Effects of Radiation and Temperature on Tiller Survival, Grain Number and Grain Yield in Winter Wheat

Effects of the environment on shoot survival were studied inwinter wheat cv. Avalon grown in microplots at a density of247 plants m^–2. The incident radiation and mean temperaturewere altered during one of three periods of between 14 and 29d duration, the first (P1) starting at the end of tiller productionand the last (P3) finishing near the end of the tiller deathphase, about three weeks before anthesis. Plants were giventemperature and radiation treatments in growth rooms in twoexperiments and extra light outdoors in a third experiment:they were at other times grown outdoors. Increasing radiation by between 60 and 100 per cent during P1had negligible effects on shoot number; during P2 it alwaysdelayed tiller death but increased final ear number in onlyone experiment; during P3 it consistently increased ear numberby up to 100 m^–2. Increased radiation always increasedcrop dry weight immediately after treatment but only sometimesdid this increase persist to maturity. Grain dry weight wasincreased by treatment during P3 of one experiment. Increasingthe temperature by 4 C decreased shoot number, usually onlytemporarily, by hastening death of some tillers. Warmer temperaturesdecreased crop growth after, but not during, treatment and decreasedgrain dry weight. Radiation and temperature rarely interacted. Variation in grain yield within and between experiments relatedwell to variation in number of grains m^–2, which in turnrelated to variation in ear dry weight at anthesis. Triticum aestivum L., wheat, radiation, temperature, tillers, grain yield, grain number     

The duration and rate of grain growth, and harvest index, of wheat (Triticum aestivum L.) in response to temperature and CO2

Winter wheat (Triticum aestivum L. cv. Hereward) was grown inthe field inside polyethylene-covered tunnels at a range oftemperatures at either 380 or 684 µmol mol^–1 CO₂.Serial harvests were taken from anthesis until harvest maturity.Grain yield was reduced by warmer temperatures, but increasedby CO₂ enrichment at all temperatures. During grain-filling,individual grain dry weight was a linear function of time fromanthesis until mass maturity (attainment of maximum grain dryweight) within each plot. The rate of progress to mass maturity(the reciprocal of time to mass maturity) was a positive linearfunction of mean temperature, but was not affected by CO₂ concentration.The rate of increase in grain dry weight per ear was 2.0 mgd^–1 greater per 1 C rise, and was 8.0 mg d^–1 greaterat 684 compared with 380 µmol mol^–1 CO₂ at a giventemperature. The rate of increase in harvest index was 1.0%d^–1 in most plots at 380 µmol mol^–1 CO₂ andin open field plots, compared with 1.18% d^–1 in all plotsat 684 µmol mol^–1 CO₂. Thus, the increased rateof grain growth observed at an elevated CO₂ concentration couldbe attributed partly to a change in the partitioning of assimilatesto the grain. In contrast, the primary effect of warmer temperatureswas to shorten the duration of grain-filling. The rate of graingrowth at a given temperature and the rate of increase in harvestindex were only independent of the number of grains per earabove a critical grain number of 23–24 grains per ear({small tilde}20 000 grains m^–2). Key words: Winter wheat, grain growth, temperature, CO₂, harvest index, critical grain number     

The Effect of High Temperature at Different Stages of Ripening on Grain Set, Grain Weight and Grain Dimensions in the Semi-dwarf Wheat 'Banks'

Grain number in the wheat cultivar Banks was reduced by up to11 % with a rise in temperature from 21/16 °C to 30/25 °Cover a 10-d period immediately following first anthesis in general,the upper ‘d’ and ‘c’ florets were moreaffected by high temperature than the basal ‘a’and ‘b’ florets within a spikelet and florets fromthe upper spikelets were more sensitive than those lower onthe ear Grain weight and grain length at maturity were most affectedby a 10 d period of high temperature commencing 7–10 dafter anthesis However, if dry-matter accumulation between thestart of a treatment and grain maturity was used as a base forcomparison, the response was more uniform throughout development,with a peak in sensitivity 25 d after anthesis Although grainposition within an ear did not have a large effect on the responseto temperature, grains from the basal spikelets were more sensitivethan those from the apex, and the upper floret grains of a spikeletwere more sensitive to high temperature than those at the base There is a need to obtain, for a range of cultivars, more comprehensivedata on the effect of the timing and degree of temperature stressfollowing anthesis, for use in interpreting the response torising temperatures late in the development of the crop in thefield Triticum aestivum L, wheat, temperature, grain development     

