On lettuce, carrot and red beet natalija Galzina, Maja Šćepanović, Matija Goršić, Ivana Turk




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ALLELOPATHIC EFFECT OF INVASIVE SPECIES ABUTILON THEOPHRASTI Med. ON LETTUCE, CARROT AND RED BEET
Natalija Galzina, Maja Šćepanović, Matija Goršić, Ivana Turk*

Department of Herbology, Faculty of Agriculture, University of Zagreb, Svetosimunska 25, 10000 Zagreb, Croatia, e-mail: ngalzina@agr.hr

*Student of Faculty of Agriculture, University of Zagreb (Part of Final (BSc) thesis of Ivana Turk defended on 26. September 2008. at the Faculty of Agriculture, University of Zagreb)
Abstract
Velveatleaf (Abutilon theophrasti Med.) is present for a long time in Croatia but as a weed in agriculture is known since 1980's. Last few years velvetleaf spreads very fast and uncontrollably. It is mostly distributed in the continental part of the country but recently it is also found in coastal areas. Besides competitive abilities it also has allelopathic potential. In this study the aqueous extract of velvetleaf was prepared from mature capsule with seeds to investigate the effect of velvetleaf on germination, and the length of radicule and shoot of three test plants: lettuce, carrot and red beet. Germination inhibition was significant only in carrot (41,2%) while the reductions in the length of radicule and shoot were significant for all test plants. Velvetleaf inhibited the length of radicule in carrot by 83,8%, in red beet by 49,4% and lettuce by 37,4%. Length of shoot was reduced by 88,1% in carrot, 66,4% in red beet and 7,7% in lettuce.
Keywords: Velvetleaf (Abutilon theophrasti Medik.), allelopathy, lettuce, carrot, red beet
Introduction
Abutilon theophrasti is an invasive plant species in Croatia and one of the most important weed species from Malvaceae family (Novak, 2007).

First data about its presence in Croatia were published in 1869. (Schlosser and Farkaš-Vukotinović, 1869.), and Šulek in 1879. Although velvetleaf is present for a long time in Croatia, as a weed in agriculture is known since 1980’s and especially after mid 1990’s (Novak, 2007). Velvetleaf is distributed in continental part, from east to Karlovac but recently is more often found in coastal parts of Croatia (Novi Vinodolski, Matulji, Poreč, Imotski, Ploče, valley of river Neretva). Last few years velvetleaf spreads very fast and uncontrollably in Croatia (Flegar and Novak, 2005). It appears in big populations and sometimes with more than 200 individual plants per square meter. It is more often present in crops than as a ruderal weed (Novak, 2007).

Velvetleaf is a troublesome weed in numerous row crops, especially corn, soybean, sugarbeet, potato, sunflower and onion (Novak, 2007). Many studies have reported decreases in crop yield due to competition from A. theophrasti. Velvetleaf is efficient under conditions of low sunlight. It grows well when partially shaded and can complete its life cycle even under a crop canopy (Mitich, 1991). When emerging simultaneously with corn, velvetleaf can surpass corn growth by the end of the season, develop a layer of leaves above the corn canopy and, therefore, interfere with crop light interception (Sattin et al. 1992).

Besides competitive abilities it also has allelopathic potential which inhibits germination and emergence of concurrent plants. Rice in 1974. defines allelopathy as any direct or indirect effect by one plant, including micro-organisms, on another through the production of chemical compounds that escape into the environment and subsequently influence the growth and development of neighboring plants. IAS in 1996. extended definition as „any process involving secondary metabolites produced by plants, algae, bacteria and funghi that influences the growth and development of agricultural and biological systems“ (in Novak, 2007).

Allelopathic effects of different weed species on cultivated plants, mainly arable crops, are topic of numerous research studies. In Croatia, Novak (2007) confirmed the inhibitory allelopathic effect of velvetleaf root extract, stem extract and leaf extract on the length of radicule of oilseed rape, soybean and winter oat. On the other side, the same extracts diluted with water in ratio 1:2 stimulated the length of oilseed rape shoot. Author did not determine any allelopathic effect of velvetleaf on sunflower and popcorn. Kazinczi et al (2004) note that sunflower fresh weight was reduced by water extract of velvetleaf root, while shoot extract did not influence the fresh weight of sunflower. Šćepanović et al. (2007) confirmed the velvetleaf inhibitory effect on radicule, shoot and germination of corn.

