Effect Of Vernalization Research Articles

Phyllochron Response to Vernalization and Photeperiod in Spring Wheat

An understanding of how environment controls the initiation and development of the leaf is required to construct dynamic crop simulation models. The aim of this study was to determine the effect of vernalization and photoperiod on total number of leaves at anthesis, leaf emergence rate, and phyllochron in 20 spring wheat genotypes (Triticum aestivum L.). An experiment was conducted under greenhouse conditions during spring 1992 at ICARDA, Tel Hadya, Syria, with all combinations of three photoperiods (8‐, 12‐, and 16‐h daylength) and two vernalization treatments (vernalized and nonvernalized). Total number of leaves on the main stem at anthesis decreased with increasing photoperiod. Vernalization reduced the total number of leaves on main stem at anthesis in the eight vernalization‐sensitive genotypes. Leaf number on the main stem was linearly (r = 0.99) related to accumulated growing degree days (°C d). Genotypes differed in leaf emergence rates. Leaf‐emergence rate increased with increasing photoperiod. Phyllochron decreased with increased daylength from 124 °C d leaf−1 at 8 h to 97 °C d leaf−1 at 16‐h photoperiod. These results suggests that, to model leaf appearance and canopy development in wheat, genotypic coefficients of phyllochron need to be determined in relation to photoperiod. Additionally, the effect of vernalization at inductive photoperiods on the phyllochron in genotypes adapted to heat‐prone tropical environments needs further study.

Performance of North American Strawberry Cultivars under Conditions Mimicking California Production Systems

Runner plants from 16 strawberry (Fragaria ×ananassa Duch.) cultivars were grown using annual Mediterranean production systems to test for differences in productivity, performance traits, and vegetative growth attributes. Genotypes were included from germplasm adapted to four geographic regions: California and northwestern, northeastern, and mid-Atlantic or southeastern United States. The California genotypes were divided further into day-neutral and June-bearing categories. With these treatments, California cultivars had significantly larger plants and grew more rapidly during the fall and winter, had larger fruit, and produced at least twice the quantity of fruit of cultivars from the other regions. Variance components due to region explained 64% and 26% of the phenotypic variance for early and total yield, respectively, whereas differences among cultivars within regions explained 12% and 7% of the variance for these traits. Cultivars from all regions had significantly larger plants and were more productive when treated with 3 weeks of artificial vernalization. However, region × vernalization effects were nonsignificant for all traits, a result suggesting that selection in Mediterranean environments has not adapted germplasm specifically for low vernalization conditions.

Effect of time of sowing on flowering in faba bean (Vicia faba)

Sequential sowings of faba bean (Vicia faba) were conducted to examine the effect of sowing date and a vernalisation treatment on the phenology of a range of faba bean accessions. There was very little difference between accessions in the rate of germination. Delayed sowing increased the time to establishment, but the thermal time from sowing to emergence did not vary greatly. On average 208�C.day was required for emergence and the base temperature for germination was near 0�C for all accessions. The shortest time from emergence to first flower averaged over all sowing dates was 43 days for Accession 286 (range 29-52 days), and the longest was 73 days for Accession 863 (50-96 days). The greatest response to vernalisation occurred when the seed was sown in early autumn (April). When sown in late winter (August), however, there was little response to vernalisation despite the plants being exposed to higher mean temperatures. In that case, long and lengthening days partly overcame the vernalisation requirement of some cultivars. For the range of sowing dates normally expected in dryland crops in southern Australia, there was little effect of vernalisation on the time to flowering and the major controls of development were through responses to temperature and daylength. The range of maturity types in the current breeding program appears sufficient to extend the range of environments in which faba bean is grown.

