Terrestrial Plant Growth Research Articles

WRKY Transcription Factors Modulate the Flavonoid Pathway of Rhododendron chrysanthum Pall. Under UV-B Stress.

The depletion of the ozone layer has resulted in elevated ultraviolet-B (UV-B) radiation levels, posing a significant risk to terrestrial plant growth. Rhododendron chrysanthum Pall. (R. chrysanthum), adapted to high-altitude and high-irradiation environments, has developed unique adaptive mechanisms. This study exposed R. chrysanthum to UV-B radiation for two days, with an 8 h daily treatment, utilizing metabolomic and transcriptomic analyses to explore the role of WRKY transcription factors in the plant's UV-B stress response and their regulation of flavonoid synthesis. UV-B stress resulted in a significant decrease in rETR and Ik and a significant increase in 1-qP. These chlorophyll fluorescence parameters indicate that UV-B stress impaired photosynthesis in R. chrysanthum. Faced with the detrimental impact of UV-B radiation, R. chrysanthum is capable of mitigating its effects by modulating its flavonoid biosynthetic pathways to adapt positively to the stress. This study revealed changes in the expression of 113 flavonoid-related metabolites and 42 associated genes, with WRKY transcription factors showing significant correlation with these alterations. WRKY transcription factors can influence the expression of key enzyme genes in the flavonoid metabolic pathway, thereby affecting metabolite production. A theoretical reference for investigating plant stress physiology is provided in this work, which also offers insights into the stress responses of alpine plants under adverse conditions.

Chemical determination of silica in seagrass leaves reveals two operational silica pools in Zostera marina

Silicon is a major driver of global primary productivity and CO2 sequestration, and is a beneficial element for the growth and environmental stress mitigation of many terrestrial and aquatic plants. However, only a few studies have examined the occurrence of silicon in seagrasses, and its function within seagrass ecosystems and the role of seagrasses in silicon cycling remain largely unexplored. This study uses for the first time two methods, the wet-alkaline digestion and the hydrofluoric acid digestion, to quantify silicon content in seagrass leaves using the species Zostera marina and elaborates on the potential role of silicon in seagrass biogeochemistry and ecology, as well as the role of seagrass ecosystems as a silicon reservoir. The results revealed that seagrass leaves contained 0.26% silicon:dry-weight, which is accumulated in two forms of silica: a labile form digested with the alkaline method and a resistant form digested only with acid digestion. These findings support chemical digestions for silicon quantification in seagrass leaves and provide new insights into the impact of seagrasses on the marine silicon cycle. Labile silica will be recycled upon leaf degradation, benefiting siliceous organisms, while refractory silica will contribute to the ecosystem’s buried silica stock and coupled carbon sequestration. In the Bay of Brest (France), the seagrass silicon reservoir was estimated at 0.18 ± 0.07 g Si m⁻2, similar to that of benthic diatoms, underscoring the potential role of seagrasses in silicon biogeochemistry in the land–ocean continuum, where they might act as a buffer for silicon transport to the ocean.

Metabolic and Transcriptional Analysis Reveals Flavonoid Involvement in the Drought Stress Response of Mulberry Leaves.

Abiotic stress, especially drought stress, poses a significant threat to terrestrial plant growth, development, and productivity. Although mulberry has great genetic diversity and extensive stress-tolerant traits in agroforestry systems, only a few reports offer preliminary insight into the biochemical responses of mulberry leaves under drought conditions. In this study, we performed a comparative metabolomic and transcriptomic analysis on the "drooping mulberry" (Morus alba var. pendula Dippel) under PEG-6000-simulated drought stress. Our research revealed that drought stress significantly enhanced flavonoid accumulation and upregulated the expression of phenylpropanoid biosynthetic genes. Furthermore, the activities of superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) content were elevated. In vitro enzyme assays and fermentation tests indicated the involvement of flavonol synthase/flavanone 3-hydroxylase (XM_010098126.2) and anthocyanidin 3-O-glucosyltransferase 5 (XM_010101521.2) in the biosynthesis of flavonol aglycones and glycosides, respectively. The recombinant MaF3GT5 protein was found to recognize kaempferol, quercetin, and UDP-glucose as substrates but not 3-/7-O-glucosylated flavonols and UDP-rhamnose. MaF3GT5 is capable of forming 3-O- and 7-O-monoglucoside, but not di-O-glucosides, from kaempferol. This implies its role as a flavonol 3, 7-O-glucosyltransferase. The findings from this study provided insights into the biosynthesis of flavonoids and could have substantial implications for the future diversified utilization of mulberry.

