Alelopatija je pojam koji opisuje biokemijske reakcije između biljaka uslijed lučenja
alelokemikalija. Mnoge invazivne biljne vrste imaju visok alelopatski potencijal. Invazivna
alohtona vrsta pajasen (Ailanthus altissima (Mill.) Swingle) je jedna od najčešće
istraživanih vrsta radi izolacije i pronalaženja alelokemikalija s herbicidnim učinkom.
Cilj ove disertacije je odrediti alelopatski učinak vodene otopine korijena pajasena i iste
količine izoliranog ailantona na klijavost i početni rast i razvoj dvije korovne vrste,
oštrodlakavog šćira (Amaranthus retroflexus L.) i muhara (Setaria pumila (Poir.) Schult.)
te kultiviranu vrstu kukuruz (Zea mays L.). Vodena otopina korijena pajasena pripremljena
je od mladih izbojaka. Identifikacija i kvantifikacija ailantona iz vodene otopine korijena
pajasena određena je tekućinskom kromatografijom kojom je određena koncentracija
ailantona od 0,48 mg/ml. Potom je diklormetanom izoliran ailanton iz vodene otopine
korijena pajasena. Od pripremljenih vodenih otopina izoliranog ailantona i korijena
pajasena pripremljena je koncentrirana otopina i pet razrjeđenja destiliranom vodom u
omjeru 3/2; 1/2; 1/4; 1/8 i 1/16 koja su ekvivalent određenoj koncentraciji ailantona u
vodenoj otopini korijena pajasena, koncentrat s 0,48 mg/ml ailantona i pet razrjeđenja s
0,32; 0,24; 0,12; 0,06 i 0,03 mg/ml ailantona. Pripremljena razrjeđenja vodene otopine
izoliranog ailantona i vodene otopine korijena primijenjena su na sjeme (pre-em) i na list
(post-em) kad su test-biljne vrste muhar i kukuruz bile u stadiju rasta 3 lista (BBCH 13), a
oštrodlakavi šćir u stadiju rasta 2 - 4 lista (BBCH 12-14).
Dokazano je da se istraživane test-biljne vrste razlikuju u osjetljivosti prema vodenoj
otopini izoliranog ailantona i vodenoj otopini korijena pajasena. Primjenom vodenih
ekstrakata na sjeme muhara dokazan je inhibirajući alelopatski učinak na sva istraživana
svojstva (klijavost, duljina korijena klice i duljina izdanka klice), a najznačajnija povezanost
između alelopatskog učinka i istraživanih koncentracija ailantona dokazana je kod
klijavosti kad su test- biljne vrste tretirane s vodenom otopinom korijena pajasena. Obje
istraživane vodene otopine su inhibirale duljinu korijena i izdanka klice oštrodlakavog
šćira. Najznačajnija povezanost alelopatskog učinka i koncentracija ailantona kod
oštrodlakavog šćira dokazana je za klijavost kad je tretiranje obavljeno s vodenom
otopinom korijena pajasena. Za razliku od korovnih vrsta, kod kukuruza je dokazano
inhibitorno djelovanje samo na duljinu korijena klice uz statistički značajnu povezanost
istraživanih koncentracija i alelopatskog učinka kad je tretiranje obavljeno s obje vodene
otopine. Nasuprot inhibiciji, kod kukuruza je utvrđena i stimulacija kod djelovanja na
duljinu izdanka klice kad je tretiranje obavljeno s vodenom otopinom korijena pajasena.
Primjenom na list, obje istraživane vodene otopine izoliranog ailantona i korijena pajasena
iskazale su inhibirajuće djelovanje na sve tri istraživane test-biljne vrste. Jedino je
koncentracija od 0,48 mg/ml ailantona iz vodene otopine izoliranog ailantona povećala
masu nadzemnog dijela kukuruza, ali povećanje nije bilo statistički značajno. Statistički
najznačajnija povezanost intenziteta alelopatskog učinka i istraživanih koncentracija
ailantona dokazana je kod oštrodlakavog šćira kad je tretiranje obavljeno s obje vodene
otopine. Kod muhara nije dokazana statistički značajna razlika u povezanosti između
alelopatskog učinka i istraživanih koncentracija ailantona iz obje vodene otopine.
