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1.
Winter wheat has replaced spring wheat to a large extent under the climatic conditions of Western and Central Europe. But spring wheat genotypes are still important under the warm climate in large parts of Africa and Central America, since spring wheat needs no vernalization. To reach optimal yield, genotypes must be well adapted to heat stress. In this study 11 spring wheat varieties of Egypt, Sudan, CIMMYT and Germany were exposed to high temperatures at ear emergence and beginning of anthesis. There were reductions in kernel yield and kernel number of the main ear for all genotypes, but the differences in reduction were remarkable. The German variety 'Naxos' was best adapted. Some varieties showed an increased number of florets per spikelet under heat treatment, but this does not prohibit a reduction in kernel number per spikelet.  相似文献   

2.
High temperature is a major environmental factor that limits wheat (Triticum aestivum L.) productivity. Climate models predict greater increases in night‐time temperature than in daytime temperature. The objective of this research was to compare the effects of high daytime and high night‐time temperatures during anthesis on physiological (chlorophyll fluorescence, chlorophyll concentration, leaf level photosynthesis, and membrane damage), biochemical (reactive oxygen species (ROS) concentration and antioxidant capacity in leaves), growth and yield traits of wheat genotypes. Winter wheat genotypes (Ventnor and Karl 92) were grown at optimum temperatures (25/15 °C, maximum/minimum) until the onset of anthesis. Thereafter, plants were exposed to high night‐time (HN, 25/24 °C), high daytime (HD, 35/15 °C), high daytime and night‐time (HDN, 35/24 °C) or optimum temperatures for 7 days. Compared with optimum temperature, HN, HD and HDN increased ROS concentration and membrane damage and decreased antioxidant capacity, photochemical efficiency, leaf level photosynthesis, seed set, grain number and grain yield per spike. Impact of HN and HD was similar on all traits. Greater impact on seed set, grain number and grain yield per spike was observed at HDN compared with HN and HD. These results suggest that HN and HD during anthesis cause damage of a similar magnitude to winter wheat.  相似文献   

3.
Low temperature seriously depresses seed germination and seedling growth in winter wheat (Triticum aestivum L.). In this study, wheat plants were sprayed with abscisic acid (ABA) and fluridone (inhibitor of ABA biosynthesis) at 19 days after anthesis (DAA) and repeated at 26 DAA. The seeds of those plants were harvested, and seed germination and offspring's seedling growth under low temperature were evaluated. The results showed that exogenous ABA application decreased seed weight and slightly reduced seed set and seed number per spike. Under low temperature, seeds from ABA‐treated plants showed reduced germination rate, germination index, growth of radicle and coleoptile, amylase activity and depressed starch degradation as compared with seeds from non‐ABA‐treated plants; however, activities of the antioxidant enzymes in both germinating seeds and seedling were enhanced from those exposed to exogenous ABA, resulting in much lowered malondialdehyde (MDA) and H2O2 concentrations and production rate. In addition, the maximum quantum efficiency of photosystem II was also enhanced in ABA‐treated offspring's seedlings. It is concluded that exogenous ABA treatment at later grain‐filling stage could be an effective approach to improve cold tolerance of the offspring during seed germinating and seedlings establishment in winter wheat.  相似文献   

4.
Grain yield and yield components (grains per ear, grain weight, 1000-grain weight, ear weight, ear seed ratio and dry matter partitioning between ear and seed) were examined in a wheat genotype (PBW-343) with well-filled grains and a Triticale genotype (DT-46) with poorly filled grains (showing grain shrivelling) grown in pots. Six days after anthesis (DAA), benzyladenine (BA) @2 µg ear−1 and abscisic acid (ABA) @4 µg ear−1 were injected at the base of the mother shoot ear in both species. It was observed that, in both wheat and Triticale , BA increased the grain weight, grain number and partitioning of dry matter between ear and seed, whereas ABA decreased the grain weight, grain number and dry matter partitioning between ear and seed. However, these decreases were slower in Triticale than in wheat. BA treatment increased the grain dry matter accumulation, which in turn resulted in better filling of grains and increased the grain weight in both wheat and Triticale . The average grain weight of Triticale was lower than that of wheat. Thus, it appears that variation in grain weight between wheat and Triticale might be due to different availabilities of growth-promoting phytohormones such as cytokinins and assimilates.  相似文献   

5.
Increases in atmospheric carbon dioxide (CO2) concentration have stimulated interest in the response of agricultural crops to elevated levels of CO2. Several studies have addressed the response of C3 cereals to CO2, but the interactive effect of nutrient supply and CO2 on apical development and spikelet set and survival has not been investigated thoroughly. Hence, an experiment was conducted in the greenhouse to evaluate the effect of high (700 μmol CO2mol?1 air) and low (400 μmol mol?1) levels of atmospheric CO2 on apical development, spikelet set and abortion, and pre- and post-anthesis growth in spring barley (Hordeum vulgare L.) grown under high N (0.3 g N pot?1 before sowing ?1–0.11 g N pot?1 week?1) and low N (0.3 g N pot?1) regimes. The plants were grown in 5 L pots. Development of spike was hastened due to CO2 enrichment, and the C+ plants pollinated few days earlier than the C— plants. Carbon dioxide enrichment had no effect on date of ripening. Development of spike slowed following application of extra N, and plants pollinated 10 days later and matured 2 weeks later when compared with plants under low N. Carbon dioxide enrichment did not affect the number of spikelets at anthesis. Excess N decreased spikelet abortion and the increased maximum number of spikelets under both [CO2]. Barley plants did not tiller when grown in low [CO2] and low N. Increased endogenous IAA concentration in those plants, recorded three days before tillers appeared in other treatments, may have contributed to this. Carbon dioxide enrichment increased the C concentration of plants, but decreased the N concentration under high N regime. Both the C and N concentration of plants were increased under high N regime. Carbon dioxide enrichment increased the total dry matter of mature plants by 9 % under high N regime and by 21 % under low N regime. Under high [CO2] increased kernel number on tiller spikes, and increased kernel weight both on main stem and on tiller spikes resulted in a 23 % increase in kernel yield under low N regime and 76 % increase in kernel yield under high N regime. The rate of N application influenced growth and yield components to a greater extent than CO2 enrichment. At maturity, plant dry matter, kernel weight, the number of kernels per spike, and the number of spikes per plant were higher under high N regime than under low N regime. Long days (16 h), low light intensity (280 μmol m?2s?1), and at constant temperature of 20 °C high [CO2] increased kernel weight and the number of kernels on tiller spikes under high and low N application rate, but did not increase the number of kernels on main stem spike, or the number of tillers or tiller spikes per plant.  相似文献   

6.
不同播期和品种小麦小花结实的粒位差异   总被引：7，自引：0，他引：7  
确定小麦不同小穗位和小花位发育与结实特性是实现大穗多粒的重要前提，本文通过对冬，春性小麦品种分期播种试验得出，较高的小穗结实力是增加穗粒数的重要因素，不同播期，品种之间，小穗粒重和粒数呈现相同的变化趋势，中部以及基部小穗粒重与穗粒重之间呈高度正相关，体现环境差异的播期效应以对中部小穗发育的影响为主，而冬，春性品种的基因型差异可反映在各个小穗位上，第2小花粒的子粒发育状况反映整个小穗的生产能力，结果表明，促进中部优势小穗（第5－15小穗）结实和第1－3小花位子粒发育是提高小花结实率和穗粒重的关键。  相似文献   

7.
Two generations of recurrent phenotypic selection for seed yield per plant under controlled pollination were carried out to combine improved seed yield with improved forage grass performance in perennial ryegrass (Lolium perenne L.). Selected and unselected varieties (AberDartand AberElan respectively) and control varieties were grown for seed in pots in a glasshouse experiment and in two field plot experiments over 5 harvest years. Seed yield components and seed yield were measured. Significant improvements in seed yield of the selected AberDart over the unselected AberElan were observed both in individual plants grown in the glasshouse and in field plots. Detailed observations of the individual components of seed yield showed that the increased seed yield of AberDart can be attributed to a higher proportion of ovules forming seeds (% seedset), greater seed number per tiller and more reproductive tillers per plant. This improvement in seed yield of AberDart was also observed when it was grown in field plots with AberElan, experimental selection lines and commercial varieties. AberDart produced more seeds per tiller than the other commercial varieties and selection lines studied. The implication of this approach for the breeding of perennial ryegrass varieties that combine good agronomic performance and acceptable seed yields is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
为明确灌水模式对运城盆地晚播冬小麦产量和水分利用的影响,以济麦22为供试材料,以传统播期灌2水为对照（CK）,在晚播增密条件下,设置全生育期不灌水、返青起身期1水、拔节期1水、返青起身期+开花期2水、拔节期+开花期2水共5个灌水处理,分别记为W1、W2、W3、W4和W5。结果表明,与CK相比,W1、W2和W3处理产量降低;干旱年W4和W5处理冬小麦产量显著高于CK,平水年冬小麦产量则以CK最高。晚播增密灌2水条件下,2个试验年度均以W5处理产量最高,W4处理次之,但2个处理产量差异不显著,W4处理冬小麦的成穗数、成穗率、花前营养器官干物质运转量、运转率以及对籽粒的贡献率均高于W5处理。水分利用效率以W2和W3处理最高;W4和W5处理的水分利用效率相当。综合产量、抗寒性和水分利用等方面表现,晋南冬小麦适度晚播增密未浇冬水条件下,返青起身期+开花期2水能够维持产量稳定,同时延缓冬小麦穗分化进程,提高春季抗霜冻能力。  相似文献   

9.
Volunteer plants of oilseed rape (Brassica napus L.) from persistent seeds in soil can affect subsequent crops. Apart from the agricultural disadvantages, the environment and the marketing of the seeds may also be affected, particularly if plants with special ingredients or genetically modified (gm) plants are grown. In order to investigate the influence of soil cultivation and genotype on seed persistence and gene flow via volunteers, a field experiment was set up testing four tillage treatments and two cultivars in a split-plot design. The cultivars tested were near-isogenic to two gm cultivars. To simulate harvesting losses, 10 000 seeds m−2 were broadcast on a soil in July. The subsequent tillage treatments were combinations of immediate or delayed stubble tillage by a rotary tiller, primary tillage with plough or cultivator, or zero tillage. Over the following year, the fate of the seeds was determined. Immediate stubble tillage with following cultivator or plough resulted in 586 resp. 246 seeds m−2 in the soil seed bank. After delayed stubble tillage with following plough, 76 seeds m−2 were found, and no soil seed bank was built up in the zero tillage treatment. Nevertheless, in the zero tillage treatment, several robust volunteer plants survived the herbicide application before the direct drilling in autumn until following spring. In the zero tillage treatment and in the cultivator treatment, 0.19 volunteers m−2 resp. 0.06 volunteers m−2 flowered simultaneously to ordinarily sown oilseed rape in the following crop of winter wheat and produced 73 resp. 18 seeds m−2. Delayed stubble tillage reduced the risk of gene escape via the soil seed bank, while zero tillage resulted in the highest risk of gene escape by pollen and by production of a new generation of seeds. In terms of a labelling threshold for gm food this number of seeds would be below the threshold of 0.9% of transgenic parts in conventially bred food or feed.  相似文献   

10.
为发掘利用高活力小麦种质材料,揭示不同小麦品种间(系)的种子活力差异及其内在生理原因,本研究以置于常温种子库老化6年的180个小麦品种(系)的种子为材料进行了种子活力比较研究。结果表明:不同小麦品种(系)间发芽率存在显著差异,其中35个小麦品种(系)的种子完全失活、不能发芽,种子活力最高的3个品种分别为豫麦18(92%),西农3517(76%)和浏虎98(72%);测定了种子浸出液电导率、种子含水量和籽粒品质性状并与发芽率进行了相关分析,发现发芽率与电导率和籽粒淀粉含量呈极显著负相关,与含水量呈显著负相关,但与籽粒总蛋白质含量相关不显著;进一步对种子活力高低差异显著的6个品种(系)进行了种子萌发关键激素赤霉素(GA3)和脱落酸(ABA)的测定,发现3个高活力小麦品种(系)(豫麦18、西农3517、浏虎98)种子中GA3/ABA的比值均显著高于3个低活力品种(系)(西农2003、洛麦21和陕麦107)。本研究表明,种子活力性状在小麦种质资源中存在广泛变异,植物内源激素GA3和ABA的相对含量是影响种子活力高低的关键因素。  相似文献   

11.
A wheat cultivar (Condor) was grown in two experiments (thermal regimes 18/13 and 21/16°C) under low (298 μE m-2: s-1) radiation regimes during either an early phase from seedling emergence to terminal spikelet initiation (S2), a late phase from terminal spikelet initiation to anthesis (S2), or for the full period from seedling emergence to anthesis (S12), or high (560 μE m-2s-1) radiation throughout the growing period (S12) to determine whether developmental events are affected by radiation. The main developmental events considered in this study were the timing of terminal spikelet initiation and anthesis, the final number of leaf and spikelet primordia initiated in the apex and the rate of leaf appearance. Number of grains per spike and culm height were also measured. The duration of each phenophase was not affected by radiation intensity. Temperature affected the rate of wheat development, but the acceleration of development due to temperature during the seedling emergence - terminal spikelet initiation phase only slightly reduced (from 24.8 to 23.2 days). Differences in time from terminal spikelet initiation to anthesis were greater than in the earlier phases, having been the duration reduced from 24.6 to 20.0 days due to high temperature. Associated with the lack of effect of radiation on phasic development and the negligible effect of temperature on the duration of the early phases of development, final Leaf number was practically unchanged in this study by either the radiation level or the growing temperature. Thus, radiation did not affect the rate of leaf initiation. The number of spikelets was affected by neither the treatments nor the thermal environment. The rates of leaf appearance were accelerated by temperature. Radiation, on the other hand, did not significantly alter the rates of leaf appearance in any of the treatments. As expected from many sources in the literature, the number of grains per spike was significantly affected by radiation during the phase from terminal spikelet initiation to anthesis. Due to the lack of significant effects of radiation on the developmental patterns of wheat, the changes in number of grains per spike were due to changes in the number of grains born in each spikelet. The results of the present study were compared with others available in the literature on the effects (or lack of them) of radiation and CO2 concentration on phasic development, plastochron and phyllochron in wheat to reach the general conclusion that the rate of developmental events in wheat, in contrast to other plants, is almost completely independent of the availability of assimilates, with a possible exception for the Equatorial latitudes.  相似文献   

12.
Increasing climatic variability is projected to affect large‐scale atmospheric circulation, triggers and exacerbates more extreme weather events, including winter warming and more frequent extreme low temperatures in spring. Historical data from 1961–2000 indicate these temperature fluctuations may seriously affect grain yield of winter wheat crops. In this study, a field air temperature control system (FATC) was used to simulate the winter warming, spring cold and freezing events in the field experiment in 2010–2011 to explore their impacts on growth and yield of winter wheat. Eight elite wheat varieties released during 1961–2000 were included and four temperature scenarios were applied, including late spring freeze alone, winter warming + late spring freeze, early spring cold + late spring freeze and the normal temperature condition as control. Winter warming combined with late spring freeze significantly decreased tiller survival rate, leaf photosynthetic rate and leaf growth in wheat plants, and reduced the spike number and kernel number per spike, and the final grain yield. In contrast, the wheat plants experienced early spring cold had higher tiller survival rate, leaf photosynthetic capacity and sugar accumulation and improved tolerance to the late spring freeze, resulting in less yield loss, as compared with those without experiencing early spring cold. Both the meta‐analyses and the field experimental data demonstrated that the effects of later spring freeze stress on wheat yield were exacerbated by winter warming but were extenuated by early spring cold events. Therefore, it is important to consider the characteristics of temperature fluctuations during winter to spring for precise evaluation of climate change effects on wheat production.  相似文献   

13.
为进一步完善普通小麦春化特性理论基础,从不同春化特性小麦品种RNA-Seq结果中筛选得到一个春化诱导上调表达的EST序列Unigene3230,经NCBI比对与小麦wcor14a基因序列一致。为进一步明确该基因在春化过程中的功能,利用荧光定量PCR分析了wcor14a基因在非生物胁迫下的表达特性,结果显示,wcor14a基因能够响应低温、ABA、干旱等非生物胁迫。对wcor14a基因在不同春化发育特性小麦品种中的表达分析表明,该基因在不同发育特性小麦品种中的表达总体表现为春性半冬性冬性强冬性,而且表达时间表现为冬性和强冬性早于春性和半冬性。  相似文献   

14.
The aim of this study was to analyse (i) the crop attributes that determine flowering time (i.e. final leaf number, FLN; and phyllochron, Phy), (ii) the dynamics of tiller appearance and (iii) the synchrony between leaf and tiller appearance in wheat and barley plants exposed to waterlogging. Two experiments were carried out in pots, in which wheat and barley cultivars were exposed to five waterlogging treatments, during different periods throughout the crop cycle, from emergence to maturity. The appearance of leaves and tillers on the main stem was measured twice a week in labelled plants. Waterlogging from emergence to flag leaf appearance significantly delayed time to flowering. The delay was greater when waterlogging occurred at the beginning of tillering, lengthening the period from emergence to flowering 24 % (13–15 days) in barley and 10–15 % (6–10 days) in wheat, as compared to control. Phy was the main attribute explaining the delay in flowering, as FLN was not altered. Waterlogging during the early stages of development reduced tiller appearance rate (TAR) in both species, but this effect was partially counterbalanced by a lengthening of the tillering phase, so the effect on final tiller number at maturity was limited. In conclusion, the exposure of wheat and barley to waterlogging during early stages of development delayed time to flowering and reduce TAR in both species. Waterlogging during more advanced crop stages produced slight effects on tillering dynamics, which would indicate that waterlogging affected structure generation more than mortality.  相似文献   

15.
陈新红  刘凯  奚岭林  王志琴  杨建昌 《作物学报》2005,31(11):1406-1414
在盆栽和土培池条件下,研究了结实期轻度土壤水分胁迫与氮素营养对水稻地上部脱落酸和细胞分裂素含量及籽粒灌浆的影响。轻度土壤水分胁迫提高了籽粒的灌浆速率,缩短了灌浆期。在高氮（HN）水平下,轻度土壤水分胁迫处理使结实率、粒重和产量较正常灌溉条件下提高。土壤水分胁迫降低了稻株中的玉米素（Z）＋玉米素核苷（ZR）含量,显著增加了稻株中特别是籽粒中脱落酸（ABA）含量。籽粒灌浆速率与籽粒ABA含量极显著正相关,而与籽粒中Z+ZR含量的相关不显著。灌浆前期（花后9～13 d）对在HN和正常灌水下生长的稻株喷施ABA,显著提高了籽粒中蔗糖合成酶、淀粉合成酶、淀粉分枝酶、可溶性酸性转化酶和腺苷二磷酸葡萄糖焦磷酸化酶的活性,增加了粒重。喷施氟草酮(ABA合成抑制剂)的结果与喷施ABA相反。表明轻度土壤水分胁迫促进籽粒灌浆,ABA起重要的调控作用。  相似文献   

16.
A field study was conducted to investigate the effects of variation in levels of daily irradiance on the level of spike-let abortion and the rate of development using two cultivars of spring barky ( Hordeum vulgare L.), Schooner and Weeah. Three different irradiance treatments were imposed from the cessation of spikelet primordia initiation until anthesis: a reduced irradiance treatment (high competition treatment, HCT); an untreated control for medium competition treatment; MCT); and an increased amount of irradiance (low competition treatment. LCT). Variation, in natural daily irradiance (MCT) was imposed by either shading plants with shadecloth (HCT) or by exposing plants to relatively low inter-row irradiance competition effects by obstructing adjoining plant rows with plastic mesh (LCT). The duration of the spikelet growth phase was longer by 5 days (Schooner) and 9 days (Weeah) for HCT when compared to MCT, but there was no difference in its duration between LCT and MCT. Spikelet abortion occurred at 8–16 days before anthesis, but this was dependent on treatment. LCT For both cultivars showed a trend towards higher spikelet numbers per spike, although the increase was not significant over MCT, and HCT was significantly lower in both cultivars. Grain yield and biomass were lower (P < 0.05) for HCT compared to both LCT and MCT.  相似文献   

17.
Grain yield and the number of grains per ear of wheat decreased under the low temperature after jointing stage. In order to explore the physiological reasons of the decrease of grains number per ear by low temperature in spring, the spring wheat variety Yangmai 16 and the semi-winter wheat variety Xumai 30 were used as tested varieties to analyze the effects of low temperature in spring on the fertility of pollen and the formation of grain numbers at the appearance of the penultimate leaf stage (5℃/-3℃, day/night), booting stage (8℃/-1℃, day/night), and anthesis stage (12℃/4℃, day/night). The results showed that low temperature at the appearance of the penultimate leaf stage and booting stage resulted in abnormal metabolism of starch and protein in the anther both at the binuclear and tri-nuclear pollen stages and delayed degradation of the tapetum. The low temperature at the booting stage caused abnormal meiosis of pollen mother cells, abnormalities in chromosome pairing, which affected the formation of male gametophyte. The abortion rate of pollen was more significantly increased under low temperature at the appearance of the penultimate leaf stage than that at the booting stage, and it was the minimum at anthesis stage. The abortion rate of pollen in Xumai 30 was higher than that in Yangmai 16. The low temperature at three stages had significant effects on the number of spikelets, the number of fertile spikelets and the number of grains per spikelet. The effect of low temperature at the appearance of the penultimate leaf stage on grains number per spikelet was the most significant. There was a significant positive correlation between the number of grains per spike and pollen fertility, which was affected by abnormal meiosis, delayed degradation of the tapetum, and undersupply of nutriment for anther development. Therefore, the decline of pollen fertility caused by low temperature in spring is the main reason for the decrease of grains number per spike.  相似文献   

18.
春季低温对小麦花粉育性及粒数形成的影响   总被引：1，自引：0，他引：1  
小麦拔节后遭遇春季低温,每穗粒数下降,产量降低。为探明春季低温引起每穗粒数减少的生理原因,以春性小麦扬麦16和半冬性小麦徐麦30为供试品种,研究小麦倒二叶出生期(昼夜5℃/–3℃)、孕穗期(昼夜8℃/–1℃)和开花期(昼夜12℃/4℃)分别进行低温处理对小麦花粉育性及每穗粒数形成的影响。结果表明:倒二叶出生期和孕穗期低温均导致2个小麦品种在二胞花粉期和三胞花粉期花药中的多糖物质淀粉和蛋白质的代谢异常,绒毡层解体延迟;孕穗期低温还造成花粉母细胞减数分裂中染色体配对异常、出现微核等情况,影响正常雄配子体形成;花粉败育率表现为倒二叶出生期低温处理>孕穗期低温处理>开花期低温处理,徐麦30败育率高于扬麦16;3个时期低温均显著降低了2个小麦品种结实小穗数、每小穗结实粒数和每穗粒数,以倒二叶出生期低温处理穗粒数降低的幅度最大。相关分析表明,春季低温引起花粉母细胞减数分裂异常、绒毡层延迟解体、花药营养物质供给不足导致的花粉育性下降,是春季低温导致小麦每穗粒数减少的主要原因。  相似文献   

19.
Summary The effect of temperature on seed set and embryo development in reciprocal crosses of barley and wheat was assessed in crosses involving two spring barley varieties (Betzes, Martonvásári 50) and one wheat variety (Chinese Spring). Detached tillers placed in nutrient solution were pollinated in controlled environments at constant day-night temperature regimes (12, 15, 18 and 21° C) with a light intensity of 30,000 lux and a relative humidity of 80%. When barley was used as the female, lower temperatures (12 and 15° C) produced the maximum seed set, whereas for the reciprocal cross, the highest temperature (21° C) produced the best seed set in the Chinese Spring × Betzes combination.Low temperature retarded the embryo development. The highest numbers of hybrid plants were produced at 18° C and 21° C in the barley × wheat cross and in the wheat × barley cross, respectively. Embryos of about 1.5 mm length in the barley × wheat cross, and of about 1.0 mm length in the wheat × barley cross germinated successfully. The smallest embryo giving rise to hybrid plants was 0.57 mm in the barley × wheat cross and 0.51 mm in the wheat × barley cross.  相似文献   

20.
Winter triticale (cv. Grado) and winter wheat (cv. Taras) were grown in Rostock, Germany (54.2°N) for 5 years (1985–91) each with up to four sowing dates. Shoot apex development of the main stem and the two most developed tillers was observed by sampling eight plants every 3–10 days. The developmental submodel of the AFRCWHEAT2 simulation model was tested to predict the developmental events: emergence, start of floral initiation, double ridge, start of floret initiation, end of spikelet initiation and anthesis.Anthesis of main shoots was observed 8 days earlier for triticale than for wheat which was explained by an earlier start of reproductive development in triticale than in wheat. Variation in the dates of phenological events was greater for floral initiation and double ridges than for floret initiation and anthesis in both cereals. Dates of the early stages of development varied more in triticale than in wheat and more for main shoots than for tillers. For both species, standard deviations of the differences between observed and model predicted dates of phenological events were larger among developmental stages than between cultivars. Prediction of the early stages of development (floral initiation and double ridge) was poor for both species. The beginning of floret initiation and anthesis were simulated more accurately. We suggest that progress in simulating the development of cereals is more limited by lack of knowledge about plant physiology, rather than by the process of modelling. Better quantification of the vernalization requirements of different species is identified as an important topic for future work. Developmental parameters calculated for main shoots could also be used to closely predict the development rates of tillers. Differences between the development rates of main shoots and tillers were explained by the weather conditions each tiller group experienced and not by differences in their physiological responses to climatic factors. More research is needed to describe differences in development and vernalization requirements of a tiller when compared with that of a main shoot.  相似文献   

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