Root-respired delta super(13)CO sub(2) can be useful for exploring plant carbon allocation and root respiratory fractionation as well as for partitioning soil-surface CO sub(2) emissions into plant ...root and soil organic matter (SOM) sources, a necessary measure for calculating the contribution of heterotrophic respiration of soil carbon to net ecosystem exchange. Root CO sub(2) is usually sampled from excised roots, however, excision alters respiration rate and isolates the root sample from aboveground plant processes. To improve the integrity of root efflux delta super(13)CO sub(2) measurements, we designed a chamber for sampling root-respired CO sub(2) in situ from minimally disturbed tree roots. We compared root delta super(13)CO sub(2) values from excised and attached roots in the field and we pruned mature Scots pine trees to induce a measureable change in root delta super(13)CO sub(2). Excised root samples containing root wounds gave more super(13)C-depleted measurements of root-respired delta super(13)CO sub(2) than intact roots by 1.8 ppt. Using chambers to sample CO sub(2) from attached roots, we measured a diurnal change in root-respired delta super(13)CO sub(2) of 3-4 ppt, triggered by pruning foliage from the trees. This chamber system permits high-frequency sampling of live root-respired delta super(13)CO sub(2) that enables greater insight into plant respiratory processes and more accurate partitioning of soil-surface CO sub(2) emissions.
Tree stems are an overlooked source of volatile organic compounds (VOCs). Their contribution to ecosystem processes and total VOC fluxes is not well studied, and assessing it requires better ...understanding of stem emission dynamics and their driving processes. To gain more mechanistic insight into stem emission patterns, we measured monoterpene, methanol and acetaldehyde emissions from the stems of mature Scots pines (Pinus sylvestris L.) in a boreal forest over three summers. We analysed the effects of temperature, soil water content, tree water status, transpiration and growth on the VOC emissions and used generalized linear models to test their relative importance in explaining the emissions. We show that Scots pine stems are considerable sources of monoterpenes, methanol and acetaldehyde, and their emissions are strongly regulated by temperature. However, even small changes in water availability affected the emission potentials: increased soil water content increased the monoterpene emissions within a day, whereas acetaldehyde and methanol emissions responded within 2–4 days. This lag corresponded to their transport time in the xylem sap from the roots to the stem. Moreover, the emissions of monoterpenes, methanol and acetaldehyde were influenced by the cambial growth rate of the stem with 6–10‐day lags.
Scots pine (Pinus sylvestris L.) stems are a considerable source of monoterpenes, methanol and acetaldehyde. Their emissions depend strongly on temperature, but the temperature‐normalized emissions are affected by relatively small changes in soil moisture and cambial growth of stem.
Drought stress severely impedes plant growth, and only a limited number of species exhibit long-term resistance to such conditions. Pinus sylvestris var. mongolica, a dominant tree species in arid ...and semi-arid regions of China, exhibits strong drought resistance and plays a crucial role in the local ecosystem. However, the molecular mechanisms underlying this resistance remain poorly understood.
Here, we conducted transcriptome sequence and physiological indicators analysis of needle samples during drought treatment and rehydration stages. De-novo assembly yielded approximately 114,152 unigenes with an N50 length of 1,363 bp. We identified 6,506 differentially expressed genes (DEGs), with the majority being concentrated in the heavy drought stage (4,529 DEGs). Functional annotation revealed enrichment of drought-related GO terms such as response to water (GO:0009415: enriched 108 genes) and response to water deprivation (GO:0009414: enriched 106 genes), as well as KEGG categories including MAPK signaling pathway (K04733: enriched 35 genes) and monoterpenoid biosynthesis (K21374: enriched 27 genes). Multiple transcription factor families and functional protein families were differentially expressed during drought treatment. Co-expression network analysis identified a potential drought regulatory network between cytochrome P450 genes (Unigene4122_c1_g1) and a core regulatory transcription factor Unigene9098_c3_g1 (PsNAC1) with highly significant expression differences. We validated PsNAC1 overexpression in Arabidopsis and demonstrated enhanced drought resistance.
These findings provide insight into the molecular basis of drought resistance in P. sylvestris var. mongolica and lay the foundation for further exploration of its regulatory network.
