Section D Physiology
and Cultivation
Allelopathic Effect of Buckwheat (Fagopyrum Esculentum Moench) Jana Kalinova Faculty ofAgriculture, University of South Bohemia , Studentska 13, 37005 Ceske Budejovice, Czech Republic, E-mail:
[email protected] Abstract: Common buckwheat belongs to good weed competitors. The influence of buckwheat rest, soil extracts, hull extract and germinating achenes of buckwheat on germination of testing plant (Lactuca sativa) in laboratory conditions. Varietal differences were evaluated as well. Extracts from buckwheat hulls and germinating achenes significantly inhibited the growth of lettuce. Emka variety inhibited the growth of lettuce more than that of the others. The rest of buckwheat inhibited the lettuce growth in all tested concentrations. No varietal differences were found in the biotests with soil extracts. The results indicate a greater importance of leachates from the aboveground biomass in the allelopathy of buckwheat. Keywords: Allelopathy; Achenes; Soil; Post-harvest rest
INTRODUCTION Utilisation of allelopathic and suppressive effects of crops against weeds is one of the hopeful bases for integrated systems of production. In some crops, breeding programmes were specified for the selection to allelopathic effects against weeds (Lockerman & Putnam, 1979). Allelopathic crops as cover crop, mulch, smother crops, green manure, or integrated in rotational sequences are helpful in reducing noxious weeds and plant pathogen, improve soil quality and crop yield. Those crop plants are suggested for use as natural herbic ides (Khanh et al., 2(05). Allelopathy is defmed as a biochemical interaction between different plant species. Its basic characteristic is presence of allelopathic substances, secondary metabolites, and chemical compounds, which function especially as information carriers (Klejdus&Kuban, 1999). They include phenolics, terpenoids, alkaloids, coumarins, tannins, flavonoids, steroids and quinines (Indejrit et al., 1999). Allelochemicals are released from crop plants through leachation, decomposition of crop residues , volatilization (especially terpenes) , root exudates, and also from pollen of some crop plants (Indejit et al., 1999). They can have inhibitive or toxic effects on other plants. Although the allelopathic impacts in fields are short terms (about 10 days) and the weeds may re-emerge, the weeds are then suppressed by crop shading (Xuan et al., 2(05). The inhibition of allelopathic crops on weeds is selective. Buckwheat is valued except its high nutritive value also for its short growing season (about 4 months) and fast growth in poor soil conditions. It gives possibility for its utilisation as a catch crop, green manure or function as cover crops. Buckwheat plants are often incorporated in soil also to weed reduction. Therefore the crop is frequent part of crops rotation in ecological systems of farming (Edwardson, 1996). Common buckwheat belongs to good weed competitors (especially annual weeds) for the quickly growth (Berglund, 1995; Tominaga&Uezu, 1995). Weeds did not influence total dry matter of buckwheat at the end of growing season. Field pennycress (Thlaspi arvense), gallant soldier (Galinsoga parviflora), and barnyardgrass (Echinochloa crus-galli) belonged to most frequent weeds in the buckwheat stand. Plants of buckwheat decreased weight of field pennyc~ess, Canadian thistle and ribwort plantain statistically significant (Kalinova, 2006). Germinated buckwheat achenes.significant
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Proceedings ofthe 1d international symposium on buckwheat
reduced root length of ryegrass, mustard and lettuce (Kalinova, 2004). The aim of this contribution was to evaluate the influence of buckwheat rest, soil extracts, hull extract and germinating achenes of buckwheat on germintaion of testing plant in laboratory conditions. Varietal differences were evaluated as well.
MATERIALS AND METHODS Varieties of common buckwheat (Pyra - from The Czech Republick, Emka - Poland, Krupinka - The Ukraine) were grown in four replications on plots (size of one plot 10 m2) in Ceske Budejovice (48 0 57' 42", 140 2 8 ' OS", 380 m a.s.l., sandy-loam soil, mean temperature 8.2·C, total
precipitation 529 mm) in year 2004 and 2005.
