籼稻颖花分化与退化对不同播期温光的响应

试验以三系杂交籼稻‘五优308’和‘天优华占’以及常规籼稻‘黄华占’为材料,在大田条件下,设置10个播期,研究田间不同温光条件对籼稻生育期天数、颖花分化和退化数的影响.结果表明: 温度对3个籼稻品种生育期的影响比日照长度大,平均温度升高1 ℃,播种-穗分化始期天数平均减少1.5 d,而穗分化历期天数与光照和温度的关系均不密切.不同播期间每穗颖花数和颖花分化数存在显著差异.穗分化期间平均温度、最高温度和最低温度升高,有效积温增加,昼夜温差扩大,光辐射增强,有利于穗分化期干物质积累和颖花分化,各品种趋势一致.穗分化期间有效积温增加50 ℃,颖花分化数增加10.5朵,昼夜温差扩大1 ℃,颖花分化增加14.3朵,总光辐射量增加50 MJ·m^-2,颖花分化数增加17.1朵.颖花退化率与温度呈现二次项相关,极端高温或极端低温的自然条件不利于颖花形成,但低温天气对颖花退化的影响大于高温.温度低于临界温度,颖花退化率大幅增加,穗分化期临界积温为550～600 ℃,日平均温度为24.0～26.0 ℃,日最高温度为32.0～34.0 ℃,日最低温度为21.0～23.0 ℃.适宜高温、昼夜温差大、光照辐射强的自然条件利于颖花分化,并减少颖花退化.     

Effects of N and P nutrition on spike development in spring wheat

The effects of N and P on the number of spikelets of spring wheat (Triticum aestivum L.), grown in nutrient solution, were studied under 8 h and 16 h photoperiods. The effect of P was apparent only at a high rate of N supply and the effects of N were increased significantly at a high rate of P supply. Increasing N supply increased the number of spikelets due to a promotion of the rate of spikelet initiation. It also increased the leaf-blade area and the dry matter weight of the plants at the stage of terminal spikelet initiation. These effects of N were much greater under the short photoperiod than under the long photoperiod. The practical significance of these findings for winter-grown wheat in temperate regions is pointed out.     

Development and Floret Survival in Wheat Ears With Supernumerary Spikelets

In the supernumerary spikelet wheat, AUS159I0, the supernumeraryspikelet primordia appeared just after the ear reached the terminalspikelet stage. Appearance of the primordia of the multiplesessile spikelets preceded that of indeterminate rachilla spikelets.Supernumerary spikelets had a lower number of potentially fertileflorets per spikelet than normal (non-supernumerary) spikeletsin the ear and thus a smaller number of grains per spikelet.Mean weight per grain in the supernumerary spikelet wheat waslower than in the cultivar, Meering, without supernumerary spikelets.Total grain number in the supernumerary spikelet ear was greaterthan in the normal ear despite the lower spikelet fertilityin the former. Within the supernumerary spikelet ear the multiplesessile spikelets had a higher number of grains per spikeletand mean weight per grain than the indeterminate rachilla spikelets.It appears possible to improve the productivity of the supernumeraryspikelet ear by breeding for reduced expression of the indeterminaterachilla spikelets. Wheat, ear development, floret survival, supernumerary spikelets, grain number     

Zebularine treatment is associated with deletion of FT‐B1 leading to an increase in spikelet number in bread wheat

The number of rachis nodes (spikelets) on a wheat spike is a component of grain yield that correlates with flowering time. The genetic basis regulating flowering in cereals is well understood, but there are reports that flowering time can be modified at a high frequency by selective breeding, suggesting that it may be regulated by both epigenetic and genetic mechanisms. We investigated the role of DNA methylation in regulating spikelet number and flowering time by treating a semi‐spring wheat with the demethylating agent, Zebularine. Three lines with a heritable increase in spikelet number were identified. The molecular basis for increased spikelet number was not determined in 2 lines, but the phenotype showed non‐Mendelian inheritance, suggesting that it could have an epigenetic basis. In the remaining line, the increased spikelet phenotype behaved as a Mendelian recessive trait and late flowering was associated with a deletion encompassing the floral promoter, FT‐B1. Deletion of FT‐B1 delayed the transition to reproductive growth, extended the duration of spike development, and increased spikelet number under different temperature regimes and photoperiod. Transiently disrupting DNA methylation can generate novel flowering behaviour in wheat, but these changes may not be sufficiently stable for use in breeding programs.     

