Journal of Horticultural Science & Biotechnology (2003) 78 (3) 381±385
An investigation of the effects of environmental factors on Lantana camara L. subsp. camara responses to paclobutrazol and mepiquat chloride By A. S. MATSOUKIS and A. G. CHRONOPOULOU-SERELI* Department of General Sciences, Agricultural University of Athens, Iera Odos 75, Athens 118 55, Greece (e-mail:
[email protected]) (Accepted 27 January 2003) SUMMARY
Potted plants of Lantana camara L. subsp. camara were sprayed with paclobutrazol (0, 50, 100, 200 and 500.mg l±1) and mepiquat chloride (125, 250, 500 and 1000.mg l±1) and their growth and ¯owering were determined under shading (0%, 27% and 66%) under greenhouse conditions. Growth (measured as a growth index combining height and width data) was found to decrease as paclobutrazol concentration ±1increased while the number of ¯ower heads per plant increased up to a maximum at the concentration of 100.mg l with a decrease afterwards, at all shading levels. The growth index of the controls increased and the number of ¯ower heads per plant decreased signi®cantly at all concentration levels, as shading increased from 0% to 66%. The treatments with mepiquat chloride increased the growth index at all levels of shading. All plants treated with this regulator had more ¯ower heads than the controls. At all concentration levels the growth index increased as shading increased from 0% to 66% while the number of ¯ower heads was increased at 27% shading with a decrease afterwards. The most attractive plants (small with maximum ¯owering) were obtained with 100.mg l±1 paclobutrazol at 0% shading. ne of the major aims of commercial ¯oriculture is O to supply markets with desirable pot plants (small, uniform with many ¯owers) for various ornamental
This paper presents an evaluation of the effectiveness of paclobutrazol and mepiquat chloride on the development of compact plants of Lantana camara L. subsp. purposes, especially in the urban areas. The need for camara with good ¯ower potential by studying their growth control can be served with the use of plant growth and ¯owering under various environmental growth regulators which interfere with gibberellin conditions resulting from different shading levels. synthesis (Andersen and Andersen, 2000). Paclobutrazol, a gibberellin (GA) biosynthesis inhibitor (Martin et.al., 1994) seems to have a wider range of activity than MATERIALS AND METHODS other growth retardants (Halevy, 1985). Paclobutrazol, The experiments took place from June to November applied commonly as foliar spray (Million et al., 1999), 1997 and 1998 in a greenhouse in Attica (37 48 20 N, retards plant growth in several ornamental plants 23 57 48 E), Greece. Rooted cuttings of lantana were (Banko and Stefani, 1988; Gent, 1997). This regulator produced under mist propagation 16±18.cm long midmay have positive (Wilkinson and Richards, 1987; stem cuttings, each with one leaf pair. The cuttings were Andrasek, 1989) or negative (Chronopoulou-Sereli treated with a commercial growth regulator (Rooton et.al., 1998; Plummer and Wann, 1998) effects on the 0.066% I.B.A., Sege, Greece) and placed in perlite rooting medium. Temperatures were 15±20 C and 20 C ¯owering of other ornamental plants. Literature provides insuf®cient information on the in the air and rooting substrate, respectively. Eleven effects of mepiquat chloride, a GA biosynthesis blocking weeks later, rooted cuttings were placed in 1.1 litre onium-type compound (Rademacher, 1991), on orna- (14.cm diameter) plastic pots (one cutting per pot) mental plants. Yang et al. (1995) refer that this regulator containing a white peat potting substrate (Klasmannincreases several growth parameters of Hosta plantagi- Deilmann GmbH, Germany), pruned and transferred to the greenhouse. After four weeks the plants received a nea `Undulate' and `Decorata'. Light intensity can in¯uence uptake and translocation commercial liquid fertilizer containing trace elements of growth regulators (Muzik, 1976) and can be changed (Complesal Fluid-AgrEvo; Hellas Co., Athens, Greece), by the use of shading materials and, combined with with 50.ml solution per pot (1.ml per litre water, growth regulators, may be helpful in commercial 5N-8P-10K). Ten days later the plants were pinched in the second internode from the tips; the experiments production (Kamoutsis et al., 1998). Lantana camara L., a tropical ornamental shrub started 12.d later (on 24 and 20 June, for 1997 and 1998 (Howard, 1969) with dense attractive foliage and respectively) when the new-developing stems had a multi-coloured ¯owers (Pizzetti and Cocker, 1975), is length of about 1.cm. There was no presence of ¯ower used as an outdoor plant in regions with mild climate; it buds. Paclobutrazol (Cultar 25% w/v, Zeneca, USA) and is also an excellent subject for pot culture. mepiquat chloride (Pix 5 A.S. 5% w/v, BASF AG, *Author for correspondence. Germany) were applied as foliar spray solutions (0.25.l 8
