Cyanide Inhibition of Phloem Transport along the Stolon of Saxifraga sarmentosa L

Long thin stolons of Saxifraga were treated with cyanide inboth the solution and gaseous forms; the latter was much moreeffective. Cyanide strongly inhibited the transport of ¹³⁷Csand of natural ¹⁴C-assimilates. As judged by a variety of approaches,including the use of ¹⁴C-cyanide, the inhibition was certainlyeffective in the sieve tubes themselves. Callose formation didnot seem to be promoted. The inhibition was completely reversible,and was never accompanied by a build-up of tracer in, or before,the treated zone; failure to traverse it was not due thereforeto membrane damage and consequent leakage. For these reasonsthe results are held to favour a mechanism of mass flow invokingactive pumping in the sieve tubes.     

Development of the Sieve Plate in Saxifraga sarmentosa L.

The differentiating sieve plate in the phloem of the stolonof Saxifraga sarmentosa L. was studied with the electron microscope.Development of the pore site begins with differentiation ofa pair of collar-like areas around the plasmodesma which canbe seen in the youngest identifiable sieve plates. Further growthof the collars occurs by deposition of an amorphous substance,presumably caflose. Although the growth of the collars is simultaneouswith the growth of the surrounding cell wall it is rapid atfirst and the pore sites appear asdome-shaped protuberances.It also involves deposition of callose over an increasinglywider area of the cell wall and since the thickening of thenormal cell wall continues only where notcovered by callose,the collars assume a conical form. There seems to be no displacementor lysis of normal cell wall material during growth of the collars.Eventually the growth of the cell wall in thickness overtakesthe pore sites so that when the growth of the cell wall is completethe pore sites appear as depressions in the sieve plate. Theperforation of a pore site is accomplished by widening of theplasmodesmatal cylinder which begins at the middle lamella byremoval of callose. Endoplasmic reticulum is found in closeproximity to the plasmodesma andis believed to penetrate it.     

The Effect of Inhibitors on Callose Formation in the Sieve Tubes of Saxifraga sarmentosa L.

Electron-microscope studies on stolons undergoing transportinhibition under nitrogen, HCN, and DNP treatment show no evidenceof callose-blockage of the sieve plates. Inhibition must thereforebe interpreted in terms of interruption of the sieve-tube energysupply; this weights the evidence in favour of theories of activemass flow such as those invoking electro-osmosis or proteincontractility.     

The effect of low temperatures on the phloem transport of radioactive assimilates in the stolon of Saxifraga sarmentosa L.

Abstract. The movement of naturally assimilated ¹⁴C down the stolon of Saxifraga sarmentosa under the influence of localized cold treatments (0°-10°C) applied over lengths up to 10 cm was followed by finding the distribution of tracer at the termination of the experiment. Inhibition is slight at 10°C and very considerable at 0°C. It is very dependent on the length treated, but is definite even when this is only 0.8 cm. Cooling the daughter plantlet to 0°C has a smaller inhibitory effect than might be expected. This is difficult to understand if 'unloading' is metabolic; perhaps the concentration free energy of the sucrose or other solute can be utilized in the sink terminals on the lines of the chemi-osmotic hypothesis. If so the same source of non-respiratory free energy might be available to energize an active sieve-tube mechanism in mid-path chilling experiments.     

The influence of dinitrophenol on phloem transport along the stolon of Saxifraga sarmentosa

Summary Dinitrophenol in concentrations of 5×10^-3 M applied to the centre 30 cm of 60–70 cm stolons of Saxifraga produces a strong and reversible inhibition of the phloem transport of ¹³⁷Cs or ¹⁴C-assimilates. There is every reason to believe that this effect is localised in the sieve tubes; callose formation does not occur. This evidence is very difficult to reconcile with the Münch hypothesis; it seems on the contrary to demand a theory of active pumping.This work formed part of that submitted for the degree of Ph.D. of London University.     

Unidirectional movement of tracers along the stolon of Saxifraga sarmentosa

Summary When radioactive tracer is applied locally to the stolon of Saxifraga its long-distance movement after 18 hours is found to be strongly polarised; there is in addition a short-distance movement which is unpolarised. With caesium, the long-distance movement is predominantly in the phloem; with strontium in the xylem. These interpretations, a priori probable, were confirmed by artifically reversing, separately, the xylem and the phloem currents. With long pieces of excised stolon only the unpolarised short-distance movement is observed. These results constitute evidence against simultaneous bidirectional translocation in the same sieve tube, and are consistent with either the Münch or the electro-osmotic theory.     

