Wide-Range Distribution of Insertion Sequences Identified in B. halodurans among Bacilli and a New Transposon Disseminated in Alkaliphilic and Thermophilic Bacilli

All of the insertion sequences (ISs) except for IS663 and agroup II intron identified in the alkaliphilic Bacillus haloduransC-125 genome were also detected in nine other strains of thesame species by PCR and Southern blot analysis. The transposaseof IS653 identified in the genomes of the 10 strains of B. haloduranswas found to have become the most diversified of all ISs identifiedin the genomes of 10 strains. A new IS element designated IS661belonging to the IS1380 family with inverted repeats (IRs) 17bp in length was present within IS658 identified in the genomeof B. halodurans A59. In addition, a new transposon designatedTn3271bh was identified within the IS642 element in the A59genome, which is similar to a transposon identified in thermophilicGeobacillus stearothermophilus T-6. The new transposon, Tn3271bh,generated an 8-bp duplication of the target site sequence andcarries a 21-bp IR. On the other hand, all kinds of ISs exceptfor IS643 and IS658 were distributed in the genome of obligatelyalkaliphilic Bacillus alcalophilus. Three ISs (IS652, IS653,and IS660) and a group II intron (Bh.Int) were widely dispersedin other Bacillus species without a correlation with the phylogeneticplacement based on 16S rDNA sequences.     

Replicon Size, Mean Rate of DNA Replication and the Duration of the Cell Cycle and its Component Phases in Eight Monocotyledonous Species of Contrasting DNA C Values

Various aspects of the cell cycle were measured in the apicalmeristem of primary and seminal roots of eight monocotyledonousangiosperms: Oryza sativa (0.6 pg), Zea mays (2.4 pg), Pennisetumamericanum (2.5 pg), Aegilops umbellulata (5.1 pg), Hordeumvulgare (5.5 pg), Triticum monococcum (6.2 pg), Secale cereale(8.6 pg) and Tulipa kaufmanniana (22.6 pg), representing a 38-foldvariation in DNA C values. Using 4-d-old roots of the firstseven species and 21-d-old Tulipa roots, replicon size and ratesof replication were determined by DNA fibre autoradiography,and the duration of the cell cycle and its component phasesby the percentage labelled mitoses method. When tested withDNA C value, no significant relationships existed for repliconsize, rate of DNA replication or duration of G 1. Significantpositive linear relationships were found between DNA C valueand cell cycle duration, duration of mitosis and G2 durationwhen all data were tested, but not when the Tulipa data wereexcluded. The only characters significantly related to DNA C value whenthe Tulipa data were included or excluded were the durationof S-phase, and the ratio of the interval required for a repliconto replicate its allotted DNA (Rs) to the duration of S-phase(Ds). The Rs: Ds ratio is a measure of synchrony of repliconactivation, and the higher the DNA C value the lower this ratiobecame. We concluded that there was a nucleotypic effect ofDNA C value on this ratio and that the interval between activationof replicons became protracted and hence S-phase lengthenedas C value increased. Cell cycle, NA C value, DNA replication, replicon, S-phase     

Background context and decision making in hoarding gray jays

If decision makers assign stable fitness-related values to options, preference for the most valuable of simultaneously encounteredoptions should be independent of background context (i.e.,prior options). The tendency to choose optionx versus y shouldbe unaffected by whether the decision maker has already beengiven a choice betweenx' and y' or between x' and y'. Here, food-hoarding gray jays (Perisoreus canadensis) were given aninitial choice between x' (one raisin, 0.5 m into a tube) and y' (three raisins, 0.5 m) or between x' and y' (both identicalto x'). All subjects were then given a choice between x' (oneraisin, 0.3 m) and y' (three raisins, 0.7 m). In violationof the principle of irrelevant alternatives, the "market share"ofx depended on prior options. Subjects initially exposed tocontext {x', y'} showed a stronger preference for x than did subjects initially exposed to {x', y'}, which implies thatthe jays did not assign a fixed value to each option. Subjectsthat initially could obtain a large reward (y') for about thesame "price" (perceived danger) as a small reward (x') apparentlydevalued the large reward (y) in the subsequent choice. Thiseffect may be the joint byproduct of cognitive constraints andan adaptive tendency to use information provided by the context.     

