Interactions Among Number of Spikelets, Number of Grains and Grain Weight in the Spikes of Wheat (Triticum aestivum L.)

In a field experiment, comprising four spring wheat cultivars,the frequency and final weight of the grains developing fromeach individual floret were determined in intact spikes andin spikes of which up to nine spikelets had been removed. Theextent of damage caused by the cutting procedure was estimated. Characteristic distributions of the frequencies and weightsof the individual grains were found for each cultivar. Removalof spikelets resulted, in most cases, in a small increase inthe number of grains and in a considerable increase in the weightof the grains of the remaining spikelets. These increases compensatedonly partially, and differently in the different cultivars,for the loss of the removed spikelets. Defoliation at the timeof earing caused a subsequent reduction in grain yield of intactspikes but no reduction in the yield of spikes from which ninespikelets had been removed. The removal of the upper floretsin each spikelet resulted in a certain increase in the weightof the two basal grains. It is concluded that an increase in the number of spikeletsper spike may reduce grain weight but will nevertheless contributeto yield. The number of grains per spikelet is cultivar dependentbut not causally associated with grain weight. Grain set indistal florets is expected to add rather small grains to thespike's yield. Under conditions of limited supplies it may causea reduction in the weight of the basal grains. Any increasein grain weight is anticipated to contribute to grain yieldand is not liable to affect spikelets per spike or grains perspikelet. Wheat cultivars, Triticum aestivum, growth of inflorescence, grain yield, spikelet number     

Mixed Nitrogen Nutrition and Productivity of Wheat Grown in Hydroponics

The objective of this study was to study the effects of nitrogen(N) supplied as either mixtures of NO₃ and NH₄ or as all NO₃on the final yield of spring wheat. Two separate greenhouseexperiments evaluated the durum spring wheat (Triticum durumL.) cultivar ‘Inbar’ in 1986, and the hard red springwheat (Triticum aestmum L.) cultivar ‘Len’ in 1987.Nitrogen treatments consisted of all NO, or mixtures (75/25or 50/50) of NO₃ and NH₄. At maturity, plants were harvested,separated into leaves, stems, roots, and grain, and each partanalysed for dry matter and chemical composition Compared to plants receiving only NO₃ as the source of N, mixedN nutrition resulted in greater accumulation of whole plantreduced-N (49 to 108% more), phosphorus (38 to 69% more), andpotassium (25% more) for both cultivars. In all cases, plantsproduced higher grain yields (28% for Len to 78% for Inbar)when grown with mixed N nutrition than with only NO₃. The yieldincrease was not associated with heavier grains or more grainsper ear, but rather with an increase in the number of ear-bearingtillers per plant. For both cultivars, the higher yields withmixed N resulted from the production of more total biomass (36to 76%) as the partitioning of dry matter between plant partswas not altered by N treatment. Under the hydroponic conditionsof this experiment, the utilization of both NO₃ and NH₄ resultedin greater growth, nutrient absorption, and yield than NO₃ alone,which was primarily associated with an enhancement in tillerdevelopment Triticum aestivum L., Triticum durum L., spring wheat, hydroponics, ammonium nutrition, nitrate nutrition, tillering, yield components, partitioning     

Effects of Soil Flooding on Growth and Grain Yield of Populations of Tetraploid and Hexaploid Species of Wheat

Single populations of three hexaploid species of wheat, Triticumaestivum, Triticum spelta and Triticum macha, and two populationsof the tetraploid wheat, Triticum dicoccum (Pontus and Bordeaux),were grown in a greenhouse experiment at a range of soil floodingregimes: free draining, two levels of transient flooding andcontinuous flooding. Increasing severity of flooding treatment resulted in increasedsoil reduction and an increase in the concentration of reducediron and manganese in the experimental soil, and also resultedin a reduction in vegetative growth, number of inflorescences,grain number and grain weight. There were, however, large differencesbetween the wheat populations in the degree of reduction inyield caused by flooding. The population of T. macha was muchmore flooding-tolerant than the other hexaploid species andthe ‘Pontus’ population of the emmer wheat, T. dicoccum,was more tolerant than the ‘Bordeaux’ populationof this species and than T. spelta and T. aestivum. The results are discussed in relation to the origin of the populations. Soil flooding, Triticum aeslivum, Triticum macha, Triticum spelta, Triticum dicoccum     

