Abnormal Sporogenesis in Wheat (Triticum aestivum L.) Induced by Short Periods of High Temperature

Plants of Triticum aestivum L. cv. Gabo, grown at 20 °C,were exposed to 30 °C for short periods during the timebetween the beginning of meiosis in the pollen mother cellsand anthesis. Plant water deficit at this temperature was avoidedby maintaining a high atmospheric relative humidity and tissuewater potential did not change. This temperature treatment appliedfor 3 days, at the time of reduction division and tetrad breakup in the male tissue, lowered grain yield through a drasticreduction in grain set, but was without effect at other stagesof development. Grain set was also reduced by exposing plantsto 30 °C for 1 day only or to a 30 °C day, 20 °Cnight (16 h photoperiod) regime for 3 days during the sensitiveperiod. A reduction in grain set did not result in a compensatoryincrease in the weight of remaining grains. The female fertility of previously heat-stressed plants wasassessed by pollinating with pollen from plants grown at a lowertemperature (20 °C). Grain set in such plants was less thanthat in plants grown at the lower temperature and hand pollinatedwith similar pollen, indicating that female fertility was reducedby high temperature. This was not the sole reason for reducedgrain set, however, as some anthers on heat-stressed plantswere small and neither extruded nor dehisced normally. Suchanthers contained pollen grains that were mostly shrivelled,had abnormal cytoplasm and showed no reaction to 2, 3, 5-triphenyltetrazolium chloride. Similar effects were also noted in pollenfrom apparently normal anthers on heat-stressed plants. Triticum aestivum, wheat, heat stress, pollen, sporogenesis, grain set, male sterility, female sterility     

Evidence on the Saltatory Origin of the G Genome in Wheat: the Description of a Triticum timopheevi-like Mutant

A spontaneously occurring somatic mutant of Triticum turgidumdicoccoides showed close morphological resemblance to T. timopheevi(AAGO). The hybrid between the mutant and the T. turgidum dicoccoides‘ mother’ plant was completely sterile, with verylow pollen fertility (0·33 percent). It exhibited a reasonablyhigh frequency of trivalents and quadrivalents at first metaphaseof meiosis, indicating that the mutation involved substantiallevels of chromosome rearrangement. The hybrid between the mutantand T. timopheevi had reasonably high fertility (53·5per cent) and high pollen fertility (86·6 per cent) andalmost regular bivalent formation at first metaphase of meiosis. It is proposed that T. timopheevi could have arisen in consequenceof somatic macromutation from T. turgidum dicoccoides givingrise to spontaneous speciation. The G genome of T. timopheeviis possibly monophyletic in origin, arising from rearrangementof chromosomes of the B genome of tetraploid wheat. Triticum turgidum dicoccoides, wheat, G genome, mutant     

A light and electron microscopy analysis of the events leading to male sterility in Ogu-INRA CMS of rapeseed (Brassica napus)

Ogura cytoplasmic male sterility (CMS) occurs naturally in radishand has been introduced into rapeseed (Brassica napus) by protoplastfusion. As with all CMS systems, it involves a constitutivelyexpressed mitochondrial gene which induces male sterility tootherwise hermaphroditic plants (so they become females) anda nuclear gene named restorer of fertility that restores pollenproduction in plants carrying a sterility-inducing cytoplasm.A correlative approach using light and electron microscopy wasapplied to define what stages throughout development were affectedand the subcellular events leading to the abortion of the developingpollen grains upon the expression of the mitochondrial protein.Three central stages of development (tetrad, mid-microsporeand vacuolate microspore) were compared between fertile, restored,and sterile plants. At each stage observed, the pollen in fertileand restored plants had similar cellular structures and organization.The deleterious effect of the sterility protein expression startedas early as the tetrad stage. No typical mitochondria were identifiedin the tapetum at any developmental stage and in the vacuolatemicrospores of the sterile plants. In addition, some strikingultrastructural alterations of the cell's organization werealso observed compared with the normal pattern of development.The results showed that Ogu-INRA CMS was due to premature celldeath events of the tapetal cells, presumably by an autolysisprocess rather than a normal PCD, which impairs pollen developmentat the vacuolate microspore stage, in the absence of functionalmitochondria. Key words: Brassica napus, cell death, light and electron microscopy, mitochondria, plastids, pollen development, Ogu-INRA cytoplasmic male sterility, transgenic-restored plants, tapetum Received 30 September 2007; Revised 11 December 2007 Accepted 20 December 2007     

Effect of Water Deficit on Sporogenesis in Wheat (Triticum aestivum L.)