Predator-prey interactions between Isochrysis galbana and Oxyrrhis marina. III. Mathematical modelling of predation and nutrient regeneration

A mathematical model was derived to simulate ingestion, growthand nitrogen (N) regeneration for the phagotrophic dinoflagellateOxyrrhis marina. Two types of experimental study were undertaken:prey-deplete O.marina were supplied with lsochrysis galbanain continuous darkness (thus preventing growth of the prey),and predator-prey interactions were also followed in culturesmaintained in a light-dark cycle (allowing growth of the prey).During light-dark cycles, Oxyrrhis volume increased more inthe light phase than in the dark. Digestion of isochrysis lasted{small tilde}0.3 days. with an average maximum ingestion rateof 55 prey predator–1 day–1 During active predation,30% of Oxyrrhis-carbon (C) was lost from the particulate phase:per day, with this loss falling to 10%: per day at the cessationof herbivory when cannibalism became noticeable. Ingestion wasmodelled as a function of prey density, C-loss and divisionas functions of cellular predator C. with cannibalism by Oxyrrhisalso included. Two N-regeneration expressions were investigated:one proposed by D.A.Caron and J.C.Goldman (Journal of Protozoology.35, 247–249, 1988) and an alternative function which relatedN regeneration to intracellular carbon and N based on the conceptof an optimal Oxyrrhis C:N ratio. The latter was more successfulin simulating batch culture data and did not require a priorcalculation of Oxyrrhis gross growth efficiency. The model ofOxyrrhis numbers, C and N contained only nine parameters whosevalues were fully obtainable from batch culture experiments.By using this model, we were able to use a single parameterset to simulate the transient dynamics of Oxyrrhis ingestingN-replete and N-stressed prey. Further experiments in whichOxyrrhis grew on Isochrysis in light-dark cycles were simulatedby combining the Oxyrrhis model with the nutrient-processingmodel for Isochrysis of K.Davidson et al. (Journal of PlanktonResearch, 15, 351–359, 1993). The dynamics of the fullpredator-prey model were found to be sensitive to the levelof sophistication of the prey model; the Quota model was foundto be less successful than the nutrient-processing prey model.Theoretical model runs indicated the importance of being ableto simulate changes in both prey numbers and biomass, and alsoin including realistic equations for nutrient regeneration frompredators in microbial predator-prey models.     

Photosynthesis and Transpiration in Leaves and Ears of Wheat and Barley Varieties

Carbon exchange rate (CER) and transpiration were measured inflag leaves, whole ears, glumes (referring to the total areaof glumes and lemmas) and awns, in six hexaploid spring wheats(Triticum aestivum L.), three cultivated tetraploid spring wheats(T. turgidum L.), four wild tetraploid wheats (T. dicoccoides),eight six-rowed barleys (Hordeum vulgare L.) and five two-rowedbarleys (H. vulgare L.). Differences between varieties and between species in total earCER and transpiration were associated largely with differencesin ear surface area rather than with rates per unit area. Ratesof CER and transpiration per unit area of ears were 40–80%of those of flag leaves, depending on the species. However, since ear surface area was greater than flag leaf areaby a factor of 1.1, 3.9, 5.5 and 4.4, in hexaploid wheat, tetraploidwheat, six-rowed barley, and two-rowed barley, respectively,total ear CER reached up to 90% of that of the flag leaf. The contribution of awns to total ear CER depended largely ontotal awn surface area per ear, rather than on CER per unitawn area. Awns contributed about 40–80% of total spikeCER, depending on the species, but only 10–20% of spiketranspiration. The disproportionately small contribution ofawns to ear transpiration was caused by the very low rate oftranspiration per unit area of awns. Thus, while transpirationratio (CER/transpiration) was about the same in flag leavesand glumes, it was higher by several orders of magnitude inthe awns. A large amount of awns in the ear is therefore a drought adaptiveattribute in these cereals, for which tetraploid wheat exceededhexaploid wheat and six-rowed barley exceeded two-rowed barley. Key words: Carbon exchange rate, Transpiration, Barley, Wheat     

