ON THE PROTONEPHRIDIA AND 'LARVAL KIDNEYS' OF NASSARIUS (HINIA) RETICULATUS (LINNAEUS) (CAENOGASTROPODA)

Protonephridia in marine streptoneuran gastropods are describedfor the first time. The organization of these paired organsof the intracapsular veliger larva of Nassarius reticulatusis described. The ciliary flame is formed by a single terminalcell. The duct is formed by one tubular cell and the aperturalcell, which forms the lips of the excretory pore. In addition,the surface of the apertural cell is covered to a great extentby the post-velar bud cell (usually termed ‘larval kidney’).Protonephridia like these are considered to be widely distributedamong streptoneuran gastropods. The homology of these organswith those of opis-thobranchs and pulmonates is suggested. Thepost-velar buds (= ‘larval kidneys’) are suggestedas a synapomorphous character of Caenogastropoda. The functionof the postvelar buds is discussed taking into considerationthe existence of a protonephridium and a possible functionalconnection between these two structures. (Received 14 June 1990; accepted 1 September 1990)     

Larval fish assemblages and geostrophic circulation in Bahia de La Paz and the surrounding southwestern region of the Gulf of California

We analyze spatial–temporal relationship between larvalfish assemblages and geostrophic surface flow in Bahíade La Paz and the neighboring Gulf of California (May, Julyand October 2001 and February 2002). The analysis of fish larvaedistribution in relation to geostrophic circulation and hydrographyis an innovative interdisciplinary approach for the understandingof fish larvae ecology. The Bray–Curtis Index definedtwo larval fish assemblages with spatial–temporal variations:coastal assemblage dominated by epipelagic coastal species (e.g.Sardinops caeruleus) and oceanic assemblages—oceanic andtransitional oceanic assemblages both dominated by mesopelagicspecies (e.g. Vinciguerria lucetia and Benthosema panamense)but with different larval abundance. The assemblage variationsappear to be related to water exchange between the bay and theGulf through the North Mouth. During July–October, thegeostrophic flow through the entrance is strong, and the oceanicassemblages spread in the whole bay, whereas during February–Maywhen the geostrophic transport is weak, the coastal assemblageis distributed over the whole bay. The strong summer–autumnwater interchange between bay and gulf is in agreement withthe annual evolution of the surface water properties insidethe bay, from high-salinity Gulf of California Water duringwinter–spring to fresher Tropical Surface Water duringsummer–autumn, when the highest species number was recorded.     

Properties of Mitochondria Prepared by Two Different Isolation Procedures From the Cotyledons of Germinating Bean Seedlings

Mitochondria from 1-day-old bean cotyledons were isolated bya ‘slow’ isolation procedure involving a wash andby a ‘rapid’ procedure. The mitochondria isolatedby the ‘rapid’ procedure were more tightly coupledthan those isolated by the ‘slow’ procedure. Anexogenous supply of cytochrome c or NAD was shown to improvethe activity of mitochondria isolated by the ‘slow’procedure, but not those isolated by the ‘rapid’procedure. The phosphorylative abilities of the latter weremuch greater than the former and were retained for longer periods.It was found that there was a leakage of NAD out of the mitochondria.     

Fish larvae assemblages in the Gulf of California

The distributional diversity and assemblages of fish larvae in the Gulf of California indicated two main seasonal stages and two transitional periods: in winter, the tropical water mass is confined to the south‐east portion of the mouth of the Gulf and larval fish assemblages are dominated by subtropical and temperate‐subarctic species; in summer; tropical water invades the Gulf and assemblages are dominated by tropical species. Both seasonal stages are separated by transitional periods coinciding with strong latitudinal temperature gradients. During the autumn and spring transitional periods, the Gulf of California splits into three regions: a northern region where temperate and subarctic species spawn from autumn to spring, a southern region dominated by tropical and subtropical species year round and a central region where tropical and temperate assemblages merge. Seasonal changes in the location of the regions, as well as the borders between them, show expansion and contraction of the northern and southern faunas related to the general oceanic circulation patterns during the year.     

