Leaf and Tiller Production of Prairie Grass (Bromus willdenowii Kunth) and Two Ryegrass (Lolium) Species

A detailed morphological study of three prairie grass cultivars(Bromus willdenowii Kunth) was conducted under ‘vegetative’and ‘reproductive’ growth conditions (short andlong photoperiods) and at different temperatures. Perennialryegrass (Lolium perenne L.) and Westerwolds ryegrass (Loliummuhiflorum Lam.) were compared during vegetative growth. Prairie grass had higher leaf appearance rates (leaves per tillerper day) and lower site filling (tillers per tiller per leafappearance interval) than the ryegrass species. Tillering rates(tillers per tiller per day) were also lower, except under vegetativeconditions at 4C. Low tiller number in prairie grass was notdue to lack of tiller sites but a result of poor filling ofthese sites. Lower site filling occurred because of increaseddelays in appearance of the youngest axillary tiller and lackof axillary tillers emerging from basal tiller buds. In prairiegrass, no tillers came from coleoptile buds while only occasionallydid prophyll buds develop tillers. Low tiller number in prairiegrass was compensated for by greater tiller weight. Prairiegrass had more live leaves per tiller, greater area per leafand a high leaf area per plant. Considerable variation between cultivars was found in prairiegrass. The cultivar ‘Bellegarde’ had high leaf appearance,large leaves and rapid reproductive development, but had lowlevels of site filling, tillering rate, final tiller numberand herbage quality during reproductive growth. ‘Primabel’tended to have the opposite levels for these parameters, while‘Grasslands Matua’ was intermediate and possiblyprovided the best balance of all plant parameters. prairie grass, Bromus willdenowii Kunth, perennial ryegrass, Lolium perenne L., Westerwolds ryegrass, Lolium multiflorum Lam., temperature, photoperiod, leaf appearance, leaf area, tillering, site filling, tillering sites, yield     

Plant Growth Analysis: Growth and Yield Component Responses to Population Density in Forage Maize

Forage maize (Zea mays L.) was grown in monocultures at populationdensities ranging from 4·9 to 11·1 plants m^–2.Data for plant growth analysis were obtained from six harvestscarried out from 21 to 115 d after planting. Conventional plantgrowth analysis indicated that improvements in forage productivityper unit land area by high population density resulted directlyfrom increased plant presence. Reduction in dry weight per shootat high population density was associated with reduced unitleaf rate. Leaf area ratio was little affected, which may implythat competition for soil nutrients or oxygen was the chiefcause of plant interference. Yield component analysis demonstratedthe increasing importance of population density treatments asa source of variation as growth progressed. Direct relationshipsbetween variation in yield per plant and variation in two yieldcomponents, stem diameter and the inverse of leaf area ratio,were demonstrated. Both conventional plant growth analysis andyield component analysis indicated complex physiological andmorphological adjustments to species population density. Plant growth analysis, yield component analysis, Zea mays L     

A Comparison of Soil Microbial Community Structure, Protozoa and Nematodes in Field Plots of Conventional and Genetically Modified Maize Expressing the Bacillus thuringiens is CryIAb Toxin

Field trials were established at three European sites (Denmark, Eastern France, South-West France) of genetically modified maize (Zea mays L.) expressing the CryIAb Bacillus thuringiensis toxin (Bt), the near-isogenic non-Bt cultivar, another conventional maize cultivar and grass. Soil from Denmark was sampled at sowing (May) and harvest (October) over two years (2002, 2003); from E France at harvest 2002, sowing and harvest 2003; and from SW France at sowing and harvest 2003. Samples were analysed for microbial community structure (2003 samples only) by community-level physiological-profiling (CLPP) and phospholipid fatty acid analysis (PLFA), and protozoa and nematodes in all samples. Individual differences within a site resulted from: greater nematode numbers under grass than maize on three occasions; different nematode populations under the conventional maize cultivars once; and two occasions when there was a reduced protozoan population under Bt maize compared to non-Bt maize. Microbial community structure within the sites only varied with grass compared to maize, with one occurrence of CLPP varying between maize cultivars (Bt versus a conventional cultivar). An overall comparison of Bt versus non-Bt maize across all three sites only revealed differences for nematodes, with a smaller population under the Bt maize. Nematode community structure was different at each site and the Bt effect was not confined to specific nematode taxa. The effect of the Bt maize was small and within the normal variation expected in these agricultural systems.     

