HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Search for Related Content PubMed Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Agricola Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Related Collections Crop Growth and Development Other Crop Management

CROP ECOLOGY, MANAGEMENT & QUALITY

Plant Growth Regulator and Daylength Effects on Preanthesis Main Shoot and Tiller Growth in Conventional and Dwarf Oat

^a MTT Agrifood Research Finland, Plant Production Research, FIN-31600 Jokioinen, Finland
^b Univ. of Minnesota, Dep. of Agronomy and Plant Genetics, 1991 Buford Circle, Borlaug Hall, St. Paul, MN 55108-6026, USA

* Corresponding author (pirjo.peltonen-sainio{at}mtt.fi)

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Plant growth regulators (PGRs) alter tiller growth in cereals. This response may be dependent on daylength (DL). Standard height (HE) and dwarf oat cultivars were grown at 14- and 18-h DLs. Foliage was sprayed with chlormequat chloride (CCC) and ethephon at early growth stages to evaluate PGR effects on the growth of the main shoot and tillers. Two successive experiments with 10 replicates were arranged in two growth chambers (14-h and 18-h DL) at the University of Minnesota. Preanthesis main shoot and tiller HEs and dry weights (DWs) were measured. In Exp. 1, the numbers of leaves and green leaves were counted. Relative growth rate (RGR), relative elongation rate (RER), and shoot DW:HE ratio were measured. Plant growth regulators retarded growth of the main shoot in conventional oat cultivars without stimulating growth of T1 and T2 tillers. Response of the dwarf cultivar to PGRs was modest. Only ethephon enhanced T1 tiller growth at 18-h DL. However, PGR-treated plants had up to five more green leaves per plant at preanthesis due to stimulated leaf emergence on T3 and T4 tillers especially at the 18-h DL. In Exp. 1, PGR treatments reduced the DW to HE ratio, that is, shortened rather than strengthened the stem. In Exp. 2, measurements were made more frequently and ethephon first increased this ratio followed by a decrease. Thus, even though long-day conditions somewhat enhanced DW accumulation and stem elongation, few marked differences in oat response to PGR treatments were noted when comparing short- and long-day conditions.

Abbreviations: CCC, chlormequat chloride • DAT, days after treatment • DL, daylength • DW, dry weight • HE, height • PGR, plant growth regulator • RER, relative elongation rate • RGR, relative growth rate • ZGS, Zadock's growth stage

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
PLANT GROWTH REGULATOR effects on growth and yield formation of oat (Avena sativa L.) have not often been studied (Rajala and Peltonen-Sainio, 2000), but some results have shown that oat responds to PGRs when grown at high latitudes (Peltonen and Peltonen-Sainio, 1997; Pietola et al., 1999; Peltonen-Sainio and Rajala, 2001). For example, when plants did not lodge, CCC applied at the two-node stage [Zadock's Growth Stage (ZGS) 32, Zadoks et al., 1974] resulted in slightly increased grain yield. This was due to more panicles per square meter and higher tiller contribution to grain yield (Peltonen-Sainio and Rajala, 2001). Similarly, CCC and ethephon applications have resulted in enhanced tiller growth in barley (Hordeum vulgare L.) and wheat (Triticum aestivum L., Naylor et al., 1987; Woodward and Marshall, 1987; Craufurd and Cartwright, 1989). However, in general, the contribution of tillers to grain yield is modest in oat when grown at high latitudes (Peltonen-Sainio and Järvinen, 1995). Therefore, it is hypothesized that the yield response of cereals to PGRs may differ depending on DL. Furthermore, as PGRs used on cereals alter endogenous hormone biosynthesis, either through inhibiting gibberellin synthesis or by enhancing ethylene release, the effect of PGRs on tiller growth may differ. This study was conducted to test under controlled-environment conditions with varying DL, whether CCC and ethephon-induced effects on tiller growth are dependent on DL.

As tillers differ in their ability to exert dominance, according to morphological position and chronology (Lauer and Simmons, 1988), it is likely that the response of tillers to PGR treatments differs as well. For example, Lauer and Simmons (1988) showed that photoassimilates flow to and from the tillers in the axils of the first and second leaves on the main shoot, depending on growth stage and availability of photoassimilates. Therefore, we examined PGR effects on tiller growth by spraying PGRs at early growth stages when the first leaf subtending tiller (T1) started to emerge. Further, we followed the PGR effects on dry matter accumulation and shoot elongation separately on main shoot and tillers T1, T2, and T3 (tiller subtending the third leaf) when grown at 14- and 18-h DL.

