Application Of BA Research Articles

Benzyladenine Treatment Significantly Increases the Seed Yield of the Biofuel Plant Jatropha curcas

Jatropha curcas, a monoecious perennial biofuel shrub belonging to the family Euphorbiaceae, has few female flowers, which is one of the most important reasons for its poor seed yield. This study was undertaken to determine the effects of the plant growth regulator 6-benzyladenine (BA) on floral development and floral sex determination of J. curcas. Exogenous application of BA significantly increased the total number of flowers per inflorescence, reaching a 3.6-fold increase (from 215 to 784) at 160 mg/l of BA. Furthermore, BA treatments induced bisexual flowers, which were not found in control inflorescences, and a substantial increase in the female-to-male flower ratio. Consequently, a 4.5-fold increase in fruit number and a 3.3-fold increase in final seed yield were observed in inflorescences treated with 160 mg/L of BA, which resulted from the greater number of female flowers and the newly induced bisexual flowers in BA-treated inflorescences. This study indicates that the seed yield of J. curcas can be increased by manipulation of floral development and floral sex expression.

Effect of 6-benzyladenine application time on apple thinning of cv. 'Golden Delicious' and cv. 'Idared'

Apple thinning of cv. 'Golden Delicious' and cv. 'Idared' was studied after the application of 6-benzyladenine (BA) 100 mgl-1 and 50 mgl-1 respectively, applied at different time of blooming period and over a wider range of fruitlet diameter. When BA 100 mgl-1 was applied on cv. 'Golden Delicious', significant reduction in final fruit number per tree was observed if applied at the end of blooming period or when fruitlet diameters were 6 mm, 15 mm or 20 mm, but thinning was not significant if applied at full bloom or at 10 mm or 25 mm fruitlet diameter. The share of bigger fruits of cv. 'Golden Delicious' (> 65mm) was increased at all BA application time treatments, but significantly only in the treatment of hand thinned trees. Regarding the BA applications carried out on cv. 'Idared', significant thinning response was noticed in the case of BA sprayed at the end of bloom and at 10 mm of fruit diameter. The mean fruit weight of cv. 'Idared' apples was increased significantly only if BA was applied at 10 mm fruitlet diameter. Although the thinning results were inconsistent for two studied cultivars it was demonstrated from the trial that BA could be active as a thinner if applied over a wider phenological interval, at the end of blooming period up to 20 mm fruitlet diameter.

1-Naphthaleneacetic acid and 6-benzyladenine thinning of a common slender spindle ‘Jonagold’/M.9 apple orchard. II: Partial tree spraying

SummaryMature slender spindle ‘Jonagold’/M.9 apple (Malus × domestica Borkh.) trees were thinned using 10 mg l–1 1-naphthaleneacetic acid (NAA) or 100 mg l−1 6-benzyladenine (BA) and an axial fan sprayer at a spray volume of 1,500 l ha−1 applied to the whole canopy, or with smaller volumes, where only the upper half of each canopy was sprayed. Partial spray applications of NAA or BA (at 1,000 l ha−1, 750 l ha−1, or 500 l ha−1) to the upper half of the trees did not cause any reduction in final fruit numbers on the upper half, or on the lower half of each tree. When the whole tree was sprayed to run-off with the same thinning agent, or at 1,500 l ha−1, successful thinning on both the upper and lower parts of the canopy occurred. Good spray coverage (from 51% to 77%) was also observed on leaves at all canopy positions measured, when whole trees were sprayed at 1,500 l ha−1.The development of an innovative crop load regulation strategy was an objective of the ISAFRUIT Smartfruit Project.

Ausdünnungsstrategien für die Apfelsorte ‘Elstar’ – Erfahrungen mit Ammoniumthiosulfat, Calciumhydroxid und Benzyladenin

‘Elstar’, the most widely grown apple variety in the Netherlands, requires adequate fruit thinning to obtain regular bearing and the commercially desired fruit size and fruit quality. During several years studies have been carried out to look for alternative thinning methods to replace carbaryl, an insectide which also induced thinning when applied to young fruitlets, but that is no longer registered in the Netherlands. During recent years research on apple thinning has focused on the use of ammonium thiosulphate (ATS) as a flower thinner combined with 6-benzyladenine (BA) as a fruitlet thinner. This paper reports on a trial in which the fruit thinning efficacy of this combined treatment with ATS and that of BA on its own were evaluated. In addition, the use of slaked lime (Ca(OH)2) to cover the leaves and reduce leaf photosynthesis at three different times during fruitlet development was tested, alone or in combination with an application of BA. The best chemical thinning treatment of this trial was the combination of 3 applications of ATS during flowering followed by BA at a fruit size of 13.8 mm. This treatment gave 82% of the thinning necessary to obtain the target fruit load. This treatment also effectively improved fruit size distributions, fruit colour and internal fruit quality. Slaked lime did not thin ‘Elstar’ effectively, most probably because it did not cause sufficient reduction of light interception by the canopy.