The synergy of microplastics with the heavy metal zinc has resulted in reducing the toxic effects of zinc on lentil (Lens culinaris) seed germination and seedling growth

There is growing recognition of the impact of the rising presence of microplastics (MPs) on terrestrial plant growth and, in general, the terrestrial ecosystem. Simultaneously, there is growing heavy metal accumulation in agricultural lands at an astonishing rate owing to the overwhelming use of chemical fertilizers, herbicides, and weedicides. Thus, there is a need to investigate the synergetic effect of MPs along with heavy metals on the inducing combined toxicity. This study investigates effects at smaller exposure periods of a few hours using a novel optical imaging technique, Biospeckle Coherence Tomography. Biospeckle Optical Coherence Tomography (bOCT) is a novel optical imaging technique that we successfully demonstrated earlier in visualizing the internal activity of plants. Previous studies of authors using the bOCT technique have demonstrated its potential in the independent application of polyethylene microplastic (PEMPs) as well as zinc within 6 h after their treatments. The strong inhibitory effect of 100 mg L−1, Zn, and PEMPs alone on the germination of Lens culinaris could be visualized with bOCT. The current study demonstrated that against expectation, combined effects of Zn toxicity were reduced when combined with MPs. This is suggested due to the significant reduction of Zn uptake by the seedlings through the interaction of Zn and MPs in an aqueous solution. Mass-spectrometry results also indicate a reduced intake of Zn. Our findings suggest that PEMPs could be able to reduce the over-availability of Zn, thus mitigating the Zn toxicity on lentils.

Insights into growth-affecting effect of nanomaterials: Using metabolomics and transcriptomics to reveal the molecular mechanisms of cucumber leaves upon exposure to polystyrene nanoplastics (PSNPs)

Polystyrene nanoplastics (PSNPs, <100nm), an artificial pollutant that is widespread in the environment, can be assimilated by plants to alter plant gene expression and its metabolic pathway; thus, interfering with physiological homeostasis and growth of plants. Recently, the biosafety and potential environmental risks of PSNPs have attracted enormous attention. However, the knowledge regarding the uptake and phytotoxicity of atmosphere PSNPs subsiding to plant leaves is still limited. Here, we separately applied 50 mg/L and 100 mg/L PSNPs on cucumber leaves to simulate the plant response to the atmosphere PSNPs. We found that the PSNPs can be accumulated on the surface of cucumber leaves and are also able to be uptake by cucumber leaf stomata. The repertoires of metabolomics and transcriptomics from cucumber leaves upon PSNPs treatment demonstrated that the deposition of PSNPs on leaves alters the biosynthesis of various metabolites and the expression of a variety of genes. The leaves exposure to low concentration (50 mg/L) of PSNPs impact the genes involved in carbohydrate metabolism and the biosynthesis of metabolites related to membrane stability maintenance, thereby, probably enhancing plant tolerance to the stress caused by PSNPs. Whereas, exposure to high concentration (100 mg/L) of PSNPs, both nitrogen and carbohydrate metabolism in cucumber leaves are affected, as well as that the photosynthetic capacity was decreased, leading to the threat to plant health. Combined omics technologies, our findings advance our understanding about how the PSNPs released to ecological environment influence the terrestrial plant growth and provide phytotoxic mechanism.

Experimental addition of marine-derived nutrients affects wildflower traits in a coastal meta-ecosystem.

Organismal movement can bring individuals, resources and novel interactions across ecosystem boundaries and into recipient habitats, thereby forming meta-ecosystems. For example, Pacific salmon ecosystems receive large marine-derived nitrogen subsidies during annual spawning events, which can have a wide range of effects on aquatic and terrestrial plant species and communities. In this study, we evaluate the effects of cross-ecosystem nutrient subsidies on terrestrial plant growth and reproduction. We conducted a large-scale field experiment with four treatments: (i) addition of a pink salmon (Oncorhynchus gorbuscha) carcass, (ii) addition of the drift seaweed rockweed (Fucus distichus), (iii) addition of both salmon + rockweed, and (iv) a control. We examined treatment effects on leaf nitrogen and fitness-associated floral traits in four common estuarine wildflower species. We found elevated leaf ∂15N in all plant species and all sampling years in treatments with salmon carcass additions but did not observe any differences in leaf per cent nitrogen. We also observed larger leaf area in two species, a context-dependent increase in floral display area in two species, and a limited increase in plant seed set in response to both salmon carcass treatments. In sum, our study suggests that marine nutrients can affect terrestrial plant growth and reproduction.

