Biology subjects

Fonti, P.

Publications and source records attributed to Fonti, P..

3 recordsLinked to original sources

bioRxiv2025

Genetic and plastic effects on trait variability in two major tree species: insights from common garden experiments across Europe

Phenotypic plasticity and genetic adaptation are key mechanisms that enable species to respond to changing environments. Tree traits do not vary independently but rather in coordination. However, our understanding of whether functional traits are governed by the same mechanism is far from complete. Thus, we aim at assessing the drivers of trait variability of sessile oak and European beech provenances across their distribution ranges. We estimated growth-related and leaf morphological traits from 9 and 11 provenances of oak and beech, respectively, grown in four different common gardens distributed across their respective distribution areas. Overall, phenotypic plasticity played a dominant role in explaining individual trait variability. For most oak traits, variation among provenances and genetically based plasticity were correlated with the climate of origin, whereas fewer significant associations were found for beech. In oak, climate-transfer distance analyses revealed that traits such as DBH, height, specific leaf area, and long-term growth responses to summer temperature decreased when provenances were moved away from their local precipitation regime. In beech, significant climate-transfer distances were fewer and primarily related to temperature-related parameters. These results suggest that natural selection and local adaptation may play a secondary but notable role. The pattern of multi-trait phenotypes indicates that resource-use strategies among provenances covary with the temperatures of origin in both species. The limited genetic responses in beech could hinder its survival if it reaches the boundaries of trait plasticity, while oak may better adjust through adaptation. Our study contributes to a better understanding of the interplay between genetic adaptation and phenotypic plasticity in long-lived forest trees.

ecology↗

bioRxiv2024

Implications of carbon source-sink feedbacks for plant growth responses to environmental factors

Current global models of vegetation dynamics are largely carbon (C) source-driven, with behaviour primarily determined by the environmental responses of photosynthesis. However, real plants operate as integrated wholes, with feedbacks between sources, such as photosynthesis, and sinks, such as growth, resulting in homeostatic concentrations of metabolites such as sugars. A parsimonious approach to implementing this homeostatic coupling of C sources and sinks in a tree growth model is presented, and its implications for the responses of net photosynthesis and growth to environmental factors and tree size assessed. Hill functions describe inhibition of C sources (net photosynthesis) and activation of sinks (structural growth) as sucrose concentration increases. The model is parameterised for a typical tree growing at a site in the Amazonian rainforest and its qualitative behaviour is found to be consistent with observations. A key outcome is that sinks and sources strongly regulate each other. Hence environmental factors that affect potential net photosynthesis, such as atmospheric CO2, have greatly reduced effects on growth when homeostatic feedbacks from sucrose concentrations are considered. For example, compared with a C-source-only-driven approach (as in most current global models), the response of tree biomass for a tree currently 300 yr old, to increasing atmospheric CO2 projected to the end of this century under a high scenario, is reduced by ca.77%, from +122% to +29%, with net photosynthesis and growth rate responses reduced by a similar amount. Furthermore, in this coupled approach, any direct controls on growth (either environmental or through phenological controls on xylogensis) will influence source activity through the sucrose feedback. For example, a reduction in potential growth through temperature constraints on cell-wall construction increases sucrose concentrations, resulting in a compensating reduction in net photosynthesis. While net photosynthesis controls growth, growth controls net photosynthesis. In addition, we find a strong effect of changing tree allometry on C source-sink relations as the tree grows. Larger trees are less source-limited due to a higher ratio of sapwood area (and hence potential C assimilation rate) to potential growth rate, consistent with the observed decline in growth response to atmospheric CO2 as trees age. We suggest that the implications of including C source-sink coupling in models of vegetation dynamics, such as dynamic global vegetation models, are likely to be profound.

plant biology↗

bioRxiv2020

Wood formation in an evergreen conifer is controlled by phloem transport of labile carbon, but nonstructural carbon concentrations are not

Wood formation is a crucial process for carbon sequestration, yet how variations in carbon supply affect wood formation and carbon dynamics in trees more generally remains poorly understood. To better understand the role of carbon supply in wood formation, we restricted phloem transport using girdling and compression around the stem of mature white pines and monitored the effects on local wood formation and stem CO2 efflux, as well as nonstructural carbon concentrations in needles, stems, and roots. Growth and stem CO2 efflux varied with location relative to treatment (i.e., above or below on the stem). We observed up to a two-fold difference in the number of tracheids formed above versus below the manipulations over the remaining growing season. In contrast, the treatments did not affect mean cell size noticeably and mean cell-wall area decreased only slightly below them. Surprisingly, nonstructural carbon pools and concentrations in the xylem, needles, and roots remained largely unchanged, although starch reserves declined and increased marginally below and above the girdle, respectively. Our results suggest that phloem transport strongly affects cell proliferation and respiration in the cambial zone of mature white pine, but has little impact on nonstructural carbon concentrations. These findings contribute to our understanding of how wood formation is controlled. HighlightRestrictions in phloem transport designed to affect carbon supply, lead to changes in wood formation and stem respiration of mature white pines without substantially changing local nonstructural carbon concentrations.

plant biology↗