Function of silica bodies in the epidermal system of rice (Oryza sativa L.): testing the window hypothesis

Silicon has been considered to be important for normal growthand development of the rice plant (Oryza sativa L.). To investigatethe physiological function of deposited silica in rice leaves,the hypothesis that silica bodies in the leaf epidermal systemmight act as a ‘window’ to facilitate the transmissionof light to photosynthetic mesophyll tissue was tested. Thesilica content of leaves increased with supplied silicon andwas closely correlated with the number of silica bodies perunit leaf area in the epidermal system. There was a significantdifference in silica deposition and formation of silica bodiesbetween Si-treated and non-treated leaves; silicon was polymerizedinside the silica cells and bulliform cells of the epidermis,in Si-treated leaves. Although the ‘windows’ wereonly formed in leaves with applied silicon, optical propertiesof leaf transmittance, reflectance and absorptance spectra inSi-treated and non-treated leaves were almost equal. Furthermore,light energy use efficiency and quantum yield of Si-treatedleaves were less than in leaves not containing silica bodies.Thus, silica bodies, at least based on the data, do not functionas windows in rice leaves. Key words: Silicon, window hypothesis, rice, optical property, quantum yield     

SEASONAL CHANGES IN THE BIOCHEMICAL COMPOSITION OF A TROPICAL INTERTIDAL PROSOBRANCH MORULA GRANULATA (DUCLOS)

Seasonal changes in total carbohydrates, glycogen, free sugars,proteins, TNPS and lipids, were studied in different body components(foot, gonad-digestive gland complex and viscera) of Morulagranulata from January to December 1982. All biochemical constituentsshowed a progressive increase during May–October and adecrease during November–April; some exhibited a secondaryJanuary peak. These changes were correlated to the reproductivecycle and feeding of the animal. Utilisation of lipids was greaterduring the reproductive season indicating a ‘lipid-oriented’ metabolism. Seasonal changes in the water content offoot, gonad-digestive complexand viscera were also reported.The results are discussed in relation to other observationson gastropods and other molluscs. (Received 24 May 1984;     

The Extraction, Solubility, and Characterization of Two Groups of Barley Storage Polypeptides

This paper reports further studies on the characteristics ofthe storage protein fraction (hordein) of barley. Hordein consistsof two groups of polypeptides (termed ‘B’ and ‘C’)coded by two separate but linked loci. Whereas the ‘C’polypeptides are readily soluble and extracted in 60% (v/v)ethanol at room temperature, the ‘B’ group is moresoluble in, and therefore more efficiently extracted by, 50%(v/v) propan-1-ol or 45% (v/v) propan-2-ol at elevated temperaturesand in the presence of 2-mercaptoethanol. However, the mostefficient conditions for hordein extraction (50% propan-1-ol+ 2% (v/v) 2-mercaptoethanol at 60 °C) also extract somecontaminating non-hordein polypeptides resulting in an apparentlyincreased lysine content of the hordein fraction. Amino acid analysis of the purified ‘B’ and ‘C’hordein groups shows that, whereas ‘C’ hordein containsmore glutamate + glutamine, proline, and phenylalanine than‘B’ hordein, it contains only traces of lysine andsulphur amino acids in contrast to ‘B’ hordein whichcontains 0·5% lysine 0·6% methionine, and 2·5%cysteine. Equilibrium sedimentation analyses carried out on the purified‘B’ and ‘C’ groups indicates that thepreparations were reasonably monodisperse with molecular weightsof approximately 32 000 and 52 000 respectively. These valuesare considerably lower than those previously determined by SDS-PAGE.     