Movement of [14C]sucrose along the stolon of Saxifraga sarmentosa

Summary The characteristics of ¹³⁷Cs transport along the stolon of Saxifraga previously reported have been confirmed for applied sucrose and natural assimilate. Long-distance transport is strictly unidirectional, with a symmetrical short-distance spread from the point of application. Only the latter takes place in a long piece of excised stolon. Transport is readily reversed when the parent plant is darkened and the daugther, plantlet allowed to photosynthesise. These findings strongly support a mass-flow mechanism for the stolon. They also confirm the value of ¹³⁷Cs as a tracer for assimilate movement, though in contrast to assimilate it suffers appreciable lateral leakage. Pulse labelling of the subtending leaf failed to produce a sharp peak of activity in the stolon. A flattening with time of the ¹⁴C profile is considered to be due to differing linear velocities in parallel sieve tubes.This work formed part of that submitted for the degree, of Ph. D. of the University of London.     

Zur Cytotaxonomie der Gattung Saxifraga L.

Im Zuge unserer cytotaxonomischen Untersuchung der Gattung SaxifragaL. werden Sippen der S. exarata-moschata-Gruppe untersucht. S. exarata ssp. exarata aus den Seealpen ist diploid mit 2n = 20. S. exarata ssp. leucantha (Thomas) Br.-Bl. aus dem Unterwallis (Vernayaz) ist tetraploid mit 2n = etwa 48 bis 52 und gehört unseres Erachtens zu den intermediären Formen zwischen S. exarata und S. moschata. Für S. moschata liegen weitere Zahlenangaben aus den Alpen und den benachbarten Gebirgen vor: 2n = 26 (Allgäu, ötztaler Alpen, Waadtländer Alpen), 2n = 24 (ötztaler Alpen, Hohe Tatra), 2n = 32, 34, 36 (Kantabrien). Intermediäre Formen zwischen S. exarata und S. moschata mit 2n = etwa 48 bis 52 wurden im Wallis, Zentralalpen, untersucht. Bei zwei Pflanzen einer Population oberhalb Saas-Fee wurden 2n = 48 bzw. 2n = 52 Chromosomen gefunden. Diploide und tetraploide Pflanzen lassen sich nur nach der Pollengröße unterscheiden (2x = 20 bis 22 ?; 4 × = 22 bis 24 ?). Neben einer Punktkarte der Verbreitung fast aller bis jetzt cytologisch untersuchten Sippen im Alpengebiet werden Chromosomenbilder, Blattumrisse mit den jeweiligen Behaarungstypen und Ausbildung der Nervatur gebracht.     

Saxifraga rivularis L. on Beinn Eighe

Summary

A new locality for Saxifraga rivularis is described from Beinn Eighe, Wester Ross. Species lists from the site and from two nearby sites are compared in relation to soil analyses.     

Reproduction of the rare monocarpic species Saxifraga mutata L.

The aim of the study is to investigate the impact of reproduction and genetic variation on the persistence of populations of the prealpine, monocarpic Saxifraga mutata L. The species grows on erosion slopes or rocks, and its local populations are often small and isolated. Crossing experiments resulted in better seed-set than selfing, but both yielded viable seeds. Agamospermy did not occur. In an early-successional species like S. mutata , successful selfing is important in the colonization of new habitats. Flowers of S. mutata were visited by Syrphidae and unspecialized Hymenoptera. A germination rate of 40% was reached in cultivation after 20 weeks but germination continued until the end of the experiment after 92 weeks. Seeds stored dry for 30 months at room temperature mostly lost their germinability. In natural habitats, seedlings were found almost throughout the year with a peak in spring. Suitable safe sites were small patches of open soil, bare marl on erosion slopes, and rock crevices. AU individuals investigated were diploid with 2n = 26. Allozyme electrophoresis showed a lack of segregation within the populations. Intra- and interpopulation genetic variation was low. These results were in partial disagreement with theoretical expectations in a mixed mating species. It is concluded that demographic rather than genetic processes are the main cause of extinction of populations of S. mutata , at least in the short-term.     

