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Test of potential allelopathic ability of Allium ursinum L.

Abstract

Diplomsko delo obravnava temo alelopatskega učinkovanja čemaža (Allium ursinum) na kalitev semena vrtne kreše (Lepidium sativum) in okuženost čemaža z ličinko muhe Cheilosia fasciata. Ker večina avtorjev upošteva možnost, da naj bi bil čemaž potencialno alelopatski, smo s pomočjo bioloških testov poskušali prikazati vsebnost potencialno alelopatskih snovi v čemažu. S pomočjo vzorčenja smo dokazali, da liste čemaža zajeda ličinka muhe Cheilosia fasciata. Zanimalo nas je, ali imajo okuženi listi z ličinko muhe Cheilosia fasciata drugačen (slabši/boljši) alelopatski učinek kot zdravi listi. Ker se čemaž dobro vegetativno razmnožuje in tvori goste sestoje v gozdni podrasti, smo med seboj primerjali lastnosti rastlin in okuženost sredi takega gostega sestoja ter rastline iz skrajnega roba sestoja. Ves čas pojavljanja listov (sedem tednov) smo opazovali sestoj čemaža, beležili število rastlin, pri čemer smo za vsako rastlino zabeležili število vseh listov, število zdravih listov, število okuženih listov z ličinko muhe Cheilosia fasciata in ocenili površino okuženega dela lista. Tako smo lahko spremljali razvoj rastlin in spreminjanje okuženosti od razvoja prvega lista do propada večine listov. Preverili smo tudi, ali so čebulice čemaža okužene z ličinkami muhe Portevinia maculata, česar nismo potrdili. Spremljevalne okoljske meritve so obsegale meritve svetlobe, najbolj spremenljiv dejavnik od centra sestoja proti robu, in meritve globine opada, ki je v korelaciji pojavljanja ličink muh. Za namene preverjanja potencialne alelopatske sposobnosti smo izvedli biološke teste kalitve semen vrtne kreše v petrijevkah (Lepidium test). Opazovali smo učinke vodotopnih ekstraktov različnih koncentracij in učinke ekstraktov iz vzorcev tal (v sestoju čemaža in izven njega) na kalitev semen vrtne kreše. Zanimala sta nas kalivost ter razvoj kalice in njene korenine v primerjavi s kontrolnimi poskusi. Iz dobljenih rezultatov lahko spremljamo populacijske parametre v sestoju čemaža in hkrati tudi dinamiko listov od razvoja do propada. Razberemo lahko, da je število rastlin na vzorčno ploskev sčasoma naraščalo, naraščala sta tudi njihovo število listov in delež okuženih listov ter da se je večala površina okuženega dela lista. V gozdu je bilo več rastlin kot na njegovem robu. Rastline v podrasti so imele več listov, pri tem več okuženih listov, in površina okuženega dela lista je bila večja kot na gozdnem robu. S svetlobo ni bilo statistično značilnih korelacij s številom rastlin, številom vseh listov, številom okuženih listov, številom zdravih listov in s površino okuženega dela. Površina okuženega dela lista je naraščala z globino opada. Naši rezultati kažejo, da lahko predvidevamo, da je čemaž alelopatski. Vodni ekstrakti iz zdravih in okuženih listov čemaža so namreč zavirali in upočasnili kalitev semen vrtne kreše. Ekstrakti višjih koncentracij so imeli močnejši zaviralni učinek. Na sam razvoj kalic, ki so kalile v vodnih ekstraktih iz okuženih in zdravih listov čemaža, nismo zaznali statistično značilnega učinka. Prav tako se kalice, ki so rastle v različnih vzorcih tal, med seboj niso statistično razlikovale v svoji celotni dolžini, kot tudi ne v dolžini korenin.The thesis deals with the topic of allelopathic effect of wild garlic (Allium ursinum L.) on germination of garden cress seeds (Lepidium sativum) and with infestation of wild garlic leaves with the fly Cheilosia fasciata larvae. Since most of the authors claim that the wild garlic is potentially alleopathic, we used bioassays to test presence of such substances. With sampling we demonstrated that wild garlic is being infected by larvae of flies Cheilosia fasciata in the field. The main objective of the thesis was to test whether infected leaves had weaker potential allelopathic effect than healthy leaves. Because wild garlic exhibits strong vegetative reproduction and often forms dense stands in the forest understorey, we compared characteristic of plants growing in a dense stand with plants from the margin of the stand, usually located at the forest edge. The whole period (seven weeks) when leaves were present in the field we performed observations of the wild garlic stand. We recorded the number of plants, where we counted the total number of leaves, number of healthy and infected leaves by Cheilosia fasciata larvae and estimated the area of the leaf occupied by the feeding tunnel of larvae. In such manner we recorded the development of plants and changes in infestation from the first developed leaf to the end of the majority of leaves. Additionally, we checked if bulbs are infested with Portevinia maculata larvae, which we did not confirm. Additional environmental measurements included measurements of light conditions, the most variable factor from the center towards the edge of the wild garlic stand, and measurements of the depth of litter, to which the occurrence of larvae is related. To test whether wild garlic exhibits allelopathic potential we used bioassays with germinating Lepidium sativum seeds (Lepidium test). We observed the effects of watersoluble extracts (various concentrations) and the effects of extracts from soil samples (within and outside a dense stand) on the germination of garden cress seeds. We were interested in the germination rate and seedling development (total seedling length and root length) in regard of the control conditions. From the obtained results we can monitor population parameters within the wild garlic stand and at the same time we can follow the leaf dynamics from the early development to their end. Our results show that the number of plants per surface increased with time, as did the number of leaves, ratio of infected leaves, and the leaf area occupied by the feeding tunnel. We did not found any statistically significant correlations with light conditions and number of plants and leaves per plot, number of infected leaves, number of healthy leaves or with area of the feeding tunnel. On the other hand, he latter significantly increased with litter depth. Furthermore, our results show that we can assume that aqueous extracts from healthy and infected wild garlic leaves are potentially allelopathic. Extracts with higher concentrations had a stronger inhibitory effect. Seedling development of seeds, which germinated in the presence of water extracts from healthy or infected wild garlic leaves, was not statistically significantly different. Seedlings as well, which were growing in various soil samples, were not statistically different in the seedling length nor in the root length

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