Varying the spectral composition of light is one of the ways to accelerate the growth of conifers under artificial conditions for the development of technologies and to obtain sustainable seedlings ...required to preserve the existing areas of forests. We studied the influence of light of different quality on the growth, gas exchange, fluorescence indices of Chl
, and expression of key light-dependent genes of
L. seedlings. It was shown that in plants growing under red light (RL), the biomass of needles and root system increased by more than two and three times, respectively, compared with those of the white fluorescent light (WFL) control. At the same time, the rates of photosynthesis and respiration in RL and blue light (BL) plants were lower than those of blue red light (BRL) plants, and the difference between the rates of photosynthesis and respiration, which characterizes the carbon balance, was maximum under RL. RL influenced the number of xylem cells, activated the expression of genes involved in the transduction of cytokinin (Histidine-containing phosphotransfer 1,
, Type-A Response Regulators,
) and auxin (Auxin-induced protein 1,
) signals, and reduced the expression of the gene encoding the transcription factor phytochrome-interacting factor 3
). It was suggested that RL-induced activation of key genes of cytokinin and auxin signaling might indicate a phytochrome-dependent change in cytokinins and auxins activity.
Climate change is predicted to increase atmospheric vapor pressure deficit, exacerbating soil drought, and thus enhancing tree evaporative demand and mortality. Yet, few studies have addressed the ...longer-term drought acclimation strategy of trees, particularly the importance of morphological versus hydraulic plasticity. Using a long-term (20 years) irrigation experiment in a natural forest, we investigated the acclimation of Scots pine (Pinus sylvestris) morpho-anatomical traits (stomatal anatomy and crown density) and hydraulic traits (leaf water potential, vulnerability to cavitation (Ψ50), specific hydraulic conductivity (Ks), and tree water deficit) to prolonged changes in soil moisture. We found that low water availability reduced twig water potential and increased tree water deficit during the growing season. Still, the trees showed limited adjustments in most branch-level hydraulic traits (Ψ50 and Ks) and needle anatomy. In contrast, trees acclimated to prolonged irrigation by increasing their crown density and hence the canopy water demand. This study demonstrates that despite substantial canopy adjustments, P. sylvestris may be vulnerable to extreme droughts because of limited adjustment potential in its hydraulic system. While sparser canopies reduce water demand, such shifts take decades to occur under chronic water deficits and might not mitigate short-term extreme drought events.
Aimed: The main aim of this study is to improve the mechanistic understanding of soil CO sub(2) efflux (F sub(s)), especially its temporal variation at short-time scales, by investigating, through ...modeling, which underlying process among CO sub(2) production and its transport up to the atmosphere is responsible for observed intra-day variation of F sub(s) and soil CO sub(2) concentration CO sub(2). Methods: In this study, a measurement campaign of F sub(s) and vertical soil CO sub(2) profiles was conducted in a Scots Pine Forest soil in Hartheim (Germany) and used to develop a model testing several hypotheses. A reference model taking into account a purely diffusive CO sub(2) transport and a temperature-dependent CO sub(2) production is compared to models with a more complex description of either CO sub(2) production or CO sub(2) transport. For transport, the introduction of advection and the dispersion is investigated. For the production, the emergent hypothesis of the phloem pressure concentration wave (PPCW) influence is tested. Results: We show that intra-day variation of F sub(s) and CO sub(2) is better represented when the more complex CO sub(2) production expression is taken into account compared to the more detailed description of CO sub(2) transport. Conclusion: We conclude that focus should be placed on the potential factors affecting the CO sub(2) production, rather than on the transport process description
Trichoderma spp. are proposed as major plant growth-promoting fungi that widely exist in the natural environment. These strains have the abilities of rapid growth and reproduction and efficient ...transformation of soil nutrients. Moreover, they can change the plant rhizosphere soil environment and promote plant growth. Pinus sylvestris var. mongolica has the characteristics of strong drought resistance and fast growth and plays an important role in ecological construction and environmental restoration. The effects on the growth of annual seedlings, root structure, rhizosphere soil nutrients, enzyme activity, and fungal community structure of P. sylvestris var. mongolica were studied after inoculation with Trichoderma harzianum E15 and Trichoderma virens ZT05, separately. The results showed that after inoculation with T. harzianum E15 and T. virens ZT05, seedling biomass, root structure index, soil nutrients, and soil enzyme activity were significantly increased compared with the control (p < 0.05). There were significant differences in the effects of T. harzianum E15 and T. virens ZT05 inoculation on the growth and rhizosphere soil nutrient of P. sylvestris var. mongolica (p < 0.05). For the E15 treatment, the seedling height, ground diameter, and total biomass of seedlings were higher than that those of the ZT05 treatment, and the rhizosphere soil nutrient content and enzyme activity of the ZT05 treatment were higher than that of the E15 treatment. The results of alpha and beta diversity analyses showed that the fungi community structure of rhizosphere soil was significantly different (p < 0.05) among the three treatments (inoculated with T. harzianum E15, T. virens ZT05, and not inoculated with Trichoderma). Overall, Trichoderma inoculation was correlated with the change of rhizosphere soil nutrient content.