Effect of velvetleaf on vegetable crops is less investigated. Therefore, the aim of this paper was to determine the allelopathic effect of velvetleaf on lettuce, carrot and red beet.



Materials and methods
Allelopathic effects of velvetleaf were investigated in a laboratory of the Faculty of Agriculture, University of Zagreb in May 2008. Aqueous extract of velvetleaf was prepared from mature capsule with seeds which were powdered by mixer and diluted in distilled water in ratio: 50 g of powdered plant material on 5 dl of distilled water and kept at room temperature. After 24 hours, plant material was removed and extract was filtered. In sterilized Petri dishes (100 mm x 20 mm) wetting of two filter paper layers with 5 ml of prepared extract was done. In each Petri dish 25 seeds of individual test plant were “sowed”, in four replicates. Research also included untreated control, wetted with 5 ml of distilled water. Test plants were lettuce, carrot and red beet. After “sowing” Petri dishes were placed in plastic bags in dark at room temperature (25oC) to germinate. Time of evaluation depended on test plant velocity of germination and was between five to seven days. Allelopathic effects were obtained through following values: % of germination, length of test plant ridicule, length of test plant shoot. Length of lettuce radicule and shoot was measured five days after “sowing”, and measurement for carrot and red beet was done seven days after “sowing”.
Results and discussion
As shown in table 1. aqueous velvetleaf extract had a significant effect on the development of all test plants.
Table 1. Effect of velvetleaf extract on the length of test plant radicule and shoot and germination

Test plant

Treatment

Germination (%)

Length of radicule (cm)

Length of shoot (cm)

Lettuce

Untr.

100

2,066

2,122

ABUTH

97,0 n.s.

1,294*

1,959 n.s.

Carrot

Untr.

68,0

1,742

1,812

ABUTH

40,0*

0,283*

0,216*

Red beet

Untr.

92,0

1,402

1,389

ABUTH

77,0*

0,710*

0,467*

Untr.- untreated control, ABUTH-aqueous velvetleaf extract

n.s.-not significant; *-significant difference at P=0,05


Velvetleaf significantly inhibited the germination of carrot and red beet while it did not have any effect on lettuce germination. The length of test plants radicule and shoot was significantly reduced in all test plants, but especially in carrot inhibiting the length of radicule six times and even nine times the length of shoot compared to control.
Graph 1. Inhibition of germination and length of the test plant radicule and shoot

On graph 1. is shown the inhibition of germination, length of radicule and shoot of all test plants compared to control. As shown, carrot was the most susceptible test plant on velvetleaf presence. The germination of carrot seeds was the most inhibited (41,2%), while the effect of aqueous velvetleaf extract inhibited red beet germination by 16,3%. Velvetleaf did not show significant inhibitory effect on lettuce germination.

Compared with untreated control the average length of radicule in all test plants was significantly reduced. Carrot radicule was the most reduced by 83,8% (pictures 3. and 4.), while the lowest effect aqueous velvetleaf extract had on lettuce radicule length which was reduced by 37,4% (pictures 1. and 2.). The length of red beet radicule was reduced by 49,4% (pictures 5. and 6.).

Inhibitory effect of velvetleaf was significant only on the length of carrot and red beet shoot while velvetleaf extract didn’t inhibit lettuce shoot length when compared with untreated control. Results obtained in lettuce showed that velvetleaf had inhibitory effect only on the length of lettuce radicule. Inhibitory effect of velvetleaf on carrot and red beet shoot length (88,1% and 66,4%, respectively) was similar to effect on radicule length (83,8% and 49,4%, respectively). As shown, carrot shoot length was again the most inhibited.











Fig. 1. Untreated lettuce (Photo: Šćepanović)




Fig. 2. Lettuce on aqueous velvetleaf extract (Photo: Šćepanović)








Fig. 3. Untreated carrot (Photo: Šćepanović)




Fig. 4. Inhibited carrot on aqueous velvetleaf extract (Photo: Šćepanović)








Fig. 5. Untreated red beet (Photo: Šćepanović)




Fig. 6. Inhibited red beet on aqueous velvetleaf extract (Photo: Šćepanović)

Lettuce was frequently test plant in previous studies on allelopathy. Quasem and Foy (2001) noted many references about different weed species allelopathic effect on crop plants. Many other weeds (Aristolochia clematitis, Cyperus esculentus, Galium aparine, Lolium multiflorum, L. perenne, Xanthium strumarium etc.) showed allelopathic effects on lettuce while allelopathic effects of different weeds (Amaranthus retroflexus, A. palmeri, Lepidium draba etc.) were less investigated in carrot. In addition to inhibitory effects, plants can act simulative. Golubić (2007) showed inhibitory effect of Echineacea spp. on lettuce germination and consequently the length of radicule and shoot. In contrast, Echinacea spp. stimulated all measured parameters in red beet.