Vernalization and Seeding Date Effects on Yield and Yield Components of White Lupin

Understanding the agronomic importance of planting date and cold temperatures during germination may lead to the development of better management strategies for spring‐sown white lupin (Lupinus albus L.). We conducted two experiments to determine optimum planting dates for spring‐sown white lupin and to determine the effect of vernalization on plant morphology, yield, and yield components. In Experiment I, field plots were planted in 15‐cm rows at five planting dates (14‐d intervals) at Staples, MN, from 1985 through 1989. In Experiment II, seeds were imbibed for 48 h and cold treated (vernalized at 1 °C) for 14 d, and hand planted in 76‐cm rows and compared with non‐vernalized controls at 4 planting dates (main plots) Staples and Becker, MN, in 1988 and 1989. Early to mid‐April plantings generally produced the highest yields. Delayed planting past this yield maximum resulted in a 53 kg ha−1 d−1 decrease in yield, averaged over 11 location‐years. Vernalization reduced node number 23 to 52% and plant height 8 to 53%. Height and node number were reduced by vernalization at every planting date, and varied widely across a range of temperatures to which the seedlings were exposed. This data provides evidence that vernalization is a continuous rather than discrete response. Yield was generally reduced by vernalization, except at later planting dates when 75% of the vernalized plot's yields were equal to or greater than controls (vernalization × planting date interactions were significant in all years). Yield differences were largely determined by the number of plants which produced fertile branch inflorescences. Pod number was increased at both the mainstem and the branch reproductive sites of these morphological types, compared with plants which set only mainstem pods. Seeds per pod and seed weight were also positively correlated with yield. Sowing white lupin within a relatively narrow window of seeding dates in mid.April is important to reduce the wide variation in performance often observed with this crop.

Thermoinductive Regulation of Gibberellin Metabolism in Thlaspi arvense L. (II. Cold Induction of Enzymes in Gibberellin Biosynthesis).

Vernalization of Thlaspi arvense L. results in the alteration of gibberellin (GA) metabolism such that the metabolism and turnover of the GA precursor ent-kaur-16-en-19-oic acid (kaurenoic acid) is dramatically increased. This cold-induced change in GA metabolism is restricted to the shoot tip, the site of perception of cold in this species (J.P. Hazebroek, J.D. Metzger [1990] Plant Physiol 94: 157-165). In the present report additional biochemical information about the nature of this low-temperature-regulated process is provided. The endogenous levels of kaurenoic acid in leaves and shoot tips of plants were estimated by combined gas chromatography-chemical ionization mass spectrometry at various times after 4 weeks of vernalization at 6[deg]C. The endogenous levels in shoot tips declined 10-fold by 2 d after the plants were returned to 21[deg]C; this decline continued such that there was nearly 50-fold less kaurenoic acid by 10 d after the end of vernalization. No effect of vernalization on the endogenous levels of kaurenoic acid in leaves was observed. An in vitro enzyme assay was developed to monitor changes in the ability of tissues to convert kaurenoic acid to ent-7[alpha]-hydroxykaur-16-en-19-oic acid (7-OH kaurenoic acid). The activity of this enzyme rapidly increased in microsomal extracts from shoot tips following the end of vernalization. No thermoinduced increase in activity was observed in leaves. The enzymic oxidation of ent-kaurene to ent-kaurenol was also induced in shoot tips by vernalization. However, this reaction does not appear to be rate limiting for GA biosynthesis, because substantial amounts of kaurenoic acid accumulated in noninduced shoot tips. These results corroborate our hypothesis that the conversion of kaurenoic acid to 7-OH kaurenoic acid is the primary step in GA metabolism regulated by vernalization in Thlaspi shoot tips.