8
9
8
381
9
99
99
8
382
Lantana and growth regulators
Mean daily values of air temperature, relative humidity and photosynthetically active radiation (PAR) in the plots R1, R2 and R3 (0%, 27% and 66% shading, respectively) for the years 1997 and 1998. For the calculation of mean PAR the hourly values from 1600 to 0500 hours Greenwich Mean Time were excluded Photosynthetically Maximum Minimum Relative active radiation temperature temperature humidity 2 (W/m ) (8C) (8C) (%) Plot 1997 1998 1997 1998 1997 1998 1997 1998 R1 130 143 30.4 33.0 17.5 18.1 64.8 59.3 R2 95 103 29.6 31.7 17.3 18.0 65.3 59.5 44 48 27.2 29.3 17.1 17.7 70.1 62.8 R3 Table I
per plant) to runoff, 11.d after pinching to plants of lantana at concentrations of 0, 50, 100,±1 200, 500.mg l±1, and of 125, 250, 500 and 1000.mg l respectively. A surfactant (Agral 90, 94.8% w/w nonylphenolethoxylate Zeneca, USA) was combined with each application at a rate of 0.25 ml per litre solution. After the applications with the growth regulators, plants were placed to three plots (each 3.2.m long, 2.0.m wide and 1.5.m high) where different levels of photosynthetically active radiation (PAR) were achieved, with the aid of shading nets. Plants were rotated within each plot weekly to ensure, approximately equal light exposure. The experiments, separately for each growth regulator, were carried out according to the two-factor completely randomized design. The ®rst factor had three shading levels, two (R and R ) created using shading polyethylene nets (one2 black 3thin and one dense woven, models 103 and 201, respectively, Manioudaki Bros S.A. knitting factory, Greece) and one (R1) unshaded. The second factor had ®ve levels corresponding to each regulator concentrations (including the 0.mg l±1 concentration). There were eight single-plant replicates. Fresh randomization for both shading and concentration levels and also plant replicates was carried out in the second experimental period (1998). Environmental data including temperature and relative humidity were monitored by three dataloggers 903 (Wilh. Lambrecht GmbH, Germany) with sensors for these parameters (Model 809 L 0-100 of Wilh. Lambrecht GmbH, Germany; accuracy 60.38C at 08C and 62.5% for temperature and relative humidity respectively). The sensors were shielded from radiation. PAR measurements were taken hourly during daytime, at the top of the plant canopies, with three cosine corrected sensors (Model SKE 510 of Skye Instruments Ltd., UK; sensitivity 1.mV per 100.W m±2 in the waveband 400±700.nm) connected to a datalogger (Model datahog 2 of Skye Instruments Ltd).
Biometrical measurements were carried out until 18 and 23 November 1997 and 1998 respectively, after the beginning of the experiments and included plant height (at the level of the tallest shoot from pot rim), maximum plant diameter (width 1), perpendicular width to maximum diameter (width 2) and the number of ¯ower heads per plant (with three at least open ¯orets). Growth was measured as a growth index (GI) combining height and width data according to Ruter (1996). To study growth after pinching and the total number of ¯ower heads per plant, statistical models were used (Dimopoulos, 1997) and also analysis of variance (after the exclusion from each treatment of the highest and lowest value). All growth data were obtained from the measurement of GI at the end of each experimental period with the initial GI subtracted from it. For the ®gures, standard errors (SE) were calculated from the residual variances (Roussos and Pontikis, 2001). Statistical analysis (using SPSS version 8.0 for Windows) was conducted separately for each year of the experiments because there were signi®cant differences in the measured plant characteristics between years in some treatments, probably due to the different environmental conditions between years. RESULTS AND DISCUSSION Mean daily maximum and minimum temperatures decreased as shade increased and temperatures were higher in 1998 than 1997 (Table I). The mean daily relative humidity was lower in 1998 and differed by a maximum of 5.3% between shade plots. Mean values of PAR were higher in 1998 than in 1997 (Table I) and showed greater reduction with increased shading than other environmental parameters. Plants grew larger and with more ¯ower heads in all shade plots in 1998 than in 1997, presumably due to the higher temperature and PAR in 1998. The GI and the