Buckwheat achenes were sown in 12.5 cm wide rows by seed drill for precise drilling with 200 plants/rrr', Plants, achenes and their hulls (only in year 2005) were sampled after harvest. Soil (O-I00,mm) depth was sampled at the begging of branching, at full flowering and one day before the buckwheat harvest on 8th of September 2004 and lOth of October 2005. . A) Effects of hull extracts Hulls were used immediately after sampling, ground (the size of particles under lmm) and extracted with distilled water (l : 10) at 23 'C 24 h. The control was only distilled water. B) Effects of soil extracts Soil samples were extracted with distilled water in mass ratio 1:1 (w/v ) at 23'C for 24 h. An extract of soil without plants was used as a control. In either case (A and B) the mixture was ftltered through cheesecloth and then through filter paper (Filpap KA2). 3 ml of extract were applied on filter paper (Filpap KAl) with 30 seeds of lettuce (Lactuca sativa L. cv. 'Capitata') in Petri dish (9 em dia), which were kept in dark by temperature 22±2 ~C. Every dish was enclosed with parafilm to reduce evaporation. The length of roots and hypocotyl was measured after 3 days. The biotests were replicated four times. C) Effects of germinating seeds Bioassay with germinating seeds of buckwheat and lettuce had three treatments: 15 lettuce seeds x 15 buckwheat achenes - in rows, 30 buckwheat achenes and 30 lettuce seeds. Seeds were sown on filter paper with 3 ml distilled water in Petri dishes and were kept in dark by temperature 22+2 'C . The length of roots and hypocotyl was measured after 3 days. D) Effect of buckwheat rest We used 20 lettuce seeds sown in 300 g dry-soil, immediately moistened with 10 ml of distilled water. The 0,5; I; 1.5 g of dried and ground stems were mixed with soil. The seeds of lettuce were sown in four rows,S seeds per row. They were incubated at 20'C for 4 weeks. Dry matter of biomass and germination was evaluated.
RESULTS AND DISCUSSION Extracts from buckwheat hulls significantly inhibited the growth of lettuce. The intensity of the allelopathic effect was on the level of buckwheat roots. Varietal differences were significant in Emka and Krupinka, which inhibited the growth of the lettuce hypocotyl more than that Pyra (Table 3). The varietal differences were evident, but in case of lettuce root they were not statistically significant for high variability. The hulls could be a partial source of the allelopathic substances during germination. The comparison of soil extracts from different stages of the growing season indicated that the strongest inhibition in lettuce growth was at the stage of flowering in 2005 and at the beginning of the growing season in 2004. The strong allelopathic activity of soil at the beginning of the season probably corresponded with the releasing effective substances into soil during germination; however, the differences compared to the control were
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Section D Physiology and Cultivation
not significant. The effects of allelopathic substances were only statistical significant in 2005 at flowering stage, when the soil samples were 'sampled after a rain and so had a stronger inhibitive effects than samples from the same period of the year in 2004. This confmns the importance of precipitation in this process. The influence of year on the allelopathic activity of soil extracts from all stages was statistically significant (Table 4) According to Wu et al. (2000) re-screening of 22 selected wheat accessions showed that the allelopathic potential of wheat varieties is consistent over different years, under the same conditions. It confirms that environmental conditions modify the allelopathic activity very significantly. Although the buckwheat root system is known for its high activity, this due to its ability to release different organic acids e.g. oxalic acid which is responsible for the aluminium resistance of buckwheat (Zheng et al., 1998). These results indicate a greater importance of leachates from the aboveground 'biomass in the allelopathy of buckwheat. No varietal differences were found in the biotests with soil extracts. However, the used volume of water could cause the non-significant inhibitive effects of the soil extracts. Compounds, which were produced by the germinating achenes produced, had negative influences on the growth of lettuce root in both years (Table 6). The varietal differences were significant in 2005, when Emka inhibited the growth of lettuce more than that of the others. In 2004, the varietal differences were not significant, but Emka also showed the highest value of inhibition as well. The influence of year on the allelopathic activity of achenes was statistically significant only in case of the lettuce hypocotyl (Table 4) The rest of buckwheat inhibited the lettuce growth in all tested concentrations (Table 5). Although significant diferences were not found between concentration, the negative correlation between the number of ,germinated plants and the concentration of buckwheat rest is evident from mean values. The same dependence was established in the case of dry matter of lettuce plant. The results indicate that buckwheat rest or achenes have more important role than root exudates in allelopathic response of buckwheat. Table 1 The influence of water extracts from buckwheat hulls on the growth of the lettuce root and hypocotyl in 2005 (% of inhibition (.)/stimulation (+) over the control) Variety