Effects of Photoperiod and Vernalization on the Number of Leaves at Flowering in 32 Arabidopsis thaliana (Brassicaceae) Ecotypes

Effects of Photoperiod and Vernalization on the Number of Leaves at Flowering in 32 Arabidopsis thaliana (Brassicaceae) Ecotypes

EFFECTS OF PHOTOPERIOD AND VERNALIZATION ON THE NUMBER OF LEAVES AT FLOWERING IN 32 ARABIDOPSIS THALIANA (BRASSICACEAE) ECOTYPES

The extent of natural variation among wild type Arabidopsis thaliana L. Heynh for response to environmental stimuli that affect flowering is poorly documented. The effects of photoperiod and vernalization on the number of rosette leaves at the time of anthesis was measured for 32 Arabidopsis ecotypes. All ecotypes were vernalized 24 days at 4 C under continuous illumination. Vernalized and nonvernalized plants were transplanted into 8‐ (short‐day) and 20‐hour (long‐day) photoperiods in controlled environment growth chambers. Two ecotypes failed to flower after 110 days. Mean leaf number was less for all ecotypes under long day compared to short day. Sixteen ecotypes responded to vernalization; eight had reduced leaf number regardless of photoperiod, and eight had reduced leaf number only under short day. Two ecotypes required vernalization to flower in this study. For three ecotypes, vernalization and short day resulted in a reduction in leaf number whereas vernalization and long day resulted in increased leaf number. Documentation of the effects and interactions of photoperiod and vernalization across many ecotypes provides a broader range of described natural variation for genetic and physiologic study.

The Effectiveness of Vernalization of Immature Embryos of Winter Wheat var. Grana as Related to Age and Exogenous Phytohormones

AbstractStarting from the 10th day after pollination, immature embryos of winter wheat var. Grana were isolated and then vernalized for 4 to 8 weeks on Murashige and Skoog nutrients containing BAP (0.5 or 2 mg/dm3), NAA (0.5 or 2 mg/dm3), or GA3 (5 or 20 mg/dm3). Vernalized seedlings were cultivated in a greenhouse and the number of days to the heading of individual plants as well as the percentage of plants capable of generative development were estimated.The lower limit of size for 50 % survival of embryos strongly depended on the phytohormone used: from 0.9 mm in control, 1.1 mm in nutrient containing BAP, 1.2 mm for NAA, up to 1.7 mm in nutrient with GA3.Exogenous GA3 was lethal for embryos younger than 18 days but induced elongation of older embryos.Embryos isolated 2.5 to 4 weeks after pollination showed minimal requirements for the length of vernalization.BAP increased the percentage of heading plants originated from the youngest embryos.GA3 improved partial vernalization, strongly increasing the percentage of heading plants, but did not change the time from the end of vernalization to heading. It has been postulated that GA3 increases number of plants capable of overcoming the threshold of induction of generative development but does not accelerate the flowering process.Hormonized plants showed no deformation of generative development. As the effectiveness of vernalization increased, the heading of plants was faster but they were shorter, forming spikes with a smaller number of spikelets and producing fever lateral shoots.The very young embryos probably have in reserve sufficient amounts of auxins and gibberellins and therefore exogenous GA3 decreases their viability or even exerts a deleterious effect. However, as the embryos' ageing, gibberellin starvation develops. This being especially pronounced during vernalization.The de novo synthesis or activation of gibberellins takes place during the second stage of vernalization. This is why exogenous hormone improves the effectiveness of partial vernalization, though it is not possible to substitute by gibberellins the vernalization requirements of immature embryos.

Effects of Higher Temperatures, Photoperiod and Seed Vernalisation on Development in Two Spring Wheats