A comparison of different thinning products applied to the apple variety ‘Elstar Elshof’ in the Lower Elbe region

6-Benzyladenine (BA) showed only a slight thinning effect which was probably correlated with low temperatures during application. It is concluded that under the current climate of the Lower Elbe region temperature is a more important factor than fruit size for determining the time-point of BA application. Ethephon at 300 ppm produced a stronger effect, even if this was still insufficient in the present case. Higher concentrations (450–600 ppm) are required for strongly flowering ‘Elstar’ plantations older than 4 years, but this invokes the risk of excessive thinning. Therefore, the application of Ethephon requires a high degree of experience on part of the fruit farmer. Metamitron, applied once at 350 ppm, showed similar effects to Ethephon. An enhanced effect might have been obtainable if a second treatment had been applied some 10 days later. No phytotoxic damage was observed. Metamitron would be an interesting fruit thinning agent and should be considered for registration in Germany. Naphthalene acetic acid (NAA) and NAA + BA gave the best results in the experiment for 2006 described here. It is not yet clear whether the degree of flowering for 2007 will be influenced in a similarly positive manner as for Ethephon. Since NAA and Metamitron have not been registered for Germany, their practical use cannot be recommended.

Roles of Auxin and Cytokinin in Soybean Pod Setting

Soybean plants differentiate abundant floral buds, but most of them fail to grow pods and abort during development. Many studies indicated promotive effects of exogenously applied cytokinin on pod setting, but the effects of auxin application on pod set are ambiguous. In this study, we examined the changes in the concentrations of endogenous auxin and cytokinin in racemes and the effects of application of the two hormones on pod setting to clarify the role of auxin and cytokinin in soybean pod setting. The long-raceme soybean genotype IX93-100 was grown in pots and in the field. The auxin (IAA, indoleacetic acid) concentration in racemes was high for a long period from pre-anthesis to 9 days after anthesis (DAA) of the first flower on a raceme, but the cytokinin concentration was high for a short period, with a peak at 9 DAA. The IAA concentration was higher in distal portions of racemes, but the cytokinin concentration was higher in basal portions of racemes. In pot-grown plants, IAA applied to racemes tended to reduce the number of flowers and pods. In contrast, 6-benzylaminopurine (BA) applied to racemes before anthesis tended to reduce the number of flowers and pods, and that applied around 7 DAA significantly increased the pod-set percentage. However, these effects of IAA and BA application were slight in field-grown plants. These results indicate that the concentration of endogenous auxin and cytokinin in racemes changes in a different manner, and that cytokinins have a positive, and auxin a negative effect on pod setting when respective hormones are applied to racemes after the anthesis stage.

Effects of abscisic acid or benzyladenine on pigment contents, chlorophyll fluorescence, and chloroplast ultrastructure during water stress and after rehydration

With the aim to contribute to the elucidation of the role of phytohormones in response of plants to adverse environmental conditions, seedlings of Phaseolus vulgaris, Nicotiana tabacum, Beta vulgaris, and Zea mays were supplied with water, 100 µM abscisic acid (ABA), or 10 µM N6-benzyladenine (BA) immediately before imposition of water stress (WS). In all four species, contents of chlorophylls (Chls) and carotenoids were markedly decreased during WS and after rehydration only in plants pre-treated with water but not in those pre-treated with ABA or BA. Contents of pigments of xanthophyll cycle increased during WS more in plants pre-treated with ABA or BA than in those pre-treated with water, but the degree of their de-epoxidation was highest in the later. Similarly, the efficiency of photosystem 2, determined as variable to maximal Chl fluorescence ratio, was not markedly decreased in bean plants pre-treated with ABA or BA in contrast to those pre-treated with water. The imposed WS was not severe enough to damage chloroplast ultrastructure. However, different changes in a size of starch inclusions were observed. In bean plants, the amount of starch increased considerably in plants pre-treated with water, while it decreased in BA pre-treated plants and no change was found in ABA pre-treated ones. The starch content declined under WS in sugar beet and tobacco plants but only moderate changes were found in ABA or BA pre-treated plants. Thus the application of BA and especially of ABA reduced the negative effects of subsequent WS.