Effects of CO2 Enrichment at Different Irradiances on Growth and Yield of Wheat: I. EFFECTS OF CULTIVAR AND OF DURATION OF CO2 ENRICHMENT

Wheat, Triticwn aestivum L., the winter cultivars Hobbit andCappelle-Desprez, and the spring cultivars Sicco and KJeiber,were grown in normal air or air enriched with CO₂ either outdoorsin a glass-roofed cage or in controlled environment rooms. Inneither the winter nor the spring wheat was growth increaseddue to enrichment with CO₂ before anthesis. Enrichment of thetwo winter wheat cultivars increased shoot dry weight significantlyat 15 d after anthesis but produced no significant increasein grain yield. With the spring cultivars there was a significantincrease in shoot dry weight by 18 d after anthesis and thegrain yield was also larger due to an increase in grain size.Shoot weight increased because the stems were larger, and therewas a diversion of assimilate from grain growth to late tillerproduction. Root tissue comprised less than 20% of the totaldry matter at anthesis (for all cultivars); effects of CO₂ enrichmenton root growth appeared to be less important than effects onshoot and ear growth. Growth and yield responses to CO₂ enrichmentwere observed (for the spring cultivars) at irradiances of both250 and 635 µE m^–2 s^–1, but the effects weregreater at the lower irradiance. Key words: CO₂ enrichment, Wheat, Cultivar     

Temperature Response of Vernalization in Wheat: A Developmental Analysis

The vernalization response of wheat ( Triticum aestivum L.)was reinterpreted from a developmental perspective, using currentconcepts of the developmental regulation of wheat morphologyand phenology. At temperatures above 0 °C, the effects ofthe process of vernalization per se in wheat are confoundedby the effects of concurrent vegetative development. These effectsare manifested by differences in the number of leaves initiatedby the shoot apex prior to floral initiation, which in turnaffects the subsequent rate of development to ear emergenceand anthesis. Leaf primordia development during vernalizationand total leaf number at flowering were used to develop criteriato define both the progress and the point of saturation of thevernalization response. These criteria were then used to reinterpretthe results of Chujo ( Proceedings of the Crop Science Societyof Japan 35 : 177–186, 1966), and derive the temperatureresponse of vernalization per se for plants grown under saturatinglong day conditions. The rate of vernalization increased linearlywith temperature between 1 and 11 °C, such that the timetaken to saturate the vernalization response decreased from70 d at 1 °C to 40 d at 11 °C. The rate declined againat temperatures above 11 °C, and 18 °C was apparentlyineffective for vernalization. Total leaf number at saturation,however, increased consistently with temperature, as a resultof the balance between the concurrent processes of leaf primordiuminitiation and vernalization. Total leaf number at saturationincreased from 6 at 1 °C to 13.3 at 15 °C, which inturn influenced the time taken to reach ear emergence. The advantagesof using this developmental interpretation of vernalizationas the basis for a mechanistic model of the vernalization responsein wheat are discussed. Triticum aestivum L.; wheat; vernalization; rate; temperature; primordia; leaf number; flowering     

The Uptake and Utilization of Phosphorus and Nitrogen by Diploid, Tetraploid and Hexaploid Wheats (Triticum spp.)