Earlier studies unexpectedly showed that stem elongation of dwarf oat with Dw6 gene was enhanced, rather than inhibited, following CCC applications (Peltonen-Sainio and Rajala, 2001). Therefore, when studying the effects of DL in Finland (18 h) and Minnesota (14 h), standard HE oat cultivars Virma and Milton were compared with dwarf cultivar Pal, which was developed and released in Minnesota. By this means, we evaluated whether enhanced stem elongation following antigibberellin treatment detected by Peltonen-Sainio and Rajala (2001) was evident in controlled environment conditions and whether this response occurred only when an oat cultivar carrying the Dw6 gene was grown under long-day conditions.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
Experiments were carried out in growth chambers at the University of Minnesota, St. Paul, MN, USA. Two replicated and successive experiments were conducted in two identical growth chambers at the same time. The DL was adjusted to 18/6 h day/night (longer day) in one chamber and 14/10 h in another (shorter day). In both chambers, lights turned on at 0600 h. Temperature regime was the same in both chambers, that is, from 0600 to 2000 h the temperature was 20°C and from 2000 to 0600 h, 13°C. Three oat cultivars were included in the experiments; two were intermediate HE: Virma, a cultivar grown in Finland, and Milton grown in Minnesota. In addition, a dwarf cultivar Pal, carrying the Dw6 dwarfing gene, was included because its tillering pattern differs markedly from that of conventional HE oats (Mäkelä et al., 1996). As DL differed in the two growth chambers, the factor was regarded as random. Within each DL, PGR-treatments and cultivars were regarded as fixed factors and were arranged by using a completely randomized design with 10 replicates.

The first trial was sown on 15 Nov. 1996 and the second one on 16 Jan. 1997. Six to eight seeds were sown in each 1000-mL pot. Field soil and pH-adjusted peat with vermiculate (Sunshine mix 1, Sun Gro Horticulture, MB, Canada) were used in a mixture ratio of 3:1 vol:vol. After emergence, the number of seedlings per pot was thinned to five and seven in Exp. 1 and 2, respectively. The pots were fertilized at thinning with 8.5 mL of controlled release fertilizer per pot (N-P-K 17-6-12 with micronutrients, longevity 12 to 16 wk at 20°C, Sierra, Grace Sierra Horticultural Products Co., CA). The pots were top-watered when needed, that is, more often under long-day conditions. Pots were rotated two times per week in the growth chambers due to differences in light intensity between the central and in the outer areas of the chambers. After the two-leaf stage (ZGS 12), light intensity was measured once a week and then adjusted to 300 to 500 µmol m^-2 s^-1 in the upper parts of the canopy (Quantum/Radiometer/Photometer model LI-185A, LI-COR, Lincoln, NE).

Two PGR treatments, CCC and ethephon, in addition to a no-PGR control were included in the design. Preliminary experiments were conducted at the University of Helsinki, Department of Plant Production, to test the amount of active ingredient of PGR needed in pot experiments to emulate the degree of stem shortening corresponding to that recorded in field conditions. Therefore, 0.5% CCC [vol:vol; Cycocel, Olympic Horticultural Products Co., PA; a.i. chlormequat (2-chloroethyl)-trimethylammonium chloride] and 0.35% ethephon [vol:vol; Floral, Southern Agricultural Insecticides, Inc., NC; a.i. ethephon (2-chloroethyl) phosphonic acid] were sprayed with a manual sprayer (at 4 mL per pot) at the four-leaf stage (ZGS 14) when the T1 tiller was just emerging from the leaf sheath.