The intention of this work was to examine to what degree development in wheat is modified by increased temperature when other environmental factors are also varied. The genotypes used were an early season wheat, Hartog, and a closely related mid-season line, Late Hartog. Plants were grown throughout in temperature regimes of 25/15�C or 17/7�C and photoperiods of 9, 11, 13 or 15 h with 9 h of natural summer radiation. Seeds were vernalised for 0, 2 or 4 weeks. Increased temperature extended the thermal time to ear emergence, particularly in Late Hartog, and particularly under short days after plants had been vernalised for 4 weeks. Phyllochron intervals on the main shoot were increased by higher temperature, as were spikelet numbers in Late Hartog under long photoperiod. However, in Hartog and in Late Hartog exposed to short days, spikelet numbers were reduced by increased temperature. Long seed vernalisation significantly reduced leaf and spikelet number in Late Hartog but only at the higher temperature. Fewer spikelets were produced per leaf at short photoperiod. The apparently complex interactions between temperature, photoperiod, genotype, and seed vernalisation on development are explained in terms of their effects on the timing of floral initiation and the related numbers of primordia accumulated on the apex at that stage. We hypothesise that, in the absence of source limitation, delays in floral initiation such as occur through shortening of photoperiod can increase numbers of leaves and spikelets, though at a decreasing rate with increasing delay. When source is limiting, as under higher temperature and unchanged or reduced radiation, long delays result in a greater reduction in the rate of production of organs and their final number. We further propose that much of the change may be associated with the interplay between the plastochron and phyllochron intervals. Published data are examined to show that high temperatures delay ear emergence in other genotypes both in controlled environments and in the field.

Effect of temperature, vernalization and water stress on phyllochron and final main-stem leaf number of HY320 and Neepawa spring wheats

An understanding of the effect of environment on leaf growth is needed to accurately simulate phenological development of a cereal crop. This study was conducted to determine the effect of temperature, cold (vernalization) and water stress on the phyllochron (degree-days leaf−1) prior to the terminal spikelet stage and on the final leaf number produced by the main stem (FLN) of two spring wheat varieties (Triticum aestivum L.), Neepawa and HY320, grown on the Canadian prairies. Within each of five day/night temperature regimes (30/25 °C, 24/19 °C, 21/12 °C, 16/7 °C and 7/2 °C, with means of 28 °C, 22 °C, 18 °C, 13 °C and 5 °C, respectively), the varieties were grown under two cold (not vernalized and vernalized) and two water (wet and dry) treatments. Within a given temperature regime, both varieties responded similarly to the cold treatments. Vernalization reduced phyllochron and FLN in all but the lowest temperature regime, where phyllochron increased and FLN was unaffected. When effective, severe water stress increased phyllochron and decreased FLN. HY320 was relatively more affected by vernalization and less affected by severe water stress than Neepawa. For both varieties, phyllochron was curvilinearly related to temperature and increased as temperature increased. The relationships were noticeably altered by vernalization and severe water stress. When not vernalized, FLN for HY320 increased as temperature increased; FLN for Neepawa reached a maximum at 20 °C. When vernalized, FLN was independent of temperature under optimum water; the reduction of FLN by severe water stress increased as temperature increased. The results of this study suggest that the effect of environmental change on both phyllochron and FLN must be accounted for when accurate and reliable modelling of the early development of spring wheat is required.Key words: Spring wheat, phyllochron, leaf number, temperature, water stress, vernalization

Influence of Warm Intervals on the Effects of Vernalization and the Composition of Phospholipid Fatty Acids in Seedlings of Winter Wheat

AbstractExcised embryos of winter wheat were submitted to a different number of vernalization (2 °C) and devernalization (20 °C) cycles of different lengths. In all treatments sum of cold and warm intervals was 50 and 10 days, respectively. The influence of different temperature conditions of seedling growth on the effectiveness of vernalization and correlations between effectiveness of vernalization and final content of phospholipid fatty acids were analyzed.All indexes of generative development of plants (length of vegetative phase, % of generative plants, number of side shoots) showed the most effective was uninterrupted vernalization beginning immediately after excision of embryos. Increasing the number of 2 ° C/20 °C cycles rapidly depressed effectiveness of vernalization, which reached the minimum with the 8.3 days at 2 °C and 2 days at 20 °C cycle and then improved again as cycles became shorter and more numerous.Correlations between indexes of generative plant growth and indexes describing composition of fatty acids in seedlings showed that from 50 % to 60 % of variability in the composition of phospholipid can be associated with changes in the degree of generative induction. A higher degree of generative induction was associated with a higher share of < 16, 16: 0 and 18:2 acids and a lower share of 18: 3 acid and also with a lower value of the 16: 0/< 16 ratio of phospholipids.The relation between the generative induction of plants and the composition of phospholipid fatty acids may however be blurred when induction proceeds under conditions of alternate short spells of vernalization and devernalization temperatures.