Twenty genotypes of Triticum and Aegilops wheats including diploid,tetraploid and hexaploid types, were grown under contrastingphosphorus (P) regimes (control and low P) at 15 °C by dayand 10 °C at night. Dry-matter production and phosphorusand nitrogen uptake and distribution were measured on matureplants. Phosphorus efficiency (PE) was considered in terms of yieldper unit of P in the main shoot and concentration of phosphorusin grain (per cent P). In the low-P set, PE, which ranged from110 to 715 mg grain mg^–1 P, increased as the yield perculm and dry-matter partitioning (harvest index) increased,with hexaploid > tetraploid > diploid. In both the controland low-P plants percentage P in grain decreased in the orderdiploids > tetraploids > hexaploid wheats. Grain phosphoruswas highly negatively correlated with the log of grain yield(r = –0.74; –0.88) and the log of harvest index(r = –0.80 and –0.88) for control and low-P plants,respectively. This suggests that future gains in plant harvestindex will cause smaller reductions in grain phosphorus concentrations.But, within either a high or low phosphorus supply, wheats witha given grain harvest index have significantly different grainphosphorus concentrations, and conscious selection for thischaracter is feasible. Low-P plants had similar grain nitrogen concentrations but lowernitrogen harvest indexes than control plants. Aegilops spp., Triticum spp., wheat, yield components, harvest index, polyploidy, evolution, phosphorus efficiency     

Growth, Development, and Yield of Spring Wheat in Artificial Climates

Spring wheat was grown to maturity in three growth rooms providing:(a) 18 h of light at 20° C and 6 h of darkness at 15°C (hot long days, HL); (b) 18 h of light at 15° C and 6h of darkness at 15° C (cold long days, CL); (c) 14 h lightat 20° C and 10 h of darkness at 15° C (hot short days,HS). Plants were moved between environments at spikelet initiationand anthesis, so dividing the growth period into three. Meanlengths in days of these periods in the different environmentswere: Period 1: HL 16, CL 18, HS 25; Period 2: HL 42, CL andHS 61; Period3: HL 53, CL 83, HS 63. The length of periods 2and 3 also depended on previous treatments. Grain dry weight was affected by environmental differences inall periods and effects in successive periods were additive.Compared with HL, CL or HS in period I before initiation increasedgrain yield by 6 per cent by increasing grain number per ear,HS in period 2 between initiation and anthesis decreased itby 24 per cent by decreasing the number of grains per spikeletand the proportion of spikelets that contained grain; CL inperiod 2 increased it by 21 per cent by increasing the numberof ears; CL in period 3 after anthesis increased it by 16 percent because leaves died later; HS in period 3 decreased itby 14 per cent because there was less radiation and hence lessphotosynthesis. Dry weight of shoot and root at maturity wasincreased by CL or HS in periods 1 or 2, and increased by CLand decreased by HS in period 3. The effects on final yieldof treatment during periods 1 and 2 were the consequence ofsimilar effects already produced at anthesis, and shoot androot dry weight changed little during period 3. The effects of environmental differences on grain dry weightcould not be explained by differences in leaf-area durationafter anthesis (D₃), except that CL in period 3 increased bothyield and D₃ but not proportionately, so that, as with HS inthe same period, grain: leaf ratio was decreased. Environmentaldifferences in periods 1 and 2 appeared to affect grain weightby altering the capacity of the ear to accumulate carbohydrates,determined by the number of grains per ear, rather than by alteringthe supply of carbohydrates, determined by D₃. There were some interactions between environments in differentperiods which were usually small compared with the main effects.     

The effect of temperature and CO2 on seed quality development in wheat (Triticum aestivum L.)