Anatomy, Growth and Survival of a Long-hypocotyl Mutant of Cucumis sativus Deficient in Phytochrome B

Plant dry matter (DM) partitioning, survival rates, stem anatomy,and stem water conductivity were investigated in wild-type (WT)and long-hypocotyl (lh) mutant seedlings of cucumber (Cucumissativus) grown as isolated individuals under natural radiation.The lh mutant is severely deficient in phytochrome B. Wild-typeseedlings accumulated more DM than lh seedlings over a 4-weekgrowth period in the glasshouse. Leaf and root DM were higherin the WT but stem DM was higher in the lh mutant. Stem DM perunit length was larger in WT than in lh mutant seedlings, evenwhen the two genotypes were compared at equal whole plant DM,which was achieved by growing the plants under different irradiance.In WT seedlings, the hypocotyl was shorter but thicker, withlarger average cell diameter than the lh mutant. In hypocotyltransverse sections the area occupied by load-bearing tissues(xylem and phloem fibres) and the number and diameter of xylemvessels were larger in WT than lh seedlings. Survival ratesof the lh mutant were normal in the glasshouse but very lowoutdoors due to hypocotyl fracture. The water conductivity ofhypocotyl sections was higher in WT than lh seedlings, but nosignificant differences in water conductivity were observedwhen the root remained attached to the hypocotyl. These resultssuggest (a) that compared to the WT, tall and slender lh plantsare more susceptible to mechanical stresses created by windimpact, and (b) that if the lh lesion affects the phyB geneonly, phytochrome B plays a role in the elicitation of anatomicaland morphological changes that specifically increase fitnessin open environments.Copyright 1994, 1999 Academic Press Cucumis sativus (cucumber), light phenotypes, phytochrome, photomorphogenesis, shade phenotypes, stem growth     

Grazing and nutrient influences of Daphnia and Eudiaptomus on phytoplankton in laboratory microcosms

In two experiments, top-down and bottom-up influences of theherbivorous crustaceans Daphnia pulicaria and Eudiaptomus grac$$$loideson phytoplankton were compared in laboratory microcosms. Ina long-term experiment (63 days), both grazers were able toestablish populations. The Daphnia population exerted strongergrazing pressure, whereas Eudiaptomus fed more selectively.Daphnia retained relatively more phosphorus (P) and thus causedalgal P limitation; with Eudiaptomus as a grazer, both nitrogen(N) and P remained limiting. In a short-term experiment (1 day),N and P release rates and algal-specific grazing rates by bothconsumers were measured. In this experiment, the increase inconcentrations of soluble mineral nutrients (     

Variations in the Levels of cis- and trans-Ribosylzeatins and Other Minor Cytokinins during Development and Growth of Cones of the Hop Plant

The endogenous cytokinins in cones of the hop plant (Humuluslupulus L. cv. Shinshuwase) were identified by combined gaschromatography and selected ion current monitoring (GC-SIM)and high performance liquid chromatography as ribosyl-cis-zeatin,ribosyl-trans-zeatin, cis-zeatin, trans-zeatin and ribosyl-trans-zeatin-O-glucoside.The contents of these cytokinins in both fertilized and unfertilizedcones at various growth stages were determined using GC-SIMand/or bioassay. Based on these data, the rapid growth of thefertilized cone is attributed mainly to ribosyl-trans-zeatinwhich accumulates mostly in the seed. Ribosyl-cis-zeatin wasfound in both fertilized and unfertilized cones. In the latter,ribosyl-cis-zeatin was quantitatively a major cytokinin andseemed to cooperate with ribosyl-trans-zeatin and trans-zeatinin promoting the growth. (Received January 12, 1981; Accepted February 10, 1981)     