Influence of Seed Pre-treatments with Plant Growth Regulators on Metabolic Alterations of Germinating Maize Embryos Under Stressing Temperature Regimes

The germination performance of maize seeds (Zea mays L. cv.Partap-1) pre-treated individually with the substituted phthalimideAC 94,377 (1-(3-chlorophthalimido)-cyclohexanecarboxamide),GA₄₊₇ and ABA was markedly improved under sub- and supra-optimaltemperature regimes. ABA was especially stimulatory at the sub-optimaltemperature. Metabolic alterations in the germinating embryosof treated seeds revealed an increased accumulation of solublesugars and proteins compared with the controls under stressingtemperatures. The activities of acid phosphatase, invertase,catalase and peroxidase were seemingly related to the alleviationmetabolism. It is suggested that gibberellins and abscisic acidmay have positive regulatory effects in triggering the systemfor stress alleviation. Germination, Zea mays, temperature, growth regulators, embryos, metabolism     

The Effects of Soil Bulk Density on the Morphology and Anchorage Mechanics of the Root Systems of Sunflower and Maize

The effects of soil bulk density and hence strength on two contrastingspecies of herbaceous annuals, the dicot sunflower (HelianthusannuusL.) and the monocot maize (Zea maysL.), were investigatedby comparing the morphology and mechanics of field-grown plantsin soil with a low and high bulk density. Soil with a low bulkdensity had a significantly lower penetration resistance (118±4.4kPa) than the high bulk density soil (325±12.2 kPa;P<0.0001).Soil strength affected shoot and root systems of both speciesbut had no significant effect on shoot height. In both speciesroots were thicker closer to the stem base in strong soil comparedto those in weaker soil. Sunflower tap-roots growing in strongsoil tapered more rapidly than those in weak soil. Only in maize,however, were roots growing in weak soil stiffer than thosein strong soil. Despite only small absolute differences in thepenetration resistance of the soil both species growing in strongsoil had greater anchorage strength than those in weak soil.As a consequence more plants in weak soil lodged compared withthose growing in strong soil. This study shows that plants can,to a small extent, respond to changes in soil strength, butthat changes do not appear to compensate fully for alterationsin soil conditions. Furthermore it may be possible, by manipulatingsoil strength, to control lodging.Copyright 1999 Annals of BotanyCompany Roots, compaction, soil strength, anchorage mechanics, bulk density, thigmomorphogenesis, lodging,Helianthus annuusL.,Zea maysL.     

Relationship Between Photosynthate Supply and Endosperm Development in Maize

Maize (Zea mays L., cultivar Pioneer 3925) plants were givenshaded, thinned and control light treatments during 10 d or20 d periods surrounding pollination. Glucose, sucrose, starch,and dry matter (DM) contents were measured at intervals in compositesamples of pericarp/nucellus (PN), and in endosperms taken fromdeveloping kernels. Total kernel DM per ear at maturity washigher in the thinned treatment than control and shaded treatmentsdue to higher kernel set in apical regions of ears. In PNs at11 d after pollination (DAP), DM and sucrose contents were slightlygreater in thinned than control and shaded plants. Glucose contentswere substantially greater than controls in PNs of thinned plantsand were less than controls in shaded plants. In endospermsfrom apical kernels at 8 to 12 DAP (during cell division), DM,glucose and sucrose contents were substantially less in shadedthan control and thinned plants. Sucrose contents were greaterin endosperms of thinned than control plants. Sugar contentsin endosperms from basal kernels were nearly the same in thethree light treatments. At 12 DAP, apical and basal endospermsin shaded plants had fewer nuclei than those of the other lighttreatments. The light treatments appeared to effect apical kernelgrowth by influencing the extent of cell division. Zea mays L, maize, light treatment, endosperm, cell division, glucose, sucrose, starch     

Calcium and Rhizodermal Differentiation in Primary Maize Roots

Rhizodermal differentiation of maize (Zea mays L. cv. LG 11)roots cultured in humid air was influenced by a pretreatmentfor 2 h in CaCl₂ or CaSO₄ solutions. This increased the numberof hair-producing roots and the density of hairs. Ethylene glycol-bis-(ß-aminoethylether)N,N'-tetraacetic acid (EGTA) was inhibitory. Root hairsemerged in the part of the cell nearer to the tip. Trichoblastswere shorter and elongated more slowly than atrichoblasts. Theelongation of the lower part of the trichoblast was less thanthat of the upper part. Key words: Cell length, cell number, hair position     