Winter wheat (Triticum aestivum L.) cv. Hereward was grown inthe field in two double-walled polyethylene-covered tunnelswithin each of which a temperature gradient was superimposedon diurnal and seasonal fluctuations in temperature. The meantemperature between anthesis and harvest maturity varied from14.3 to 18.4C among plots within these tunnels. The CO₂ concentrationwas controlled at different values in each tunnel; seasonalmean concentrations were 380 and 684 µmol CO₂ mol^–1air. Crops were also grown outside the tunnels at ambient temperaturesand CO₂. Samples of seeds were harvested sequentially from eachplot between anthesis and harvest maturity. Seed germinationand seed survival during subsequent air-dry storage were determinedfor each sample. The onset of both ability to germinate anddesiccation tolerance (ability to germinate after rapid desiccationto 10–15% moisture content and subsequent rehydration)coincided in all environments. Full germination capacity (>97%, determined at 10C) was reached 4–18 d before theend of the seed-filling phase (mass maturity) in most cases.There was little or no decline in germination capacity duringsubsequent seed development and maturation. Differences in seedquality were evident, however, throughout seed development andmaturation when seed survival curves during subsequent storagewere compared. Potential longevity in air-dry storage (assessedby the value K₁ of the seed viability equation) improved consistentlyboth before and after mass maturity. There was a significantpositive relation between the rate of increase in potentiallongevity (dK₁Idt) and temperature (the minimum temperaturefor seed quality development was 4.8 C), but neither CO₂ concentrationnor production within the polyethylene tunnels affected thisrelation. Key words: Wheat, Triticum aestivum L., seed development, seed longevity, carbon dioxide, temperature     

Partitioning of Dry Matter and the Deposition and Use of Stem Reserves in a Semi-dwarf Wheat Crop

An experiment was carried out within a crop of spring wheat(cv. Condor) to examine dry matter partitioning between thedeveloping stem and ear, and to estimate the magnitude of carbonstored in the stem both before and after anthesis, and the subsequentutilization of these reserves during grain growth. The amount of reserve laid down and mobilized was estimatedfrom analysis of data for changes in masses of stem and leaffrom frequent harvests. The rate of change of the dry mass ofthe individual plant organs was expressed as a proportion ofthe rate of change of the total dry mass of the large culm.This value was called the Allocation Ratio (AR). It was assumedthat assimilate was transferred directly from the stem intothe growing ear, and not into other organs. This paper providesevidence for the idea that the stem intemodes of wheat are ableto accumulate and subsequently mobilize a dry matter reserve.The accumulation and subsequent mobilization of fructans inthe stem was demonstrated using ascending thinlayer chromatography.On a dry matter basis the large culms of the wheat crop accumulatedall of their stem reserves after anthesis (0–41 g perlarge culm; 98·4 g m^–1). After adjusting the lossof mass by 33% to allow for respiration, it was concluded thatpost-anthesis stem reserves may have contributed at least 21%of the final grain yield of this crop. Triticum aestivum L., semi-dwarf spring wheat, dry matter partitioning, stem reserves, fructans     

Effects of Nitrogen Fertilizer on Growth and Yield of Spring Wheat

Nine amounts of nitrogen fertilizer, ranging from 0 to 200 kgN ha^–1, were applied to spring wheat cv. Kleiber in the3 years 1972-1974. In 1972 grain dry weight with 125 kg N ha^–1or more was 100 g m^–2 (23 per cent) greater than withoutnitrogen. Grain yield was unaffected by nitrogen in the otheryears. Leaf area at and after anthesis was increased throughoutthe range of nitrogen tested, most in 1972 and least in 1973.Consequently, the addition of 200 kg N ha^–1 decreasedthe amount of grain produced per unit of leaf area by approximately25 per cent in all years. The dry weight of leaves and stems at anthesis and maturitywas increased by nitrogen in all years, similarly to leaf area.However, the change in stem dry weight between anthesis andmaturity was not affected by nitrogen; stems increased in dryweight for about 20 days after anthesis and then decreased tovalues similar to those at anthesis. The uptake of CO₂ per unit area of flag leaf or second leaf(leaf below the flag leaf) was slightly decreased by nitrogenwhen the increase in leaf area caused by nitrogen appreciablydecreased the light intensity at the surface of these leaves.In spite of such decreases the CO₂ absorbed by flag and secondleaves per unit area of land was always increased by nitrogen,and relatively more than was grain yield. It is suggested that increases in respiratory loss of CO₂ withincreasing nitrogen fertilizer may explain why nitrogen increasedvegetative growth and leaf area relatively more than grain yield.     

