Experimental and Analytical Studies of Pteridophytes XXIV. Investigations on Marsilea: 4. ANATOMICAL EFFECTS OF CHANGES IN SUGAR CONCENTRATION

Sporelings of Marsilea, grown aseptically in various concentrationsof sugars, particularly glucose, have been investigated anatomically. It is shown that, corresponding to the features of the externalmorphology, the anatomy of the sporelings from the lower sugarconcentrations (1 and 2 per cent. glucose) has many characteristicsof the water forms of amphibious plants, while that of the sporelingsfrom the higher sugar concentrations (4 and 5 per cent, glucose)has the characteristics of typical land forms. A number of the differences between the two types of sporelingmay be referred to a change in the duration and direction ofcell-division in the rhizome-apex. Views as to the factors influencingthe origin of land or water forms are briefly discussed.     

Morphogenesis in Marsilea

An account is given of investigations on the development of sporelings of Marsilea using aseptic culture techniques. Special attention was paid to the heteroblastic leaf development and to the conditions leading to the origin of land or water forms. A study was made of the effects of changes in the composition and concentration of the culture medium. The substances tested included sugars, nitrogen compounds, metabolic inhibitors, auxins, gibberellic acid and kinetin.
It was concluded that the changes in leaf segmentation of Marsilea , or heteroplastic development, are correlated with changes in the size of the apical meristematic regions of the shoot, which in turn are influenced by the nutritional status of the plant. On the other hand, the differences between land and water forms are probably due to differences in the available concentration of dissolved carbohydrates in the growing parts. The results are discussed in relation to similar morphogenetic problems in other vascular plants.     

Experimental and Analytical Studies of Pteridophytes: XXVII. Investigations on Marsilea. 5. Cultural Conditions and Morphogenesis, with Special Reference to the Origin of Land and Water Forms

Experiments are described in which sporelings of Marsilea weregrown aseptically on media of similar nutrient value, but inwhich the osmotic concentration was changed by addition of mannitol,by alteration of the concentration of inorganic constituents,or by substitution of sucrose for glucose. Comparison is thenmade between the morphology of supported and submerged sporelings.Further experiments are described in which sporelings were transferredfrom high to low and from low to high sugar concentrations,from supported to submerged growth, and from glucose media tomedia containing mannitol. The principal hypotheses which seek to account for the characteristicfeatures of water plants are discussed in relation to the resultsof the above experiments. It is concluded that it is the waterbalance of the developing tissues, as determined by such factorsas the osmotic pressure of liquid media, the relative humidityof the atmosphere, or more generally, the diffusion pressuredeficit of the water of the environment, which leads to theappearance of the morphological features characteristic of landor water forms; nutritional conditions play only a subsidiaryrole.     

Plastid Replication in Vegetative Cells, Sporangia, Spores and Sporelings of Red Algae

Ultrastructural aspects of proplastid and chloroplast replicationare described as seen in sections of vegetative cells, sporangia,released spores and sporelings of the red algae Palmaria palmataand Plumaria elegans. Proplastids in apical vegetative cellsshow internal thylakoid formation from peripheral thylakoidsin both species, and proplastid formation by budding from maturechloroplasts has also been observed. Proplastid replicationby fission has been occasionally observed, and genophore divisionin the stroma of proplastids. In vegetative cells, sporangia,spores and sporelings chloroplast formation from mature plastidscan take place by elongation and fission, or by formation ofa discrete group of thylakoids which become pinched off fromthe parent chloroplast, and by irregular expansions of the parentchloroplasts with subsequent multiple fission. Plastid replication, vegetative cells, sporangia, spores, red algae     

Sugars and Starch in Developing Round and Wrinkled Pea Seeds

Soluble sugars and starch have been estimated during the first40 days of development of round and wrinkled pea seeds. At alltimes the wrinkled seeds contained more soluble sugars and lessstarch than the round seeds. The significance of these results,in relation to the expression of the round (R_aR_a) and wrinkled(r_ar_a genotypes, is discussed. Pea seeds, round, wrinkled, sugars, starch     

Effect of background colour on growth and adhesion strength of Ulva sporelings

This study examined the effects of a range of black, grey and white substrata on the growth and attachment strength of Ulva sporelings on glass and polydimethylsiloxane (Silastic®-T2) surfaces. The rate of development of sporelings was strongly influenced by the colour of the substratum on which they grew. On black backgrounds, sporelings grew slowly and germination was delayed. Laboratory screening methods for antifouling and fouling-release coatings that rely on the growth of Ulva sporelings can be compromised if samples are of different colours. Hydrodynamic removal of sporelings from coatings may also be affected by substratum colour, since smaller plants generate lower hydrodynamic forces making them more difficult to remove.     