The Utilization of Degree Days for the Characterization of Developmental Stages of 26 Winter Wheat Cultivare

Twenty six winter wheat cultivars representing early maturing (Em), medium early maturing (Mm), and late maturing (Lm) cultivar groups were grown in the field for two growing seasons. The dates at which plants reached the double ridge (DR) and terminal spikelet (TS) stages were determined using anatomical analysis of shoot apices. Thereafter the dates of anthesis (AN) and full maturity (MA) were recorded. The length of the time spans between subsequent developmental stages was then expressed both chronologically (number of days, d) and in terms of thermal time (degree day, °C d) which was calculated with the basal temperature equalling to zero. The results obtained confirmed the suitability of the utilization of degree days for the description of the time course of plant development, because the great differences in the time between subsequent developmental stages recorded between the two growing seasons when expressed in terms of numbers of days markedly diminished when expressed in terms of degree days. For example the period DR-MA expressed in number of days amounted in the year 1986 only to 87 % when related to the number of days recorded in the year 1985, whereas the corresponding value expressed in terms of degree days amounted to 98 %. The utilization of degree days is especially suitable for the AN-MA period (956 and 937 degree days in the years 1985 and 1986, respectively) within which temperature is the main factor determining the rate of plant development. Further analyses of the effects of basal temperatures, vernalization, and daylength appear to be necessary for a better understanding of the length of the period to the DR stage and differences among groups of cultivars and among different cultivars.

Measurement of response to vernalization in Australian wheats with winter habit

Development in wheat is strongly controlled by sensitivity to vernalization and photoperiod, and to a lesser degree by non-vernalizing temperature and intrinsic earliness. A method to measure effect of vernalization in wheats with winter habit is described. Twenty seven wheats with winter habit and eight with spring/facultative habit were studied, comprising breeding lines and cultivars with maturities suited to south-central New South Wales. Effect of vernalization on the development of these wheats was quantified by integrating responses to vernalizing treatments of differing duration. Intrinsic earliness was measured as time for vernalized seedlings to grow to ear emergece in an 18h photoperiod with day/night temperature of 21/16°C, and response to photoperiod as the difference in time to ear emergence between 9 and 18h daylengths. Integrated response to vernalization is sensitive to both cumulative and thresh-hold responses and is applicable to wheats of all habit type. Integrated response to vernalization and intrinsic earliness were positively associated within wheats with winter habit. Wheats were largely of restricted origin, so that there were few allelic differences at Vrn loci to disrupt this association, which suggests intrinsic earliness may modify response to vernalization. Though integrated response to vernalization was measured with artificial treatments, it was strongly associated with ear emergence for wheats with winter habit when grown at a site in New South Wales.

COMPARISON OF JUVENILITY IN TWO GENERA OF THE ASTERACEAE

Chrysanthemum × superbum, Coreopsis lanceolata, and Coreopsis grandiflora are LD flowering perennial plants. The end of juvenility could be defined as the minimum expanded leaf number required for fastest flowering once placed in LD. This research was conducted to compare juvenility and flowering requirements in dwarf and standard cultivars of these species. Plants were maintained under SD and transferred to LD upon reaching true leaf stages beginning with 0 (cotyledons only) and progressing at 2 or 3 leaf intervals to the 24 leaf stage. Coreopsis `Sunray' and Chrysanthemum `G. Marconi' were relatively unresponsive to LD whereas LD induced flowering in 70-100% of the plants in each leaf number treatment in Coreopsis `Early Sunrise'. Plants transferred at the 15 leaf stage required the least number of LD to reach anthesis. LD promoted complete flowering in Chrysanthemum × superbum `Snow Lady' plants and 90% of the SD control plants flowered as well. SD control plants from the other 3 cultivars remained vegetative. Effects of vernalization will also be presented.