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     

The Pattern of Distribution of Phosphorus and Dry Matter with Time in Spring Wheat

The pattern of distribution of dry matter and phosphorus wasfollowed in individual plants harvested from a field crop ofspring wheat throughout its development. There was a continueduptake of phosphorus with time and almost half of the totalphosphorus was accumulated in the post-anthesis period of growth.The various component parts of the main shoot were followedin detail and both individual leaves and the stem showed substantialnet losses of phosphorus with time well before they reachedtheir dry weight maxima. The ear was the major sink for phosphorusand it was estimated that approximately one third of its phosphoruscontent was supplied by retranslocation. The main shoot stemand leaves also showed a significant decline in d. wt duringthe final stages of grain development. Half-ear removal at anthesisincreased both grain set and the growth of the grain of theupper florets of the remaining spikelets. Defoliation had littleeffect on grain yield but resulted in a reduction in the phosphoruscontent of the grain. Triticum aestivum L, spring wheat, phosphorus distribution, dry matter distribution     

Influence of Chlorocholine Chloride on Grain Growth of Winter Barley (Hordeum distichon L. cv. Igri) in the Field

Green, C. F., Dawkins, T. C. K. and McDonald, H. G. 1985. Influenceof chlorocholine chloride on grain growth of winter barley (Hordeumdistichon L. cv. Igri) in the field.–J. exp. Bot. 36:1126–1133. Chlorocholine chloride was applied to winter barley either inthe Spring or Autumn. It increased grain number per unit croparea. Rates of incorporation of dry matter into the grain weredecreased, but the period of growth was extended by the treatments.Overall the final mean grain weight was reduced so that no advantagesin terms of yield resulted from the increased grain numbers. Key words: —Chlormequat, chlorocholine chloride, CCC, Hordeum distichon L., barley, grain growth, grain weight, senescence, grain yield     

Abscisic Acid Translocation and Influence of Water Stress on Grain Abscisic Acid Content

The movement of foliar applied [1-¹⁴C]abscisic acid (ABA) inwheat plants (Triticum aestivum L., cv. Kolibri) was investigatedat two stages of grain development (1000 grains, weight 19 and24 g dry matter). [1–¹⁴C]ABA seemed to be readily translocated within 12h into the developing grains as well as in other plant parts.A subsequent rapid metabolism took place leading to a decreasedactivity of the ABA-containing chromatogram fraction in theyounger plants 48 h after application. The metabolism seemodto be less intensive in the older grains, where the activityrunning with the ABA increased over 64 h. Treating the leaves of barley plants (Hordeum vulgare, L., cv.Union) 2 weeks after anthesis with a gentle stream of warm air(36° C) resulted in a significant increase in the ABA contentof all parts of the ear. The results mentioned above indicatethat this may be partially due to translocation from other partsof the plant such as the leaves.     

The Vascular System in the Rachis of a Wheat Ear

The vascular system in the rachis of ears of wheat (Triticumaestivum L. cvs Gamenya, Olympic and Bungulla) was examinedon material grown in the field and in a growth cabinet. In theinternodes, central and peripheral bundles were observed andtheir mean number and size were determined. A significant 1:1 relationship between the number of spikelets on the ear andthe number of central bundles at the base of the rachis wasestablished. The number of both central and peripheral bundlesdeclined acropetally along thé length of the rachis.The decline in peripheral bundles occurred mainly between internodes1 and 6, numbered from the base. The decline in central bundlesoccurred at a rate of less than one bundle per internode betweeninternodes 1 and 4, though in some ears, there was no decline;in larger ears, central bundles declined at a rate of one totwo bundles per internode between internodes 5 and 11. Aboveinternode 11, the rate of decline varied with ear size. Threecentral bundles consistently reached the terminal spikelet.The number and cross-sectional surface area of xylem vesselsand sieve tubes and the total vascular size also declined acropetallyalong the rachis. The decline in total vascular size was dueto (a) some bundles branching and to reductions in size, (b)the diversion or dropping of bundles into spikelets, or (c)a combination of (a) and (b). These observations are discussedin relation to the distribution of grain number and weight onthe ear. Triticum aestivum L., wheat, rachis, spikelets, vascular anatomy, xylem, sieve tubes     

Effects of Abscisic Acid on Growth of Wheat (Triticum aestivum L)