Effect of Microplastics on the Germination and Growth of Terrestrial Plants

Objectives : The human beings of our globe are heavily reliant on the use of plastic products on a daily basis. Microplastics (MPs) are tiny particles that are formed as a result of plastic degradation. MPs can be found in terrestrial environment, but previous studies focused on the effects of MPs on marine environment and there are less studies on the effects of MPs on terrestrial environment. In particular, there is still a relatively limited number of studies on the effects of MPs on terrestrial plants. Therefore, this review paper aims to examine previous studies on the effect of MPs on the germination and growth of terrestrial plants.Methods : This review summarized the previous findings on the effect of MPs on the germination and growth of terrestrial plants in order to identify the research gaps and trends on the effects of MPs on terrestrial plants.Results and Discussion : Previous studies on the effect of MPs on the germination and growth of terrestrial plants were reviewed and the observations were summarized to find the gaps in this field of research. Previous studies showed that MPs can change soil properties and these changes can be different depending on the shape and size of MPs. MPs can also release chemicals such as phthalates and heavy metals that might have toxic effects on terrestrial plants. Different forms, types, and sizes of MPs were used in previous studies to study the effects on seed germination and growth of different plants. Most studies reported that MPs have negative effects on seed germination and plant growth (e.g., biomass, chlorophyll contents). Smaller MPs tend to have more significant effects than larger MPs. The changes in the soil properties due to MPs can change microbial community structures and this, in turn, may affect the soil-plant interaction.Conclusion : This study summarizes what have been reported in the previous studies on the effect of MPs on seed germination and growth of terrestrial plants. MPs are likely to affect seed germination and plant growth negatively, and this will eventually lead to reduction in food production and food quality. Owing to the various types, forms, and sizes of MPs that could be present in the terrestrial environment as well as the chemicals that could be released from MPs, there is much to explore to better understand the effect of MPs on terrestrial plants and the underlying mechanisms of such effects.

PePYL4 enhances drought tolerance by modulating water-use efficiency and ROS scavenging in Populus.

Drought is one of the major limiting factors in the growth of terrestrial plants. Abscisic acid (ABA) and pyrabactin resistance 1/prabactin resistance-1 like/regulatory components of ABA receptors (PYR/PYL/RCARs) play a key role in response to drought stress. However, the underlying mechanisms of this control remain largely elusive in trees. In this study, PePYL4, a potential ortholog of the PYR/PYL/RCARs gene, was cloned from Populus euphratica. It was localized in the cytoplasm and nucleus, induced by ABA, osmotic and dehydration treatments. To study the potential biological functions of PePYL4, transgenic triploid white poplars (Populus tomentosa 'YiXianCiZhu B38') overexpressing PePYL4 were generated. PePYL4 overexpression significantly increased ABA sensitivity and reduced stomatal aperture. Compared with wild-type plants, transgenic plants had higher water-use efficiency (WUE) and lower transpiration. When exposed to drought stress, PePYL4 overexpression plants maintained higher photosynthetic activity and accumulated more biomass. Moreover, overexpression of PePYL4 improved antioxidant enzyme activity and ascorbate content to accelerate reactive oxygen species scavenging. Meanwhile, upregulation expression of the stress-related genes also contributed to improving the drought tolerance of transgenic plants. In conclusion, our data suggest that PePYL4 is a promising gene target for regulating WUE and drought tolerance in Populus.

Eco-corona reduces the phytotoxic effects of polystyrene nanoplastics in Allium cepa: Emphasizing the role of ROS

Nanoplastics are widespread in the environment, and their increased persistence is an indisputable and severe threat. The impacts of these nanoplastic particles on the soil system and terrestrial plant growth, as well as how the EPS secreted by soil microbes would influence their toxic effects remain largely unexplored. This study focuses on the toxic effects of polystyrene nanoplastics (PSNPs) of various surface charges (plain, aminated, and carboxylated) and concentrations (12.5, 25, and 50 mg/l) in Allium cepa and illustrates the effects of eco-corona formation in reducing the toxic impact. The endpoints evaluated included cytotoxicity, oxidative stress (total ROS, superoxide, hydroxyl radical generation and lipid peroxidation), and antioxidant enzyme activity (catalase and guaiacol peroxidase). Among the various surface charges, aminated PSNPs showed the highest toxicity for all the three concentrations tested. The results showed a concentration reliant increase in the levels of cell death, oxidative stress generation, and antioxidant enzyme activity for pristine PSNPs irrespective of their surface charges. Upon aging in the EPS medium a decrease in the toxic effects was noted for all the indicators. This could be a result of the agglomeration due to eco corona formation over the PSNPs in the EPS medium. The TEM images and MHD analysis for both pristine and the coronated PSNPs confirmed the agglomeration. • Cell physiology of onion roots treated with Polystyrene nanoplastics studied. • Eco-corona formation by soil EPS over the polystyrene nanoplastics. • Coronated Polystyrene nanoplastics tend to agglomerate reducing their cell uptake. • Reduced oxidative stress and toxic effects by coronated Polystyrene nanoplastics.