Vernalization and Phyllochron in Winter Wheat

AbstractPhyllochron (degree‐days/leaf) has been used to describe phasic leaf development in dynamic wheat (Triticum aestivum L.) crop development models. Vernalization controls the rate of crop development in winter wheat. The objective of this experiment was to determine whether vernalization affected the thermal time required for winter wheat to produce leaves. ‘Stephens’ winter wheat plants were grown in a controlled environment chamber and in outdoor pots, using both pre‐vernalized and non‐vernalized germinating seed. In the outdoor pots plants became vernalized naturally and vernalization before sowing had no effect on growth, development, or flowering. In the controlled environment, up to the time of flowering of the vernalized treatment, there were no differences in phyllochron or total leaf number per main stem between the plants seeded using pre‐vernalized and non‐vernalized germinating seed. The non‐vernalized plants continued to produce tillers until the experiment was terminated, however, while tillering ceased at stem elongation in the vernalized plants. These results support the use of a constant value for phyllochron in simulating leaf development in both vernalized and non‐vernalized seedling winter wheat plants. However, they also show the need to adequately model the effect of vernalization on development (i.e., the cessation of leaf production and tillering in conjunction with flowering) in order to simulate the development of the crop leaf canopy.

Effect of Light Quality and Vernalization on Late-Flowering Mutants of Arabidopsis thaliana

We have analyzed the response to vernalization and light quality of six classes of late-flowering mutants (fb, fca, fe, fg, ft, and fy) previously isolated following mutagenesis of the early Landsberg race of Arabidopsis thaliana (L.) Heynh. When grown in continuous fluorescent illumination, four mutants (fca, fe, ft, and fy) and the Landsberg wild type exhibited a reduction in both flowering time and leaf number following 6 weeks of vernalization. A significant decrease in flowering time was also observed for all the mutants and the wild type when constant fluorescent illumination was supplemented with irradiation enriched in the red and far red regions of the spectrum. In the most extreme case, the late-flowering phenotype of the fca mutant was completely suppressed by vernalization, suggesting that this mutation has a direct effect on flowering. The fe and fy mutants also showed a more pronounced response than wild type to both vernalization and incandescent supplementation. The ft mutant showed a similar response to that of the wild type. The fb and fg mutants were substantially less sensitive to these treatments. These results are interpreted in the context of a multifactorial pathway for induction of flowering, in which the various mutations affect different steps of the pathway.

ダイコンの採種のための春化処理

Effects of vernalization in Raphanus sativus L. cv. Harumaki-Minowase were studied. Early flowering and vigorous growth of the plant were observed in the low temperature treatment at 3°C for 2 or 3 weeks followed by incubation at 15 or 25°C. Days to flowering after low temperature were around 50, irrespective of the different conditions.Plants incubated at 3°C for 2 weeks were planted in the field during the period of March through November. They flowered and seeded, except the ones treated with low temperature in August and November. Days to flowering after planting were from around 24 days with the May-, June-and July-treatments to 96 days with the October-treatment. On the other hand, the largest number of flowers was obtained with the April-treatment, and flowering dramatically decreased with the October treatment. The number of seeds with the June- and July-treatments was 2-3 per capsule, but it was 5 in other treatments.Plants pre-incubated at 3°C for 2 weeks followed by planting in the field under summer conditions were not devernalized, but they were devernalized by 35°C after 3°C pre-incubation for 2 weeks. When the 3°C treatment was prolonged for 3 weeks, they were not devernalized. From these results, effective treatment for vernalization of ‘Harumaki-Minowase’ radish was 3°C for 2 or 3 weeks.