Cocaine and Cinnamoylcocaine Content of Erythroxylum Species

The dried leaves of 31 species and two varieties of the genusErythroxylum were quantitatively analysed for cocaine and bothcis- and trans-cinnamoylocaine, using a stable-isotope dilutionmethod and gas chromatography-mass spectrometry selected-ionmonitoring. Both cocaine and cinnamoylcocaine were detectedin all four varieties of cultivated coca (E. coca var. coca,E. coca var. ipadu, E. novogranatense var. novogranatense andE. novogranatense var.truxillense). Cinnamoylcocaines (cis andtrans) were found in much higher concentrations in both varietiesof E. novogranatense than in either variety of E. coca. Amazoniancoca (E. coca var. ipadu) contained consistently lower cocainelevels than the montane variety (E. coca var. coca). Twenty-ninewild species of Erythroxylum, selected to represent morphological,ecological and taxonomic diversity, were analysed for the samealkaloids; cocaine was detected in 13 neotropical species, representingfive sections of the genus. No cocaine was detected in the OldWorld species. Two wild species from Venezuela, E. recurrensand E. steyermarkii, contained cocaine levels comparable tothose found in the commercially cultivated species. Erythroxylaceae, Erythroxylum, coca, cocaine, cinnamoylcocaine, alkaloids, chemotaxonomy     

Twist-to-Bend Ratios and Cross-Sectional Shapes of Petioles and Stems

Two structural properties, resistance to twisting (torsionalrigidity or torsional stiffness, GJ) and resistance to bending(flexural rigidity or flexural stiffness, El), were measuredon a variety of herbaceous stems and petioles. Specimens withnon-circular cross-sections had higher values of the ratio ofEl to GJ that is, such specimens were relatively more flexiblein twisting than in bending. But both kinds had higher ratiosthan those that characterize simple, isotropic materials, andthus both structural and material factors contribute to achievinga high twist-to-bend ratio. The composite property expressedas the dimensionless variable EI/GJ appears to be a functionallyrelevant parameter in many biological situations. Key words: Stems, petioles, flexural rigidity, torsional rigidity, biomechanics     

Cloning and Sequencing of a 36-kb Region of the Bacillus subtilis Genome between the gnt and iol Operons

Within the framework of an international project for the sequencingof the entire Bacillus subtilis genome, a 36-kb chromosome segment,which covers the region between the gnt and iol operons, hasbeen cloned and sequenced. This region (36447 bp) contains 33complete open reading frames (ORFs; genes) including the fourgnt genes and one partial gene. A homology search for the productsof the 33 complete ORFs revealed significant homology to knownproteins in 16 of them such as tetracycline resistance protein(Clostridium perfringens), asparagine synthetase (Arabidopsisthaliana), aldehyde dehydrogenase (Pseudomonas oleovorans),2,5-dichloro-2,5-cyclohexadiene-1,4-diol dehydrogenase (P. paucimobilis),heat shock protein HtpG (Escherichia coli), galactose-protonsymporter (E. coli), auxin-induced protein (common tobacco),glucitol operon repressor (E. coli) and methylmalonate-semialdehydedehydrogenase (P. aeruginosa). Unlike the regions we sequencedso far, this region contained two short sequence multiplications:one was a tandem sequence duplication (409 and 410 bp), andthe other a triplication consisting of two highly conserved118-bp tandem sequences preceded by a less conserved similarsequence (129 bp). The reasons for the presence of these sequencemultiplications in the gnt to iol region were deduced.     