Traits characterizing growth of the main shoot and tillers in the control and PGR-treated oat cultivars were measured at 18 and 31 d after treatment (DAT) in Exp. 1 and at 5, 9, 14, 19, and 26 DAT in Exp. 2. Measurements were terminated when the oat plants headed (ZGS 58) at 18-h DL and when the flag leaves had emerged (ZGS 39 to 45) at 14-h DL. Heading occurred an average of 14 d later under the shorter DL conditions. Height of the main shoot and tillers from soil surface to the uppermost leaf ligule (cm) was measured, and after drying overnight at 100°C the dry mass (DW) was weighed on one plant per pot. Because the measurements were destructive, the number of plants per pot decreased with each measurement. Relative growth rate and RER were calculated for main shoots and tillers: RGR = (lnDW_i+1 - lnDW_i)/(no. of days) and RER = (lnHE_i+1 - lnHE_i)/(no. of days), where DW is measured in milligrams and HE is measured in centimeters. Furthermore, total number of leaves and green leaves per main shoot and T1, T2, T3, and T4 tillers, and number of tillers per main shoot were counted at 5, 10, 15, 20, 25, and 30 DAT in Exp. 1. Number of days from sowing to flag leaf emergence (ZGS 39, Exp. 1), full-booting (ZGS 45, Exp. 1) and heading (ZGS 58, Exp. 1 and 2) were noted.

The data from the two experiments were analyzed separately. The main effects of DL, PGR treatment, oat cultivar, and their interactions on the measured traits were tested statistically by analysis of variance using SAS Mixed Procedure (SAS Inc., Cary, NC). Repeated measures method was employed. Replication and DL were considered as random factors and PGR treatments and oat cultivars as fixed factors. If significant interactions among factors were found, the pairwise comparisons between different factor combinations were examined. Differences among least significant (LS) means were tested and letters were inserted into the tables to indicate the significance of differences at P < 0.05. In case the factor did not interact with the others, the data was pooled across it. The tables and figures were contracted on the basis of significance of interactions.

	RESULTS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
In both experiments, DL affected main shoot and tiller elongation (190 F₁ 847, P < 0.001 depending on experiment and shoot). Under 18-h DL, stem elongation of main shoot and tillers was, in general, faster than at 14-h (Table 1 and Fig. 1). In Exp. 1, time x DL x PGR (F₂ = 8.00, P < 0.001) and DL x PGR (F₂ = 18.14, P < 0.001) interactions were detected for main shoot, but not for T1 and T2 tiller stem elongation. However, time x DL interaction occurred for T1 (F₁ = 134, P < 0.001) and T2 tiller growth (F₁ = 50, P < 0.001), as did time x PGR interaction (F₂ = 5.78, P < 0.004 for T1 and F₂ = 4.90, P < 0.009 for T2 tiller). In Exp. 1, at both DLs, PGR treatments resulted in shorter main shoot and tiller stem lengths when measured 18 DAT (maximum tillering stage) and 31 DAT (ZGS 39–45 at 14-h and ZGS 58 at 18-h DL, Table 1). However, between these two growth stages, CCC slightly enhanced RER of the main shoot irrespective of DL.

View this table: [in this window] [in a new window]   Table 1. Daylength and plant growth regulator (PGR) effect on main shoot and T1 and T2 tiller height and relative elongation rate (RER) in Exp. 1. Means within each line not followed by the same letter are significantly different at P 0.05.

View larger version (30K): [in this window] [in a new window]   Fig. 1. Effect of chlormequat chloride (CCC) and ethephon on stem elongation and relative elongation rate (RER) of main shoot and T1 and T2 tillers of oat at 14- and 18-h DL in Exp. 2; DAT is days after treatment. The RER (shown as 1000 x cm cm-1 d-1) is shown between each time of measurement in a cluster of three values: The upper one is for the control, the middle one for CCC, and the lower one for ethephon treatment. At each time of measurement, the same letters indicate no significant difference at P 0.05: The upper letter is for control, the middle one for CCC, and the lower one for ethephon treatment; ns is not significant.

In Exp. 2, time x PGR x cultivar interactions occurred for stem elongation of the main shoot (F₁₆ = 2.58, P < 0.001) and T1 (F₁₆ = 1.96, P < 0.016) and T2 (F₁₆ = 3.35, P < 0.001) tillers and for accumulation of DW in the main shoot (F₁₆ = 2.58, P < 0.001) and T1 tiller (F₁₆ = 2.05, P < 0.009). Stem elongation and DW accumulation of the main shoots for the conventional cultivars Virma and Milton were retarded 6 to 34% by PGR treatments depending on growth stage (Fig. 2). In Virma and Milton, the T1 tiller was shorter at first, but after 19 DAT the T1 tiller was taller in ethephon-treated plants than the control. However, CCC inhibited T1 tiller elongation. No consistent effects of PGRs on tiller growth were detected in cultivar Pal. Also, effects of PGRs on T2 tiller elongation and DW accumulation were negligible.