Plants of Triticum aestivum L., cv. Gabo, were grown in a glasshousefor 4 weeks and then transferred to a controlled environmentwith 20±1 °C temperature and 16 h photoperiod. Theywere subjected to water deficit by withholding the water supplyduring various stages of floral development, including thoseimmediately before meiosis and all stages until just after anthesis. The proportion of apparently normal florets which produced grainwas reduced when water deficit occurred during and immediatelyafter meiosis in the generative tissues. The effect of thisreduced grain set on total grain yield was partially compensatedby an increase in the weight of the remaining grains. Cross-pollinationbetween stressed and well-watered plants showed that grain setwas reduced as a direct consequence of the induction of malesterility by water stress, whereas female fertility was unaffected.A large proportion of the anthers on water-stressed plants weresmall and shrivelled, did not dehisce normally and containedpollen which was devoid of normal cytoplasmic constituents andshowed no staining reaction with triphenyl tetrazolium chloride.This effect on male fertility was not a result of desiccationof the sporogenous tissue, but an indirect outcome of the decreasein water potential elsewhere in the plant. Water stress, Triticum aestivum L., wheat, pollen, sporogenesis, grain set, male sterility     

Male Sterility and Anther Wall Structure in Copper-deficient Plants

Anther development and pollen sterility were followed in plantsof wheat, oat, barley, sweetcorn, sunflower, petunia and subterraneumclover grown at a range of copper supplies. Copper-deficientplants had increased pollen sterility. Lignified wall thickenings were reduced or absent in the endotheciaof anthers from Cu-deficient plants. Reduced seed set may resultboth from reduced pollen fertility or failure of the stomiato rupture due to decreased lignification of anther walls. Triticum aestivum L., wheat, Hordeum vulgare L., barley, Avena sativa L., oat, Zea mays L., corn, sweetcorn, maize, Helianthus annuus L., sunflower, Petunia hybrida L., Trifolium subterraneum L., subterranean clover, male sterility, anther development, copper deficiency     

Effects of Temperature on Pollen Viability in Mango cv. 'Kensington'

The response of pollen development to low or high temperatureregimes was studied to determine the conditions suitable forthe formation of fertile pollen in the mango cv. 'Kensington'.The phase most sensitive to the degree and duration of temperaturestress was that from meiosis to the pre-vacuolate microspore(about 3 d duration at 25/20 °C) though vacuolated microsporeswere also sensitive to low temperature. Night temperatures below10 °C resulted in pollen grains with a low viability (<50%). A temperature between 15 and 33 °C during the phasefrom meiosis to the pre-vacuolate microspore was optimum forpollen development (70-85% pollen viability). Analysis of field records showed a linear negative correlationbetween percentage of pollen viability and number of days whichhad a mean night temperature lower than 10 °C during theperiod from meiosis to early mature stage (y = 77·7-3·4x,r² = 0·60). The temperature sensitive phase was estimatedto begin 155 degree days D = [(T_max + T_min)/2 - 10] before anthesisand to end 78 degree days before anthesis. This equation maybe useful as a means of predicting pollen viability in the fieldfrom temperature records and thus fruit set, date of maturityand yield. It may also aid in the selection of areas for growingmangoes in marginal climates.Copyright 1994, 1999 Academic Press Mangifera indica L. mango, microsporogenesis, pollen development, viability, sterility, temperature     

Gynodioecy in Cirsium chikushiense Koidz. (Compositae)