Repetitive DNA, Genome and Species Relationships in Avena and Arrhenatherum(Poaceae)

Repetitive sequences have been widely used for examining genomeand species relationships by in situ and Southern hybridization.In the present study, double-stranded DNA sequences, from denaturedDNA reannealed to Cot = 1, from Avena strigosa(2 n = 2x = 14;A genome; referred to as CotA) and Avena sativa(2n = 6 x =42; ACD genome; referred to as CotACD) were isolated with ahydroxyapatite column, and were used for in situ hybridizationon hexaploid A. sativa chromosomes. Probe CotACD labelled allchromosomes evenly throughout their length at the same intensity.Probe CotA labelled the 28 A and D genome chromosomes stronglyand the 14 C genome chromosomes weakly. Three cloned repetitivesequences, pAvKB9 (126 bp), pAvKB26 (223 bp) and pAvKB32 (721bp) were characterized in the A, B, C and D Avena genomes andthe genus Arrhenatherum using molecular and cytological methods.Clones pAvKB9 and pAvKB26 were absent from the Avena C genome,while both could identify the presence of the D genome by Southernhybridization. In situ hybridization to diploid and tetraploidAvena species revealed that the probes showed a dispersed genomicorganization and that they are present on both arms of all chromosomes.These sequences were excluded from areas where tandem repeats,such as rRNA genes and telomeres, are present. These resultsindicate the close relationship between A and D genomes andthe presence of common DNA sequences between A and C Avena genomes.All three clones hybridized to Southern blots containingArrhenatherumdigested genomic DNA, indicating Arrhenatherum’s closeaffinity to A, B and D Avena genomes. Copyright 2000 Annalsof Botany Company Cereals, DNA, hydroxyapatite, in situ hybridization, oats, reassociation kinetics, repetitive DNA     

Effects of Constant and Variable Nitrogen Supply on Sunflower (Helianthus annuus L.) Leaf Cell Number and Size

The effects of nitrogen (N) availability on cell number andcell size, and the contribution of these determinants to thefinal area of fully expanded leaves of sunflower (Helianthusannuus L.) were investigated in glasshouse experiments. Plantswere given a high (N =315 ppm) or low (N=21 ppm) N supply andwere transferred between N levels at different developmentalstages (5 to 60% of final size) of target leaves. The dynamicsof cell number in unemerged (< 0.01 m in length) leaves ofplants growing at high and low levels of N supply were alsofollowed. Maximum leaf area (LA_max) was strongly (up to two-fold)and significantly modified by N availability and the timingof transfer between N supplies, through effects on leaf expansionrate. Rate of cell production was significantly (P<0.05)reduced in unemerged target leaves under N stress, but therewas no evidence of a change in primordium size or in the durationof the leaf differentiation–emergence phase. In fullyexpanded leaves, number of cells per leaf (N_cell), leaf areaper cell (LA_cell) and cell area (A_cell) were significantly reducedby N stress. WhileLA_cell and A_cellresponded to changeover treatmentsirrespective of leaf size, significant (P<0.05) changes inN_cellonly occurred when the changeover occurred before the leafreached approx. 10% of LA_max. There were no differential effectsof N on numbers of epidermal vs. mesophyll cells. The resultsshow that the effects of N on leaf size are largely due to effectson cell production in the unemerged leaf and on both cell productionand expansion during the first phase of expansion of the emergedleaf. During the rest of the expansion period N mainly affectsthe expansion of existing cells. Cell area plasticity permitteda response to changes in N supply even at advanced stages ofleaf expansion. Increased cell expansion can compensate forlow N_cellif N stress is relieved early in the expansion of emergedleaves, but in later phases N_cellsets a limit to this response.Copyright 1999 Annals of Botany Company Helianthus annuus, leaf expansion, leaf cell number, leaf cell size, nitrogen, leaf growth, sunflower.     