Analysis of variance for effects of shading level and concentration of paclobutrazol on the growth index (GI) and the number of ¯owers heads/lantana plant for the years 1997 and 1998 GI (cm) Number of ¯ower heads 1997 1998 1997 1998 Source d.f1 Mean square S2 2 141.68*** 351.03*** 8060.58*** 8229.64*** 4 805.48*** 1022.85*** 7938.26*** 7223.37*** CP3 S3CP 8 34.94*** 47.33*** 226.91*** 299.26*** Residual 75 1.59 1.75 5.22 12.73 1d.f. = Degrees of freedom. 2S = Shading level (0%, 27% and 66%). 3CP = Concentration of paclobutrazol (0, 50, 100, 200 and 500 mg l±1). ***Signi®cant at P = 0.001. Table II
A. S. Matsoukis
and
383
A. G. Chronopoulou-Sereli Table III
Analysis of variance for effects of shading level and concentration of mepiquat chloride on the growth index (GI) and the number of ¯ower heads/ lantana plant for the years 1997 and 1998
1997
GI (cm)
1998
Source d.f.1 Mean square S2 3 2 1578.01*** 1990.12*** CM 4 146.81*** 129.63*** S3CM 8 8.45n.s. 13.54n.s. Residual 75 7.63 7.79 1d.f. = Degrees of freedom. 2S = Shading level (0%, 27% and 66%). 3CM = Concentration of mepiquat chloride (0, 125, 250, 500 and 1000 mg l±1). *,**,***Signi®cant at = 0.05, = 0.01, and = 0.001, respectively; n.s., not signi®cant. P
P
Number of ¯ower heads 1997 1998
583.63*** 409.01*** 22.58* 8.96
765.08*** 290.06*** 32.19** 10.60
P
total number of ¯ower heads per plant was signi®cantly affected by the concentration of both paclobutrazol and mepiquat chloride and the various shading levels (Tables II and III). There were signi®cant interactions between concentration and shading level, but the effect on GI was signi®cant only in the case of paclobutrazol. The plants which received paclobutrazol showed smaller GI (Figures 1a and 2a) than the nontreated ones; this could be explained by a lower content of their biologically active gibberellic acids (GAs) due to paclobutrazol action (Rademacher, 1991) in comparison
with the nontreated plants. Increasing concentrations of the regulator decreased growth at all shading levels. On the other hand, increasing paclobutrazol concentrations up to 100.mg l±1 increased the number of ¯ower heads up to a maximum, with a reduction at higher concentrations, at all levels of shading (Figures 1b and 2b). This±1 regulator as a drench at the concentration of 80.mg l maximized the number of ¯ower heads of L. subsp. (Matsoukis ., 2001) under similar shading levels; this number was greater than the respective number of our experimental
1 Changes of growth index (GI) after the subtraction of initial from ®nal GI and total number of ¯ower heads per lantana plant as a function of paclobutrazol concentrations (0, 50, 100, 200 and 500.mg l±1), at the plots R1, R2 and R3 (0%, 27% and 66% shading, respectively). The concentration of paclobutrazol for the controls was considered as 0.1.mg l±1 to support the ln of equations. R1obs, R2obs, R3obs and R1est, R2est, R3est are the measured and estimated 2GI (a) and ¯ower (b) values, respectively for the year 1997. R .=.Coef®cient of determination. The vertical bar is the SE (n.=.6).
2 Changes of growth index (GI) after the subtraction of initial from ®nal GI and total number of ¯ower heads per lantana plant as a function of paclobutrazol concentrations (0, 50, 100, 200 and 500.mg l±1), at the plots R1, R2 and R3 (0%, 27% and 66% shading, respectively). The concentration of paclobutrazol for the controls was considered as 0.1.mg l±1 to support the ln of equations. R1obs, R2obs, R3obs and R1est, R2est, R3est are the measured and estimated 2GI (a) and ¯ower (b) values, respectively for the year 1998. R .=.Coef®cient of determination. The vertical bar is the SE (n.=.6)
Fig.
Lantana camara
camara
Fig.
et al
384
Lantana and growth regulators
3 Changes of growth index (GI) after the subtraction of initial from ®nal GI and total number of ¯ower heads per lantana plant as a function of mepiquat chloride concentrations (0, 125, 250, 500 and 1000.mg l±1), at the plots R1, R2 and R3 (0%, 27% and 66% shading, respectively). The concentration of mepiquat chloride for the controls was considered as 0.1.mg l±1 to support the ln of equations. R1obs, R2obs and R3obs are the measured GI (a) and ¯ower (b) values while R2est and R3est are the estimated ¯ower values for the year 1997. The effects on ¯ower head number in the nonshaded plot (R1) and on GI changes in2 all plots could not be described satisfactorily by simple equations. R .=.Coef®cient of determination. The vertical bar is the SE (n.=.6). Fig.