Endogenous cytokinins in shoots of Aloe polyphylla cultured in vitro in relation to hyperhydricity, exogenous cytokinins and gelling agents

The process of hyperhydricity in tissue cultured plants of Aloe polyphylla is affected by both applied cytokinins (CKs) and the type of gelling agent used to solidify the medium. Shoots were grown on media with agar or gelrite and supplemented with different concentrations of N6-benzyladenine (BA) or zeatin (0, 5 and 15 μM). Endogenous CKs were measured in in vitro regenerants after an 8-weeks cycle to examine whether the hyperhydricity-inducing effect of exogenous CKs and gelling agents is associated with changes in the endogenous CK content. On media with agar a reduction in hyperhydricity occurred, while the gelrite treatment produced both normal and hyperhydric shoots (HS). The content of endogenous CKs, determined by HPLC-mass spectrometry, in the shoots grown on CK-free media comprised isopentenyladenine-, trans-zeatin- and cis-zeatin-type CKs. The application of exogenous CKs resulted in an increase in the CK content of the shoots. Following application of zeatin, dihydrozeatin-type CKs were also detected in the newly-formed shoots. Application of BA to the media led to a transition from isoprenoid CKs to aromatic CKs in the shoots. Shoots grown on gelrite media contained higher levels of endogenous CKs compared to those on agar media. Total CK content of HS was higher than that of normal shoots grown on the same medium. We suggest that the ability of exogenous CKs and gelrite to induce hyperhydricity in shoots of Aloe polyphylla is at least partially due to up-regulation of endogenous CK levels. However, hyperhydricity is a multifactor process in which different factors intervene.

Cytokinin and auxin inhibit abscisic acid-induced stomatal closure by enhancing ethylene production in Arabidopsis

Cytokinins and auxins are major phytohormones involved in various aspects of plant growth and development. These phytohormones are also known to antagonize the effects of abscisic acid (ABA) on stomatal movement, and to affect ethylene biosynthesis. As ethylene has an antagonistic effect on ABA-induced stomatal closure, the possibility that the antagonistic effects of these phytohormones on ABA were mediated through ethylene biosynthesis was investigated. Both the cytokinin, 6-benzyladenine (BA), and the auxin, 1-naphthaleneacetic acid (NAA), antagonized ABA-induced stomatal closure in a manner similar to that following application of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC). However, these effects were negated when ethylene signalling, perception, or biosynthesis were blocked. As stomatal aperture is regulated by changes in guard cell volume, ABA application was found to reduce the volume of the guard cell protoplasts (GCP). It was found that BA, NAA, or ACC application compensated perfectly for the reduction in GCP volume by ABA application in WT plants. The above observations suggest that cytokinins and auxins inhibit ABA-induced stomatal closure through the modulation of ethylene biosynthesis, and that ethylene inhibits the ABA-induced reduction of osmotic pressure in the guard cells.

BA Application Frequency and Concentration Effects on Two Indian Hawthorn Cultivars

Abstract Benzyladenine (BA) is a synthetic cytokinin that promotes lateral shoot development in herbaceous and woody ornamentals and may be a viable alternative to mechanical pruning in nursery production. A study was conducted to determine the effects of BA application number, interval and concentration on two Indian hawthorn [Rhaphiolepis Lindl. Cor. Poir. indica (L.) Lindl. (Crataegus indica L.)] cultivars. In spring 2002, actively growing ‘Olivia’ and ‘Eleanor Taber’ received three applications of 2500 or 5000 ppm BA at a one-, two-, or three-week interval. Data collected four weeks after initial treatment (WAT) reflected the effects of one, two, or three BA applications at each concentration. At this time new shoot counts in both cultivars and foliar injury in ‘Olivia’, but not in ‘Eleanor Taber’, increased with increasing number of applications and BA concentration. Data collected 12 WAT reflected the effects of BA application interval and concentration. At this time new shoot counts increased with decreasing application interval in ‘Olivia’, while ‘Eleanor Taber’ formed the most new shoots when BA was applied at a two-week interval. All treated plants sustained minimal to moderate injury to immature foliage. The experiment was repeated in 2003 using 1750 ppm and 3500 ppm BA on ‘Olivia’ Indian hawthorn. Applications were halted at the first sign of foliar injury resulting in plants treated at one, two, and three-week intervals receiving three, two, and two applications, respectively. New shoot counts on ‘Olivia’ treated at the three application intervals were similar, but greater than those on untreated plants. Control plants had a foliar injury rating similar to that of plants treated at a two or three-week interval, but less than that of plants treated at a one-week interval. Growth index was not affected by treatment in either year.