Floret Initiation and Development in Spring Wheat (Triticum aestivum L.)

The number and developmental stages of florets were determinedin each spikelet of the spike in the main shoots of spring wheat.Samples were taken frequently from plants grown in a phytotronand in a nitrogen application field-test. Ten stages of development,from floret initiation until anthesis, were recognized and described. Inter-spikelet variation in the total number of initiated floretswas rather small. However, the number of florets at advancedstages of development, as well as the number of grains, washighest in the central spikelets in which florets initiatedfirst. Floret initiation did not proceed beyond spike emergence,whereafter the distal florets and the spikelet apex degenerated.Grain-set was restricted to florets which had developed at leastto the stage of visible anther lobes at spike emergence. Thenumber of these florets was increased significantly by nitrogenapplication. Wheat, Triticum aestivum L., spikelet, floret, grain set, nitrogen     

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     

Barley spikelet culture: An effective tool for the analysis of biochemical events in flower development

Immature detached barley spikelets were cultured in wheat spikelet medium. Fertility of cultured barley spikelets was similar to that of cultured wheat spikelets. Barley anther development within cultured spikelets was retarded relative to in planta, but viability of developing pollen, as determined by a fluorochromatic reaction, was similar in vitro and in planta. Protein synthesis by anthers in developing barley spikelets in vitro was maximal during stage 2, when pollen grains were bicellular, and declined as pollen matured. Barley spikelet culture is an effective tool for the analysis of biochemical events in flower development.Abbreviations FRC fluorochromatic reaction - WSM wheat spikelet medium     

Effects of photoperiod, temperature and vernalization on the phenology and spikelet numbers of spring wheats

Fourteen cultivars of north temperate, Australian, Mexican and Rhodesian origins, were grown in eight treatments: 2-day-lengths (10 h and 14h) × two temperature regimes (18/13 °C and 25/20 °C) × two seed vernalization treatments (unvernalized and 28 days at 1–2 °C). Numbers of days to 50 % ear emergence, leaf numbers and spikelet numbers of the main shoots were recorded. The north temperate cultivars were the most sensitive to daylength: in long days their mean spikelet number was 15 and they headed in 40–50 days, while in short days they had a mean of 24 spikelets and failed to head in 100 days. The Rhodesian cultivars were the least sensitive, but nevertheless headed 20–30 days earlier and had three to five fewer spikelets per ear in long days. The effects of vernalization on the tropical cultivars were related to maturity class: they ranged from negligible in early cultivars such as Sonora 64 and Devuli to decreases of 20 days to heading and seven spikelets in late cultivars such as Mexico 120 and Cajeme 71 in long days. The effects of temperature varied with cultivar and with vernalization treatment. Early cultivars and vernalized late cultivars headed earlier and had fewer spikelets in the warmer regimes while unvernalized late cultivars tended to have more spikelets and headed later. It is suggested that some vernalization of these late cultivars took place in the cooler regime. The significance of the results for the understanding of the physiological basis of the adaptation of wheat cultivars to different climatic zones is discussed.     

Early Growth of the Developing Ear of Spring Barley

The change in fresh weight of the developing ear and of groupsof spikelets of Maris Mink spring barley was measured for plantsgrown under three different conditions. Growth was closely describedby a third order polynomial equation. Instantaneous values ofrelative growth rate derived from these equations showed a declineto a minimum value, which was dependent on the growing conditionsand on position along the spike, followed by a rapid rise. Theminimum value was reached about 5 d before spikelet initiationceased and the subsequent rise in relative growth rate coincidedwith the period of rapid elongation of the rachis. Within thecar there was a tendency for younger spikelets to have a slightlyhigher relative growth rate than those initiated earlier. Possiblereasons for these growth changes are discussed in relation tospikelet differentiation, vascularization of the ear and nutrientavailability. Hordeum vulgare L., Barley, shoot apex, spikelets, ear, initiation, growth rate     

DEVELOPMENT OF THE YOUNG WHEAT SPIKE: A SEM STUDY OF CHINESE SPRING WHEAT

The number of leaves on the main culm was correlated with morphological changes in the wheat spike during development, up to the terminal spikelet stage. The developmental changes were divided into nine stages, which were compared with stages described by other investigators. Several environmental conditions were utilized to determine the consistency of morphological correlations. Although the different environments did influence the length of time required to reach the various stages, the relationship between leaf number and stage of spike development was consistent. Regardless of environmental conditions, all stages were evident. Vernalization period affected the number of spikelets. Plants vernalized 6 wk produced 17–19 spikelets, compared to 21–24 spikelets on plants vernalized 3 wk. There were three major morphological events during spike development: 1) the change from vegetative to reproductive growth, 2) lateral spikelet development, and 3) the initiation and development of the terminal spikelet.     