A Study on the Genus Saxifraga L. from China

This paper presents a system of the genus Saxifraga L. from China, recognizes 2 subgenera, 8 sections, 7 subsections (including 1 new subsection), 31 series (including 23 new series), 4 subseries (new subseries) and 203 species (including 2 new species and 4 new varieties). The new taxa, statuses, combinations and names in this paper are as follows: Sect. Biro- stres (Gornall) C. Y. Wu et J. T. Pan, stat. nov.,; Sect. Punctatae (Engl.) J. T. Pan, stat. nov.; Ser. Rufescentes J. T. Pan, ser. nov.; Saxifraga lonshengensis J. T. Pan, sp. nov.; S. rufescens Balf. f. var. uninervata J. T. Pan, var. nov.; S. rufescens Balf. f. var. flabellifolia C. Y. Wu et J. T. Pan, nom. nov.; Ser. Stonoliferae J. T. Pan, ser. nov.; Ser. Stellariifoliae (Engl. et Irmsch.) J. T. Pan, stat. nov.; Subser. Aristulatae J. T. Pan, subser. nov.; Subser. Montanae J. T. Pan, subser, nov.; Saxifraga ciliatopetata (Engl. et Irmsch.) J. T. Pan var. ciliata J. T. Pan, var. nov.; Subser. Gonggashanenses J. T. Pan, subser, nov.; Subser. Car- diophyllae J. T. Pan, subser. nov.; Saxifraga egregia Engl. var. xiaojinensis J. T. Pan, var. nov.; Ser. Caveanae J. T. Pan, ser. nov.; Ser. Heterocladoideae J. T. Pan, ser. nov.; Ser. Chumbienses J. T. Pan, ser. nov.; Ser. Bulleyanae J. T. Pan, ser. nov.; Ser. Brachypodae C. Y. Wu et J. T. Pan, ser. nov.; Ser. Erinaceae J. T. Pan, ser. nov.; Saxifraga substrigosa J. T. Pan var. gemmifera J. T. Pan, var. nov.; Ser. Umbellulatae J. T. Pan, ser. nov; Ser. Yu- shuenses J. T. Pan, ser. nov.; Ser. Ungviculatae J. T. Pan, Ser. nov.; Ser. Punctu- latae J. T. Pan, ser. nov.; Ser. Candelabriformes J. T. Pan, ser. nov.; Ser. Tanguti- cae J. T. Pan, ser. nov.; Saxifraga tangutica Engl. var. platyphylla (H. Smith) J. T. Pan, comb. nov.; Ser. Yaluzangbuenses J. T. Pan, ser. nov.; Ser. Jainzhuglaenses J. T. Pan, ser. nov.; Saxifraga jainzhulaensis J. T. Pan, sp. nov.; Ser. Jacquemontianae J. T. Pan, ser. nov.; Ser. Nanae J. T. Pan, ser. nov.; Subsect. Microgynae J. T. Pan, subsect. nov.; Ser. Nangxi- anenses J. T. Pan, ser. nov.; Ser. Mucronulatae J. T. Pan, ser. nov.; Ser. Parkaenses J.T. Pan, ser. nov.; Ser. Deqenenses J. T. Pan, ser. nov.; Saxifraga mucronulatoides J. T. Pan, nom. nov.     

On the gynodioecious polymorphism in Saxifraga granulata L. (Saxifragaceae)

Sexual and vegetative fitness components in hermaphrodite and female plants of the self-compatible, perennial herb Saxifraga granulata are compared using material derived from a gynodioecious population in northern England.
Females produced only 57% as many seeds as hermaphrodites, but their ovule offspring were 1.28 times as fit as those of hermaphrodites, and females were more vegetatively vigorous. The advantages to females in ovule offspring quality and in vegetative reproduction counteract their disadvantages in pollen and seed production and therefore probably play a role in the maintenance of the gynodioecious polymorphism. Pollination ecology, resource reallocation and inbreeding depression all appear to contribute to the observed sex differences in fitness.     

The Translocation of 14C-photosynthate in Pisum sativum L.

Short-term studies were undertaken of source and sink relationshipsin Pisum sativum, cultivar Orfac, plants grown in a controlledenvironment. ¹⁴C-distribution assays were conducted after 24or 48 h ¹⁴Cphotoassimilate translocation from a single leafsubtending either a vegetative or a reproductive node. The primaryallocation of ¹⁴C-assimilate was achieved within 24 h: therewas no significant secondary movement of ¹⁴C within the subsequent24 h. The pod was strongly but not exclusively dependent onthe subtending leaf. Out of the total ¹⁴C fixed by a leaf theproportion that was exported within 24 h was related to the¹⁴C-sink capacity of the pods. A rapid non-combustive ¹⁴C-assay method is described whereby¹⁴C-tissue fragments are rendered translucent prior to directscintillation counting of the sample. In terms of cpm per mgobtained the latter method was comparable to a wet combustionmethod adapted for insoluble ¹⁴C-tissue.     

An outline of a revised classification of Saxifraga L.