A study of the morphology and function of flowers in Cirsiumchikushiense revealed that the species was distinctly gynodioecious.Self-incompatible hermaphrodite florets produced both seedsand pollen grains, while female ones produced seeds but no pollengrains at all. The degenerated stamens of females were not onlysmaller but also sometimes occurred at a lower position insidethe floral tube than in hermaphrodites. The stigmata of femalesoften developed more fully than those of hermaphrodites. Thefrequencies of female plants in natural populations varied from15·5 to 50%. Almost all the pollinators stayed on bothfemale and hermaphrodite heads only to collect nectar. The femaleplants of this species may be more specialized in their genderby saving the cost of not only pollen grains but also stamens,and may be maintained by sufficient pollinators in natural populations.This gynodioecy may provide an example of nuclear-cytoplasmicmale sterility.Copyright 1994, 1999 Academic Press Sex expression, gynodioecy, Cirsium chikushiense, Compositae, male sterility, degenerated stamen, female frequency     

Linear Relations between Carbon Dioxide Concentration and Rate of Development Towards Flowering in Sorghum, Cowpea and Soyabean

Negative linear relations were detected (P < 0·005)between the rate of progress from sowing to panicle initiationand CO₂ concentration (210-720 µmol CO₂ mol^-1 air) fortwo genotypes of sorghum [Sorghum bicolor (L.) Moench]. Relationsbetween CO₂ concentration and the rate of progress from sowingto first flowering were also negative in soyabean [Glycine max(L.) Merrill] (P < 0·025), but positive in cowpea[Vigna unguiculata (L.) Walp.] (P < 0·025), albeitthat in both grain legumes sensitivity was much less than insorghum. Thus CO₂ elevation does not delay flowering in allshort-day species. The considerable effect of CO₂ concentrationon times to panicle initiation resulted in large differencesamong the sorghum plants at this developmental stage; with increasein CO₂ concentration, plants were taller with slightly moreleaves and more pronounced apical extension. At the same timeafter sowing however, sorghum plants were heavier (P < 0·05)at 210 than at 360 µmol CO₂ mol^-1 air. In contrast, relationsbetween the dry masses of the soyabean and cowpea plants andCO₂ concentration were positive and curvilinear (P < 0·05).It is suggested that the impact of global environmental changecould be severe for sorghum production in the semi-arid tropics.Copyright1995, 1999 Academic Press Sorghum bicolor (L.) Moench., sorghum, Glycine max (L.) Merrill, soyabean, Vigna unguiculata (L.) Walp., cowpea, development, flowering, CO₂, dry matter accumulation, environmental change     

Production of 2n Gametes in Diploid Subspecies of Dactylis glomerata L. 2. Occurrence and Frequency of 2n Eggs

Whereas polyploidy has been found in more than half the Gramineae,the occurrence of 2n gametes, a potentially major mechanismof polyploid production, has been rarely studied. In the presentwork, the frequency of 2n egg production in nine diploid (n= 2x = 14) subspecies of the polyploid complex Dactylis glomeratahas been estimated by determining the ploidy level of the progenyin 98 2X-4X crosses. The 2n egg origin of the 4X offspring wasverified using enzyme markers. The frequency of 2n egg productionin each subspecies was estimated from the number of 4X offspring,the number of florets in the seed plant and the fertility ofthe subspecies. The ploidy level of the progeny was determinedby chromosome counts or nuclear DNA quantification using flowcytometry. Plants producing 2n eggs were detected in 47% ofthe fertile crosses, involving eight subspecies. Variabilitywas related to individuals and not to subspecies. Average 2negg frequency was 0·49% for all crosses, and 1·53%for crosses where 2n egg production was detected. Individualfrequencies did not exceed 3·5%, with the exception of26% in one plant. Triploid block was higher and fertility, frequencyof high 2n gamete producers and average 2n gamete frequencywere lower in the 2X-4X crosses than in the opposite 4X-2X crossesinvolving the same plants, previously studied. Diplogynous anddiplandrous gamete production were not correlated with eachother. However, the widespread occurrence of plants producingboth kinds of 2n gametes in almost all the studied subspecies,as well as the presence of several individuals able to producehigh rates of 2n eggs or 2n pollen, support the hypothesis thattetraploids can be formed anywhere and anytime by sexual polyploidizationin diploid populations of Dactylis glomerata L. 2n eggs, polyploidy, Dactylis glomerata L., flow cytometry, sexual polyploidization     