Aggregation of avian predators and zooplankton prey in Otago shelf waters, New Zealand

In Otago shelf waters surface swarms of krill (Nyctiphanes australis),hyperiid amphipods (Parathemisto spp.) and galatheid crab larvae(Munida gregaria) provide an abundant summer food source forplanktivores. We tested the hypothesis that aggregation of avianplanktivores depends upon the spatial distribution of theirprey. Gulls (Larus scopulinus, L.bulleri, L.dominicanus), sootyshearwaters (Puffinus griseus) and white-fronted terns (Sternastriata) showed significantly aggregated distributions. Thedistribution of birds sitting on the sea surface was correlatedwith the abundance pattern of krill but was not correlated withthe distribution of smaller hyperiid amphipods. The distributionof flying red-billed gulls (L.scopulinus), black-billed gulls(L.bulleri) and sooty shearwaters was correlated with the krilldistribution but black-backed gulls (L.dominicanus) were not.Stomach contents of black-billed gulls were dominated by krill,in contrast to sooty shearwaters, which ate a higher proportionof Minida, and black-backed gulls, which contained Munida andfish. No amphipods were found in bird stomachs. There was nosignificant correlation between bird distributions and the hydrographicregime, water depth or distance offshore. The distribution ofprey rather than hydrographic regime was a more important determinantof bird distributions at this spatial scale (2.6–12 km)and location.     

Sulphydryl and Disulphide Levels in Protein Fractions from Hydrated and Dry Leaves of Resurrection Plants

Significant changes in sulphydryl (‘SH’) and disulphide(‘SS’) levels during air-drying in leaves of ‘resurrection’plants (whose protoplasm survives dehydration) stemmed mainlyfrom protein turnover effects. No significant changes were foundin the SH, SS levels in leaves of the desiccation sensitivespecies Sporobolus pyramidalis following air-drying. The three tolerant species studied differed in the directionof change. Some data were consistent with Levitt's SH, SS hypothesis:increases in protein-SS levels in Sporobolus stapfianus (desiccationtolerant) were consistent with a stabilization of new proteinby SS bonds; lower reactivity of protein-SH in the tolerantspecies Talbotia elegans (which on the other hand has decreasedprotein-SS) is consistent with a second mechanism of decreasingprotein denaturation proposed in Levitt's hypothesis. Evidence of some conversion of SH to SS in the soluble proteinsof Xerophyta viscosa (a tolerant species) would on Levitt'shypothesis indicate an injurious process. Some degree of proteindenaturation might be indicated by partial inactivation of thesoluble enzyme ribulose bisphosphate carboxylase in this species,and loss of some soluble isoenzymes (peroxidase and alkalinephosphatase). An apparent lack of SH conversion to SS in thesensitive species Sporobolus pyramidalis was not consistentwith the SH, SS hypothesis. Resurrection plants, Sporobolus pyramidalis, Sporobolus stapfianus, Talbotia elegans, Xerophyta viscosa, drought resistance, desiccation tolerance, protein turnover, sulphydryl groups     

Integrated metabolite and gene expression profiling revealing phytochrome A regulation of polyamine biosynthesis of Arabidopsis thaliana

In this study, metabolite profiling was demonstrated as a usefultool to plot a specific metabolic pathway, which is regulatedby phytochrome A (phyA). Etiolated Arabidopsis wild-type (WT)and phyA mutant seedlings were irradiated with either far-redlight (FR) or white light (W). Primary metabolites of the irradiatedseedlings were profiled by gas chromatography time-of-flightmass spectrometry (GC/TOF-MS) to obtain new insights on phyA-regulatedmetabolic pathways. Comparison of metabolite profiles in phyAand WT seedlings grown under FR revealed a number of metabolitesthat contribute to the differences between phyA and the WT.Several metabolites, including some amino acids, organic acids,and major sugars, as well as putrescine, were found in smalleramounts in WT compared with the content in phyA seedlings grownunder FR. There were also significant differences between metaboliteprofiles of WT and phyA seedlings during de-etiolation underW. The polyamine biosynthetic pathway was investigated further,because putrescine, one of the polyamines existing in a widevariety of living organisms, was found to be present in loweramounts in WT than in phyA under both light conditions. Theexpression levels of polyamine biosynthesis-related genes wereinvestigated by quantitative real-time RT-PCR. The gene expressionprofiles revealed that the arginine decarboxylase 2 (ADC2) genewas transcribed less in the WT than in phyA seedlings underboth light conditions. This finding suggests that ADC2 is negativelyregulated by phyA during photomorphogenesis. In addition, S-adenosylmethioninedecarboxylase 2 and 4 (SAMDC2 and SAMDC4) were found to be regulatedby phyA but in a different manner from the regulation of ADC2. Key words: Arabidopsis thaliana, gene expression profiling, metabolite profiling, phytochrome A, polyamine biosynthesis Received 19 October 2007; Revised 17 January 2008 Accepted 18 January 2008     