View larger version (42K): [in this window] [in a new window]   Fig. 2. Effect of chlormequat chloride CCC and ethephon on stem elongation and relative elongation rate (RER) of main shoot and T1 and T2 tillers in conventional height oat ‘Virma’ and ‘Milton’ and a dwarf cultivar Pal in Exp. 2 (DAT is days after treatment). The RER (1000 x cm cm-1 d-1) is shown between each measurement in a cluster of three values: The upper one is for the control, the middle one for CCC, and the lower one for ethephon treatment. At each measurement date, the same letters indicate no significant difference at P 0.05: The upper letter is for control, the middle one for CCC, and the lower one for ethephon treatment; ns is not significant.

View this table: [in this window] [in a new window]   Table 2. Plant growth regulator effect on the ratio of dry weight of main shoot and T1 and T2 tillers to height (mg cm-1) in Exp. 1 and 2. Means within each line not followed by the same letter are significantly different at P 0.05.

View larger version (21K): [in this window] [in a new window]   Fig. 3. Accumulation of T3 tiller dry weight and relative growth rate (RGR; mg mg-1 d-1) in ‘Milton’, ‘Pal’, and ‘Virma’ at 14- and 18-h daylengths in Exp. 2 (DAT is days after treatment). The RGR is shown between each measurement date in a cluster of three values: The upper one is for Milton, the middle one for Pal, and the lower one for Virma. At each time of measurement, the same letters indicate no significant difference at P 0.05: The upper letter is for Milton, the middle one for Pal, and the lower one for Virma; ns is not significant.

View larger version (71K): [in this window] [in a new window]   Fig. 4. Effect of chlormequat chloride (CCC) and ethephon on number of green leaves (bars) and total number of emerged leaves per plant produced by the main shoot, and T1, T2, T3, and T4 tillers of oat at 14- and 18-h daylengths in Exp. 1 (DAT is days after treatment). The proportion of leaves produced by the main shoot is shown as the uppermost part of the bar, T1 tiller as the second uppermost, T2 tiller as the third uppermost, and so on. At each measurement date, the same letters indicate no significant difference at P 0.05; ns is not significant.

	DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

Even though growth of T1 and T2 tillers was most often inhibited after PGR treatments, along with growth of the main shoots, it is unlikely that this is an indication of stress caused by high dosages of PGRs. The volume we used was 10 times that used in the field to cause stem shortening, but only small amounts were likely to be intercepted by the leaves. Ethylene-releasing ethephon application is known to increase ethylene production in treated plants for several days (Foster et al., 1992; Rajala et al., 2002). Increases in ethylene evolution were evident in both treated foliage and nontreated plant parts such as roots hours after application (Rajala et al., 2002). Thus, even though T1 and T2 tillers did not receive direct ethephon application in this experiment, they were likely to have been exposed to elevated endogenous ethylene levels resulting in reduced stem growth. Chlormequat chloride application retarded T1 and T2 tiller growth to the same or greater extent than ethephon. This was unlikely the result of extra ethylene formation. Only extreme CCC concentration rates resulted in increased ethylene production and reduced root growth in oat (Rajala et al., 2002). The more likely explanation for reduced stem growth of tillers is translocation of CCC from treated plant parts to nontreated ones, an effect which is known to occur in wheat (Arissian et al., 1991). Even a minor amount of translocated CCC seems to effectively depress preheading tiller growth in oat.

Plant-growth-regulator-induced inhibition of stem elongation and DW accumulation and reduction in RER from 9 to 19 DAT on the main shoot in Exp. 2 was detected on conventional cultivars. However, Pal with the Dw6 dwarfing gene did not markedly or consistently respond to PGRs (Fig. 2). Thus the results from this study did not support earlier findings (Peltonen-Sainio and Rajala, 2001), which showed that, rather than retarding stem elongation, CCC stimulated stem growth in Pal. Furthermore, negligible cultivar differences in T1 and T2 tiller growth in response to PGRs were found in this study. Our results, obtained under controlled environmental conditions, also did not support the earlier findings of Hutley-Bull and Schwabe (1982) and Craufurd and Cartwright (1989), who found that retarded growth of main shoots released assimilates for growth of tillers highest in the dominance hierarchy. This was the case even though only minor signs of T1 tiller initiation were visible at spraying so that tillers were likely to intercept only negligible amounts of PGRs through their own foliage.