Photosynthesis, growth, and distribution of plants in lowland streams—A synthesis and new data analyses of 40 years research

Abstract This paper synthesises insights and offers new quantitative analyses of data gathered during 40 years of stream research by Danish researchers and international associates. Lowland Danish streams mostly drain fertile cropland and contain high nutrient concentrations saturating maximum yield and growth rate of plants. Concentrations of carbon dioxide (CO2) are variable, although usually high, supporting a range of wetland and permanently submerged species. All terrestrial and most amphibious species are obligate CO2 users, while the majority of permanently submerged species can supplement their inorganic carbon demand with bicarbonate. In lake outlets, the average CO2 concentration was close to air saturation during summer, whereas sites with no lake influence were 9‐fold supersaturated. The 20% increase of atmospheric CO2 concentrations over the past 40 years has marginal influence on CO2 concentrations in the streams. In lake outlets with low CO2 concentrations, calculations on 33 stream species showed essentially no underwater photosynthesis by temporarily submerged terrestrial species, low rates by amphibious species, and high rates by permanently submerged bicarbonate users. Underwater photosynthetic rates increased at sites with high CO2 concentrations (no lake influence): they were lowest for terrestrial wetland species (mean 1.8 mg O2 g dry weight−1 hr−1), followed by homophyllous (3.0) and heterophyllous amphibious species (5.6), and highest among permanently submerged species (15.0). Terrestrial and amphibious species grew very slowly when CO2 levels were low, but rapidly in CO2 rich water, or when in contact with air above the water's surface. Decreasing CO2 concentrations from upstream to downstream caused lower photosynthesis rates of amphibious species, while photosynthesis by bicarbonate users was consistently high. The relative abundance of terrestrial and amphibious species decreased significantly as CO2 resources decline from upstream to downstream, while the abundance of permanently submerged species increased as streams progressed. However, plant abundance as a function of CO2 concentrations did not differ markedly among the plant groups. We conclude that photosynthesis and growth of species of different plant types under controlled experimental conditions resembling high in situ nutrient availability are closely related to inorganic carbon supplies, while their representation in plant assemblages is influenced by the spatially and temporally highly diverse ecological conditions from upstream to downstream in the mostly CO2‐rich lowland streams. Submerged terrestrial and amphibious species restricted to CO2 use for photosynthesis can partly escape the slow gas diffusion under water by growing in very CO2‐rich streams and having apical leaves in contact with air. Thus, strong restrictions on their growth and existence should be identified at sites where CO2 concentrations are consistently low and no air contact is possible, while co‐limitation by nutrients is likely to be marginal. Generally, rising atmospheric CO2 is irrelevant to photosynthesis of permanently submerged plants because of their ability to use bicarbonate and the high CO2 supersaturation in most stream sites. In contrast, photosynthesis and growth of amphibious and terrestrial plants under water are highly dependent on CO2 concentrations varying from close to air saturation in lake outlets to supersaturation in headwaters.

Advances in the Regulation of Epidermal Cell Development by C2H2 Zinc Finger Proteins in Plants.

Plant epidermal cells, such as trichomes, root hairs, salt glands, and stomata, play pivotal roles in the growth, development, and environmental adaptation of terrestrial plants. Cell fate determination, differentiation, and the formation of epidermal structures represent basic developmental processes in multicellular organisms. Increasing evidence indicates that C2H2 zinc finger proteins play important roles in regulating the development of epidermal structures in plants and plant adaptation to unfavorable environments. Here, we systematically summarize the molecular mechanism underlying the roles of C2H2 zinc finger proteins in controlling epidermal cell formation in plants, with an emphasis on trichomes, root hairs, and salt glands and their roles in plant adaptation to environmental stress. In addition, we discuss the possible roles of homologous C2H2 zinc finger proteins in trichome development in non-halophytes and salt gland development in halophytes based on bioinformatic analysis. This review provides a foundation for further study of epidermal cell development and abiotic stress responses in plants.