plants treated with paclobutrazol at 100.mg l±1. All paclobutrazol treated plants produced more ¯ower heads than the nontreated ones. The growth and the total number of ¯ower heads per plant, in¯uenced by the various concentrations of paclobutrazol, is expressed by the equations shown in Figures 1 and 2. It is clear that model estimated and observed values were strongly correlated. The shading increase from 0% (R ) to 66% at R3 plot generally increased signi®cantly the1 growth of plants treated with the same concentration of paclobutrazol. Similarly, the growth of the nontreated plants was increased signi®cantly (Figures 1a and 2a). This response is probably an adaptive mechanism to avoid low light environments, a known feature of shade intolerant plants (Tang, 1997). A similar inverse relation between plant growth parameters and light intensity was reported by Kessler and Armitage (1992) on x `Scarletta' and by Fan . (1998) on plants. As shading increased from 0% to 66% the number of ¯ower heads was signi®cantly decreased on the plants treated with the same paclobutrazol concentration as well as for the nontreated plants (Figures 1b and 2b). The great reduction of ¯owering in the R3 plot could be due to the low light level which, in general, causes such effects (Muzik, 1976). In contrast to paclobutrazol, mepiquat chloride stimulated growth, resulting in greater GI compared with the nontreated plants (Figures 3a and 4a) although it is one of the onium-type inhibitors of GAs biosynthBegonia
¯orens-cultorum
Spathiphyllum palls
et al
semper-
4 Changes of growth index (GI) after the subtraction of initial from ®nal GI and total number of ¯ower heads per lantana plant as a function of mepiquat chloride concentrations (0, 125, 250, 500 and 1000.mg l±1), at the plots R1, R2 and R3 (0%, 27% and 66% shading, respectively). The concentration of mepiquat chloride for the controls was considered as 0.1.mg l±1 to support the ln of equations. R1obs, R2obs and R3obs are the measured GI (a) and ¯ower (b) values while R2est and R3est are the estimated ¯ower values for the year 1998. The effects on ¯ower head number in the nonshaded plot (R1) and on GI changes in2 all plots could not be described satisfactorily by simple equations. R .=.Coef®cient of determination. The vertical bar is the SE (n.=.6). Fig.
esis (Rademacher, 1991). One possible explanation is that mepiquat chloride, which possesses a quaternary ammonium group, may be a source of nitrogen after degradation by lantana plants. A similar hypothesis was suggested for plants treated with chlormequat chloride (Groves and Lang, 1970), a regulator possessing, like mepiquat chloride, a quaternary ammonium group (Rademacher, 1991). All plants treated with mepiquat chloride had more ¯ower heads than the nontreated ones at all shading levels. The change in the total number of ¯ower heads per plant, with the increased concentrations of mepiquat chloride, is expressed by the equations shown in Figures2 3b and 4b. The high coef®cients of determination (R ) indicated strong correlation between model estimated and observed values. The progressive decrease of PAR from R to R2 and R3 plots caused signi®cant increases of GI1 for plants treated with the same concentration of mepiquat chloride. For these plants the number of ¯ower heads was increased with the increase of shading at R plot, with a decrease then at R3 plot (Figures 3b and 4b).2 For mepiquat chloride, to our knowledge, no comparable studies have been conducted for other ¯oricultural plants. Scrophularia marilandica
and Plants treated with paclobutrazol exhibited darker green foliage than the nontreated ones which was mentioned for Lantana camara `New Gold' treated with this regulator (Ruter, 1996). Some leaf distortion was noticed in plants treated with paclobutrazol concentrations above 100.mg l±1. The new-expanding leaves of plants at the time of treatments with mepiquat chloride presented slight discoloration, which was not present on leaves formed after treatments. Pool (1982) found slight, non-permanent chlorosis on the leaves of Vitis labruscana `Concord' treated with this regulator. In this work all plants treated with paclobutrazol were attractive because of their small size and abundant ¯ower heads. In contrast, the big size of plants treated with mepiquat chloride, although having more ¯ower A. S. Matsoukis
385 heads than the nontreated ones (but fewer than the paclobutrazol treated plants), offers little improvement in the aesthetic quality of the plants or their market value. The most attractive plants were produced with paclobutrazol at a concentration of 100.mg l±1 in the nonshaded plot; they were small, with the maximum number of ¯ower heads, over three times the respective number of the nontreated plants in the same plot.
A. G. Chronopoulou-Sereli
This work was partly funded by the State Scholarships Foundation of Greece. The authors thank Prof. Charles Stirton (Director of the National Botanic Garden of Wales UK) for the identi®cation of the experimental plants.
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