Effect of Defoliation on Rate of Development and Spikelet Number per Ear in Six Wheat Varieties

The effect of leaf removal either before or at floral initiationon times from sowing to floral initiation and from floral initiationto terminal spikelet initiation, spikelet number per ear, andrate of spikelet initiation investigated in six spring wheatsunder controlled environment conditions. Defoliation delayed the times to floral and terminal spikeletinitiations significently in all varieties. However, defoliationincreased the number of spikelets per ear in the varieties 8–23,8–27 and Selkirk (up to 43 per cent in 8–27 comparedwith the control) but decreased the number in Triple Dirk, Sunsetand Kogat (up to 28 per cent in Triple Dirk). Although the rateof spikelet initiation apparently decreased in all varieties,dissection at regular intervals of Sunset and 8–23 plantsthowed that the rate dropped sharply just after defoliationin both varieties, but later the rate in 8–23 (but notin Sunset) surpassed that of the control plants. The possiblemechanism of control of spikelet number in wheat is discussed.     

越冬前增温对小麦生长发育和产量的影响

为了揭示越冬前积温增加对冬小麦生长发育进程和产量的影响,于2010-2012年在设施内进行人为控制增温模拟试验.以试验期室外环境实测温度值为对照,设置越冬前增温40、50、60 d,研究越冬前不同积温(≥0 ℃)对小麦物候期、幼穗发育进程、开花期和成熟期叶片光合生理特性及产量构成要素的影响.结果表明： 设施内越冬前增加积温在越冬前对幼穗发育进程有一定影响,对拔节期幼穗发育进程和育性影响明显,孕穗后随着发育进程的加快影响减小,成熟期大部分处理间的生物学性状差异不显著.越冬前积温增加不超过25 ℃对幼穗影响很小;积温增加大于60 ℃幼穗发育进程明显加快,积温越高变化越明显.冬前积温增加到一定幅度将导致冬小麦物候期提前,积温增加超过60 ℃,拔节期叶龄提高0.8以上,抽穗期和成熟期分别提前1 d左右.物候期的提前和幼穗发育进程的加快使小麦整个发育期缩短,容易遭受春季低温危害,造成小花败育甚至小穗冻死;冬前积温过高还导致后期旗叶光合能力下降,灌浆期缩短,并造成减产.
     

The chromosome region including the earliness per se locus Eps-Am1 affects the duration of early developmental phases and spikelet number in diploid wheat

Earliness per se genes are those that regulate flowering time independently of vernalization and photoperiod, and are important for the fine tuning of flowering time and for the wide adaptation of wheat to different environments. The earliness per se locus Eps-A(m)1 was recently mapped within a 0.8 cM interval on chromosome 1A(m)L of diploid wheat Triticum monococcum L., and it was shown that its effect was modulated by temperature. In this study, this precise mapping information was used to characterize the effect of the Eps-A(m)1 region on both duration of different developmental phases and spikelet number. Near isogenic lines (NILs) carrying the Eps-A(m)1-l allele from the cultivated accession DV92 had significantly longer vegetative and spike development phases (P<0.0001) than NILs carrying the Eps-A(m)1-e allele from the wild accession G3116. These differences were paralleled by a significant increase in the number of spikelets per spike, in both greenhouse and field experiments (P<0.0001). Significant interactions between temperature and Eps-A(m)1 alleles were detected for heading time (P<0.0001) but not for spikelet number (P=0.67). Experiments using NILs homozygous for chromosomes with recombination events within the 0.8 cM Eps-A(m)1 region showed that the differences in number of spikelets per spike were linked to the differences in heading time controlled by the Eps-A(m)1 locus. These results indicate that the differences in these two traits are either pleiotropic effects of a single gene or the effect of closely linked genes. A similar effect on spikelet number was detected in the distal region of chromosome 1AL in common wheat (T. aestivum L.).     

Influence of Vernalization and Photoperiod on Supernumerary Spikelet Expression in Wheat

Two tetraploid (Triticum turgidum L.emend gr. turgidum and gr.durum) and five hexaploid wheats (Triticum x aestivum L. emendgr. aestivum) with reported tendencies for ‘branched heads’(supernurnerary spikelets) exhibited variation in its expressionunder different vernalization photoperiod and temperature regimes. Two main types of supernumerary spikelets were identified, multiplesessile spikelets (MSS) with two or more complete spikeletsat a rachis node and indeterminate rachilla spikelets (IRS)with two to 13 spikelets on an extended rachilla. The degree of supernumerary spikelet expression in wheats withvernalization response differed from those without. Short photoperiods(9–14 h) both outdoors and in a glasshouse environment,were more conducive to supernumerary spikelet expression than24 h photoperiod in both environments. The 24 h photoperiodglasshouse environment (higher mean temperatures) was leastconducive to its expression except in lines with a strong vernalizationresponse. The high stability of supernumerary spikelet expression in certaingenotypes in the different environments indicated the feasibilityof incorporating this character in breeding and selecting commercialwheats to increase grain number per head. Triticum, wheat, ear-branching, supernumerary spikelets, vernalization, photoperiod, temperature     

Effect of photoperiod on development and number of spikelets of a temperate and some low-latitude wheats

Four low-latitude cultivars (two Mexican and two Rhodesian) and a Canadian cultivar were grown in controlled environments in four photo-periods, 16, 13, 10 and 7 h, respectively. Plants of two of the low-latitude cultivars were also transferred between long and short photoperiods during ear differentiation. The intervals from sowing to successive stages of ear development up to the formation of the terminal spikelet, and to ear emergence, and the number of leaves, all increased as photoperiod decreased. The Canadian cultivar responded most and one of the Rhodesian cultivars least to changes of photoperiod in these respects. However, with all the low-latitude cultivars, the interval between formation of the terminal spikelet and emergence of the ear responded similarly and relatively little to decreasing photoperiod except when photoperiod was reduced from 10 to 7 h. The mean rate of spikelet production decreased as the duration of the period of spikelet production (DSP) increased, i.e. as ear development slowed down with decrease in photoperiod. Accordingly number of spikelets per ear increased curvilinearly as DSP increased, suggesting a maximal number of spikelets of about thirty. Rate of spikelet production apparently differed between cultivars. Development of the ear slowed down when plants were moved to a shorter photoperiod and accelerated when they were moved to a longer photoperiod, both at the time at which the shoot apex began to elongate and at the double ridge stage. Final number of spikelets per ear increased when ear development was slowed down and decreased when it was accelerated.     

The response of development rate to temperature in the univoltine cranefly,Tipula subnodicornis Zetterstedt

Summary The cranefly, Tipula subnodicornis, emerges as an adult in the spring and has an annual life-cycle in the British Isles. This is maintained partly through the presence of a winter diapause but the response of development rate to temperature also acts to preserve the timing of the cycle. During development under constant temperature conditions in the laboratory the optimum temperature (taken as the temperature which promoted the most rapid development) dropped from 25°C, or above, in the egg stage to below 20°C in the late larval stages. It is suggested that at the warmer, southern limits of the geographical range rapid early development may be compensated by a retardation in late larval growth. In addition, the response of growth rate to change in temperature was small in the fourth, final, instar and resulted in low Q ₁₀ values; 2.4 between 7° and 10°C, 1.5 between 10° and 15°C and 0.9 between 15° and 20°C. As the fourth instar comprises the greater part of the growth period, this has the effect of minimising the effect of temperature differences which are the result of differences of latitude or altitude. Even at optimum temperatures the growth period was prolonged and larvae in the field do not reach maximum weight, and the photosensitive stage, until late autum when short daylength promotes diapause. Subsequent development in the spring, before pupation and during the pupal period, showed a reversion to the higher Q ₁₀ figures of the early stages in development.The development of final instar Tipula subnodicornis larvae is contrasted with that of Tipula melanoceros. Tipula melanoceros emerges as an adult in September and it is likely that it has an egg diapause. Consequently larval development is confined to a short period between April and late July and growth must be rapid during this period. Under constant temperature conditions in the laboratory the growth of final instar larvae showed a marked contrast to that of Tipula subnodicornis in that the response to temperature was large and remained positive over a wider temperature range.     