A chemical window into the impact of RNAi silencing of the StNAC103 gene in potato tuber periderms: Soluble metabolites, suberized cell walls, and antibacterial defense

The growth and survival of terrestrial plants require control of their interactions with the environment, e.g., to defend against desiccation and microbial invasion. For major food crops, the protection conferred by the outer skins (periderm in potato) is essential to cultivation, storage, and marketing of the edible tubers and fruits. Potatoes are particularly vulnerable to bacterial infections due to their high content of water and susceptibility to mechanical wounding. Recently, both specific and conserved gene silencing (StNAC103-RNAi and StNAC103-RNAi-c, respectively) were found to increase the load of wax and aliphatic suberin depolymerization products in tuber periderm, implicating this NAC gene as a repressor of the wax and suberin biosynthetic pathways. However, an important gap in our understanding of StNAC103 silencing concerns the metabolites produced in periderm cells as antimicrobial defense agents and potential building blocks of the deposited suberin biopolymer. In the current work, we have expanded prior studies on StNAC103 silenced lines by conducting comprehensive parallel analyses to profile changes in chemical constituents and antibacterial activity. Compositional analysis of the intact suberized cell walls using solid-state 13C NMR (ssNMR) showed that NAC silencing produced an increase in the long-chain aliphatic groups deposited within the periderm cell walls. LC-MS of polar extracts revealed up-regulation of glycoalkaloids in both StNAC103-RNAi and StNAC103-RNAi-c native periderms but down-regulation of a phenolic amine in StNAC103-RNAi-c and a phenolic acid in StNAC103-RNAi native periderms. The nonpolar soluble metabolites identified using GC-MS included notably abundant long-chain alkane metabolites in both silenced samples. By coordinating the differentially accumulated soluble metabolites and the suberin depolymerization products with the ssNMR-based profiles for the periderm polymers, it was possible to obtain a holistic view of the chemical changes that result from StNAC103 gene silencing. Correspondingly, the chemical composition trends served as a backdrop to interpret trends in the chemical barrier defense function of native tuber periderms, which was found to be more robust for the nonpolar extracts.

Impacts of low pH and low salinity induced by acid rain on the photosynthetic activity of green tidal alga Ulva prolifera

Acid rain is a serious environmental problem and has obvious impacts on the growth, reproduction, and photosynthesis of terrestrial plants. Ulva prolifera, a main blooming species of green tides, was studied on its physiological response to acid rain. The photosynthetic parameters were determined under different conditions (salinity: 1, 10, 30&permil;; pH: 3.0, 3.5, 4.5; duration: 0.5, 1.0, 2.0 h) followed by 24-h recovering under natural conditions. Results showed 1-h treatment with pH 3.5 caused 50-70% reduction in the maximal quantum yield of PSII photochemistry (Fv/Fm) and effective quantum yield of PSII photochemistry (&#x424;PSII) at normal salinity but when the low pH was combined with a salinity of 10&permil; or lower, PSII activity was almost completely inhibited. Moreover, the low salinity (1&permil; and 10&permil;) reduced the degree of photoprotection under low pH (3.5) conditions. Finally, we speculated if the pH of acid rain &le; 3.5, with 1&permil; salinity and 2-h rainfall time, the amount of U. prolifera and the scale of green tides would decrease.

Early paleozoic tropical paleokarst geomorphology predating terrestrial plant growth in the tahe oilfield, Northwest China

A deeply buried tropical paleokarst landscape that predates terrestrial plant growth was discovered in West District 10 of the Tahe Oilfield, located on the northern margin of the Tarim Basin in the Xinjiang Uygur Autonomous Region of northwestern China. The paleokarst unconformity surface at depths deeper than ~6000 m had been subjected to subaerial karstification under humid tropical climatic conditions during the first hiatus period in the Early Paleozoic. A high-quality, full-azimuthal 3D seismic survey was conducted in this study area (area of 10 × 10 km2) in order to visualize the buried paleokarst landscape with high-resolution seismic data. With this data and previous geological, geochemical, and paleomagnetic data, we reconstructed the large-scale paleokarst landform assemblage, compared it to a modern humid tropical/subtropical karst, and investigated the different controlling factors for the formation of the paleokarst and the modern karst. Results show that (1) the original landform assemblages of the tropical paleokarst landscape are distinct from those of the modern humid tropical/subtropical karst geomorphology; (2) the paleokarst denudation surface that formed in the Early Paleozoic was relatively smooth with shallow depressions, and the relative relief was less than that of the modern tropical/subtropical cockpit karst area; (3) during the time of epigenetic paleo-karstification, lithological, hydrogeological, and climate conditions were optimal for the formation of cockpit karst. The tropical paleokarst landscape demonstrates that extensive terrestrial plant growth plays an important role in creating large-scale karst landform assemblages of peak clusters and depressions (cockpit karst).