Effects of the fungal endophyte, Neotyphodium lolii, on net photosynthesis and growth rates of perennial ryegrass (Lolium perenne) are independent of In Planta endophyte concentration

• Background and Aims Neotyphodium lolii is a fungal endophyteof perennial ryegrass (Lolium perenne), improving grass fitnessthrough production of bioactive alkaloids. Neotyphodium speciescan also affect growth and physiology of their host grasses(family Poaceae, sub-family Pooideae), but little is known aboutthe mechanisms. This study examined the effect of N. lolii onnet photosynthesis (P_n) and growth rates in ryegrass genotypesdiffering in endophyte concentration in all leaf tissues. • Methods Plants from two ryegrass genotypes, Nui D andNui UIV, infected with N. lolii (E+) differing approx. 2-foldin endophyte concentration or uninfected clones thereof (E–)were grown in a controlled environment. For each genotype xendophyte treatment, plant growth rates were assessed as tilleringand leaf extension rates, and the light response of P_n, darkrespiration and transpiration measured in leaves of young (30–45d old) and old (>90 d old) plants with a single-chamber openinfrared gas-exchange system. • Key Results Neotyphodium lolii affected CO₂-limited ratesof P_n, which were approx. 17 % lower in E+ than E– plants(P < 0·05) in the young plants. Apparent photon yieldand dark respiration were unaffected by the endophyte (P >0·05). Neotyphodium lolii also decreased transpiration(P < 0·05), but only in complete darkness. There wereno endophyte effects on P_n in the old plants (P > 0·05).E+ plants grew faster immediately after replanting (P < 0·05),but had approx. 10 % lower growth rates during mid-log growth(P < 0·05) than E– plants, but there was noeffect on final plant biomass (P > 0·05). The endophyteeffects on P_n and growth tended to be more pronounced in NuiUIV, despite having a lower endophyte concentration than NuiD. • Conclusions Neotyphodium lolii affects CO₂ fixation,but not light interception and photochemistry of P_n. The impactof N. lolii on plant growth and photosynthesis is independentof endophyte concentration in the plant, suggesting that theendophyte mycelium is not simply an energy drain to the plant.However, the endophyte effects on P_n and plant growth are stronglydependent on the plant growth phase.     

Inheritance of spontaneous male sterility in pigeonpea

 A male-sterile plant was observed in the UPAS-120 cultivar of pigeonpea (Cajanus cajan). The plant was about 5–7 days late-flowering and had white translucent anthers with complete pollen sterility. The inheritance of this spontaneous male sterility was studied in a cross involving the mutant and fertile UPAS-120, including their F₁, F₂, BC₁F₁ and BC₂F₁ generations. The results suggested that the male sterility was genetic and due to a recessive gene. Received: 12 November 1996/Accepted: 17 January 1997     

Instability of the Ploidy Level in Autotetraploid Sorghum Plants from a Line with Variable Male Fertility

It was found that, in some of the plants in generations C₁–C₅ of induced tetraploids in the semisterile sorghum line AS-1-30, more than 30% of pollen grains (PGs) have sizes typical of haploid PGs. Pollen of these plants was used to pollinate different lines of sorghum with cytoplasmic male sterility (CMS). Diploid hybrids were obtained, which confirms the presence of haploid PGs in the tetraploids studied. When tetraploid plants with an increased frequency of haploid PGs were pollinated with pollen of plants from fertile diploid lines, diploid hybrids were also obtained. This demonstrates that the tetraploids studied had haploid egg cells. In generation C₄, a chimeric plant was found; one of its shoots was diploid (judging from morphological characters) and produced as many as 99% of haploid PGs. It is assumed that haploid gametes in autotetraploids are formed through somatic reduction of chromosomes at different ontogenetic stages.     

Viability and Germination of the Pollen of Sorghum [Sorghum bicolor (L.) Moench]

Previous studies have demonstrated that pollen of sorghum [Sorghumbicolor (L.) Moench] loses capacity to both germinate in vitroand to set seed in vivo soon after being shed. The current studyevaluates the capacity for dehydrated pollen to effect in vitrogermination, reduce tetrazolium chloride, and set seed on cytoplasmicmale sterile plants. Morphological changes during pollen germinationwere examined by scanning electron microscopy (SEM). Close to70% of the pollen germinated in 5 min, or less, when collectedat 80% relative humidity (RH) and stored in sealed glass vials.Pollen tubes elongated autotropically with atmospheric humidityapparently being a controlling factor in the process. Pollendehydrated at 50% RH and 25°C for 15-30 min neither germinatedin vitro, reduced tetrazolium chloride, nor set seed on malesterile plants. Rehydrating the pollen did not restore the capacityfor germination. SEM micrographs demonstrated that elongatingpollen tubes encircled the pollen grain and were contiguousto the surface. A fibrillar-like material existed on the exineof separated pollen grains at the point where the grains hadbeen previously attached.Copyright 1994, 1999 Academic Press Sorghum pollen, germination, seed-set, viability, scanning electron microscopy, Sorghum bicolor (L.) Moench     

Effect of Sporophytic Heterozygosity on the Male Gametophyte of the Tetraploid Potato (Solanum tuberosum L.)

Quantitative variation for pollen stainability was examinedin both tetraploid x diploid and tetraploid x tetraploid familiesof potato (Solanum tuberosum L.). The diploid parents, whichwere highly heterozygous, produced first division restitution(FDR) 2n pollen. The families used were not affected by cytoplasmic-geneticmale sterility. Significant differences between families werefound. FDR 2n pollen producing diploid clones had progenieswith a significantly higher pollen stainability than those derivedfrom crosses between tetraploid parents. This was related tothe level of heterozygosity in the sporophyte. In FDR 2n pollen,80% of the heterozygosity and a large fraction of epistasispresent in the diploid parent was transmitted to its tetraploidprogeny. This is important for the production of open pollinated,true potato seed, because pollen stainability is significantlycorrelated with fruit set (r = 0·85).Copyright 1994,1999 Academic Press FDR 2n pollen, gametophytic heterozygosity, true potato seed     

Uptake and Distribution of Copper in Chrysanthemum morifolium

The effects of various levels of copper on the uptake and distributionof copper in Chrysanthemum morifolium grown in solution cultureand peat-sand have been examined. Whole plants growing in shortdays were sampled at regular intervals, divided into roots,stem, leaves and lateral shoots, and analysed for copper. Thepartitioning of copper between these tissues showed that a relativelylarge proportion (30–40 per cent) of the total plant copperwas accumulated in the roots of normal plants during the harvestingperiod, compared with approximately 10 per cent in the rootsof copper deficient plants. Whilst the copper content (ug g^–1) of leaves and stemfrom normal plants was negatively correlated with the amountof dry matter produced (P < 0·001), the correspondingcopper deficient tissues showed little variation in copper contentwith increases in tissue dry weight. A more detailed investigationof the copper content of leaves from normal plants showed thatgradients existed within the plant with respect to both leafposition and time of harvest which could be described by a singlecubic surface equation (P < 0·001).     