Studies in Stomatal Behaviour: VII. EFFECTS OF ANAEROBIC CONDITIONS UPON STOMATAL MOVEMENT--A TEST OF WILLIAMS'S HYPOTHESIS OF STOMATAL MECHANISM

An experiment was carried out to investigate stomatal responsesin wheat to four ‘closing treatments’, viz. highcarbon dioxide concentration, darkness, dry air and nil, eachgiven under both aerobic and anaerobic conditions. Thus theeffect of lack of oxygen on the closing (or opening) tendencywas estimated. Changes in calculated from resistance porometer readings were used as data and reasonsare given for thinking this is the best available measure forinvestigating stomatal dynamics in wheat. Williams's hypothesisdemands that lack of oxygen should cause stomatal opening orprevent closure; the present experiment shows that anaerobicconditions significantly increase the closing tendency when‘closing treatments’ are first applied. There isalso some suggestion that oxygen-lack itself tends to causeclosure in the absence of any other ‘closing treatment’.Williams's hypothesis in its original form is thus disproved(for wheat) but the present results would be consistent withan ‘active’ uptake of water by the guard cells contributingto stomatal opening. A nearly significant interaction betweencarbon dioxide and oxygen suggests that under anaerobic conditionsa ‘closing substance’ may perhaps be formed, forexample, by the union of some intermediate in glycolysis withcarbon dioxide.     

THE SETTLEMENT OF POST LARVAL MYTILUS EDULIS (SETTLEMENT OF POST LARVAL MUSSELS)

It is probable that post larval mussels cut their byssus moorings.For those that gain their freedom in this way, two modes ofpassive flotation are possible. In the ‘summer’mode, they are lifted into the water column on the end of amucus filament; in the ‘winter’ mode, they attachthemselves to certain negatively buoyant debris which leavesthe bottom when the tide flows. Passive flotation prolongs the errant existence of post larvalmussels by increasing their drag. By enabling them to avoidsilt and keep in touch with hard substrates, passive flotationmakes it more likely that they will settle advantageously. The two modes of passive flotation pose an all-the-year-roundthreat of fouling to the cooling water systems of coastal powerstations. (Received 27 April 1982;     

The Influence of the Plant Growth-regulator, 2-Methyl-4-Chlorophenoxyacetic Acid, on the Metabolism of Carbohydrate, Nitrogen and Minerals in Solanum lycopersicum (Tomato)

The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in ‘available carbohydrate’ (starch,‘total’ and ‘reducing’ sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’and roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatments—‘nutrient’(nutrient supply to roots continued after spraying) and ‘water’(distilled water only supplied to roots after spraying) and‘water’ (distilled water only supplied to rootsafter spraying)—the sub-treatments consisting of ‘MCPA’versus ‘no-MCPA’ for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity ‘residualdry weight’ (total dry weight less ‘available carbohydrate’),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe ‘residual dry weight’ basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in ‘residual dry weight’,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram ‘residual dry weight’ of the ‘tops’)was greatly diminished while uptake of total nitrogen and ofP₂O₅ (estimated as increase in total nitrogen or of P₂O₅ ofthe whole plant per day per 1 g. ‘residual dry weight’of the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof ‘available carbohydrate’ as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The ‘tops’ presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the ‘no-MCPA’plants and also of the ‘MCPA-water’ plants showeda steady increase in available carbohydrate, those of the ‘MCPA-nutrient’plants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe ‘available carbohydrate’ supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first ‘flush’ of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium.     

The Physiology of a Wilty Pea: Abscisic Acid Production under Water Stress

‘Wilty’ (JI 1069), a mutant of Pisum sativum, hasbeen examined for its ability to produce abscisic acid (ABA)under water stress. ABA was measured using combined gas chromatography-massspectrometry and multiple-ion-monitoring employing a deuteratedinternal standard. In intact droughted plants, ‘Wilty’produced less ABA than a non-wilty line (JI 1194) and maximumproduction was delayed. Detached leaves of the wilty mutantlost significantly more water than control leaves but did notshow an increase in ABA content. Non-stressed mutant materialfrom both intact plants and isolated leaves contained less ABAthan control tissue. Key words: Pea, Wilty mutant, Abscisic acid     