Daily application of abscisic acid (ABA) to growing wheat plants,although initially inhibiting growth, resulted, after a shortlag, in an increase in the number of leaves and tillers. Thismay have been due to reduced apical dominance. At 84 days thetotal dry weight and area of all leaves produced up to thistime was less for the plants treated with ABA than for the controlplants. However, the area of green, living leaves and the dryweight were not significantly affected by the ABA treatment.Further effects of the daily ABA treatment were the inhibitionof transpiration, especially on the abaxial surface, the reductionof leaf size, the promotion of flowering and the stimulationof trichome formation on the leaf surfaces. ABA did not promoteleaf senescence in whole plants and actually increased leaflongevity. Triticum aestivum L., wheat, leaf senescence, transpiration, growth, flowering, abscisic acid     

Nitrate Effects on Growth of the First Four Main Stem Leaves of a Range of Temperate Cereals and Pasture Grasses

The effects of different applied NO₃^– concentrations onextension growth and final length and area of leaves 1–4of five cereals and six pasture grasses of temperate originwere examined. Increased applied NO₃^– in the range 0.1–50mol m^–3; caused decreased duration of growth but increasedgrowth rate and final length of leaves 2–4 of the cerealsAvena saliva, Hordeum vulgare, Secale cereale x Triticosecaleand Triticum aestivum. For all cereals, increased NO₃^–resulted in increased area of leaves 1-4. Pasture grasses weresupplied either 0.5 or 50 mol m^–3; NO₃^–. Increasedapplied NO₃^– (0.5–50 mol m^–3) resulted indecreased duration of growth and increased growth rate and finalarea of leaves 1–4 of Bromus willdenowii leaves 2–4of Festuca arundinaceae and leaves 3 and 4 of Lolium multiflorum.In addition, length of leaves 3 and 4 of B. willdenowii increasedwith increased NO₃. Increased NO₃ resulted in increased areaof leaves 2–4 of Daciylis glomerata and Lolium perenneand leaves 3 and 4 of Phalaris aquatica but had no effect onextension growth of all three species. Avena saliva L., oat, Hordeum vulgare L., barley, Secale cereaie L., rye, x Triticosecale Wittm, triticale, Triticum aestivum L., wheat, Bromus willdenowii Kunth, prairie grass, Dactylis glomerata L., cocksfoot, Festuca arundinaceae Shreb, tall fescue, Lolium multiflorum Lam, Italian ryegrass, Lolium perenne L, perennial ryegrass, Phalaris aquatica L, nitrate,, leaf extension, leaf expansion     

Effect of Post-anthesis Drought on Cell Division and Starch Accumulation in Developing Wheat Grains

Wheat plants (Triticum aestivum L., cv. Warigal) were subjectedto 20 d of water deficit during the period of endosperm celldivision. Drought accentuated the differences in final grainweight between spikelets and between grains within spikelets.The distal grains of top spikelets were most affected by drought.The maximum number of endosperm cells was, respectively, 30and 40 per cent lower in basal grains and distal grains of draughtedplants. In basal grains of middle spikelets, the number of largestarch granules per cell was unaffected but the number of smallstarch granules per cell was 45 per cent lower in grains ofdraughted plants. The initiation of small starch granules wasmore affected than cell division because severe water deficitoccurred earlier during the former process than the latter.Final dry weight appeared to correlate well with the maximumnumber of endosperm cells, but depended also on the number ofstarch granules per cell. Consequently, the amount of dry matterper cell was not constant in both treatments. The concentration of sucrose per endosperm cell was lower onlyin the droughted distal grains of top spikelets. The supplyof sucrose to endosperm cells did not regulate the initiationof small starch granules. Triticum aestivum L., wheat, drought, grain growth, cell division, starch     

Root and Shoot Growth of Plants Treated with Abscisic Acid

Young seedlings of Capsicum annum L., Commelina communis L.and maize (Zea mays L.) were subjected to a mild water-stressingtreatment and/or treated with abscisic acid (ABA). Plants rootedin soil received a soil-drying treatment and their leaves weresprayed with a 10–⁴ M solution of ABA. Plants grown insolution culture were stressed by the addition of polyethyleneglycol (PEG) to the rooting medium and ABA was also added tothe rooting medium, either with or without PEG. The effectsof both treatments on the growth of roots and shoots and theultimate root: shoot dry weight ratio were very similar. Shootgrowth was limited both by water stress and by ABA application;while there was some evidence that mild water stress and/orABA application may have resulted in a stimulation of root growth.More severe water stress reduced the growth of roots but theoverall effect of stress was to increase the ratio of rootsto shoots. Capsicum annum L., Commelina communis L., Zea mays L., water stress, abscisic acid     

