1. PHYTOTOXIC EFFECT OF ESSENTIAL OILS
FROM TEMPERATE CLIMATE HERBS AGAINST
SELECTED WEED SPECIES
Stokłosa A., Kulig E., Puła J H. Kołłątaj University of Agriculture, Kraków, Poland
INTRODUCTION
Interest in the ecological methods of weed management is increasing. Among them an important role play chemicals extracted from plants of known or observed allelopathic potential. Essential oils, composed of various groups of chemicals, are the crucial component of medicinal plants. They show mostly antibacterial and antifungal properties, and recently also their insecticidal and phytotoxic potential has been shown i.e. clove oil or lavender oil (Stokłosa et al. 2012). Our study aimed at assessing the phytotoxic potential of essential oils extracted from herbal species, cultivated and wild ones, from a temperate climate against germination of weeds.
MATERIAL AND METHODS
Herbal plants were collected from South-Eastern Poland. Essential oils were extracted using Clavenger apparatus. There were 9 essential oils tested: mint, lavender, cumin, lemon balm, thyme, sage, chamomile, calamus and tansy. In a Petri dish bioassay their phytotoxic potential was tested against six common weeds: Avena fatua, Apera spica-venti, Bromus secalinus, Amaranthus retroflexus, Chenopodium album and Centaurea cyanus. There were 5 doses of oil used and control (distilled water with 5% acetone): 0.2; 0.6; 1.2; 2.4; 7.2 g/L. After 6 days of growth the percentage of germinated seeds, their root and coleoptile length were measured. The experiment was repeated twice. The chemical composition of essential oils was assessed using GC/MS method. The statistical analysis was carried out using a non-linear regression (Ritz and Streibig, 2005). %
Avena fatua
Apera spica-venti
Bromus secalinus
Amaranthus retroflexus
Chenopodium album
Centaurea cyanus
mint
lavender
cumin
lemon balm
thyme
sage
chamomile
calamus
tansy
RESULTS
ESSENTIAL OIL (%)
MAIN CONSTITUENTS %
Cumin (2.15)
limonene
34.8
carvone
63.2
Lavender (2.85)
linalool
36.8
α-terpineol
5.6
linalyl acetate
36.0
lavandulyl acetate
1.6
Lemon balm (0.13)
citronellal
2.3
neral
28.2
geranial
40.2
Mint (2.55)
menthone
isomenthone
6.7
menthol
24.0
piperitone
1.5
menthyl acetate
7.7
piperitenone oxide
9.6
Chamomille (0.5)
(E)-β-farnesene
32.9
α-bisabolol oxide B
15.5
bisabolone oxide A
11.1
chamazulene
3.7
α-bisabolol oxide A
7.3
Sage (1.64)
1,8-cineole
10.3
α-thujone
27.6
β-thujone
12.8
camphor
viridiflorol
3.3
Caraway (2.1)
α-selinene
4.0
shyobunone (isomer)
5.7
δ-cadinene
4.2
(Z)-asarone
3.4
zierone
3.1
acorenone
5.5
Thyme (2.35)
p-cymene
7.2
γ-terpinene
4.5
thymol
72.9
carvacrol
Tansy (1.55)
sabinene
1.3
artemisia ketone
3.9
6.3
46.8
umbellulone
11.2
Table 1. Seedlings mean shoot (above) and root (below) length after 6 days of germination in the presence of the highest and the lowest dose of essential oil
Weed species
Control
Mint
lavender
Cumin
Lemon balm
Thyme
Sage
Chamomile
Caraway
Tansy
0.2
7.2
Apera spica-venti
16.2
10.8
0.3
8.5
6.7
2.6
4.9
5.0
Avena fatua
61.7
37.6
9.5
31.6
4.7
62.0
3.6
40.8
27.9
8.3
15.5
4.3
41.5
Bromus secalinus
23.9
2.5
14.6
4.8
10.0
5.6
3.0
5.8
4.0
11.5
0.9
Amaranthus retroflexus
27.7
16.4
3.5
3.7
2.3
5.9
7.8
Chenopodium album
29.0
3.8
21.7
15.1
15.8
5.2
7.6
8.7
19.4
Centaurea cyanus
38.7
9.0
12.8
13.8
5.4
6.5
4.6
1.1
CONCLUSIONS:
Essential oils substantially inhibited the germination and development of weed seedlings.
The most inhibiting effect displayed cumin and thyme oils.
The effect of oil depended on weed species, type of oil and its dose.
Wild oat (Avena fatua L.) was least susceptible to the most of oils except cumin and thyme oils.
Weed species
Control
Mint
Lavender
Cumin
Lemon balm
Thyme
Sage
Chamomile
Caraway
Tansy
0.2
7.2 0.
Apera spica-venti
16.2
8.6
8.4
5.4
2.9
6.6
3.2
Avena fatua
52.9
31.0
3.4
34.7
7.3
57.8
4.4
37.7
33.5
4.7
30.9
2.5
41.4
Bromus secalinus
44.8
2.6
21.3
11.3
15.3
3.7
3.0
11.7
4.9
18.6
0.8
13.4
Amaranthus retroflexus
7.9
22.9
7.5
4.0
10.9
16.8
10.74
Chenopodium album
28.1
16.0
15.1
6.3
1.5
8.5
12.6
14.7
Centaurea cyanus
39.9
16.5
19.4
14.2
7.7
13.2
5.8
6.1
0.6