Nasuprot tome, kod kukuruza je statistički značajna povezanost alelopatskog učinka i
koncentracija ailantona dokazana samo kad je tretiranje obavljeno s vodenom otopinom
izoliranog ailantona.
Kod muhara i oštrodlakavog šćira vodena otopina korijena pajasena primijenjena na
sjeme iskazala je jače djelovanje u usporedbi s vodenom otopinom izoliranog ailantona
kod svih istraživanih svojstava kod kojih je određena statistički značajna razlika. Nasuprot
tome, kod kukuruza je u istom roku primjene, statistički značajnije djelovanje kod svih
istraživanih svojstava dokazano kad je tretiranje obavljeno s vodenom otopinom izoliranog
ailantona. Primjenom na list vodena otopina korijena pajasena iskazala je jače djelovanje
na nadzemnu masu oštrodlakavog šćira i kukuruza, a vodena otopina izoliranog ailantona
na muhara. Vodena otopina korijena pajasena iskazala je jače djelovanje u usporedbi s
vodenom otopinom izoliranog ailantona kod većine istraživanih svojstava što upućuje na
to da ailanton nije jedina alelokemikalija u korijenu pajasena.
Iz određenih EC50 vrijednosti dokazano je da je oštrodlakavi šćir najosjetljivija, a kukuruz
najtolerantnija test-biljna vrsta.The overuse of synthetic herbicides for weed control over the last five decades has
resulted in growing public concern over their impacts upon human health, the
environment, and the evolution of herbicide resistant weeds. Natural compounds from
plants offer excellent potential for new herbicidal solutions, or lead compounds for new
herbicides. Allelopathy is the common name for biochemical reaction between plants as a
result of allelochemical secretion. Many invasive plant species have high allelopathic
potential. Invasive alien species tree of heaven (Ailanthus altissima (Mill.) Swingle) is one
of the most frequently investigated species for the purpose of isolating and finding
allelochemicals with herbicidal effect.
The aim of this dissertation was to determine the allelopathic effect of the aqueous
solution of tree of heaven‘s root and the same amount of isolated ailanthone on
germination and the initial growth and development of two weed species, pigweed
(Amaranthus retroflexus L.) and yellow foxtail (Setaria pumila (Poir.) Schult.), and
cultivated plant species maize (Zea mays L.).
The young shouts with roots of tree of heaven were collected before flowering in late
spring – early summer. Freshly collected roots were cut into small pieces (size 0.5-1 cm)
and grained. In one litter of distilled water 250 g of grained plant material was soaked into
at room temperature for 24 hours. After 24 hours, plant material was removed and
extracts were filtered through filter paper (wrinkled 21/N, Munktel & Filtrak). Identification
and quantification of ailanthone from root aqueous solution was made on HPLC.
Confirmation of identity and quantification of ailanthone from the solution was determined
by linear regression based on the calibration curve of the standard solution of the
ailanthone (purity > 98 %). In tree of heaven’s root aqueous solution the concentration of
0.48 mg/ml of ailanthone was determined. After identification and quantification, isolation
of ailanthone from one half of the root aqueous solution was performed with
dichloromethane. The extraction of ailanthone was carried out three times in the
separating funnel and the sample was further purified with sodium sulphate. The sample
was then evaporated in rotary evaporator at 50 °C to a dry residue. Six dilutions of the
root aqueous solution (1; 3/2; 1/2; 1/4; 1/8 and 1/16) and six dilutions of the ailanthone
aqueous solution which were equivalent to the determinate concentration (0.48; 0.32;
0.24; 0.12; 0.06 and 0.03 mg/ml of ailanthone) were prepared. Experiments were carried
out in the Weed Science laboratory at the Croatian agriculture and food agency - Centre
for plant protection.