Biochemical Characteristics of Membrane Fractions Isolated from Maize (Zea mays L.) Roots

Membrane fractions have been isolated from maize (Zea mays L.)roots by discontinuous density gradient centrifugation and phaseseparation methods. A number of approaches were tried with theaim of identifying specific membrane types, especially the plasmamembrane. These included the use of enzymic markers, determinationof glucose and leucine incorporation, separation of membraneproteins by SDS-PAGE, and attempts to identify the plasma membranefraction by cell surface labelling. The results are discussedin relation to the usefulness of membrane markers and the difficultiesof isolating surface membranes from higher plant tissues.     

Osmotic Adjustment and Stomatal Response to Water Deficits in Maize

A pot experiment was carried out using five maize {Zea maysL.) cultivars under three soil moisture levels (MPa 0 to –0.05,–0.3 to –0.9 and –1.2 to –1.5) to investigatethe effects of water deficits on osmotic adjustment and stomatalconductance. The degree of leaf rolling and the sugar and nutrientconcentrations in leaf cell sap were measured. Leaf water potential and osmotic potential decreased and stomatalconductance decreased with increasing water deficits. Stomatalconductance correlated positively with leaf water potentialand osmotic potential. Degree of leaf rolling was lower in cultivarswhich maintained higher turgor. Osmotic adjustment of 0.08 to0.43 MPa was found under the lowest soil moisture level in fivecultivars used. Sugar and K were the major osmotic substancesin the maize plant. Sugar, K and Mg concentrations increasedunder water deficit, and correlated negatively with a decreasein osmotic potential. Key words: Zea mays L., leaf water relations, leaf rolling, osmotic adjustment, stomatal conductance, water deficit     

Turgor Differences and Water Stress in Maize and Sorghum Leaves During Drought and Recovery

The pressure potentials (turgor pressure) in leaves of maize(Zea mays L.) and grain sorghum (Sorghum vulgare Pers.) plantssubjected to water stress in a controlled environment were estimatedfrom measurements of water and osmotic potentials. Changes inturgor pressure were larger in sorghum than in maize duringthe development of water stress and after re-watering. It issuggested that this indicates a lower cell wall elasticity insorghum than in maize. This fact may affect some of the physiologicalactivities of sorghum     

Profiles of Leaf Senescence During Reproductive Growth of Sunflower and Maize

We investigated the effect of reproductive growth on the profilesof leaf senescence in maize (Zea mays L.) and sunflower (Helianthusannuus L.). Leaf senescence after flowering was assessed usingboth structural (leaf chlorophyll, nitrogen and dry matter)and functional (photosynthesis) variables in undisturbed plants(+G) and in plants in which grain set was prevented (-G). Twoweeks after flowering, lack of grain accelerated senescencein maize and delayed senescence in sunflower as indicated byleaf chlorophyll; leaf nitrogen and dry matter were less sensitiveresponse variables. Lack of interaction between reproductivetreatment and leaf position indicates that the senescence signal,whatever its nature, was equally effective throughout the plantin both species. In both species, feedback inhibition of photosynthesiswas first detected 30–35 d after flowering; excess carbohydratein the leaves was therefore an unlikely trigger of acceleratedsenescence in maize. As reproductive development progressed,differences between +G and -G plants were more marked in sunflower,and tended to disappear or reverse in maize. In sunflower, interactionsbetween leaf position and reproductive treatment—attributableto the local effect of grain—were detected around 20–27d after flowering. Copyright 2000 Annals of Botany Company Helianthus annuus, Zea mays, chlorophyll, light, nitrogen, photosynthesis, reproductive growth, senescence, source-sink, SPAD.     