GORNALL, R. J., 1987. An outline of a revised classification of Saxifraga. A revised classification of Saxifraga is presented in which 15 sections, 19 subsections and 34 series are recognized. A total of 394 names are accounted for, including the following new taxa, combinations and names: series Hirculoideae (Engler & Irmscher) Gornall, stat. nov.; series Lychnitidae (Engler & Irmscher) Gornall, stat. nov.; series Nulanles (Engler & Irmscher) Gornall, stat. nov.; series Cinctae (H. Sm.) Gornall, stat. nov.; series Gemmiparae (Engler & Irmscher) Gornall, stat. nov.; series Spinulosae (C. B. Clarke) Gornall, stat. nov.; subsection Rosulares Gornall, nom. nov.; subsection Serpyllifoliae Gornall, subscct. nov.; subsection Hemisphaericae (Engler & Irmscher) Gornall, stat. nov.; section Merkianae (Engler & Irmscher) Gornall, stat. nov.; subsection Stellares (Engler & Irmscher) Gornall, stat. nov.; series Birostres Gornall, ser. nov.; series Melanocentrae (Engler & Irmscher) Gornall, stat. nov.; series Astasianlhes (Sternberg) Gornall, stat. nov.; subsection Micranthes (Haworth) Gornall, stat. nov.; series Aulaxis (Haworth) Gornall, stat. nov.; series Dermasea (Haworth) Gornall, stat. nov.; series Micranthes (Haworth) Gornall, stat. nov.; scries Aretioideae (Engler & Irmscher) Gornall, stat. nov.; series Juniperifoliae (Engler & Irmscher) Gornall, stat. nov.; series Lilacinae Gornall, ser. nov.; series Marginatae (Engler & Irmscher) Gornall, stat. nov.; series Squarrosae (Engler & Irmscher) Gornall, stat. nov.; series Rigidae (Engler & Irmscher) Gornall, stat. nov.; subsection Engleria (Siindermann) Gornall, stat. nov; series Subsessiliflorae Gornall, ser. nov.; series Oppositiofoliae (Hayek) Gornall, stat. nov.; series Tetrameridium (Engler) Gornall, stat. nov.; subsection Mutatae (Engler & Irmscher) Gornall, stat. nov.; subsection Florulentae (Engler & Irmscher) Gornall, stat. nov.; section Odontophyllae Gornall, sect, nov.; series Biternatae (Engler & Irmscher) Gornall, stat. nov.; subsection Triplinervium (Gaudin) Gornall, stat. nov.; series Arachnoideae (Engler & Irmscher) Gornall, stat. nov.; subsection Tridactylites (Haworth) Gornall, stat. nov.     

The effect of nitrogen on the movement of tracers down the stolon of Saxifraga sarmentosa,with some observations on the influence of light

Summary The movement of applied ¹³⁷Cs and of naturally-assimilated ¹⁴C down the long stolon of Saxifraga is strongly inhibited by confining a length of 10 to 30 cm of the stolon in an atmosphere of nitrogen. The inhibition is reversible, normal transport being restored after less then 4 h when the stolon is returned to air from 5 h in nitrogen. Callose formation does not seem to be involved. There is evidence that local darkness has a similar adverse effect on phloem transport.These findings are considered antagonistic to the pressure-flow hypothesis, but favourable to the active mass-flow theories.This work formed part of that submitted for the degree of Ph.D. of the University of London.     

A new endemic species of Saxifraga L. from Spain

A recently erected species of Saxifraga (section Porphyrion ) endemic to the Picos de Europa (Cordillera Cantábrica) is described and illustrated. S. felineri P. Vargas resembles S. aretioides and S. ferdinandi-coburgi , although the habit and leaf shape are the main characters which support its identity. The taxonomic relationships of the three species are discussed, as well as aspects of the distribution and ecology of S. felineri.     

Adaptation to variation in growing season length in arctic populations of Saxifraga oppositifolia L.

Summary

At high latitudes Saxifraga oppositifolia exists with distinct ecotypes adapted to differences in growing season length. In areas with late snow-lie and cold, wet soils increased metabolic rates and rapid shoot production compensate for ultra-short growing seasons but do not conserve carbohydrate or water for adverse periods. An opposing strategy is evident in ecotypes living in sites with an earlier resumption of growth where soils are warmer and drier and the growing season longer. Here metabolic rates are lower and result in a greater ability to conserve both carbohydrate and water. The existence of opposing strategies for survival in warm and cold habitats, suggests that even in the minimal thermal conditions of the high Arctic a high degree of biodiversity gives the species as a whole a wide ecological amplitude. This degree of diversity not only increases the sites in which the species can survive but confers an ability to adapt to climate change by changing ecotype frequencies to accommodate climatic fluctuations. This facility may have contributed to the survival of populations of this and other species in the high Arctic during the Weichselian glaciation.