoecia have attained a higher level of organisation and are derived from archetypes with primitive ecarpellate female genitalia.7From a discussion of the structure and vascularisation of the primitive angiospermous pistil of the cupulate ovule type the conclusion is drawn that the persuance of the interpretative floral morphology of one‐ovuled pistils by means of anatomical studie

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00143.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe respiratory increase observed in potato‐tuber tissue after infection withGibberella saubinetiimight be related to the synthesis of proteins in the host. Therefore the alcohol‐soluble and ‐insoluble N‐fractions have been determined in non‐infected and infected tuber halves in samples cut at various distances from the surface. Samples were cut starting from the surface. Consequently the samples at 0‐0.5 mm from the surface contained mycelium of the invading parasite; the other samples were mycelium‐free.In the samples at 0‐0.5 mm from the surface of the infected halves, and to a lesser extent in the corresponding samples of the non‐infected halves the alcohol‐insoluble N increased while the alcohol‐soluble N decreased. The total N‐content was unchanged. Apart from a wound‐reaction which may have occurred during the incubation period due to the cutting of the tubers into two halves before inoculation of one half, it is most likely that the shift in the ratio insoluble N/soluble N of the samples at 0‐0.5 mm from the infected surface is the consequence of the presence of mycelium in the tissue disks.As no change in soluble N and insoluble N could be demonstrated in the samples cut at 0.5 mm or more from the surface, no evidence has been obtained for a parallel behaviour of the respiration rate and the synthesis of insoluble nitrogenous compounds in the host tissue after infection. The possibility that synthesis and breakdown of proteins occurred simultaneously without any change in the total amount

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00144.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00145.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1964.tb00146.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY