共查询到20条相似文献，搜索用时 328 毫秒
1.
Summary Early flowering carnation cultivars, responding to artificial long days, can assist the grower to plant the onset of flowering and achieve a better distribution of flower production over the year.A comparative trial is described of 20 carnation genotypes (cultivars and backcrosses of interspecific hybrids), representing a wide variation in flowering time and response to long days. The trial was planted in September in a phytotron under a winter light intensity of 15 W/m2 for eight hours per day. In one half of the trial, daylength was increased to 24 hours for 25 days in December-January. At the end of February the plants were transferred to a glasshouse where they were observed until all primary shoots had flowered. The main purpose of the experiment was to analyse the genetic factors responsible for the large differences in flowering behaviour between genotypes. Average flowering dates varied from 132 days from pinching in a Dianthus chinensis hybrid to 181 days in the mediterranean cultivar Raggio di Sole. LD response was most pronounced in the earliest flowering Diantini selections and least in the traditional commercial cultivars. In the former the LD effect was evident in all shoots of a plant, but mostly so in the lower (older) shoots; in the traditional cultivars only the higher placed shoots responded to LD. As a result, the proportion of the shoots actually responding to LD varied from 28% in the traditional cultivars to 54% in the Diantini x D. Allwoodii cv Doris group of genotypes. 相似文献
2.
Summary Carnation cultivars vary considerably in the average weight of their cuttings. Cutting weight shows a high negative correlation with mean relative growth rate. This was initially attributed to differences in age of the cuttings when taken from the stock plants, age being defined as time elapsed since start of visible shoot growth. Shoots on a stock plant are removed as cuttings when they have reached an adequate size and number of leaf pairs. Cuttings from cultivars with a lower rate of growth are removed later, usually resulting in a higher dry weight. This could explain why a high cutting weight is associated with a low relative growth rate.The validity of this tentative explanation is tested in 13 carnation cultivars grown under controlled conditions in two trials, one with plants grown from pinched cuttings and one with plants grown from unpinched cuttings for early flowering (forcing). An analysis of the data for plant weight and leaf pair number at successive stages of development suggests that the primary cause of the negative correlation between cutting weight and mean relative growth rate is not genetic variation in age of the cuttings, but variation in the size of the fully developed axillary bud on the stock plant. Larger buds produce thicker shoots that grow more slowly. Their later harvesting as cuttings only enhances their initial weight advantage, and also the negative correlation with mean relative growth rate.When plants are pinched 20 days after planting, as is normal in a summer-grown crop, the newly developing shoots still show variation in age. This is attributed to variation in the developmental stage of the dormant axillary buds at the time of pinching, causing variation in the time interval between pinching and the start of visible shoot growth. 相似文献
3.
D. P. De Vries 《Euphytica》1977,26(1):85-88
Summary In 62 clones of cut roses the numbers of flowering and blind shoots were recorded from February 1975 to January 1976. On average about 25 shoots were harvested per plant, of which 27% were blind. No significant correlation was found between the average numbers of flowering and blind shoots. Progenitors for winter flowering roses should be selected among clones that combine a constant total shoot production with a low percentage of blind shoots. 相似文献
4.
Summary Determinate architecture is of great interest for lupin production in Europe but the extent of genetic and environmental variation in the structure and yield of determinate lupins must be evaluated. Forty-three genotypes of determinate autumn-sown white lupin were studied in four environments in France in 1991/92 and 1992/93. Wide variation was observed for phenological (dates of mainstem and branch flowering, date of end of flowering and date of maturity), morphological (numbers of branch orders, branches and leaves) and seed characters (seed yield, mean seed weight, number of seeds/m2). Both genetic and environmental effects contributed to the observed variation. Heritabilities were high for all characters, and the interaction between genotype and location effects was low. There were significant positive correlations of flowering dates with vegetative plant development including the number of branches, number of leaves and number of branch orders. Seed yield and phenological and archtectural characters were significantly correlated. Distribution of yield on the vegetative orders showed important variations according the genotype, and the variations were related to variation for the architecture. There are possibilities for yield improvement using morphological characters in determinate autumn-sown lupin. 相似文献
5.
Carbon and nitrogen allocation and grain filling in three maize hybrids differing in leaf senescence
《European Journal of Agronomy》2006,24(3):203-211
Between flowering and maturity, leaf senescence reduces green leaf area while grains are filled from photosynthesis, nitrogen (N) uptake by roots and remobilisation from shoots. The question arises of possible effects of leaf senescence on photosynthesis, N uptake and remobilisation and their modification through genetic variations in senescence. To address this question, we compared three cultivars showing different behaviours. Tarro and Nicco are two modern hybrids presenting the same important grain sink but showing different time course of senescence, the former being normally senescent the latter “stay-green”. Déa hybrid, very well known by many previous experiments was the reference hybrid.The purpose was to monitor precisely the carbon (C) and N repartition in the main organs of the plant in connection with the progress of leaf senescence (experiment 1) and to measure the changes created by variations of N supply and soil-climate conditions (experiment 2).In experiment 1, time course of leaf senescence of the different leaf stages and weight of leaves, shoots and grains and N concentration of shoots and grain were measured weekly. In experiment 2, the same three cultivars were grown at limiting and non-limiting N supply in four locations in France during 2 years. At flowering, silage and harvest stage, dry matter and N concentration were measured in the main parts of the plant, and leaf senescence was evaluated at silage stage.On soil well supplied with N, Tarro had an identical rate of leaf senescence than Nicco for leaves below the ear, but higher for leaves above the ear. After flowering, Nicco accumulated more biomass than Tarro, but kept a larger part of this total biomass in the stem. In contrast, Tarro accumulated a larger part of total biomass in the grain.After flowering, N uptake was larger in Nicco than Tarro. Shoot N concentration decreased earlier and more completely in Tarro than Nicco, indicating a larger remobilisation to the grain. Though Tarro began and finished grain filling simultaneously with Nicco, it reached 70% of final grain weight 25 °C d sooner than Nicco.The senescence due to N stress differed from the physiological senescence of a senescent hybrid. The time course of the reproductive phase and the N repartition in the plant suggest that a threshold in grain filling or in shoot nitrogen decrease could be the internal signal triggering senescence of uppermost leaves. 相似文献
6.
The results of this study indicated a great deal of genetic variation in a number of characters of horticultural interest
in kiwifruit seedling populations, and therefore, a potential to improve kiwifruit by vine selection. High narrow sense heritability
was shown for pedicel length(0.62) and flowering duration (0.50) in male vines, and pedicel length (0.67),floral shoot percentage
(0.54), leaf length-width ratio (0.64), fruit elongation (0.64) and fruit weight (0.52) in female vines. For these traits,
selection of superior seedlings should lead to rapid genetic improvement in these populations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Summary Eleven cultivars of Phaseolus vulgaris L., inoculated with a commercial inoculum of Rhizobium phaseoli, were grown in a nitrogen-free medium in the phytotron at two temperature regimes corresponding to mid-May or early June seedings. Cultivars differed in their abilities to support dinitrogen fixation under the two temperature regimes. Early June seedings fixed more dinitrogen than mid-May ones when grown for the same growth period. The amount of dinitrogen fixed was correlated with leaf area and leaf and shoot weight. It is proposed that the relationship between dinitrogen fixation and these quantitative yield characters may help bean breeders in selecting plants with superior dinitrogen-fixing abilities. 相似文献
8.
Summary Sorghum shoot fly, Atherigona soccata (Rondani) is an important pest of sorghum in Asia, Africa, and Mediterranean Europe, and host plant resistance is an important
component for the management of this pest. The levels of resistance in the cultivated germplasm are low to moderate, and therefore,
it is important to identify genotypes with different mechanisms of resistance to pyramid the resistance genes. We studied
the antixenosis for oviposition, antibiosis, and tolerance components of resistance in a diverse array of shoot fly-resistant
and -susceptible genotypes. The main plants and tillers of SFCR 151, ICSV 705, SFCR 125, and, IS 18551 experienced lower shoot
fly deadhearts at 28 days after seedling emergence, produced more number of productive tillers. The insects fed on these genotypes
also exhibited longer larval period (10.1–11.0 days compared to 9.3 days on Swarna), lower larval survival and adult emergence
(54.7–67.8 and 46.7–52.2% compared to 73.3 and 60.6% on Swarna, respectively), and lower growth and adult emergence indices
as compared to the susceptible check, Swarna. Physico-chemical traits such as leaf glossiness, trichome density, and plumule
and leaf sheath pigmentation were found to be associated with resistance, and chlorophyll content, leaf surface wetness, seedling
vigor, and waxy bloom with susceptibility to shoot fly and explained 88.5% of the total variation in deadhearts. Step-wise
regression indicated that 90.4% of the total variation in deadhearts was due to leaf glossiness and trichome density. The
direct and indirect effects, correlation coefficients, multiple and step-wise regression analysis suggested that deadhearts,
plants with eggs, leaf glossiness, trichomes on the abaxial surface of the leaf, and leaf sheath pigmentation can be used
as marker traits to select for resistance to shoot fly, A. soccata in sorghum. 相似文献
9.
Summary The concept of the uniculm habit as an important feature of a wheat ideotype for a mediterranean environment was evaluated under field conditions. A uniculm plant produces a single shoot and when sown in a stand exemplifies a non-tillering crop with a fixed density of shoots throughout the growing season. Yield and harvest index of normal tillering spring wheat was compared with that of the same crop surgically detillered throughout the growing season to a constant density of 2 shoots per plant. The use of a biculm, whilst retaining the uniculm principle of a fixed density of shoots throughout the growing season, permitted comparison on a single crop sowing at normal field density.The control plots followed the usual pattern of tillering for the region attaining a maximum of about 4.0 shoots per plant by early spring. Shoot number declined to 2.3 and 2.6 per plant by maturity in 1978 and 1979, respectively.Detillered plots outyielded the controls by 14 per cent in 1978 (2.05 v. 1.80 tonnes ha-1) and 22 per cent in 1979 (1.84 v. 1.51 tonnes ha-1). Harvest indices were 0.39 v. 0.35 in 1978 and 0.30 v. 0.24 in 1979 for detillered and control plots, respectively.Higher leaf area indices and better water relations after anthesis in biculm stands indicated more efficient water use when shoot population was controlled at near optimum level. Irrigation at anthesis reduced the difference in yield between detillered and control plots.Although the uniculm principle was demonstrated with biculms in practice control of shoot number will require the use of genetic uniculms. 相似文献
10.
J. Schipper 《Journal of Agronomy and Crop Science》1996,176(3):199-211
Relation between pattern of development of wheat seedlings (Triticum aestivum L. Fiori et Paol.) and growth rate of leaves, tillers and roots.
In two glasshouse and two phytotron experiments, the early growth and development of spring wheat and unvernalized autumn wheat in long and short days was observed by frequent assessments of dry weight of shoots and roots and by daily measurements of length and dry weight of individual leaves. In an additional experiment, the pattern of dry matter distribution during germination was studied.
The rate of leaf emergence and appearance was decelerated by short days in spring wheat and by long days in unvernalized autumn wheat.
The growth rate of individual leaves showed a pattern of successive reductions and accelerations, being highly synchronized between leaves and clearly related to the succession in emergence of leaves and tillers.
Growth rates of main shoot and tillers were apparently synchronized, while those of the seminal root system appeared to show an oppositional pattern as compared to the shoot.
It is suggested that variation in the growth rate of existing organs is based on hormone controlled variation in meristematic activity, which is influenced by day length and the state of vernalization of the plant. 相似文献
In two glasshouse and two phytotron experiments, the early growth and development of spring wheat and unvernalized autumn wheat in long and short days was observed by frequent assessments of dry weight of shoots and roots and by daily measurements of length and dry weight of individual leaves. In an additional experiment, the pattern of dry matter distribution during germination was studied.
The rate of leaf emergence and appearance was decelerated by short days in spring wheat and by long days in unvernalized autumn wheat.
The growth rate of individual leaves showed a pattern of successive reductions and accelerations, being highly synchronized between leaves and clearly related to the succession in emergence of leaves and tillers.
Growth rates of main shoot and tillers were apparently synchronized, while those of the seminal root system appeared to show an oppositional pattern as compared to the shoot.
It is suggested that variation in the growth rate of existing organs is based on hormone controlled variation in meristematic activity, which is influenced by day length and the state of vernalization of the plant. 相似文献
11.
Summary A variety must be distinguishable, uniform, stable and of sufficient productivity to be officially registered. In Italy landraces of lucerne are still widely used because they are characterized by a good persistence and productivity in their area of origin and adaptation.The landrace from Casalina (20 km south of Perugia, Central Italy) has higher dry matter production than many other commercial cultivars. The objective of this paper was to measure the variation of the landrace Casalina and compare it with that of the commonest cultivars available on the market and with some lines selected from the landrace Casalina.The experiment consisted of 11 entries: Casalina, two selections from Casalina (one for high seed yield and one for frequent cuttings), the registered landrace Italia Centrale and 7 registered cultivars. Each entry was represented by 80 genotypes transplanted in the field 60×40 cm apart in a randomized block design with 4 replications. In 1991 the following characters were recorded on a single plant basis: time of first flowering, height, number of shoots and dry matter yield at the first harvest, time of second flowering, leafiness, height, number of shoots and dry matter yield at the second harvest, height, number of shoots and dry matter yield at the third and fourth harvest. Height, number of shoots and dry matter yield at the first harvest, dry matter at the second and third harvest were recorded during the 1992 season.Casalina was as variable as the other entries in 77% of the comparisons; it was more variable in 8% of the comparisons and less variable in 15% of the comparisons. In conclusion, the variation of landrace Casalina is equal to or less than that of registered varieties so that it could be directly registered at the National Registry of Varieties. 相似文献
12.
Multiple shoots were efficiently regenerated from cotyledonary node and shoot tip explants of Pisum sativum within 15 days on MS medium containing B5 vitamins and supplelmented with 2.0 mgl-1 6-benzylaminopurine. The elongated shoots produced on the same medium were excised and transferred to MS medium containing
half strength ammonium nitrate (8.25 gml-1) and supplemented with auxins (indole-3-butyric acid or naphthalene acetic acid) either alone or in combinations with gibberellic
acid. Rooting and flowering were observed on the 7th and 15th day after their transfer to rooting medium. The flowers self-fertilised
in vitro and produced mature pods within 25 days of rooting. These seeds were germinable both in vitro and in vivo. In vitro seeds sown in pots under field conditions developed into flowering plants, and subsequently produced pods with viable seeds.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
为了解‘吉尔’杧果秋梢生长规律及结果母枝质量与开花率的关系,应用调查研究和数理统计的方法,对‘吉尔’杧果采后一次秋梢与二次秋梢,结果母枝质量与末级梢成花率及花序大小的关系进行分析。分析结果表明：一次秋梢直径对二次秋梢直径和一次秋梢叶面积对二次秋梢叶面积有显著影响。随二次秋梢直径增粗,二次秋梢叶片数和叶面积增加;随二次秋梢长度加长,二次秋梢叶片数和叶面积增加。末级梢成花率与结果母枝直径为负相关关系,随结果母枝直径增粗,末级梢成花率下降;要获得80%~85%的末级梢成花率,结果母枝直径应在0.48~0.51 cm左右;花序体积与结果母枝直径关系最密切,与结果母枝长度、叶片数、叶面积也有显著相关。 相似文献
14.
Edmar I. Teixeira Derrick J. Moot Hamish E. Brown Andrew L. Fletcher 《European Journal of Agronomy》2007,26(4):394-400
The productive life of lucerne (Medicago sativa L.) stands depends on the rate of mortality of individual plants. However, self-thinning of plant populations may be compensated for by increases in other yield components, namely shoots/plant and individual shoot mass. Frequent defoliation reduces lucerne yield but it is unclear whether this is caused by an acceleration of plant mortality or changes in these other yield components. To investigate this, crops with contrasting shoot yields were created using constant 28 or 42-day regrowth cycles applied to a ‘Kaituna’ lucerne crop in Canterbury, New Zealand during the 2002/2003 and 2003/2004 growth seasons. Two further treatments switched from 28 to 42 or 42 to 28 days grazing frequency in mid-summer (4th February) of each year. The annual yield of shoot dry matter (DM) ranged from 12 to 23 t/ha for the treatments defoliated consistently each 28 or 42 days, respectively. Plant population was unaffected by treatments and declined exponentially from 130 plants/m2 in June 2002 to 60 plants/m2 in September 2004. The dynamics of plant and shoot population were associated with the light environment at the base of the canopy. The slope of the size/density compensation (SDC) of plants was −1.67 for the treatment defoliated each 42 days, near the expected self-thinning slope of −1.5 for stands at constant leaf area index (LAI). Self-thinning of shoots resumed after each defoliation when the LAI reached 2.1 and the transmission of photosynthetically active radiation (PARt) was 0.20. At this point the proportion of aerial DM in the tallest (dominant) shoots increased non-linearly from 30 to >80%, due to the mortality of intermediary and suppressed shoots. The average maximum shoot population in each rotation was 780 shoots/m2 and unaffected by the decline in plant population due to a compensatory increase from 6 to 13 shoots/plant as the stand thinned. A lower asymptote of 43 plants/m2 was estimated as the minimum plant population at which yield component compensation would maintain the productive potential of these ‘Kaituna’ stands. Differences in shoot yield were explained (R2 = 0.97) by changes in the individual shoot mass (ISM) that were consistently lowered by frequent defoliation treatments. Frequent defoliations reduced crop productivity by limiting the assimilation of biomass into each individual shoot with negligible impact on shoot appearance rate, the number of shoots per plant at an LAI of 2.1 or the rate of plant population decay. Inter-specific competition for light was proposed as the main factor controlling self-thinning of plants and shoots regardless of their individual C:N status. 相似文献
15.
Medium, Explant and Genotype Factors Influencing Shoot Regeneration in Oilseed Brassica spp. 总被引：9，自引：0，他引：9
G. X. Tang W. J. Zhou H. Z. Li B. Z. Mao Z. H. He K. Yoneyama 《Journal of Agronomy and Crop Science》2003,189(5):351-358
The effects of culture media, explants and genotypes on shoot regeneration in oilseed Brassica species were examined in this study. The maximum shoot regeneration frequency was obtained in Murashige and Skoog medium supplemented with 3 mg l?1 6‐benzylaminopurine and 0.15 mg l?1 1‐naphthaleneacetic acid. The addition of 2.5 mg l?1 AgNO3 was very beneficial to shoot regeneration in B. napus and Ag2S2O3 (10 mg l?1) was even superior to AgNO3 (2.5 mg l?1). Explant age, explant type and carbon source also significantly affected shoot regeneration. Four‐day‐old seedlings of cotyledonary explants showed the maximum shoot regeneration frequency and number of shoots per explant. Of the four explants – peduncles, hypocotyls, cotyledons and leaf petioles – cotyledons produced the highest shoot regeneration frequency (56.67 %). Four carbon sources – glucose, maltose, starch and sucrose – were compared for their respective effects on shoot regeneration from cotyledonary explants. Sucrose appeared to be the best carbon source for shoot regeneration with the highest shoot regeneration frequency (76.00 %). Considerable variation in shoot regeneration from cotyledonary explants was observed both between and within Brassica species. The shoot regeneration frequency ranged from 10.00 % for cv. R5 (B. rapa) to 83.61 % for cv. N1 (B. napus). Two B. napus, one B. carinata and one B. juncea cultivars exhibited shoot regeneration frequency higher than 70 %. In terms of the number of shoots produced per explant, B. rapa showed the highest variation, ranging from 5.64 for cv. R3 to 1.33 for cv. R5. Normal plantlets were regenerated from all induced shoots and developed normally. The regenerated plants were fertile and identical with the source plants. 相似文献
16.
Summary Six diploid perennial ryegrass populations, two diploid F1 hybrid families and the autotetraploid cv. Tove were grown in a glasshouse and the mean length and mean width of epidermal cells on the abaxial leaf surface of young fully expanded leaves compared. The diploids varied in cell length by 26%, in cell width by 9% and in length: width ratio by 39%. The cells of cv. Tove were 25% longer and 12% wider than those of the highest ranking diploid and the length: width ratio 9% higher. The DNA contents per telophase root-tip cell nucleus of a large-celled and a small-celled diploid population were similar, suggesting that the variation in epidermal cell size among diploids was due to the action of specific genes and not to differences in genome size. The mean epidermal cell dimensions of four of the above populations growing as plots in a field trial employing three levels of fertiliser nitrogen and four harvesting frequencies were measured on three occasions. Varietal ranking in cell dimensions was consistent over the different managements and dates, and agreed well with the glasshouse results. The results indicate that measurements of leaf epidermal cell length and width can be useful aids both in breeding for herbage yield and in distinguishing varieties with similar flowering dates. 相似文献
17.
Summary Wheat root characters which influence vital plant processes have scarcely been explored for their genetic control. This study was conducted to i) examine the diversity of root traits and associated shoot traits in spring wheat (Triticum aestivum L.) cultivars; ii) study the nature of genetic control of selected traits; and iii) examine associations among root and shoot traits. Three experiments were conducted in the greenhouse with plants grown in the vermiculite medium in clear plastic tubes. In the first experiment, 42 spring wheat cultivars were grown for three weeks and measurements were taken on root length, leaf length, root number, leaf number, root dry weight, and top dry weight. In the second study, 15F1's originating from a partial diallel mating of six cultivars along with the parents were evaluated for 4 weeks. The data on root length, leaf length, and root number were subjected to diallel analysis according to Griffing's method 4, fixed model. A third experiment consisted of studying 2 F2 populations with 141 plants per population. In the first study the 42 cultivars exhibited a wide range of variation for all six traits. Diallel analysis revealed significant effects of both general combining ability (GCA) and specific combining ability (SCA) for root length, leaf length, and root number. Parents with high GCA estimates were identified. Significant positive correlation coefficients were found among root and shoot traits. Analysis of F2's for root length indicated quantitative nature of inheritance of root length. 相似文献
18.
T. Han C. Wu R. S. Mentreddy J. Zhao X. Xu J. Gai 《Journal of Agronomy and Crop Science》2005,191(4):255-262
Pre-flowering photoperiod effects on floral initiation, flowering time and yield components of various crops have been well studied, but the post-flowering photoperiod effects on major field crops are not clearly understood. A controlled environment study was carried out using six long-day (LD) crops, flax, sugar beet, broad bean, triticale, wheat, and rapeseed, and seven short-day (SD) crops including Adzuki bean, potato, rice, peanut, mungbean, cotton and corn with a major objective of evaluating the post-flowering photoperiod effects on their reproductive development and yield components. There were significant inter- and intra-specific differences in their response to post-flowering photoperiod treatments. The effects of short days on LD crops were similar to LD effects on SD crops. The post-flowering duration was prolonged by short photoperiod in LD crops and long photoperiod in SD crops. There was, however, significant genotypic variation within a species for such effects. The post-flowering LD treatment caused abscission of flowers and pods and the resumption of vegetative growth in Adzuki bean. The post-flowering LD treatment also delayed the shoot senescence of one of the two potato varieties and decreased the number of tubers per plant in both varieties. The LD treatment delayed maturation of rice and mungbean, and decreased seed yield and 100-seed weight of peanut, although the shoot senescence of peanut was not apparently affected. Rapeseed, wheat, cotton and corn genotypes in this study did not show any sensitivity to post-flowering photoperiod. In triticale (an LD crop) exposure to short photoperiod post-flowering increased the number of spikes per plant perhaps due to a greater assimilate accumulation over a longer duration. The results from the current study as well as those from our previous experiments suggest that post-flowering photoperiod responses do exist in diverse field crops, and that there are strong genotypic differences in sensitivity and magnitude of response to post-flowering photoperiod. Photoperiod after flowering substantially regulates the source/sink relationship, and promotes partitioning and accumulation of assimilates to storage organs of crops when it favours the reproductive development of crops. 相似文献
19.
Summary Seedlings of Trifolium repens showed considerable variation with regard to the morphology and growth of their calli, and their ability for in vitro differentiation of shoots. One of the lines selected for regeneration in primary callus cultures also showed shoot formation from protoplasts. Somatic embryogenesis in callus cultures of T. pratense and T. arvense occurred only in selected seedling lines. This paper highlights the importance of screening a large number of plants within a cultivar of outbreeding species to achieve reproducible plant regeneration from tissue culture. 相似文献
20.
D. L. Jennings 《Euphytica》1979,28(3):747-750
Summary When grown in Scotland, eight blackberry cultivars of diverse origin showed considerable variation in the dates when their first fruits ripened. These dates were determined in part by variation in the date of their first open flower and in part by variation in the number of days required from flowering to ripening. Genotype x environment interactions were important for both components, but especially for the second, where they could be attributed to heterogeneity of regressions against the environmental means. Temperature was considered the important environmental factor determining the number of days required from flowering to repening, and accumulated heat units successfully quantified the differences between cultivars for this component: cultivars required similar numbers of heat units in each season and there were no interaction effects. Heat units were not useful for study of flowering dates, however.The implications for breeding early ripening cultivars for Scotland are discussed. 相似文献