Experimental and Analytical Studies of Pteridophytes: XIX. Investigations on Marsilea

It is shown that in plants of Marsilea growing in aseptic culturereversion to juvenile leaves may be obtained by depriving thecultures of either sugar or mineral nutrients. Reduction toa protstele and other anatomical observations are also described. Juvenile leaves were produced by excised spices of mature plants,and by lateral branches developing on feeble decapitated plants.The problem of heteroblastic development is discused in relationto these and other observations.     

Chemical Factors Controlling Floral Bud Formation of Torenia Stem Segments Cultured in Vitro I. Effects of Mineral Nutrients and Sugars

Internodal segments of Torenia fournieri Lind. were culturedon various media to investigate chemical factors influencingin vitro flowering. The elimination or dilution of ammoniumnitrate from Murashige and Skoog's medium increased the formationof adventitious buds which subsequently differentiated floralbuds. The dilution of mineral salts in Murashige and Skoog'smedium enhanced adventitious bud formation, but did not influencethe ratio of cultures with floral buds to those with adventitiousbuds. Among various media tested, in vitro floral bud formationand development of Torenia was best on a medium having 1/5 ofthe mineral salts and no NH₄NO₃. Eighty-seven percent of thecultures produced floral buds on this medium. Using this medium,the effects of various sugars were also examined. Increasingthe concentration of sucrose in the medium (up to 60 g/liter)increased the rate of cultures with floral buds, and stimulatedthe development of floral buds led to anthesis. (Received January 17, 1981; Accepted February 21, 1981)     

The arrival of propagules of marine macroalgae in the intertidal zone

The composition and abundance of macroalgal propagules contained in sea water arriving at intertidal rocky shores was estimated monthly at Pelancura, central Chile, from June to December, 1984. Samples from surface water and from water running off rocky platforms with mixed algal vegetation were cultured in laboratory conditions and examined for development of sporelings. Thirty eight macroalgal entities grew in the cultures, 75% of them with opportunistic life-styles. The total number of sporelings was similar in the surface water of sites separated by 300 m. Marked variability in composition and number of sporelings was, however, observed between samples taken simultaneously at one site and between different months, suggesting patchiness in the dispersal of propagules. Marked differences were established in the ratio run-off water/surface water in the number of sporelings, which could be related to the dispersal shadows of the various taxa. Sporelings of late successional algae showed marked spatial and temporal variations in number. Some taxa of opportunistic algae were characterized by the development of several thousand sporelings per litre of sea water while in others the number of sporelings was two or three orders of magnitude less, suggesting differences in reproductive effort.     

Reproduction in Halopteris (Sphacelariales)

Oogamy is recorded in five southern species of Halopteris. Ineach the gametangia and asexual sporangia occur in similar sori,although situated on separate plants. The plurilocular antheridiaand the unilocular oogonia occur within one and the aame sorus.In both the dehiscence is apical. In H. congesta fertilization has been observed in cultures.The polarity of the zygote is established by the direction ofthe first-formed wall. Early divisions convert it into a nodulecomposed of small cells. First rhizoids appear and then cylindricalshoots arise from the opposite pole. Sporelings of five NewZealand species of Halopteris have been raised in culture. Theconditions in the culture greatly affected the character ofthe sporelings, the simplest of which at the end of 2 months'growth were only uniseriate filaments. The best developed sporelingshad a compact basal disc with up to four upright shoots showingthe beinnings of branching.     

Irrigation and Seed Quality Development in Rapid-cycling Brassica: Soluble Carbohydrates and Heat-stable Proteins

