Methods for studying plant-fungal interactions – reflecting on the old, the new and the upcoming
Date
2024-01-08
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Abstract
Muld kubiseb inimeluks vajalikest organismidest, mille uurimist takistab nende väiksus ja ligipääsmatus. Paljud bakterid, seened ja pisiloomad elavad koos taimejuurtega mullas. Nende organismide hulgas on eriti olulised juursümbiontsed seened. Meedias populaarseks saanud puudevahelise suhtlusvõrgustiku (i.k. wood-wide-web) kontseptsioon viitab sellele, et metsad on omavahel seotud mullaseente kaudu, mis võimaldavad puudel omavahel suhelda. Teaduslik kriitika seab aga selle võrgustiku leviku ja olulisuse kahtluse alla.
Väidetakse, et varem kasutatud meetodid ei suuda tõestada et puudevahelise suhtlusvõrgustiku olemasolu. Käesolevas doktoritöös käsitleti uue meetodi - fluorestseeruvate nanoosakeste - kasutamist. Selleks hinnati erinevate bioloogiliste ja keskkonnauuringute tulemused. Laboratoorsed katsed näitasid, et nende osakeste rakendamine keeruliste looduslike süsteemide, nagu näiteks puudevaheline võrgustik, uurimisel on praegu väga keeruline. Nanoosakeste, seente ja mullaosakeste vastasmõju kohta on siiani väga vähe teada. Kuigi süsinikupõhised osakesed olid lihtsas neeldumiskatses paljulubavad, on varasemad meetodid praegu puudevahelise võrgustik ja seeneniidistiku uurimiseks sobivamad.
Doktoritöö sisaldab ka eksperimentaalset uuringut, milles kasutati molekulaarseid meetodeid seente määramiseks mullast. Tuvastati, kuidas taimeindiviidide vahelised geneetilised erinevused mõjutavad juurtes elavate seente elurikkust ja suhtelist arvukust, paljastades indiviidide erinevusi nende võimes olla mükoriissetele juureseentele peremeestaimeks. Eri laiuskraadidelt pärit populatsioonide vahel nendes võimetes erinevusi ei olnud. Need tulemused näitavad, kuidas mullas elavad seened võivad avaldada mõju puude konkurentsivõimele ja seega tuleks arvesse võtta geneetilisi tegureid ka puude võrgustiku uuringutes. Doktoritöö panustab puudevahelise võrgustiku arutellu, rõhutades metodoloogilisi kaalutlusi.
Soils are filled with organisms crucial for life. However, their study is hindered by their size and inaccessibility. Plants roots connect to the soil environment and many bacteria, fungi and small animals live in close connection with them. Among these organisms, root symbiotic fungi are particularly important. The "wood-wide-web" concept, popularized in media, suggests that forests are interconnected through fungi that enable talking among trees. However, scientific critique questions their spread and significance. It has been argued that previously used methods cannot prove that the wood-wide-web exists. Thus, the utilization of a new method, so-called fluorescent nanoparticles, was explored in this thesis. Results from previous studies in different biological and environmental studies were reviewed. Practical experimentation revealed that the application of these particles in the study of complex natural systems like the wood-wide-web is at present very difficult. Many things about the interactions between the particles and fungi and soil are unknown. While carbon-based particles showed some promise in a simple uptake experiment, previous methods are currently more suitable for the study fungal networks. The thesis also includes an experimental study utilizing more traditional DNA metabarcoding. This study examined how genetic differences between plant individuals affect the diversity and abundance of fungi living in the roots, revealing that individuals have differences in their ability to host root fungi. There were no differences in these abilities between populations from different latitudes. These results could have implications for tree competitiveness, and genetic factors should thus be considered in studies of the wood-wide-web as well. This thesis contributes to the discourse on the wood-wide-web, emphasizing methodological considerations.
Soils are filled with organisms crucial for life. However, their study is hindered by their size and inaccessibility. Plants roots connect to the soil environment and many bacteria, fungi and small animals live in close connection with them. Among these organisms, root symbiotic fungi are particularly important. The "wood-wide-web" concept, popularized in media, suggests that forests are interconnected through fungi that enable talking among trees. However, scientific critique questions their spread and significance. It has been argued that previously used methods cannot prove that the wood-wide-web exists. Thus, the utilization of a new method, so-called fluorescent nanoparticles, was explored in this thesis. Results from previous studies in different biological and environmental studies were reviewed. Practical experimentation revealed that the application of these particles in the study of complex natural systems like the wood-wide-web is at present very difficult. Many things about the interactions between the particles and fungi and soil are unknown. While carbon-based particles showed some promise in a simple uptake experiment, previous methods are currently more suitable for the study fungal networks. The thesis also includes an experimental study utilizing more traditional DNA metabarcoding. This study examined how genetic differences between plant individuals affect the diversity and abundance of fungi living in the roots, revealing that individuals have differences in their ability to host root fungi. There were no differences in these abilities between populations from different latitudes. These results could have implications for tree competitiveness, and genetic factors should thus be considered in studies of the wood-wide-web as well. This thesis contributes to the discourse on the wood-wide-web, emphasizing methodological considerations.
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Keywords
mükoriisa, sümbioos, mullaökoloogia, fluorestsentsanalüüs, uurimismeetodid, mycorrhiza, symbiosis, soil ecology, fluorescence analysis, research methods