Differences of Starch Granule Distribution in Grains from Different Spikelet Positions in Winter Wheat

Wheat starch development is a complex process and is markedly difference by changes in spikelet spatial position. The present study deals with endosperm starch granule distribution and spatial position during filling development. The study was conducted with pure starch isolated from wheat (Triticum aestivum L.), Jimai20 and Shannong1391, at 7–35 days after anthesis (DAA). The results showed that grain number, spikelet weight and grain weight per spikelet in different spatial position showed parabolic changes. Upper spikelets had highest starch and amylose content followed by basal spikelets, then middle spikelets. The paper also suggested the volume percents of B-type and A-type granule in grain of middle spikelets were remarkably higher and lower than those of basal and upper spikelets, respectively. However, no significant difference occurred in the number percents of the two type granule. The ratio of amylase to amylopectin was positively correlated with the volume proportion of 22.8–42.8 µm, but was negatively related to the volume proportion of <9.9 µm. The results indicated that the formation and distribution of starch granules were affected significantly by spikelet position, and grains at upper and basal spikelet had the potential of increasing grain weight through increasing the volume of B-type granules.     

Effect of decapitation on morphogenesis of stem and spike in various wheat species

Decapitation induced an additional formation of secondary shoots and anomalous spikes in all the species. The moan numbers of nodes, spikelets per spike, seeds per spikelet and spike, and the mean length of the stem and spike were reduced on secondary shoots of decapitated plants, while the mean and peak numbers of flowers per spikelet and the peak number of seeds per spikelet increased. The increase in the number of flowers per spikelet was the most striking on spike base; the seeds regularly occurred even in spikelets with an expressively increased number of flowers. The post-decapitation changes of the spike could be well expressed quantitatively according to the increased mean number of the flowers per one seed. Morphological ohanges in anomalous spikes of all the wheat species resemble phylogenetic reversions described in literature. Moreover, the peak numbers of flowers and seeds per spikelet were recorded in 52 varieties belonging to 21 wheat species. As compared with the decapitation trial, the greatest variability and the greatest differences between the speoies were also reoorded in the tetraploid group, and the smallest variability and differences between the species in the diploid group. We suppose that the striking morphological differences in post-decapitation spikes take place because the apical dominance was interrupted before differentiation of the recent form had been controlled in meristems on the decapitated stem base. Ancestral forms were morphologically realized with the help of an assimilating part of the decapitated stem.     

High temperature stress and spikelet fertility in rice (Oryza sativa L.)

In future climates, greater heat tolerance at anthesis will be required in rice. The effect of high temperature at anthesis on spikelet fertility was studied on IR64 (lowland indica) and Azucena (upland japonica) at 29.6 degrees C (control), 33.7 degrees C, and 36.2 degrees C tissue temperatures. The objectives of the study were to: (i) determine the effect of temperature on flowering pattern; (ii) examine the effect of time of day of spikelet anthesis relative to a high temperature episode on spikelet fertility; and (iii) study the interactions between duration of exposure and temperature on spikelet fertility. Plants were grown at 30/24 degrees C day/night temperature in a greenhouse and transferred to growth cabinets for the temperature treatments. Individual spikelets were marked with paint to relate fertility to the time of exposure to different temperatures and durations. In both genotypes the pattern of flowering was similar, and peak anthesis occurred between 10.30 h and 11.30 h at 29.2 degrees C, and about 45 min earlier at 36.2 degrees C. In IR64, high temperature increased the number of spikelets reaching anthesis, whereas in Azucena numbers were reduced. In both genotypesor=33.7 degrees C at anthesis caused sterility. In IR64, there was no interaction between temperature and duration of exposure, and spikelet fertility was reduced by about 7% per degrees C>29.6 degrees C. In Azucena there was a significant interaction and spikelet fertility was reduced by 2.4% degrees Cd-1 above a threshold of 33 degrees C. Marking individual spikelets is an effective method to phenotype genotypes and lines for heat tolerance that removes any apparent tolerance due to temporal escape.     

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