Effect of High Temperature Stress at Anthesis on Grain Yield and Biomass of Field-grown Crops of Wheat

Spring wheat (Triticum aestivumL., ‘Chablis’) wasgrown under field conditions from sowing until harvest maturity,except for a 12-d period [70–82 days after sowing (DAS)coinciding with anthesis] during which replicated crop areaswere exposed to a range of temperatures within two pairs ofpolyethylene-covered temperature gradient tunnels. At 82 DAS,an increase in mean temperature from 16 to 25 °C duringthis treatment period had no effect on above-ground biomass,but increased ear dry weight from 223 to 327 g m^-2and, at 83DAS, reduced root biomass from 141 to 63 g m^-2. Mean temperatureover the treatment period had no effect on either above-groundbiomass or grain yield at maturity. However, the number of grainsper ear at maturity declined with increasing maximum temperaturerecorded over the mid-anthesis period (76–79 DAS) and,more significantly, with maximum temperature 1 d after 50% anthesis(78 DAS). Grain yield and harvest index also declined sharplywith maximum temperature at 78 DAS. Grain yield declined by350 g m^-2at harvest maturity with a 10 °C increase in maximumtemperature at 78 DAS and was related to a 40% reduction inthe number of grains per ear. Grain yield was also negativelyrelated to thermal time accumulated above a base temperatureof 31 °C (over 8 d of the treatment from 5 d before to 2d after 50% anthesis). Thus, grain fertilization and grain setwas most sensitive to the maximum temperature at mid-anthesis.These results confirm that wheat yields would be reduced considerablyif, as modellers suggest, high temperature extremes become morefrequent as a result of increased variability in temperatureassociated with climate change.Copyright 1998 Annals of BotanyCompany Triticum aestivum, spring wheat, temperature, grain number, grain yield, root growth.     

The Development of Wheat Grain in Relation to Endogenous Growth Substances

Changes in the endogenous gibberellins and abscisic acid ofthe developing grains of Triticum aestivum L. have been studiedin relation to growth of the grain. The maximum grain volumeis inversely related to temperature and is reached while thedry weight is still small. This stage is associated with a sharpincrease in gibberellins. Starch formation is the principalfeature of the next stage of development and this ceases shortlyafter the beginning of a period of rapid water loss. This waterloss is preceded by an increase in the abscisic acid content.Changes in the endosperm are associated with changes in thebiochemical and physical attributes of the pericarp; these alsohave been correlated with changes in growth substances. Theresults are related to the ripening process and the final dryweight of the grain.     

Predicting the Growth Interactions between Plants in Mixed Species Stands using a Simple Mechanistic Model

The Conductance model is a simple mechanistic model used topredict the growth of species in monoculture or mixtures fromparameter values derived from plants grown in isolation. Incontrast to many mechanistic models that require extensive parameterization,the Conductance model is able to capture the growth of a broadrange of species using a few simplified assumptions regardingplant growth and easily derived species-specific parameter values.We examine the assumptions within the Conductance model thattotal leaf area per plant is proportional to total plant weight,and that an isolated plant has a projected crown zone area thatis proportional to the 2/3 power of its weight. Power ratherthan linear relations were found between weight and leaf areafor Brassica oleracea, Daucus carota, Matricaria inodora, Solanumnigrum,Stellaria media , Trifolium repens and Veronica persica.For all seven species, the value of the power was less thanunity. All species also exhibited a power relation between crownzone area and weight, with the slope of this relation beingless than 2/3 for B. oleracea, D. carota and S. media. Althoughmorphology type accounted for some of the variation in the parametervalues relating to light interception, there were considerabledifferences between species within upright or prostrate foliagespecies groups. The Conductance model was used to predict yieldsof B. oleracea, S. nigrum and V. persica grown in both monocultureand binary weed-crop mixtures over a range of temporal and spatialscales. After calibrating the model to non-competing plants,the model was used to predict growth of the weed and crop speciesin contrasting densities and stand types. In some crop-weedcombinations, predicted crop and weed weights were within 17%of observed values, with no systematic deviations. In others,systematic and large deviations occurred.Copyright 2001 Annalsof Botany Company Brassica oleracea L., Daucus carota L., Matricaria inodora L., Solanum nigrum L.,Stellaria media L., Trifolium repens L., Veronica persica L., competition, growth, leaf area, crown zone area, light, shoot morphology, canopy architecture     