Effects of CO2 Enrichment at Different Irradiances on Growth and Yield of Wheat: II. EFFECTS ON KLEIBER SPRING WHEAT TREATED FROM ANTHESIS IN CONTROLLED ENVIRONMENTS IN RELATION TO EFFECTS ON PHOTOSYNTHESIS AND PHOTORESPI RATION

Spring wheat plants were grown in a cage with a glass roof untilthree days after anthesis and then subjected to treatments inconstant environment rooms with any one of all combinationsof four irradiances and two concentrations of carbon dioxide.The photoperiod was 16 h and day/night temperatures 19?C/14?C.Growth and yield of grain were saturated at the two brightestirradiances. Carbon dioxide enrichment from 350 to 1200 mm³dm^–3 increased shoot dry weight and grain yield at finalharvest at all irradiances, by averages of 10.5 (not significant)and 23.5 (significant) percent respectively. However, increasingthe irradiance from 150 to 613 µE m^–2 s^–1caused much larger yield increases (approximately 3-fold). Increasedgrain production by increased light was caused by both increasesin dry weight per grain and by increases in grain number perspikelet. The increase caused by CO₂ enrichment was mainly becauseof increased dry weight per grain. Increase in ear dry weightcaused by CO₂ enrichment took place between 30 and 60 d afteranthesis. The increase in shoot dry weight took place immediatelyafter exposure to increased CO₂ from 3 to 15 d after anthesis.Net photosynthesis by flag leaves on the main shoots was almostdoubled 16 d after anthesis by the CO₂ enrichment even thoughstomatal resistance was also doubled. However, this increasewas not reflected by a proportional increase in yield, probablybecause increased mutual shading by bigger stems and late tillersreduced total assimilation and because of increased respirationby the shoots. The increase in photosynthesis was not due toa decrease in photorespiration but to an increase in gross photosynthesis. Key words: CO₂enrichment, Photosynthesis, Photorespiration     

Carbon Dioxide Exchange of Spring-wheat in Relation to Age and Photon-flux Density at Different Growth Temperatures

CO₂-exchange rates (CER) of the sixth and the flag leaves oftwo spring-wheat varieties, Kolibri and Famos, were comparedusing an open-circuit infrared gas analysing system. Measurementswere repeated every two weeks starting when leaf blades werefully expanded. Single plants were grown in a controlled environmenthaving a photopuiod of 15 h and a day/night temperature of 24/19°C(H), 18/13 °C (M), and 12/7 °C (L) respectively untilapprox. 2 weeks after anthesis and at 18/13 °C until maturity.The photosynthetic photon-flux density (PPFD) at the top ofthe plants was 500 µE m^–2 sec^–1. During themeasurements PPFD was gradually reduced from 2000 to 0 µEm^–2 sec^–1 whereas the temperature was maintainedat the respctive growth-temperatures during the light period.The CER of the sixth leaf declined fairly similarly for bothvarieties, except for Kolibri where a faster decline was observedduring the first two weeks after full leaf expansion. The CERof the flag leaf declined more slowly than that of the sixthleaf. With the flag leaf of Famos, the decline was nearly linear,whereas with Kolibri it was very slow during the first few weeksbut rapid as the leaves further senesced. This pattern becamemore pronounced as the growth temperature decreased. The declinein relation to leaf age was much smaller at low PPFD than athigh PPFD during the same period. At full leaf expansion Kolibrireached higher maximum CER than Famos except at H. As the PPFDwas reduced the difference became smaller and at very low PPFDsuch as 50 µE m^–2 sec^–1 was reversed for thesixth leaf. Under optimum growth conditions maximum values ofCER were greater than 50mg CO₂ dm^–2h^–1 and PPFDfor light saturation was close to 2000 µE m^–2 sec^–1.A comparison between the actual CER and a fitted curve widelyused, PN=(a+b/l)^–1–DR, showed that the goodnessof fit strongly depends on cultivar, treatment and leaf ageas well as on the number and the level of PPFD from which datafor calculations are taken. Triticum aestivum, L., wheat, photosynthesis, photon-flux density, light response, carbon, dioxide exchange     

A Comparison of the Effect of High Temperature on Grain Development in Wheat and Rice