IDENTIFICATION AND EVALUATION OF THE FLAVOR-SIGNIFICANT COMPONENTS OF GINGER ESSENTIAL OIL

The flavorfully significant compounds in ginger essential oilwere selected statistically by use of a step-wise multiple regressionanalysis which treated individual peak quantitities on a gaschromatogram as independent variables and taste panel scoresfor ginger flavor intensity as dependent variables. The statisticalanalysis showed that four gas chromatographic peaks, consistingof a terpineol, citral a, citral b (peak 11), ß-sesquiphellandrene,ar-curcumene (peak 14), nerolidol (peak 19), and a sesquiterpenealcohol (peak 29), accounted for 85% of the panel's flavor response(R²=0.85). Taste panel evaluations of the isolated components indicatedthat ß-sesquiphellandrene and ar-curcumene are theprime contributors to the characteristic ‘ginger’attribute. -Terpineol, citral a and citral b contribute to the‘lemony’ attribute of ginger oil and may thereforebe desirable additives to whole ginger oil to intensify its‘lemony’ character. Nerolidol contributes to the‘woody’ or ‘soapy’ attribute and doesnot appear to be a good potential additive to ginger oil. A trained sensory panel judged a mixture of -terpineol, citrala, citral b, ß-sesquiphellandrene, ar-curcumene andnerolidol to be characteristic of ginger oil. The panel founda mixture of these chemicals, in combination with ginger heatchemicals, to be a suitable imitation ginger flavor. The study has shown that statistics can be used in selectingthe individual flavor contributing components of a flavor essence.This approach can greatly reduce the number of compounds whichneed be identified in the investigation of the composition ofnatural flavoring substances. ^* Scientific Article No. A1996, Contribution No. 4938, MarylandAgricultural Experimental Station (Food Science Program).     

Structural and Histochemical Changes in Palisade Cells of Prosopis juliflora Seed Coat in Relation to its Water Permeability

Histochemical investigations on the Prosopis juliflora seedcoat indicate the occurrence of a hydrophobic ‘strip’as the primary water barrier. Its position and the structureand histochemistry of the palisade cells of the seed coat differaccording to their location on the seed. These differences maybe responsible for differences in the water permeability ofvarious parts of the seed coat. In particular, parts of theseed coat in which the hydrophobic ‘strip’ is locatedmore superficially tend to be more water impermeable than partslike the chalaza, in which the ‘strip’ is more deeplylocated within the palisade cells. Prosopis juliflora, seed coat impermeability, palisade cells, hydrophobic ‘strip’     

The Nitrogen Content of Plants and the Self-thinning Rule of Plant Ecology: A Test of the Core-skin Hypothesis

The ‘core-skin’ hypothesis postulates that secondarilythickened plants behave energetically as an inert ‘core’covered by an active ‘skin’, the ‘skin’being two-imensional, the ‘core’ three-dimensional.This would explain the ‘self-thinning ‘or‘–3/2’ rule of plant ecology, that is, the tendencyfor log (dry weight per plant) and log (number of plants perunit area) to progress along a straight line relationship, withslope = – 3/2’. The hypothesis was tested as follows. Plant nitrogen contentwas used as an estimate of the mass of ‘skin’ perplant, and dry weight as an estimate of the mass of the ‘core’.As plants mature the slope of the relationship between y = log(mass of nitrogen per plant) and x = log (mass of dry matterper plant) is expected to decline from an initial value of 1.0towards a final value of 0.66. The intercept of the relationshipis expected to reflect the intrinsic content of ‘skin’per unit of ‘core’. Genotypic variation in thisparameter should cause genotypic differences in the maximumattainable yield of biomass per unit area. The expectations were investigated by fitting the function y= p+qx+r exp – x to 30 sets of data on plant nitrogencontent, plant weight and time in 18 different vegetables. Simplelinear regressions of y on x were fitted to more limited setsof data on weights and nitrogen contents of mature trees. Theexpectations were, with some minor exceptions, confirmed. Nitrogen, yield, plant competition, self-thinning     

Ayala, F.J., Fitch, W.M. and Clegg, M.T. Variation and evolution in plants and microorganisms: toward a new synthesis 50 years after Stebbins

In January 2000, an impressive cohort of evolutionary biologistsconvened in Irvine, California, to celebrate the 50th anniversaryof the publication of G. Ledyard Stebbins’ Variation andevolution in plants. The brief introductory appreciation ofStebbins by Peter Raven describes Variation as ‘the mostimportant book on plant evolution of the 20th century’(p. 5). This strongly worded claim is not entirely without justification.Among the ‘New Synthesists’, Stebbins achieved forbotanists what Theodosius Dobzhansky (later to be a colleagueof Stebbins at UC Davis) had previously achieved for geneticists,Ernst Mayr for zoologists and G. G. Simpson for palaeontologists.Admittedly, the     