Changes in soluble carbohydrates and heat-stable proteins havebeen examined in relation to the acquisition of desiccationtolerance and/or potential seed longevity during seed developmentin rapid-cycling brassica [Brassica campestris (rapa)L.]. Ratesof seed development were moderated by different irrigation regimes.At the early stages, glucose, fructose and sucrose predominated.The raffinose series oligosaccharides accumulated during seedmaturation, and occurred earliest in seeds from plants irrigatedonly until 16 days after pollination. Stachyose content correlatedpositively, and monosaccharide content correlated negatively,with the ability of seeds to tolerate rapid desiccation andwith their potential longevity (the constantK_iof the seed viabilityequation). Similarly, the ratio of oligosaccharide[ratio]totalsugars provided strong positive correlations with ability totolerate desiccation and with potential longevity. Most of theheat-stable proteins selected for study accumulated comparativelylate, i.e. during maturation drying. The imposition of waterstress induced earlier accumulation of heat-stable proteins.The ability to tolerate desiccation was correlated with thecontent of selected heat-stable proteins, but potential longevityprovided stronger correlations. The content of a 58 kDa heat-stableprotein provided the strongest positive correlation with potentiallongevity. A simple multiple regression model of the relationsbetween potential longevity and both the oligosaccharide[ratio]totalsugar ratio and the 58 kDa heat-stable protein content was developedfor all three plant irrigation regimes to show the combinedeffect of certain sugars and proteins on seed quality. The modelsuggests that these sugars and proteins are equally likely tobe required for seed quality development, and that initiallythe sugars tend to accumulate at a greater rate than the proteins,but that during maturation drying the heat-stable proteins accumulateat the greater rate.Copyright 1998 Annals of Botany Company Brassica campestris (rapa) L., rapid-cycling brassica, potential longevity, seed development, desiccation tolerance, soluble sugars, oligosaccharides, dehydrins, heat-stable proteins.     

Apical Dominance in Marsilea, with Particular Reference to the Effects of 3-Indolylacetic Acid,3-Indolylacetonitrile, and Coumarin on Lateral Bud Development

An account is given of the effects of 3-indolylacetic acid,3-indolylaceto-nitrile, and coumarin on the development of thelateral buds of intact plants, decapitated plants, and excisednodes of Marsilea Drummondii in aseptic culture. In all the plant materials used, lateral buds grew out at allphysiological concentrations of the two auxins, an observationwhich is considered to refute the hypothesis that correlativeinhibition is caused by direct inhibition by auxi. Other hypothesesand recent work on the subject are also discussed.     

The Effect of Inhibitors on the Increase in Invertase Activity and RNA Content of Beet Disks During Ageing

The effect of several inhibitors on the development of invertaseactivity and the increase in RNA content of red beet disks agedunder aseptic conditions has been studied. Purine and pyrimidinebases (I.o mM) do not affect, but the corresponding analoguesmay inhibit or stimulate, the development of the enzyme. Theincrease in activity is not inhibited by I.o mM proline andphenylalanine, but is strongly inhibited by similar concentrationsof hydroxyproline and p-fluorophenylalanine. Development isalso inhibited by high concentrations of actinomycin D. Substanceswhich inhibit development also inhibit increase in the RNA content.These results are discussed and a possible mechanism is suggested.     

Storage of Pollen Grains in Organic Solvents: Effect of Organic Solvents on Leaching of Phospholipids and its Relationship to Pollen Viability

In vitro germinability and membrane integrity (as revealed bythe fluorochromatic reaction (FCR) test) of pollen grains ofCrotalaria retusa L. stored in various organic solvents forsix months at –20±2 °C were studied and correlatedwith leaching of lipids, phospholipids, sugars and free aminoacids from pollen grains into organic solvents during storage.Pollen grains stored in organic solvents with low dielectricconstants (a measure of their non-polar nature), such as hexane,cyclohexane and diethyl ether, showed high scores for germinationand FCR and very little leaching of phospholipids, sugars andamino acids. Pollen grains stored in solvents with high dielectricconstants (a measure of their polar nature) such as isopropanoland methanol did not show germination or positive FCR scores,but showed extensive leaching of phospholipids, sugars and freeamino acids. The viability of pollen grains stored in organicsolvents seems to be determined largely by the effect of theorganic solvents on pollen phospholipid composition, which inturn affects membrane integrity and consequently pollen viability. Crotalaria retusa, organic solvents, pollen storage, viability, phospholipids     

Establishment of in vitro Cultures of Tapinanthus bangwensis (Engler and K. Krause) Danser and the Effects of Sugars on Growth

Culturing of organs in vitro has been successfully employedin studies on morphogenesis and nutritional requirements ofparasitic and semi-paraaitic angiosperms. Tapinanthus bangwensis,a semi-parasite, has been successfully cultured on chemicallydefined media. By and large the parasite will thrive well ina medium of mineral salts and sucrose at its optimal concentration(4 per cent). However, the parasite is able to metabolize awide range of sugars most of which show similar concentrationoptima Although the growth in vivo was simulated in vitro inthe early stages, it was found that in the later stages growthin vitro was much slower than growth in vivo. The growth differencesobserved in the different media may reflect some of the physiologicaldifferences that are responsible for the selective nature ofthe parasite's development and establishment on different hosts     

Effects of Humic Acid on Protein Synthesis and Ion Uptake in Beet Discs

Humic acids stimulate the development of phosphate uptake-capacityin beet discs during ageing under aseptic conditions withoutaffecting phosphate uptake per se. Chloride uptake is inhibitedby humic acids as is the development of chloride uptake capacity.The uptake of proline and leuoine is not influenced by ageingin humic acid. While measurements of the incorporation of theseamino acids into the sub-cellular particles of discs indicatethat humic acid does not affect protein synthesis in general,the stimulation of invertase development during ageing doesshow a definite effect on some aspect of protein synthesis.     