Variation of Alkaloid Content in Erythroxylum coca Leaves from Leaf Bud to Leaf Drop

A sequential study describing the content (%) of alkaloids inleaves of Erythroxylum coca var. coca Lam. from leaf bud developmentto leaf drop has not previously been conducted. The length oftime the leaf resides on the plant and its concurrent metabolicactivity also has not been defined. In the present study, cocaine,methyl ecgonine, hygrine, tropinone, trans -cinnamoylcocaine,cis-cinnamoylcocaine, tropacocaine and cuscohygrine were monitoredto determine: (1) their content and patterns of accumulationfrom leaf bud to leaf drop; (2) the time leaves resided on theplant; and (3) whether leaves were metabolically active untilleaf drop. E. coca plants were grown in a controlled environmentfor 37 months. Leaves similar in chronological age were extractedand analysed for alkaloid content by gas chromatography (GC)and gas chromatography/mass spectrometry (GC/MS). Cocaine washighest in 7 d old rolled leaves (0·75%) and declinedto 0·39% at leaf drop. Cocaine, methyl ecgonine, hygrine,tropinone, trans -cinnamoylcocaine, cis-cinnamoylcocaine, cuscohygrineand tropacocaine content in 35 d old (mature) leaves was 0·61,0·59, 0·68, 0·08, 0·31, 0·55,0·52, and 0·05%. respectively. Cocaine, methylecgonine, hygrine, cis -cinnamoylcocaine, and cuscohygrine displayeda gradual decline from week 2 to week 36 of leaf duration. Tropinoneand tropacocaine were the least abundant of the alkaloids monitored.Cis-cinnamoylcocaine content exceeded cocaine at week 12, 16,and weeks 19 to 23 of leaf duration. Trans -cinnamoylcocainewas highest in rolled leaves (week 1) and in expanded leavesafter week 30. The monitored alkaloids appeared to be part ofthe metabolically active pool of the leaf. Leaves remained onthe E. coca plants for 36 weeks.Copyright 1994, 1999 AcademicPress Cocaine, methyl ecgonine, hygrine, tropinone, trans-cinnamoylcocaine, cis-cinnamoylcocaine, cusco-hygrine, tropacocaine, leaf bud, rolled leaves, expanded leaves, alkaloids, patterns, fluctuation, Erythroxylum coca var. coca, E, coca     

Local Differentiation Among Populations of Arabis stelleri var. japonica in a Sand Dune Habitat

Local variation in ecological and genetic traits was analysedin the perennial herb Arabis stelleri var. japonica in a sanddune area in western Japan. Plants of this species are establishedin three contiguous habitats (subpopulations): sand dune, forestand an ecotonal zone between both habitats. Morphological, ecologicaland genetic traits of A. stelleri var. japonica plants wereanalysed to discover the extent of microdifferentiation amongthese subpopulations. All plants in nine quadrats were markedand followed during 2 years. The ecotonal zone presented thehighest number of mature individuals per quadrat. Plants mayproduce the same number of shoots per plant but rosette sizewas larger in plants from sand dune and forest subpopulationsthan the ecotone. Plants in the sand dune showed the highestnumber of large capsules per plant. Mortality of seedlings andmature plants was slightly higher in the ecotone than in theother two subpopulations. Sand dune plants had the highest variationamong quadrats in almost all traits measured. In the electrophoreticanalyses, 21 loci were detected on twelve enzyme systems. Fifteenloci were monomorphic and six loci had 1·2 alleles perloci. Genetic distances and genetic identity Nei's values werevery similar among subpopulations (means I = 0·994, D= 0·006). The total genetic diversity (H_T) was 0·340and the within-population component (H_s) was 0·333 indicatinglow genetic differentiation among subpopulations. Gene flowvaried between genes but most of the values were high (meanNm = 188·3). Subpopulations of A. stelleri showed differentiationin morphological and ecological traits and low genetic differentiationin the loci studied. This may be related with the plastic responseof plants to different microenvironments and a significant geneflow between habitats.Copyright 1994, 1999 Academic Press Arabis stelleri var. japonica, Brassicaceae, gene flow, genetic diversity, local differentiation, mortality, plant population, reproduction     