In contrast to T1 and T2 tiller growth, PGRs tended to increase growth of T3 and, occasionally, T4 tillers, particularly under long-day conditions, when measured as contribution of these tillers to total and green leaf number per plant (Fig. 4). This possibly indicates that over time additional assimilates, which were not used for growth of PGR-treated main shoots and T1 and T2 tillers, were available and, hence, were used for later initiation of T3 and T4 tillers. Due to higher contributions from T3 and T4 tillers, application of PGRs resulted in up to five more green leaves per plant. Thus, the highest green leaf number also occurred later at preanthesis, compared with the control plants (Fig. 4). The beneficial effect of PGRs on the number of leaves per plant was not as evident at 14-h DL as at 18-h. Also, CCC-treated plants in most of the measurement times had fewer green leaves per plant than control and ethephon-treated plants at 14-h DL. Furthermore, even though dwarf cultivars tend to produce more of their yield on tillers than conventional oat plants do (Mäkelä et al., 1996), we did not find any evidence under either DL condition that dwarfism was associated with enhanced T1, T2, and T3 tiller growth before anthesis (Fig. 2 and 3). The contribution of T1 and T2 tillers to grain yield in oat grown under long-day conditions is rather modest and the T3 and T4 tiller contributions were insignificant (Peltonen-Sainio and Järvinen, 1995). Thus, the nonproducing tillers (T3, T4) appear to not increase yield; however, they may play some role as a temporary storage and reserve of assimilates for the main shoots prior to grain growth (Lauer and Simmons, 1988). In later growth stages, reserves in these tillers are likely broken down, transported, and used for growth or maintenance elsewhere in the plant.

Compared with short days, long-day conditions in general enhanced development and growth of oat, but no marked differences in oat response to PGRs were recorded when comparing 14-h with 18-h DL. This response is contrary to prior experiences with wheat (Hutley-Bull and Schwabe, 1982; Craufurd and Cartwright, 1989). Under long-day conditions, tillering of oat is inhibited and tiller contribution to grain yield, in particular, is usually negligible (Peltonen-Sainio and Järvinen 1995). This study concentrated on growth before anthesis only; however, it showed that as many as four tillers per plant were initiated and emerged (Fig. 4) when oats were grown at 18-h DL. Persistence of leaf area was further enhanced by PGRs. Increase in leaf area and duration of green leaves may indicate an enhanced capacity to produce biomass, but this was not the case in our trials. Recorded growth retardation may, however, have been a temporary phenomenon as noted by Cox and Otis (1989), because our experiments were terminated at 26 to 30 DAT.

In conclusion, preanthesis PGR treatments inhibited growth of main shoots in conventional oat cultivars, but the response of the dwarf cultivar Pal was minimal. Plant-growth-regulator-induced suppression of main shoot growth was not associated with stimulated T1 and T2 tiller growth. However, across time, T3 and T4 tiller growth was enhanced and these tillers markedly contributed to PGR-induced increases in green leaf number under 18-h DL. Even though long-day conditions enhanced DW accumulation and stem elongation, few marked differences in oat response to PGR treatments were noted.

	ACKNOWLEDGMENTS

 
We thank Marcelo Morelli for his technical support.

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 
This study was partially financed by the Academy of Finland (32728).

Received for publication November 28, 2001.

	REFERENCES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION REFERENCES

 