Influence of gibberellic acid and N6-benzyladenine on the development of seed and shot berries in the seedless grape (Vitis vinifera L.) cv. Perlette

Gibberellins have been used to improve quality of grapes in several cases. However, gibberellic acid (GA) alone is not enough to improve the quality in Perlette. A field experiment was conducted on 3-year-old grape cv. Perlette trained on pergolas, to investigate the effect of bunch dipping with GA3 and N6-benzyladenine (BA) on reducing the problem of shot berries and improving the productivity of grapevines. Our observations proved that the stage of application of GA3 and BA is crucial to avoiding seed formation in seedless varieties such as Perlette for table grapes. The results showed that BA at low (10 µL/L) or high concentration (30 µL/L) at 50% of full bloom caused seed development in the seedless grape cv. Perlette, whereas no seed was formed when BA was used later at the fruit set stage. Based on our studies, we found that bunch dipping with 30 µL/L GA3 (at 50% of full bloom) and 10µL/L BA (at pea size) significantly reduced the problem of shot berries, and improved the yield and quality in grape cv. Perlette.

Corrigendum to: Influence of gibberellic acid and N6-benzyladenine on the development of seed and shot berries in the seedless grape (Vitis vinifera L.) cv. Perlette

Gibberellins have been used to improve quality of grapes in several cases. However, gibberellic acid (GA) alone is not enough to improve the quality in Perlette. A field experiment was conducted on 3-year-old grape cv. Perlette trained on pergolas, to investigate the effect of bunch dipping with GA3 and N6-benzyladenine (BA) on reducing the problem of shot berries and improving the productivity of grapevines. Our observations proved that the stage of application of GA3 and BA is crucial to avoiding seed formation in seedless varieties such as Perlette for table grapes. The results showed that BA at low (10 �L/L) or high concentration (30 �L/L) at 50% of full bloom caused seed development in the seedless grape cv. Perlette, whereas no seed was formed when BA was used later at the fruit set stage. Based on our studies, we found that bunch dipping with 30 �L/L GA3 (at 50% of full bloom) and 10�L/L BA (at pea size) significantly reduced the problem of shot berries, and improved the yield and quality in grape cv. Perlette.

An Innovative Vegetative Propagation System for Large-scale Production of Globe Artichoke Transplants. Part I. Propagation System Setup

A research project was conducted at the University of Tuscia, Viterbo (central Italy), to set up a vegetative propagation system for producing diseasefree artichoke transplants (Cynara cardunculus var. scolymus) of the Romanesco type (cultivar C3). The system included the following steps: 1) micropropagated plantlets were grown in a soilless culture year-round in greenhouse conditions, starting at the end of August; 2) stock plants were periodically treated with a chemical growth regulator [6-benzylamino purine (BA)] and then cut back at the collar level to promote offshoot production; 3) offshoots were periodically harvested and cold stored; and 4) cuttings were rooted at the end of spring under conditions of high humidity in multi-pack trays so as to be ready for summer transplanting. Results showed that the foliar application of BA to the stock plants increased the offshoot number quadratically to 200 mg·L-1. The rooting percentages of cuttings and root growth were enhanced by raising the cutting weight class (30-45 g) and by the application of naphthaleneacetic acid (NAA) to the cutting root zone at a rate of 2000 mg·L-1. The percent rotten cuttings increased as the 2 °C cold-storage time increased from 30 to 150 days. Similarly, the percentage of rooting and root growth decreased approximately from 60 to 150 days.

Interactive effects of Al, Ca and other cations on root elongation of rice cultivars under low pH.