Growth and Photosynthesis in Sorghum bicolor Infected with Striga hermonthica

Sorghum plants were grown in the laboratory with the root systemof each plant split between two pots. Three split pot treatmentswere established: (– –) treatment, where both halvesof the root were free from Striga; (– +) treatment, wherethe soil in one half of the pot had been inoculated with Strigaseed; (+ +) treatment, where the soil in both halves of thepot had been inoculated with Striga. Seed, stem and leaf weight were reduced by 82, 60 and 26 percent respectively in (+ +) plants compared to (– –)plants. Partially infected plants (– +) behaved similarlyto (+ +) plants. Rates of light saturating carbon dioxide fixation in (+ +) and(– +) plants were only 60 per cent of those measured in(– –) plants. This reduction was independent ofchanges in stomatal conductance. The effects of Striga on the growth and photosynthesis of sorghumappear to be independent of the degree of parasitism to whichthe host is subjected. The difference in production betweeninfected and uninfected plants was greater than could be accountedfor in term of competition with the parasite for resources,and Striga appears to have a pathological effect on the host. Sorghum, Striga, parasitic angiosperm, growth, photosynthesis     

Restoration of Fertility in Cytoplasmic Male-Sterile Nicotiana tabacum (Cytoplasm N. bigelovii) by Protoplast Fusion with X-Irradiated Protoplasts of N. tabacum, SR-1

The ‘donor–recipient’ fusion method was usedto investigate the intraspecific transfer of organelles andorganelle-encoded traits from donor to recipient Nicotiana speciesunder conditions which were selective for chloroplast transfer.An alloplasmic male sterile line of N. tabacum carrying thecytoplasm of N. bigelovii as the recipient and N. tabacum SR-1,a mutant with maternallyinherited streptomycin resistance, asthe cytoplasm donor were used. Organelle composition of 13 cybridplants was investigated by analysis of tentoxin and streptomycinsensitivities, chloroplast and mitochondrial DNA restrictionpatterns, and alloplasmic male sterility Chloroplast DNA analysisand the tentoxin test both showed that all 13 cybrid plantspossessed chloroplasts from the N. tabacum, SR-1 parent only.Analysis of mitochondrial DNA from second generation plantsderived from 11 of the original cybrid plants indicated verylittle heterogeneity with nine of the plants expressing pureparental-type mtDNAs. Although conditions were selective fordonor-type chloroplast transfer, the results indicate the generationof novel cytoplasmic combinations; pure donor chloroplasts incombination with either pure or recombinant-type recipient mitochondria.Our results support previous findings that the ‘donor-recipient’fusion method can be used to restore fertility of CMS linesof Nicotiana Key words: Nicotiana, cytoplasmic male sterility, chloroplast DNA, mitochondrial DNA, somatic hybridization     

Partitioning of Dry Matter in Tanier (Xanthosoma spp.) Irrigated with Fractions of Evapotranspiration

The accumulation and partitioning of dry matter was determinedin tanier plants irrigated with fractions of the water lostthrough evapotranspiration (WLET) in an effort to establishgrowth analysis data from which a tanier growth (simulationmodel could be developed. The irrigation regimes were basedon Class A pan factors ranging from 0·33 to 1·32with increments of 0·33. Tanier plants were planted inthe field and harvested for biomass production about every 6weeks during the growing season. At each harvest, plants wereseparated into various plant parts, and their dry matter contentwas determined. The first 90 d after planting (DAP) were characterizedby low rates of dry matter accumulation, with only leaves andpetioles showing substantial growth. A grand growth period followedin which leaves, petioles, and roots rapidly accumulated drymatter until 278 DAP. During this period, plants that received0·99 and 1·32 WLET exhibited similar total drymatter content, and this was significantly greater than in plantssupplied with 0·33 and 0·66 WLET. Cormel dry mattercontent peaked at 29% of total plant dry matter by 322 DAP inplants replenished with 1·32 WLET. Partitioning of drymatter to cormels in other treatments was significantly reduced.Partitioning of dry matter to corms increased linearly throughoutthe growing season in all treatments. Dry matter partitioningto suckers and the number of suckers formed from plants replenishedwith 0·33 and 0·66 WLET was greater than in themore irrigated treatments.Copyright 1994, 1999 Academic Press Tanier, Xanthosoma spp., growth, dry matter partition, irrigation, evapotranspiration