Biomechanical Responses of Chamaedorea and Spathiphyllum Petioles to Tissue Dehydration

Data are presented for the mechanical responses to dehydrationof petioles from two monocotyledons (Chamaedorea erumpens andSpathiphyllum Clevelandii). These data were used to test thehypothesis that the mechanical properties (elastic modulus Eand flexural stiffness EI) of petioles from C. erumpens arealtered significantly less by dehydration than those of petiolesfrom Spathiphyllum. Dehydration, resulting from either dryingat room temperature or from submergence in various concentrationsof mannitol solutions, produced significant increases in E anddecreases in EI (due to geometric distortions) in both youngand mature Spathiphyllum petioles. Similar trends were observedfor young petioles of C. erumpens, but significantly less sofor mature petioles of this species. Regardless of petiolarage, E increased allometrically as a linear function of tissuedensity, which in turn correlated with the volume fraction oflignified tissues in petioles; however, the proportional increaseof E as a function of tissue density was significantly greaterfor C. erumpens petioles than for Spathiphyllum. Anatomicalanalyses of petiolar transections indicated that Chamaedoreapetioles had larger volume fractions of lignified tissues thanthose of Spathiphyllum and that these tissues were located tomaximize stiffness. These data (and previously reported allometricrelationships between EI and petiolar length) shed light onthe difficulties in evaluating the ‘costs’ of committingtissues to mechanical support. Petioles, biomechanics, leaf anatomy, monocotyledons     

Leaf Properties Related to the Photosynthetic Response to Drought in Upland and Lowland Rice Varieties

Four upland and two lowland varieties were grown on floodedand dry soil in pots in a glasshouse. Photosynthetic rate (P),transpiration rate (T), and water content (W) of the secondexpanded leaf from the top of the main stem were measured undercontrolled aeration and illumination in a leaf chamber in thelaboratory, together with leaf area (La), dry matter content(DM), nitrogen content (N), stomatal frequency (Sf), and totalvessel cross-sectional area at the base of the leaf blade (Va).P/La was positively related to T/La and Sf/La among six varietieswhen they were grown on flooded soil. IR 8, a semidwarf indicalowland variety, showed the highest P/La with the highest Sf/Laand T/La. When grown on dry soil P/La was positively correlatedwith W/DM, the latter being negatively related to T/Va. Twoupland varieties, African Moroberekan and Brazilian IAC 1246,showed the highest P/La on dry soil, keeping a higher W/DM witha lower T/La and a lower T/Va. Daytime leaf diffusive conductance(l/r_L) and leaf water potential (_L) measured on the same orthe same stage leaf in the glasshouse were positively correlatedwith the W/DM measured in the laboratory among varieties grownon dry soil. Simultaneous observation of P, T and W in the laboratoryindicated nonstomatal reduction in P/La due to leaf water deficitin sensitive varieties, although these varieties also showeda markedly lower daytime l/r_L in the glasshouse as comparedwith resistant varieties. Oryza sativa L., rice, drought resistance, photosynthesis, transpiration, water deficit, stomatal frequency, vessel size     