The first part of the research that relates to the pre-emergence effect of the aqueous
solutions on the test species was carried out in Petri dishes. In each sterilized Petri dish,
25 seeds of yellow foxtail, pigweed and maize were placed on two filter paper layers in
four replicates. Before placing seeds, 4 ml of aqueous solution for yellow foxtail and
pigweed, and 8 ml of aqueous solution for maize were added per Petri dish. For the
control treatment, distilled water was used. Petri dishes were placed in darkness at 25 -
27 °C and relative humidity 70 % in a climate chamber. Percentage of germination, radicle
length and shoot length were determined for each variant. All investigated attributes were
determined at the same time for each test-species. Pigweed germination, radicle length
and shoot length were measured 5 days after sowing, yellow foxtail was measured 7 days
after sowing and maize was measured 6 days after sowing. It has been found that the test
plants of studied species differ in the sensitivity to the aqueous solution of isolated
ailanthone and the aqueous solution of the tree of heaven’s root. By applying aqueous
solutions to the seeds of yellow foxtail, inhibitory allelopathic effects for all the investigated
attributes (germination, radicle length and shoot length) were determined. The most
significant correlation between the allelopathic effect on yellow foxtail and the investigated
concentrations of ailanthone were determined for the germination in the treatment with the
root aqueous solution. The both investigated aqueous solutions also inhibited the radicle
length and shoot length. The most significant correlation between the allelopathic effect
and the investigated concentrations of ailanton was also determined for germination in the
treatment with the root aqueous solution. Unlike weed species, the effect of the
investigated aqueous solutions inhibited only the radicle length of maize with a significant
correlation between the investigated ailanthone concentrations in the treatments with both
aqueous solutions. In contrast to the inhibition, in the case of corn, stimulation was found
in the effect for the shoot length in the treatment with aqueous root solution. The second
part of the research that relates to the post-emergence effect of the aqueous solutions on
test - species was carried out by breeding 10 plants of yellow foxtail, pigweed and maize
per repetition in containers. The containers were placed in a climate chamber. The
experiment was set up in three repetitions. The application of all investigated
concentrations of aqueous solutions and distilled water as control was made when the
test- species reached the development stage of two to four leaves (BBCH 12 - 14). The
allelopathic effect of the investigated solutions on the mass of the fresh plant mass of test
- species was determined 16 days after application. Both investigated aqueous solutions
of isolated ailanthone and tree of heaven’s roots showed inhibitory effect on all three
studied test - plant species. Only a concentration of 0,48 mg/ml of ailanthone from
aqueous solution of isolated ailanthone increased the above - ground mass of the corn,
but it was not statistically significant. The highest correlation between the allelopathic
effect and the investigated concentrations of ailanthone was found for the pigweed on
treatments with both aqueous solutions. The statistical significant correlation between the
effect and the investigated concentrations of ailanthone from both aqueous solutions was
not established for the yellow foxtail. In contrast, in maize, statistically significant
correlation was established only in the treatment with aqueous solution of isolated
ailanthone.
In the case of yellow foxtail and pigweed, in the pre-emergence application, the aqueous
solution of the tree of heaven’s root showed a stronger effect compared to the aqueous
solution of the isolated ailanthone for the all investigated attributes in which a statistically
significant difference was established. As for maize, in the same application period, the
aqueous solution of isolated ailanthone showed a stronger effect for all investigated
attributes compared to the aqueous solution of the tree of heaven’s root. In the postemergence
application, the aqueous solution of the root showed a stronger effect on the
above - ground mass of the pigweed and maize, and an aqueous solution of isolated
ailanthone on yellow foxtail. The aqueous solution of tree of heaven’s roots generally
showed a stronger effect compared to the aqueous solution of the isolated ailanthone for
the most investigated attributes, suggesting that the ailanthone is not the only
allelochemical in the root of tree of heavens, but was certainly the most potent one.
The most sensitive test-species was a pigweed, and the most tolerant maize