Environmental Control of Flowering in Barley (Hordeum vulgare L.). I. Photoperiod Limits to Long-day Responses, Photoperiod-insensitive Phases and Effects of Low-temperature and Short-day Vernalization

Barley plants were grown at a mean diurnal temperature of 15 °C and reciprocally transferred between different photoperiods (from 16 h d−1 to 8, 10 or 13 h d−1 or vice versa at 4, 8, 16 or 32 d after germination). Ten contrasting genotypes were examined, including seven spring-sown types-Mona, BGS T16-2, Athenais, Emir, Funza, USDA-016525 and S-37, and three autumn-sown types-Gerbel B, Arabi Abiad and Ager. In the latter two all treatments were repeated on plants grown from seeds which had been vernalized at 2 °C for 42 d. The results suggest that, between the critical photoperiod (below which there is a delay in flowering) and the ceiling photoperiod (below which there is no further delay), there is a linear relation between photoperiod and the reciprocal of the time taken to flower (awn emergence). In all genotypes the ceiling photoperiod was ≲, 10 hdd−1; the critical photoperiod was always > 13 hdd−1 often > 14 hdd−1, and sometimes > 16 hdd−1. All genotypes were initially insensitive to long days. At 15 °C this pre-inductive phase typically lasted for 8–10 d after germination in spring-sown types and in vernalized autumn-sown types, but continued for more than 32 d in non-vernalized autumn-sown types. It was followed by an inductive phase, the duration of which depended on photoperiod, being longer in shorter days. Finally, there was a photoperiod-insensitive, post-inductive phase, which probably began about 2 weeks before awn emergence. The low-temperature seed-vernalization treatment considerably hastened awn emergence in Arabi Abiad and in Ager; in Arabi Abiad low-temperature vernalization could be partly replaced by treating young plants with short days (8 or 10 h dd−1). Both low-temperature and short-day vernalization advanced flowering by advancing ear initiation (reducing the duration of the pre-inductive phase), whereas long days stimulated the rate of development following ear initiation.

The influence of soil temperature on vernalization of Chinese cabbage

SummaryThe influence of soil-heating (30°C) on bolting of Chinese cabbage (Brassica pekinensis (Lour.) Rupr. cv. Spring A1) was studied under inductive air temperatures in growth rooms. In two experiments it was shown that warm roots had no influence on the vernalization effect but that soil heating can decrease the effect of vernalization by heat transfer into the growing point. The heat transfer is favoured by insulating the soil surface and by a short hypocotyl.

Effects of Temperature, Photoperiod and Seed Vernalization on Flowering in Faba Bean Vicia faba

Factorial combinations of three photoperiods (10, 13 and 16 h), two day temperatures (18 and 28 °C) and two night temperatures (5 and 13 °C) were imposed on nodulated plants of six diverse genotypes of faba bean (Vicia faba L.). Plants were grown in pots in growth cabinets from both vernalized (1.5±0.5 °C for 30 d) and non-vernalized seeds. The times from sowing to the appearance of first open flowers (f) were recorded. Seed vernalization decreased the subsequent time taken to flower in almost all genotype x growing environment combinations (the exceptions were plants of the cv. Maris Bead grown in three cooler, short-day regimes). The influence of temperature and photoperiod on the rate of flowering was quantified, using a model applied previously to other long-day species of grain legume in which positive linear relations between both temperature and photoperiod and the rate of progress towards flowering are assumed to apply. A significant positive linear response of rate of progress towards flowering to limited ranges of mean diurnal temperature was detected in all six genotypes, but in three genotypes (Syrian Local Large, Aquadulce and Maris Bead) the 28 °C day temperature reduced the rate of progress towards flowering - suggesting that the optimum temperature for flowering in these genotypes is below 28 °C. In four genotypes (Maris Bead, Giza-4, Aquadulce and BPL 1722) a significant positive response to photoperiod, typical of quantitative long-day plants, was observed only in plants grown from vernalized seeds. In contrast, plants of the genotype Zeidab Local grown from both non-vernalized and vernalized seeds showed the same positive response to photoperiod, whereas plants of the land-race Syrian Local Large were consistently unresponsive to photoperiod. The implications of this range of responses amongst diverse genotypes are discussed in relation to screening germplasm.