As with other crop species, Al tolerance in rice (Oryza sativa) is widely different among cultivars, and the mechanism for tolerance is unknown. The Ca2+-displacement hypothesis, that is, Al displaces Ca2+ from critical sites in the root apoplast, was predicted to be the essential mechanism for causing Al toxicity in rice cultivars. If displacement of Ca is an essential cause of Al toxicity in rice, Al toxicity may show the same trend as toxicities of elements such as Sr and Ba that are effective in displacing Ca. The interactive effects of Al, Ca, Sr and Ba on root elongation of rice cultivars with different Al tolerances were evaluated in hydroponic culture. Al and Ca accumulation in root tips was also investigated. Not only Al but also Sr and Ba applications inhibited root growth of rice cultivars under low Ca conditions. As expected, rice cultivars more tolerant of Sr and Ba were also tolerant of Al (japonica > indica). Although Mg application did not affect Sr or Ba toxicity, Mg alleviated Al toxicity to the same level as Ca application. In addition, Ca application decreased the Al content in root tips without displacement. These results suggest that Ca does not have a specific, irreplaceable role in Al toxicity, unlike Sr and Ba toxicities. Alleviation of Al toxicity with increasing concentrations of Ca in rice cultivars is due to increased ionic strength, not due to decreased Al activity. The difference in Al tolerance between indica and japonica cultivars disappears under high ionic strength conditions, suggesting that different electrochemical characteristics of root-tip cells are related to the significant difference in Al tolerance under low ionic strength conditions.

Effect of exogenous cytokinins, auxins and adenine on cytokinin N-glucosylation and cytokinin oxidase/dehydrogenase activity in de-rooted radish seedlings

The role of cytokinin N-glucosylation and degradation by cytokinin oxidase/dehydrogenase (CKX, EC 1.5.99.12) in response to application of exogenous auxins (2,4-dichlorophenoxyacetic acid [2,4-D] and α-naphthaleneacetic acid [NAA]) and cytokinins (N6-benzyladenine [BA] and trans-zeatin [Z]) was investigated in de-rooted seedlings of Raphanus sativus L. cv. Rampouch. Both auxins applied for 24 h at 1 and 10 μM concentration increased N-glucosylation of exogenously applied [3H]dihydrozeatin (DHZ) by up to 20%. The level of endogenous 7N-glucosides (of Z, isopentenyladenine [iP] and DHZ) was increased by 2,4-D and NAA at 10 μM concentration by 28 and 23%, respectively, the level of Z being decreased by 90 and 59%, respectively. 2,4-D and NAA suppressed CKX activity ca. by half. Exogenous cytokinins Z and BA applied at 1 and 10 μM concentration stimulated 7N-glucosylation of [3H]DHZ (by up to 40%). BA both at 1 and 10 μM, increased the level of endogenous Z by up to 35% and that of 7N-glucosides by up to 27%. BA application also strongly stimulated CKX activity (by up to 180%). Feeding with 1 and 10 μM Z resulted in ca. 100-fold and 2000-fold increase of Z level, respectively. The main metabolite, Z7G, was increased ca. 6-fold and 60-fold, respectively. Levels of Z 9-glucoside (Z9G), trans-zeatin riboside (ZR) and Z O-glucoside (ZOG) were elevated to lesser extent. As compared to BA, Z had only negligible effect on CKX activity. Adenine (1–500 μM) was preferentially 7N-glucosylated inhibiting competitively 7N-glucosylation of [3H]DHZ. At high concentrations (100–500 μM) it increased endogenous levels of active cytokinins, especially of Z, however, it had no effect on CKX activity. Cytokinin N-glucosylation proved to be involved in down-regulation of active cytokinins in response to auxin and in the re-establishment of cytokinin homeostasis following application of exogenous cytokinins.

Effects of Pre-Treatments with Abscisic Acid and/or Benzyladenine on Gas Exchange of French Bean, Sugar Beet, and Maize Leaves During Water Stress and After Rehydration

Net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) during water stress and after rehydration were measured in Phaseolus vulgaris, Beta vulgaris, and Zea mays. Immediately before imposition of water stress by cessation of watering, plants were irrigated with water (control), 100 μM abscisic acid (ABA), and/or 10 μM N6-benzyladenine (BA). In all three species, application of ABA decreased gs, E, and PN already 1 h after application. However, during water stress gs, E, and PN in plants pre-treated with ABA remained higher than in plants pre-treated with water. Positive effects of ABA application were observed also after rehydration. In contrast, the effects of pre-treatment with BA were species-specific. While in bean plants BA application ameliorated negative effect of water stress, only very slight effects were observed in maize, and in sugar beet BA even aggravated the effects of water stress.