The Effects of Modifying Sucrose Concentration on the Development of Maize Kernels Grown in vitro

Intact Zea mays L. kernels attached to cob tissue develop tomaturity when grown in vitro. This experiment was designed todetermine if it is possible to prolong kernel growth by refreshingthe culture medium. Blocks of maize kernels were grown in vitroon media containing several concentrations of sucrose. Kernels,at all concentrations of sucrose, developed to maturity at 30–35d post-pollination, indicating that it is not possible to extendthe kernel growth phase by supplying a carbohydrate source.Kernels grown on media containing 80 g 1^–1 or higher sucroseconcentration had a significantly greater percentage of kernelsthat developed to maturity, and had greater weight and starchcontent per seed. Zea mays, kernel culture, seed development, starch     

A 3D Architectural and Process-based Model of Maize Development

A 3D architectural and process-based model of maize developmentwas implemented on the basis of the L-system software Graphtal,interfaced with physical models computing microclimate distributedon the 3D canopy structure. In a first step, we incorporatedin the software Graphtal additional functions that enable bi-directionalcommunication with external modules. A simple model for distributedphotosynthetically active radiation and the model for apex temperatureby Cellieret al. (Agricultural and Forest Meteorology63: 35–54,1993) were interfaced with Graphtal. In a second step we developeda L-system model for maize, where production rules for growthand development of organs are based on the current state ofknowledge of maize development as a function of temperature.Visual representation of the plant is based on the geometricalmodel of leaf shape by Prévot, Aries and Monestiez (Agronomie11:491–503, 1991). Finally, various data sets were used toevaluate the physiological aspects and the geometrical representation.It is concluded that environmental L-systems are a convenienttool to integrate biophysical processes from organ to canopylevel, and provide a framework to model growth of individualplants in relation to local conditions and ability to foragefor resources. However, progress is needed to improve both theknowledge of physiological processes at the organ level andthe calculation of physical environmental parameters; some directionsfor future research are proposed.Copyright 1998 Annals of BotanyCompany Growth model; 3D plant architecture;Zea maysL.; corn; temperature; L-system modelling; developmental physiology; virtual plant.     

Comparative Leaf Surface Morphology and the Glossy Characteristic of Sorghum, Maize, and Pearl Millet

Leaf surfaces of seven genotypes of Sorghum bicolor, two ofmaize, Zea mays, and two pearl millet, Pennisetum americanum,were examined by scanning electron microscopy for possible morphologicaldifferences. Leaves 1, 3, 5 and 7 were photographed and printswere used to estimate waxiness, hairiness or pubescence andstomatal density. Glossiness was determined by spraying water,which adhered to the glossy leaves. Cuticular transpirationof detached third and fifth leaves was estimated from the rateof water loss after abscisic acid induced stomatal closure.Sorghum lines SC283, CSM63, CSM90, and pearl millets Souna andTiotioni (all from Mali), were non-glossy, well covered withwax, and exhibited variable hairiness. Older leaves of sorghumvarieties Martin and Redlan were glossy and, like older leavesof the other glossy lines SC1096 and SC90, had little or nowax deposits on their cuticles. The two maize cultivars, NB611and N7A, were non-glossy with dense wax covering; no trichomeswere observed until the 5 to 7 leaf stage. Thus, the glossycharacter was correlated with the reduction or absence of waxdeposits on the leaf surfaces, while hairiness might occur ineither glossy or non-glossy genotypes. Unlike sorghum and maize,in which all leaves after the fifth or seventh were glossy,pearl millet showed no glossiness through the ninth leaf. Measurementsshowed that cuticular transpiration of glossy leaves was oftenmore than double that of non-glossy leaves. Comparisons amongsorghums showed that non-glossy lines had higher stomatal densitiesthan glossy lines. Epicuticular wax, trichome, glossy mutant, stomata, cuticular transpiration, Sorghum bicolor, (L.) Moench, Zea mays L., Pennisetum americanum, (L.) Leeke     

Effect of the Osmotic Environment on Assimilate Transport in Isolated Developing Embryos of Maize (Zea mays)

Embryos obtained from developing kernels of maize (Zea maysL.) were incubated in a bathing medium, to measure the effectof the osmotic environment on the balance between uptake andrelease of assimilates by the embryo. Net efflux of sucroseand amino acids from the embryo decreased with increasing mannitolconcentration in the bathing medium and net uptake of [¹⁴C]valine increased with increasing mannitol concentration. Therole of a high osmolality of the seed apoplast in seed developmentis discussed Zea mays, maize, embryo, seed development, assimilate transport, turgor-sensitive transport     