Grain weight at maturity of the wheat cultivar Banks was reducedby about 5% for each 1 °C rise in daily mean post-anthesistemperature in the range from 17.7 to 32.7 °C, using grainweight at 17.7 °C as the base. In contrast, the rice cultivarCalrose had a stable grain weight up to 26.7 °C and abovethat showed a 4.4% drop in weight per 1 °C increase in meanpost-anthesis temperatures up to 35.7 °C, using grain weightat 26.7 °C as the base. In both wheat and rice there wasa reduction in the duration of grain growth with increasingtemperature up to a mean of 26.7 °C. In this range rice,but not wheat, showed a compensating increase in the rate ofdry-matter accumulation. Above 26.7 °C the rate of dry-matteraccumulation fell in both species, although this was more stablein rice than in wheat. In wheat the duration of grain growthcontinued to decrease at temperatures above 26.7 °C, butshowed little change in rice up to 35.7°C, the maximum tested.These data are discussed in relation to the physiological, biochemicaland physical constraints that may act to regulate grain developmentin wheat and rice at high temperature. Triticum aestivum, oryza sativa, grain development, high temperature effects     

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     

Effects of crop thinning and reduced grain numbers per ear on grain size in two winter wheat varieties given different amounts of nitrogen

To study the importance for final grain size in wheat (Triticum aestivum, L.) of assimilate supply and the storage capacity of the grain, two field experiments were done. In 1976 nitrogen was applied in the range from none to 180 kg ha^-1, part of the crop was thinned, and the top halves of some ears of the short variety Hobbit and of the tall variety Maris Huntsman were removed soon after anthesis. In 1977 ears of Maris Huntsman were halved 5 days after anthesis or at 30 days after anthesis when grain volume was maximum. Thinning the crop from 360 to 180 ear-bearing shoots m^-2 30 days before anthesis increased the number of grains per ear, except in the absence of nitrogen fertiliser, but did not increase grain size, grain dry weight per ear or total dry weight per culm. Removing the upper half of ears of Hobbit 5 days after anthesis increased dry weight per grain, but when this treatment was applied to Maris Huntsman either 5 days after anthesis in 1976 and 1977, or when grain volume was maximal in 1977, the grains failed to increase in dry weight. Non-grain dry weight of both varieties was increased by halving the ear. In both varieties the maximum volume of grains in halved ears was larger than in intact ears. Grain dry weight increased relatively less than volume after halving the ear of Hobbit, and the decrease in volume up to maturity was greater in halved than intact ears of both varieties. The larger grain volume in halved ears of Maris Huntsman in 1977 was associated with more endosperm cells.     

Dark Respiration of Several Varieties of Winter Wheat Given Different Amounts of Nitrogen Fertilizer

Carbon dioxide production in the dark by ears and by the restof the shoot of winter wheat grown in the field was measuredin 2 years during grain growth. The respiration rate per g d.wt of the ears was increased by nitrogen fertilizer. Ears ofthe semi-dwarf varieties Maris Fundin and Hobbit respired moreslowly than ears of Maris Huntsman and Cappelle-Desprez. Respirationrates of the rest of the shoot were unaffected by nitrogen orvariety. The amount of carbohydrate required to provide the CO₂ respiredduring the whole period of grain growth varied from 163 to 443g m^–2, or 42 to 76 per cent of the dry weight of the grain.More than half the CO₂ lost was respired by the ear. The additionof 180 kg N ha^–1, which increased grain yield by 78 percent in 1975, almost trebled the amount of CO₂ lost by the ears.The semi-dwarf varieties lost less CO₂ from ears and shootsthan did the taller ones, and had larger yields of grain. Respiration was also estimated from the difference between the¹⁴C contents of shoots sampled immediately after a 30 s exposureto ¹⁴CO₂ and at maturity. When 14C was supplied 10 days afteranthesis, the loss by maturity amounted to 16–28 per centof that initially absorbed by flag leaves and 40 per cent ofthat absorbed by the leaf below the flag leaf. Most of the lossoccurred in the first day. The loss of 14C by maturity was significantlyincreased by nitrogen fertilizer in 1975. Triticum aestivum L., wheat, respiration, nitrogen supply, fertilizer treatment     