Rehydration of Sugar Beet Plants after Water Stress: Effect of Cytokinins

The possibility to improve the recovery of sugar beet plants after water stress by application of synthetic cytokinins N6-benzyladenine (BA) or N6-(m-hydroxybenzyl)adenosine (HBA) was tested. Relative water content (RWC), net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), chlorophyll (Chl) a and Chl b contents, and photosystem 2 efficiency characterized by variable to maximal fluorescence ratio (Fv/Fm) were measured in control plants, in water-stressed plants, and after rehydration (4, 8, 24, and 48 h). Water stress markedly decreased parameters of gas exchange, but they started to recover soon after irrigation. Application of BA or HBA to the substrate or sprayed on leaves only slightly stimulated recovery of PN, E, and gs in rehydrated plants, especially during the first phases of recovery. Chl contents decreased only under severe water stress and Fv/Fm ratio was not significantly affected by water stress applied. Positive effects of BA or HBA application on Chl content and Fv/Fm ratio were mostly not observed.

Differential responses of BA injection on yield and specific grain growth in contrasting genotypes of wheat (Triticum aestivum L.)

The effect of exogenous cytokinin (benzyladenine) was investigated on location specific grains in three contrasting wheat genotypes tolerant or susceptible to post anthesis high temperature conditions. Seeds were sown in earthen pots under natural environment in November and January for normal and late sowings, respectively. Grain weight was increased by the application of benzyladenine at anthesis under late sown stress only in those genotypes, which are known, to posses temperature tolerance in developing grains. However, under normal sowing conditions BA application was effective irrespective of genotype response to late sown stress. The effect was most visible in distal spikelets in the spike and distal grains in the spikelet which resulted in higher increment in weight of younger grains (c and d) as compared to older grains (a and b). It has been suggested that the responsiveness of the genotype to BA application under late sown stress is important and may be developed as an indicator to screen wheat genotypes for relative tolerance to late sown stress under irrigated conditions.

The effect of plant-growth regulators on the production of out-of-season greenhouse tomatoes (Lycopersicum esculentum)

The yield of greenhouse tomatoes produced in spring and midwinter is reduced by unfavourable environmental conditions involving low temperatures and low light intensities. This study has evaluated the role of various plant growth regulators including: synthetic cytokinin (CPPU) at 1ml.L−1, auxins 1-naphthylacetic acid at 1ml.L−1 and 4-chlorophenoxyacetic acid (4-CPA) at 30mg.L−1, gibberellins (GA3) ‘ProGibb 4%′ and SupaGibb 4SL’ both at 1ml.L−1, and a mixture of benzyladenine (6-BA) plus GA4+7 at 1ml.L−1. Treatments were applied in improving fruiting characteristics of out of season tomatoes up to three times successively when three or more flowers of an inflorescence reached anthesis. PGR's, CPPU, 1-NAA, 4-CPA, ‘ProGibb’, ‘SupaGibb’ and BA plus GA4+7, at three applications, induced higher tomato yields by increasing the truss mass. Synthetic auxins, 1-NAA and 4-CPA, increased the average fruit mass as well as the number of fruit with a diameter larger than 37 mm but also increased the percentage of malformed fruit. Three applications of the mixture BA plus GA4+7 provided the most promising results by improving the yield of marketable fruit through increases in the number of fruit set, the number of fruit per truss and the overall truss mass. No detrimental affects on fruit shape were associated with this treatment.

Genotypic and Environmental Variation of Lag Period of Pod Growth in Soybean

Pod growth in soybean (Glycine max(L.) Merr.) begins several days after flower opening, compared with more immediate growth in other beans. We investigated the relationship between genotype, raceme order of pod set, assimilate supply or photoperiod and the length of lag period of pod growth (LP, days from flower opening to the time when pod length reaches 10 mm). Soybean (five cultivars) plants were grown in a greenhouse and in the field in 2001. The lengths of pods developed from 20 flowers which opened on the same day and set on the same raceme order, were measured every other day. The length of LP varied with the cultivar from 5 to 16 days and it was longer in late cultivars. The LP in the primary raceme (early flowers) was 15 days but that in the secondary raceme (late flowers) was 8 days. Both late sowing and short photoperiod (lOh) after the start of flowering shortened the LP by up to 7 days in Enrei and 5 days in Fukuyutaka. However, neither sink (except the target racemes) removal nor BA application to the target racemes at the start of flowering affected the length of LP, even though these treatments were expected to stimulate pod growth.