Leaf Characteristics and Net Gas Exchange of Diploid and Autotetraploid Citrus

The effect of tetraploidy on leaf characteristics and net gasexchange was studied in diploid (2x ) and autotetraploid (4x) ‘Valencia’ sweet orange (Citrus sinensis (L.)Osb.) and ‘Femminello’ lemon (Citrus limon (L.)Burm. f.) leaves. Comparisons between ploidy levels were madeunder high irradiance (I) in a growth chamber or low total Iin a glasshouse. Tetraploids of both species had thicker leaves,larger mesophyll cell volume and lower light transmittance thandiploids regardless of growth I. Mesophyll surface area perunit leaf area of 2x leaves was 5–15% greater than on4x leaves. Leaf thickness and mesophyll cell volume were greaterin high I leaves than low I leaves. In high I, average leafarea was similar for 2x and 4x leaves, whereas in low I it was30% greater in 4x than in 2x leaves. Nitrogen and chlorophyllconcentration per cell increased with ploidy level in both growthconditions. The ratio of chlorophyll a:b was 25% greater in2x than in 4x leaves. When net CO₂assimilation rate (A_CO2) wasbased on leaf area, 4x orange leaves had 24–35% lowerA_CO2than their diploids. There were no significant differencesin A_CO2between 2x and 4x orange or lemon leaves when expressedon a per cell basis. Overall, lower A_CO2per unit leaf area oftetraploids was related to increase in leaf thickness, largermesophyll cell volume, the decrease in mesophyll area exposedto internal air spaces, and the lower ratio between cell surfaceto cell volume. Such changes probably increased the resistanceto CO₂diffusion to the site of carboyxlation in the chloroplasts. Cell volume; chlorophyll; irradiance; leaf thickness; nitrogen; photosynthesis; ploidy; Citrus limon ; C. sinensis ; ‘Valencia’ sweet orange; ‘Femminello’ lemon     

Nuclear DNA Content in Twelve Species of Alstroemeria L. and Some of their Hybrids

Nuclear DNA content (2C-value), estimated through flow cytometryusing propidium iodide (PI), was shown to vary from 36.5 pgto 78.9 pg among 29 accessions of 12Alstroemeria species (2n=2x =16). The extremes were found inA. magnifica ssp.magnificaand inA. ligtu ssp.simsii , both belonging to the Chilean speciesgroup. The four Brazilian species exhibited less variation innuclear DNA content (49.8–56.4 pg), than the eight Chileanspecies (36.5–78.9 pg). Nuclear DNA content was positivelycorrelated (r =0.92,n =7,P <0.01) with the total chromosomelength. It was also positively correlated (r =0.85,n =5,P <0.01)with the length of C-bands, when only the Chilean species wereconsidered. When both karyotype parameters, length of non-C-bandedchromosome regions (x) and length of C-bands (y) were determined,it was possible to predict the nuclear DNA content (z) withthe formula z=0.65x +1.31y-0.45 (R ²=0.97,P =0.004). The DAPI fluorescence of most accessions was proportional tothe PI fluorescence (r =0.98,P <0.001), except for one accessionofA. ligtu , that had a relatively high PI/DAPI ratio (1.88).The PI/DAPI ratios of the Brazilian species were lower (1.59–1.67)than those of the Chilean species (1.68–1.88), which mightreflect a difference in base pair composition. Four groups ofspecies could be distinguished on the basis of fluorescencevalues. Diploid interspecific hybrids were shown to have a DNAcontent intermediate to the values of the parents involved.Both the PI and the DAPI fluorescence values of these hybridsapproximated the mid parent values. Tetraploids, derived fromselfing of diploids, had PI and DAPI fluorescence values thatwere twice that of the diploid hybrids. It was possible to distinguishaneuploids from euploids based on fluorescence values. Alstroemeria ; aneuploidy; C-banding; DAPI; evolution; flow cytometry; genome size; geophytes; karyotypes; Inca Lily; nuclear DNA; propidium iodide