ERRATA

WARBURG, M. R., 1965. On the water economy of some Australianland snails. Proc. malac. Soc. Lond. 36, 297–305. Page 298: second line from bottom, should read ‘within± 1 µg for Themapupa’. Page 300: Fig. 2 legend, should read ‘Evaporative waterloss from Sinumelon remissum (a), Pleuroxia sp. (b) and Themapupaadelaidae (c)’. Page 300: section 4 heading, should read ‘Continuous curvesfor water loss’. Page 301: second line, for ‘Fig. 9’ read ‘Fig.3’. Page 301: Table 1, last line, for ‘0.120024’ read‘0.12024’. Present address: Israel Institute for Biological Research, Ness-Ziona,Israel.     

Comparative Studies of Seed Germination of two Newly Isolated Lines of Grand Rapids Lettuce

Two lines of Grand Rapids lettuce were isolated by self-pollinationof single plants. Seeds of one line, designated ‘A’,germinate in the dark at 25 °C. Seeds of the second line,designated ‘B’ germinate in a manner typical oftheir variety. The lines differ in sensitivity to red (R) andfar-red (FR) light, in the ability of their seeds to overcomeresistance of an external osmotically active medium, in theresponse of mature seeds to abscisic acid, and in the responseof young seeds to gibberellin and benzyl adenine. ‘A’seeds germinate faster than ‘B’ seeds in the darkor after R or FR irradiation.     

The Suction Potential of Plant Cells and Some Related Topics

This paper is a theoretical discussion of the concept of suctionpotential or suction pressure as applied to plant cells, especiallywith reference to the possible occurrence of ‘active’water-secreting mechanisms. Following an attempt to define whatis meant by suction potential there is a discussion of the distinctionbetween ‘active’ and ‘passive’ agenciesin relation to water movement and a tabulation of such agencies. Some of the less commonly considered mechanisms are discussedin some detail, and an attempt is made to evaluate how effectivethey might be in producing increments of turgor pressure. Theconclusion is reached that if active mechanisms are operativein cell-water relations, then suction potential cannot adequatelybe denned in the ordinary way—in fact the ‘water-absorbingeffort’ of a cell cannot be completely specified in termsof pressure alone. There are appendixes on the possible role of frictional or contactelectrification in cell physiology; on the increase of permeabilityof the plasma membrane to ions and water caused by electricalforces; and on the energy requirement of active water-secretingmechanisms.     

Factors Determining Petal Colour of Baccara Roses II: THE EFFECT OF PIGMENT CONCENTRATION

‘Blueing’ in young and senescing petals was comparedin the red rose cv. Baccara. The ‘blueing’ of senescingflowers is accompanied by a bathochromic shift in the lightreflectance curve, a rise in the pH value and a decrease inthe malic acid concentration of the petal tissue. These factorsindicate that a complex with a co-pigment is produced. Similarchanges were not found in the ‘blueing’ of youngflowers, where a decrease was found in pigment concentrationper unit weight as well as per unit area of petal. A similar‘blueing’ was achieved by diluting a solution ofcrystalline cyanin. The phenomenon of ‘blueing’by dilution is discussed in the light of Bougeur's law.     

A Model of Plant Hydraulics Under Non-equilibrium Conditions: II. LEAVES

The hydraulic system in leaves was investigated in some detailand analysed in terms of an electrical transmission line analogy.The equivalent ‘circuit elements’ in the leaf wereidentified and their values calculated. The values of the ‘capacitative’and ‘inductive’ terms were calculated for variousleaf water potentials and for various changes in potential.They both exhibited considerable non-linearity. The calculatedvalues were used to derive values for the ‘impedance’of the pathways through the leaf xylem, and through the mesophyllcell walls, and to investigate the characteristics of thesetwo pathways when oscillations, or fluctuations, in leaf waterstatus were occurring.