The Responses of Field-grown Sunflower and Maize to Mechanical Support

The effects of mechanical support on two contrasting speciesof herbaceous annual, the dicot sunflower (Helianthus annuusL.) and the monocot maize (Zea mays L.), were investigated bycomparing the growth and mechanical properties of supportedplants and those which were left to sway freely in the wind. Providing support had its greatest effect on the more highly-stressedbasal areas of the plants, such as the lower stem and the baseof the lateral roots. The diameter of the stem bases of bothspecies was approx. 10% lower in supported plants, but therewas no difference between treatments in the diameter of thestem above 50 cm. Roots of both species also showed a reductionin rigidity and bending strength of 40–50% in the supportedplants compared with freely swaying plants. There was a significantreduction in the partitioning of biomass to the root systemsof supported plants of both species. There were differences in the way in which sunflower and maizeresponded to the provision of support; in sunflower, the reductionin lateral diameter was about twice that in maize, whereas inmaize the decrease in the number of first-order laterals wastwice that of sunflower. This study suggests that thigmomorphogenesismay be a localized response, but that different species canrespond in different ways to mechanical stimulation. Wind; support; anchorage; thigmomorphogenesis; Helianthus annuus L.; sunflower; Zea mays L.; maize     

Depletion of Oxygen in Roots of Wheat and Maize by Respiration Following Encasement in Olive Oil

The extent to which isolated root systems of 14-d-old seedlingsof wheat (Triticum aestivum) and maize (Zea mays) were depletedof oxygen by respiration was measured after immersing them inoutgassed olive oil to exclude oxygen entry from the air. Atintervals over 45 min, gas from the roots was removed underpartial vacuum and oxygen partial pressures measured by gaschromatography. Contrary to earlier findings (Erdmann and Wiedenroth,1988), roots were able to utilize almost all of their oxygenwithin 20 min at 25°C, including that dissolved in the thinwater covering interposed between roots and oil. The rate ofaerobic respiration could be estimated readily from the timecourse of oxygen depletion.Copyright 1993, 1999 Academic Press Triticum aestivum, Zea mays, roots, anaerobiosis, respiration, oxygen, methods     

Genetic Variation in Sorghum for the Inhibition of Maize Pollen Tube Growth

Aniline blue fluorescence was used to study the growth of maizepollen tubes in the stigmas of 13 diverse sorghum accessions.In 12, only short maize pollen tubes were formed, but in thesingle exception (Sorghum nervosum Nr481) maize pollen tubesgrew at least as far as the base of the style. The S. bicolorgenotypes S9B and CMS (a cytoplasmic male sterile line) werehybridized with Nr481, and analysis of maize pollen tube growthin F₁ plants, and BC₁ plants using Nr481 as the recurrent parent,suggested that differences in inhibition of pollen tube growthwere due to variation at a single locus, which we propose todesignate lap (Inhibition of alien pollen tubes). AccessionNr481 appears to be homozygous for a recessive allele permittingmaize pollen tube growth. Attempts were made to produce sorghumx maize hybrids using Nr481 and CMS derivatives which were knownto allow maize pollen tube growth to the base of the style.A putative hybrid endosperm was obtained in one Nr481 x Seneca60 maize cross, but this was not repeatable and no hybrid plantswere produced. A fundamental problem may be the large size ofthe maize pollen tube, which could have difficulty growing throughthe sorghum ovary and in entering the micropyle. Sorghum bicolor spp. bicolor (L.) Moench, Zea mays L, sorghum, maize, pollen tube growth, hybridization barriers     

Cell Membrane Stability and Leaf Water Relations as Affected by Potassium Nutrition of Water-Stressed Maize

A field experiment was conducted to investigate the effect ofK nutrition under water stress conditions on cell membrane stabilitymeasured by the polyethylene glycol test, plant growth, internalplant water relations and solute and mineral concentrationsin maize (Zea mays L.). Water-stressed plants showed greateradaptation to water deficits at higher K levels. Cell membranestability increased, leaf water potential and osmotic potentialdecreased, turgor potential increased and stomatal resistancedecreased with increasing K nutrition. Osmotic adjustment wasevident and it may have been influenced by increased K⁺ concentrationsin leaf tissues with increasing K nutrition. Higher leaf thicknessand higher leaf water content were observed at higher K levels.Results suggested that higher supplies of K nutrition may increaseplant production during periods of water stress. Key words: Zea mays L., cell membrane stability, leaf water potential, osmotic adjustment, osmotic potential, potassium nutrition, water stress