Effect of background colour on growth and adhesion strength of Ulva sporelings

This study examined the effects of a range of black, grey and white substrata on the growth and attachment strength of Ulva sporelings on glass and polydimethylsiloxane (Silastic-T2) surfaces. The rate of development of sporelings was strongly influenced by the colour of the substratum on which they grew. On black backgrounds, sporelings grew slowly and germination was delayed. Laboratory screening methods for antifouling and fouling-release coatings that rely on the growth of Ulva sporelings can be compromised if samples are of different colours. Hydrodynamic removal of sporelings from coatings may also be affected by substratum colour, since smaller plants generate lower hydrodynamic forces making them more difficult to remove.     

RNA and protein metabolism in the particulate fractions of the gametophytes of bracken fern during growth in red and blue light

Summary The metabolism of RNA and protein in the gametophytes of bracken fern (Pteridium aquilinum) is affected by the quality of light in which they are grown. When sporelings were grown as two-dimensional gametophytes in blue light, particulate fractions separated from the sporelings exhibited greater incorporation of uridine-³H and leucine-³H into RNA and protein, respectively, than those from sporelings grown as one-dimensional protonema in red light. After various periods of exposure of gametophytes to red or blue light in the presence of uridine-³H, the nuclei-rich fraction showed the highest specific activity in RNA, and irrespective of incubation time, blue light was more effective than red light. The possibility that enhanced synthesis of RNA in the nucleus in response to blue light is significantly related to the morphological growth pattern of the gametophytes, is discussed.     

Cell Wall Autolysis During Kiwifruit Development

Cell walls prepared from developing kiwifruits showed autolyticactivity. The proteins extracted from active walls were alsoable to release carbohydrates from inactive cell walls. Analysisof the sugars released, using both procedures, showed that uronicacids were the major component, especially during the firsthours of incubation, although neutral sugars such as glucoseand galactose were also present. Most of the carbohydrates autolyticallyreleased from the cell wall eluted in the void volume on a BioGel P2 column. However, carbohydrates released from inactivecell walls by the protein extract mostly eluted in the monosaccharideuronic acid and glucose peaks. The autolytic activity of isolatedcell walls, as well as the glycosylhydrolase activity of theproteins extracted from the cell walls, showed important changesduring fruit development. The differences between autolyticactivity and the glycosylhydrolase activity against the cellwall suggest that the glycosylhydrolases ‘in muro’are subjected to some regulatory mechanism which disappearswith their extraction. Finally, the role of glycosylhydrolases,such as polygalacturonases and galactosidases, in relation tocell wall changes in fruits, is discussed.Copyright 1998 Annalsof Botany Company Actinidia deliciosa; autolysis; cell wall enzymes; fruit growth; glycosylhydrolases; kiwifruit.     

Development of the Recalcitrant (Homoiohydrous) Seeds of Avicennia marina: Anatomical, Ultrastructural and Biochemical Events Associated with Development from Histodifferentiation to Maturation

Early histodifferentiation of the embryo of Avicennia marina(Forssk) Vierh was characterized by the formation of endospermhaustoria Once the growth phase was initiated, subsequent embryodevelopment was extra-ovular The mature seed, therefore, wasenclosed by a pericarp originating entirely from the ovary wallGrowth and reserve deposition was not initiated until 45–50d after fruit set (DAFS), when respiratory activity had peakedWater content remained constant from the earliest stages ofembryogenesis to seed abscission and respiratory activity, althoughdeclining somewhat after the completion of histodifferentiation,remained relatively high throughout seed development The ultrastructureof the meristematic root primordia was indicative of metabolicactivity, remaining essentially similar in all respects fromthe end of histodifferentiation until the mature seeds wereabscised During this phase cotyledon cells became highly vacuolatedand the soluble sugars, which constituted the major nutrientreserves of mature seeds, increased considerably Seeds of A,marina initiate germination, without the requirement for additionalwater, as soon as they are shed It is proposed that the accumulationof soluble sugars, rather than insoluble complex reserves, isa major factor in the developmental strategy of these highlyrecalcitrant seeds Anatomy, Avicennia marina, biochemistry, homoiohydrous, recalcitrant, seed development/maturation, ultrastructure