Sirvi Autor "Torsus, Mari" järgi

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Phenotypic plasticity masks evolutionary change in grasslandplant traits in response to land use abandonment
(2026-01) Tõnisson, Anastasia; Eck, Jenalle; Jing, Yuying; Kängsep, Piia; Laaspere, Lauri; Wu, Jianlu; Puura, Laura; Torsus, Mari; Koorem, Kadri; Moora, Mari; Sepp, Siim-Kaarel; Davison, John; Semchenko, Marina
Traditionally managed grasslands are among the most biodiverse habitats in Europe, but are threatened by land use abandonment. While the negative impacts of grazing and mowing cessation on species richness are well documented, little is known about potential evolutionary changes within species. Yet, intraspecific functional diversity is critical for successful grassland restoration and ensuring adaptive potential to future climate change. To disentangle the heritable and non-heritable components of population-level response to land use change in semi-natural grasslands, we examined 22 populations of a common grass, Briza media, from grazed sites and sites where grazing was abandoned, with resulting tree and shrub encroachment. We measured a range of traits under field conditions and following clonal propagation under common garden conditions. Field surveys revealed that abandonment resulted in litter accumulation, greater shading by woody and herbaceous vegetation, and lower temperature and moisture fluctuations compared with grazed sites. Plants responded to conditions at abandoned sites with phenotypic plasticity in traits that enhanced competitive ability for light (greater height and specific leaf area) but reduced tissue protection against stress (lower dry matter content). However, when the same genotypes were measured after clonal propagation in common conditions, counter-gradient variation was apparent, with heritable shifts towards increased tissue protection in populations from abandoned sites. When measured under field conditions, trait diversity was higher in sites with higher levels of shading and productive sites with higher variation in light conditions. However, high heritable trait diversity was instead characteristic of grazed sites with high densities of flowering B. media individuals. Synthesis. These findings demonstrate that land use change can cause evolutionary shifts and changes in heritable trait diversity that are masked in the field by phenotypic plasticity. Hence, the assessment of functional trait variation based on field observations is not a reliable way to assess the genetic variation essential for population adaptive potential.
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Taimede kasvustrateegiliste omaduste mõju juureeritiste kogusele genotüübi tasandil
(Tartu Ülikool, 2024) Torsus, Mari; Semtšenko, Marina, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond; Tartu Ülikool. Botaanika osakond
Käesoleva töö eesmärgiks on uurida liigisiseseid seoseid juureeritiste koguse ja kasvustrateegiliste tunnuste vahel. Töö kirjanduslikus pooles antakse ülevaade juureeritiste olemusest ja peamistest funktsioonidest. Lisaks iseloomustatakse kiire ja aeglase kasvustrateegiaga taimi ning neile omaseid tunnuseid. Uurimuslikus osas kirjeldatakse töö käigus läbi viidud katset, mis uuris kahe kõrrelise liigi (Briza media ja Holcus lanatus) juureeritiste kogust iseloomustavate tunnuste varieeruvust sõltuvalt teistest taimetunnustest. Saadud tulemuste põhjal püütakse paigutada juureeritiste kogus taimede kasvustrateegia teljestikule. Linking root exudates to plant economics spectrum at the genotypic level The aim of this thesis is to study intraspecific relations between traits describing root exudate quantity and traits related to plant economics spectrum. The literature review of the thesis gives an overview of the essence of root exudates and their main functions. In addition, plant economic strategies and their relation to root exudates are characterized. The research part describes the experiment carried out within the thesis, which investigated the variability of root exudate quantity characteristics of two grass species (Briza media and Holcus lanatus) depending on the plant economic strategy. Based on the obtained results, it is aimed to place the quantity of root exudates on the axis of plant growth strategy.