Foliar Uptake and Movement of Chlormequat in Cereals: Influence of Dose and Addition of Related Chemicals

Increased amounts of chlormequat applied to leaves of barleyand wheat resulted in a greater proportion being taken up andmoving to the tips of treated leaves. Combined foliar applicationwith certain other amines also increased uptake and movementof chlormequat - choline and glycine betaine were particularlyeffective - but a few others had the reverse effect. Ammoniumand sodium salts of acetic, butyric and hydrochloric acids alsoincreased movement of ¹⁴C-chlormequat Hordeum vulgare L., barley, Triticum aestivum L., wheat, chlormequat, foliar uptake     

Effects of NORIN 10 and Tom Thumb Dwarfing Genes on Morphology, Physiology and Abscisic Acid Production in Wheat

The pleiotropic effects of three genetically related dwarfinggenes were investigated in near-isogenic lines of wheat. TheNORIN 10 semi-dwarfing alleles, Rht 1 and Rht 2, and the TomThumb allele, Rht 3, were assessed for effects on some vegetativemorphological and physiological characters. The Rht allelesaffected leaf size with a resultant decrease in leaf area ofthe whole plant. Rht 3, which had the most marked effects, reducedleaf area in young plants by as much as 30 per cent. Althoughflag leaf dimensions and stomatal distributions of the flagleaf were altered, the gene had no effect on its area, stomatalconductance or net CO₂ exchange rate. Comparisons of Rht andtall plants revealed no differences in the abscisic acid (ABA)levels of either turgid or partially dehydrated leaves. Triticum aestivum L., wheat, dwarfing genes, leaf structure, abscisic acid, stomatal conductance, CO₂, exchange, relative growth rate     

The Developing Endosperm of Wheat -- A Stereological Analysis

A stereological analysis of light and electron micrographs ofwheat endosperm during grain formation and development providesinformation on a range of parameters of cell structure. Thecell volume increases approximately ten-fold; mitochondrialnumber per cell increases but the individual mitochondrial volumedecreases, the overall volume fraction of the cell occupiedby mitochondria remaining fairly constant. Amyloplast divisionstops before cell division, resulting in the distribution ofpreviously-formed plastids; there are differences in starchgranule growth rate in different cell layers of the endosperm.The rough endoplasmic reticulum increases four-fold in areaper cell and its surface-to-volume ratio increases just priorto protein deposition. Triticum aestivum, L., wheat, endosperm, seed development, starch, stereology     

Enhancement in Growth and Yield of Wheat (Triticum aestivum L.) by Pre-sowing Chill Treatment to Grains

Pre-sowing chill treatments to grains of Wheat (Triticum aestivumL. cvs Kalyan sona and cv. 4530) induce enhancements in growth,tillering and yield. Further, levels of several biochemicalcomponents are also higher in the grains harvested from plantsgrown from chill-treated grains. This method applied in thelaboratory and on a farm scale, effective also in other plants,can be conveniently used for yield enhancement and improvementof seed quality. Triticum aestivumL., wheat, chill treatment     

Relationships Between Grain Weight and the Size of Floret Cavity in the Wheat Spike

The volume of the floret cavity at different floret positionsalong the spike and within a single spikelet was estimated in10 Triticum aestivum and three T. durum lines by injecting floretcavities with liquid silicone rubber which solidified thereafter.Highly significant correlation coefficients, ranging from 0.40to 0.76 were found between floret volume and grain weight; inmost lines the basal florets had a higher correlation than theterminal ones. The relationships between floret volume and grainweight were characterized by an intercept of about 30–60per cent of the mean grain weight (heavy-grained lines havinga larger intercept) and a slope of about 1 mg µI^–1.Differences in grain size and shape, both within spike as wellas among lines, closely reflected the variation in the sizeof floret cavity. The data support the hypothesis that grainweight is partly determined by the volume of the floret cavity. Grain weight, grain volume, floret cavity