不同小麦进化材料生育后期光合特性和产量

以二倍体野生一粒小麦(Triticum boeoticum)、栽培一粒小麦(T. monococcum)、节节麦(Aegilops tauschii)和黑麦(Secale cereale)、四倍体野生二粒小麦(T. dicoccoides)、栽培二粒小麦(T. dicoccum)、硬粒小麦(T. durum)、六倍体普通小麦(T. aestivum)‘扬麦9号’和‘扬麦158’及八倍体小黑麦(Triticale)为材料,采用盆栽试验研究了不同小麦进化材料生育后期旗叶光合特性的演变及产量的差异。结果表明,与六倍体普通小麦和八倍体小黑麦相比,二倍体和四倍体材料在开花前具有较高的光合速率(P_n)、气孔导度(G_s)、最大光能转换效率(F_v/F_m)和实际光化学效率(Φ_PSⅡ)。开花以后,二倍体和四倍体材料受非气孔因素的影响,光合能力下降较快;除黑麦外,旗叶光合速率在开花10 d后都低于普通小麦和小黑麦,胞间CO₂浓度(C_i)迅速增加,F_v/F_m、Φ_PSⅡ和叶绿素含量快速下降。二倍体和四倍体材料开花前单株总叶面积和旗叶叶面积较大,花后下降迅速,功能期短;单株穗数也较多,但穗粒数、千粒重、产量和收获指数却显著低于普通小麦。因此,小麦长期进化过程中,普通小麦花后较高的光合能力及较长的光合持续期是提高千粒重,进而提高产量的重要生理基础。     

The Effects of Temperature and Light Intensity on Embryo Numbers in Wheat Doubled Haploid Production through WheatxMaize Crosses

Triticum aestivumxZea mayscrosses are now widely used in theproduction of wheat doubled haploids to produce homozygous lines.Seasonal effects are known to influence the number of haploidembryos produced through wheatxmaize crosses, but the effectsof temperature and light have not been quantified. This studyinvestigated the effect of temperature and light intensity onhaploid embryo production. New Zealand wheat cultivars weregrown in a glasshouse until booting when they were transferredto growth cabinets at three temperatures (day/night; 17/12,22/17 or 27/22 °C at an irradiance of 250 µmol m^-2s^-1PAR).In another experiment, wheat lines were transferred to a growthcabinet at one of three light intensities (300, 500 or 1000µmol m^-2s^-1PAR at 22/17 °C day/night, with a photoperiodof 16 h). The temperature and light intensity at which pollinationswere made and subsequent fertilisation and embryo developmentoccurred, significantly (P<0.01) influenced the frequencyof haploid embryo production. The optimal temperature for embryorecovery was 22/17 °C. The greatest number of embryos wasproduced at a light intensity of 1000 µmol m^-2s^-1. Thesefindings will result in improvements in the overall efficiencyof the wheatxmaize system for wheat doubled haploid production.Copyright1998 Annals of Botany Company Intergeneric crossing, temperature, light intensity,Triticum aestivum,wheat,Zea mays,maize.     

Development and Evaluation of an In Vitro System to Study Strawberry Fruit Development

Growth and ripening of strawberry (Fragariaananassa Duch.)fruit harvested at immature stages of development was accomplishedby placing the peduncles of individual fruit in solutions composedof hydroxyquinoline hemisulphate (HQS) and sucrose. Fruit cultivarand developmental stage at harvest were the major determinantsof in vitro performance. ‘Pajaro’ fruit harvestedat 50 to 60% maturity exhibited the greatest and most uniformweight gain when placed in solutions containing 200 mol m^–3HQS and 88 mol m^–3 sucrose. Although the final fruit weightof in vitro-ripened fruit was less than that of field-ripenedfruit, colour development in vitro occurred at the same rateand to the same extent as field-grown fruit. Key words: Ripening, non-climacteric fruit