Radicle length
Hypocotyllength
Emka
-41.20 a
-36.12 a
Krupinka
-37.58 a
-32.73 a
Pyra
-28.30 a
-11.51 b
Average
-35.69 B
-26.79 B
Control
0.00 A
0.00 A
a.b.c etc. : Differences among varieties after Tukey HSD Test
(in the column)
A, B,C etc.: Differences between hull extract and the control after Tukey HSD Test (in the column ) Table 2 The influence of year on allelopathic activity of extracts from achenes and soil • analysis of variance (MS Effect) df Achenes
Lettuce root 172.485 ns
Lettuce hypocotyl 2821.869
**
Soil Branching Full flowering Before harvest
* 3747.500 ** 1086.760 ** 876.283
** 5751.129 ** 1380.484 * 66.1344
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Proceedings,ofthe
ur international symposium on buckwheat
Table 3 The Influence of soil extracts sampled in buckwheat stand on the growth of the lettuce root and hypocotyl ( % of inhibition (-) or stimulation (+) over the control) Radicle length
Variety
Stage
2004
2005
2004
2005
-14.16b
+2.91a
+17.08a
+8.08a
Krupinka
-8.41b
+16.12a
+15.08a
+10.37a
Pyra
-8.55b
+22 .36a
+14 .77a
+8.56a
average
- 10.37 A
+13.80 A
+15.64 A
+9.00 A
Emka
-6.20a
-53.67a
+32.19a
-37.26a
Krupinka
-9.97a
-57.18a
+31.56a
-27.03a
Pyra
-0.50a
-55.77a
+32.33a
-25.39a
average
-5.56 A
-55.54 B
+32.03 A
-29.89 B
Emka
+30.04a
-1.06a
+44.39a
+6.87a
Krupinka
+19 .73a
-7.02a
+57.44a
+7.69a
Pyra
+21.52a
-1.38a
+5.23a
+8.93a
average
+23.76 A
-3.15 A
+35.69 A
+7.83 A
OA
OA
OA
OA
Emka Branching
Full flowering
Before harvest
Hypocotyllength
Control
ns = non significant, ** P < 0.01, * P < 0.05 a.b.c etc : Differences among varieties after Tukey HSD Test
(in the column)
A, B,C etc.: Differences among soil extracts and the control after Tukey HSD Test in the given year (in the column) Table 4 The influence of germinating buckwheat achenes on the growth of the lettuce seeds (% of inhibition (-) or stimulation (+) over the control) Hypocotyllength
Radicle length
Variety
2004
2005
2004
2005
Emka
-43.51 a
-35.06 a
+12.88 a
-27.25 a
Krupinka
-39.62 a
-27.48 ab
+26 .90 a
-21.50 ab
Pyra
-28.34 a
-16.76 b
+30.59 a
-11.00 be
Average
-37.16A
-26.43 A
+23.46 A
-19 .92A
Control
o.oos
o.oo a
0.00 A
o.eo s
a. b. c etc: Differences among varieties after Tukey HSD Test (in the column) A, B, C etc.: Differences between effect of germinating achenes and the control after Tukey HSD Test in the given year (in the column) Table 5 The influence of buckwheat rest in soil on the growth of lettuce seeds Amount of buckwheat rest (g)
Number of plants
Dry matter of plants
1.5
2.5 a
0.12 a
1
6.3 a
0.16 a
0.5
9.0 a
0.47 ab
o
19.5
b
0.91
b
a.b.c etc. : Differences among varieties after Tukey HSD Test This work was supported by grant of the Ministry of Education of the Czech republic MSM : 6007665806 and Grant Agency of the Czech republic 52110310076.
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Section D Physiology and Cultivation
References [1] Berglund, D. R., 1995 : Buckwheat production. NDSU Extension Servise A-687 . [2] Edwadson, S., 1996: Buckwheat: Pseudocereal and nutraceutical. In: J. Janick (00.), Progress in new eros. ASHS Press. Alexandria, VA: 195-207. [3] Inderjit, Dakshini, K.M .M., Foy C.L., 1999 : Principles and practices in plant ecology: allelochemical interactions. CRC Press LLC, USA, 589s. [4] Kalinova, J., 2004: Influence of common buckwheat on growth of other plant species. Proceedings of the 9th International Symposiwn on Buckwheat, Praha, 529-531. [5] Kalinova, J., 2006: The effect of common buckwheat growing on weeds. Conference Biological Methods in Integrated Plant Protection a nd Production, IOBClEPRS, Poznan. 69 [6] Khanh, T. D., Chung, M. I., Xuan, T. D., Tawata, S. 2005: Allelopathy in Sustainable Agricultural Production J. Agronomy & Crop Science 191, 172-184. [7] Klejdus, B., KUban, V., 1999: Rostlinne fenoly v alelopatii. Chern. Listy 93: 243- 248. [8] Lockerman, R. H., Putnam, A. R., 1979: Evaluation of alIelopathic cucwnbers (Cucumis sativus) as an aid to weed control. Weed Sci . 27, 54-57. [9] Tominaga, T., Uezu, T., 1995: Weed suppression by Buckwheat, Current Advances in Buckwheat Research: 693-697. [10] Xuan, T. D., Tawata, S., Khanh, T. D. Chung I. M., 2005: Decomposition of Allelopathic Plants in Soil J. Agronomy & Crop Science 191.162-171. [11] Zheng S.J., Ma J.F. and Matsumoto H (1998), High aluminwn resistance in buckwheat. I. Aluminium-induced specific secretion of oxalic acid from root tips . Plant Physiology 117, 745-751
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