Results obtained agree with research of Novak (2007) and Šćepanović et al. (2007). Those authors also demonstrated a strong inhibitory effect of velvetleaf on some arable test plants. Other authors confirmed allelopathic effects of velvetleaf on some other vegetable crops. Gressel and Holm (1964) determined an inhibitory effect of velvetleaf seeds on early growth stages of tomato. Further, Retig et al. (1972) showed that cabbage grown with velvetleaf had larger roots, due to an increase in number and size of parenchyma cells. Houtz et al. in 1984. found that numerous glandular trichomes on velvetleaf stems and petioles exude liquid globules (in Sterling and Putnam, 1987). Because the exudate is water soluble, rain may enhance its movement into the soil where they can act as allelochemicals.

Except it is strong competitor results obtained show that velvetleaf can have inhibitory effect on the early growth of tested plants.


Conclusions
Aqueous velvetleaf extract had a significant effect on early development of lettuce, carrot and red beet. Velvetleaf showed the strongest inhibitory effect on carrot inhibiting carrot seed germination by 41,2%, length of radicule by 83,8% and length of shoot by 88,1%. In contrast, inhibition of the lettuce germination was the lowest and only radicule length was inhibited by velvetleaf extract. In red beet velvetleaf showed stronger inhibitory effect on shoot length (66,4%) than radicule length (49,4%). Of all tested plants, carrot was the most susceptible plant to velvetleaf extract, than red beet, while inhibitory effect was the smallest in lettuce.
References
FLEGAR Z. and NOVAK N. (2005). Europski mračnjak (Abutilon theophrasti Med.). Zavod za zaštitu bilja u poljoprivredi i šumarstvu Republike Hrvatske. Ministarstvo poljoprivrede, šumarstva i vodnoga gospodarstva Republike Hrvatske, Zagreb.

GOLUBIĆ, M. 2008. Alelopatski utjecaj teofrastovog mračnjaka, kamilice I rudbekije na klijavost cikle i salate.Diplomski rad, Zagreb

KAZINCZI, G., BERES, I., HORVATH, J., TAKACS, A. P. 2004. Sunflower (Helianthus annuus) as recipient species in allelopathic research. Herbologia 5 (2): 19

MITICH, L. W. 1991. Intriguing world of weeds. Velvetleaf. Weed Technology, 5: 253-255

NOVAK, N. 2007. Alelopatski utjecaj europskog mračnjaka (Abutilon theophrasti Med.) na neke poljoprivredne kulture. Magistarski rad, Zagreb

QUASEM, J. R., FOY C. L. 2001. Weed Allelopathy, Its Ecological Impacts and Future Prospects: A Review. In: Allelopathy in Agrecosystems (ed. Kohli R. K., Singh H. P., Batish D. R.), Food Products Press, Inc., NY, USA.

RETIG, B., HOLM, L. G. and STRUCKMEYER B. E. 1972. Effects of Weeds on the Anatomy of Roots of Cabbage and Tomato. Weed Science, 20 (1): 33-36

SATTIN, M., ZANIN, G. and BERTI A.. 1992. Case history for weed competition/population ecology: velvetleaf (Abutilon theophrasti) in corn (Zea mays). Weed Technol. 6:213–219.

SCHLOSSER J. C. and FARKAŠ-VUKOTINOVIĆ L. (1869.) Flora Croatica, Zagrabiae

STERLING T. M. and PUTNAM A. R., 1987. Possible role of glandular trichome exudates in interference by velvetleaf (Abutilon theophrasti). Weed Science 35: 308-314



ŠĆEPANOVIĆ, M., NOVAK, N., BARIĆ, K., OSTOJIĆ, Z., GALZINA G., GORŠIĆ M. 2007. Allelopathic effect of two weed species, Abutilon theophrasti Med. and Datura stramonium L. on germination and early growth of corn. Agronomski glasnik 6: 459-472

ŠULEK B. (1879.). Jugoslavenski imenik bilja, Zagreb


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