$\bullet$Our understanding of how saprotrophic and mycorrhizal fungi interact to recirculate carbon and nutrients from plant litter and soil organic matter is limited by poor understanding of their ...spatiotemporal dynamics.$\bullet$In order to investigate how different functional groups of fungi contribute to carbon and nitrogen cycling at different stages of decomposition, we studied changes in fungal community composition along vertical profiles through a Pinus sylvestris forest soil. We combined molecular identification methods with14C dating of the organic matter, analyses of carbon:nitrogen (C:N) ratios and15N natural abundance measurements.$\bullet$Saprotrophic fungi were primarily confined to relatively recently (< 4 yr) shed litter components on the surface of the forest floor, where organic carbon was mineralized while nitrogen was retained. Mycorrhizal fungi dominated in the underlying, more decomposed litter and humus, where they apparently mobilized N and made it available to their host plants.$\bullet$Our observations show that the degrading and nutrient-mobilizing components of the fungal community are spatially separated. This has important implications for biogeochemical studies of boreal forest ecosystems.
Drought-induced defoliation has recently been associated with the depletion of carbon reserves and increased mortality risk in Scots pine (Pinus sylvestris). We hypothesize that defoliated ...individuals are more sensitive to drought, implying that potentially higher gas exchange (per unit of leaf area) during wet periods may not compensate for their reduced photosynthetic area.
We measured sap flow, needle water potentials and whole-tree hydraulic conductance to analyse the drought responses of co-occurring defoliated and nondefoliated Scots pines in northeast Spain during typical (2010) and extreme (2011) drought conditions.
Defoliated Scots pines showed higher sap flow per unit leaf area during spring, but were more sensitive to summer drought, relative to nondefoliated pines. This pattern was associated with a steeper decline in soil-to-leaf hydraulic conductance with drought and an enhanced sensitivity of canopy conductance to soil water availability. Near-homeostasis in midday water potentials was observed across years and defoliation classes, with minimum values of −2.5 MPa. Enhanced sensitivity to drought and prolonged periods of near-zero gas exchange were consistent with low levels of carbohydrate reserves in defoliated trees.
Our results support the critical links between defoliation, water and carbon availability, and their key roles in determining tree survival and recovery under drought.
Rising temperatures and more frequent and severe climatic extremes as a consequence of climate change are expected to affect growth and distribution of tree species that are adapted to current local ...conditions. Species distribution models predict a considerable loss of habitats for Pinus sylvestris. These models do not consider possible intraspecific differences in response to drought and warming that could buffer those impacts. We tested 10 European provenances of P. sylvestris, from the southwestern to the central European part of the species distribution, for their response to warming and to drought using a factorial design. In this common-garden experiment the air surrounding plants was heated directly to prevent excessive soil heating, and drought manipulation, using a rain-out shelter, permitted almost natural radiation, including high light stress. Plant responses were assessed as changes in phenology, growth increment and biomass allocation. Seedlings of P. sylvestris revealed a plastic response to drought by increased taproot length and root-shoot ratios. Strongest phenotypic plasticity of root growth was found for southwestern provenances, indicating a specific drought adaptation at the cost of overall low growth of aboveground structures even under non-drought conditions. Warming had a minor effect on growth but advanced phenological development and had a contrasting effect on bud biomass and diameter increment, depending on water availability. The intraspecific variation of P. sylvestris provenances could buffer climate change impacts, although additional factors such as the adaptation to other climatic extremes have to be considered before assisted migration could become a management option.
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