• Arissian, M., D. Perissin-Fabert, A. Blouet, J.L. Morel, and A. Guckert. 1991. Effect of imazaquin on absorbtion, translocation, and pattern of distribution of chlormequat chloride in winter wheat. J. Plant Growth Regul. 10:1–4.
• Clark, R.V., and G. Fedak. 1977. Effects of chlormequat on plant height, disease development and chemical constituents of cultivars of barley, oats and wheat. Can. J. Plant Sci. 57:31–36.
• Cox, W.J., and D.J. Otis. 1989. Growth and yield of winter wheat as influenced by chlormequat chloride and ethephon. Agron. J. 81:264–270.[Abstract/Free Full Text]
• Craufurd, P.Q., and P.M. Cartwright. 1989. Effect of photoperiod and chlormequat on apical development and growth in a spring wheat (Triticum aestivum) cultivar. Ann. Bot. 63:515–525.[Abstract/Free Full Text]
• Foster, K.R., D.M. Reid, and R.P. Pharis. 1992. Ethylene biosynthesis and ethephon metabolism and transport in barley. Crop Sci. 32:1345–1352.[Abstract/Free Full Text]
• Hutley-Bull, P.D., and W.W. Schwabe. 1982. Some effects of low-concentration gibberellic acid and retardant application during early growth on morphogenesis in wheat. In Chemical Manipulation of Crop Growth and Development, ed. J.S. McLaren. London: Butterworth Scientific, p. 329–342.
• Knapp, J.S., C.L. Harms, and J.J. Volenec. 1987. Growth regulator effects on wheat culm nonstructural and structural carbohydrates and lignin. Crop Sci. 27:1201–1205.[Abstract/Free Full Text]
• Lauer, J.G., and S.R. Simmons. 1988. Photoassimilate partitioning by tillers and individual tiller leaves in field-grown spring barley. Crop Sci. 28:279–282.[Abstract/Free Full Text]
• Ma, B.L., and D.L. Smith. 1992. Growth regulator effects on aboveground dry matter partitioning during grain fill of spring barley. Crop Sci. 32:741–746.[Abstract/Free Full Text]
• Mäkelä, P., L. Väärälä, and P. Peltonen-Sainio. 1996. Agronomic comparison of Minnesota-adapted dwarf oat with semi-dwarf, intermediate and tall oat lines adapted to northern growing conditions. Can. J. Plant Sci. 76:727–743.
• Naylor, R.E.L., D.T. Stokes, and S. Matthews. 1987. Chemical manipulation of growth and development in winter barley production systems. Field Crop Abstr. 40:277–289.
• Peltonen, J., and P. Peltonen-Sainio. 1997. Breaking uniculm growth habit of spring cereals at high latitudes by crop management. II. Tillering, grain yield and yield components. J. Agron. Crop Sci. 178:87–95.
• Peltonen-Sainio, P., and P. Järvinen. 1995. Seeding rate effects on tillering, grain yield, and yield components of oat at high latitude. Field Crops Res. 40:49–56.
• Peltonen-Sainio, P., and A. Rajala. 2001. Chlormequat and ethephon effects on growth and yield formation of conventional, naked, and dwarf oat. Agric. Food Sci. Finl. 10:175–184.
• Pietola, L., R. Tanni, and P. Elonen. 1999. Responses of yield and N use of spring sown crops to N fertilization, with special reference to the use of plant growth regulators. Agric. Food. Sci. Finl. 8:423–440.
• Rajala, A., and P. Peltonen-Sainio. 2000. Manipulating yield potential in cereals by plant growth regulators. Growth Regulators in Crop Production, ed. Amarjit S. Basra. p. 27–70. Food Products Press, Binghamton, New York.
• Rajala, A., P. Peltonen-Sainio, M. Onnela, and M. Jackson. 2002. Effects of stem shortening plant growth regulators on root elongation in seedlings of wheat, oat and barley: mediation by ethylene. Plant Growth Regul. (In press).
• Sanvicente, P., S. Lazarevitch, A. Blouet, and A. Guckert. 1999. Morphological and anatomical modifications in winter barley culm after late plant growth regulator treatment. Eur. J. Agron. 11:45–51.
• Woodward, E.J., and C. Marshall. 1987. Effects of seed treatment with plant growth regulator on growth and tillering in spring barley (Hordeum distichum) cv. Triumph. Ann. Appl. Biol. 110:629–638.
• Zadoks, J.C., T.T. Chang, and C.F. Konzak. 1974. A decimal code for the growth stages of cereals. Weed Res. 14:415–421.

This article has been cited by other articles:

				K. D. Subedi and B. L. Ma Seed Priming Does Not Improve Corn Yield in a Humid Temperate Environment Agron. J., January 1, 2005; 97(1): 211 - 218. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Search for Related Content PubMed Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Agricola Articles by Peltonen-Sainio, P. Articles by Stuthman, D. D. Related Collections Crop Growth and Development Other Crop Management