Abiotic factors influencing soil microbial activity in the northern Antarctic Peninsula region

Microorganisms play a key role in the carbon (C) cycle through soil organic matter (SOM). The rate of SOM mineralization, the influence of abiotic factors on this rate and the potential behaviour of SOM are of particular interest in the northern Antarctic Peninsula and offshore islands. This is one of the most rapidly warming regions on Earth with numerous ice-free areas, some with abundant wildlife and with the greatest known soil organic carbon (SOC) storage in Antarctica. The latter implies extended Antarctic summer conditions promote increased terrestrial plant growth and soil microbial activity (SMA). SMA, determined by respirometry, is a measure of ecosystem function, and depends on microclimatic conditions and soil environmental properties. SMA and the effect of abiotic variables have been analysed in locations with different soil types, on Cierva Point (Antarctic Peninsula), Deception Island and Fildes Peninsula (King George Island). Soil microbial biomass carbon (SMBC) ranged from 5.66 to 196.6 mg SMBC kg−1and basal respiration (BR) from 2.86 to 160.67 mg CO2 kg−1 d−1. SMBC and BR values were higher in Cierva Point, followed by Fildes Peninsula and Deception Island, showing the same trend of SOM abundance. Except for Cierva Point, low nitrogen, phosphorus and C concentrations were observed. SMBC/total organic carbon (TOC) levels indicated that SOC was recalcitrant and SOM content was closely related to the extent of vegetation cover observed in situ. High metabolic quotient values obtained at Cierva Point and Deception Island (median values 7.27 and 6.53 mg C-CO2 g SMBC−1 h−1) and low SMBC/TOC in Cierva Point suggest a poor efficiency of the microbial populations in the consumption of the SOC. High SMBC/TOC values obtained in Deception Island indicates that SMBC may influence SOM stabilization. Mineralization rates were very low (negligible values to 1.44%) and sites with the lowest values had the highest SOM.

New insights into Holocene hydrology and temperature from lipid biomarkers in western Mediterranean alpine wetlands

Alpine regions of the Mediterranean realm are among the most climatically sensitive areas in the world. Thus, alpine wetlands from the southern Iberian Peninsula, in the westernmost part of the Mediterranean region, are highly sensitive sensors of environmental changes. Difficulties have surfaced in separating controls by temperature and/or precipitation in previous paleoenvironmental studies from alpine environments in this area. We present a Holocene biomarker record (n-alkanes and long-chain diols) from a high elevation lake, Laguna de Río Seco (LdRS), in the south of the Iberian Peninsula, which contributes to the identification of these forcing mechanisms. The hydrological history of the area, primarily water availability and evapotranspiration, is reconstructed by means of the n-alkane record, including the indices of average chain length, portion aquatic, and carbon preference index, as well as hydrogen isotopes (δD) of aquatic (δDaq) and terrestrial (δDwax) n-alkanes. Temperatures are also estimated using the algae derived long-chain diols. We interpret δDaq and δDwax fluctuations as showing changes in the source and amount of precipitation throughout the LdRS record. An Atlantic precipitation source appears to have predominated during the early-middle Holocene, but an occasional Mediterranean influence with an isotopic enrichment in precipitation is detected in the middle-late Holocene that is likely related to the setting of the current atmospheric pattern in southeastern Iberia under the joint control of the North Atlantic Oscillation (NAO) and the Western Mediterranean dynamics, such as the Western Mediterranean Oscillation (WeMO). Our new record from LdRS is consistent with a generalized trend of a humid early-middle Holocene with low temperature variability, evolving towards an arid middle-late Holocene with abrupt temperature changes. In addition to these long-term trends during the last ∼10,500 years, two phases of climate instability, evidenced by abrupt depletions in δDaq, have been identified at the end of these periods, one between ∼6500 and 5500 cal yr BP and another in the last ∼500 years. These episodes would represent strengthened winter cold conditions that favoured the persistence of snowpack and frozen soil in the catchment, causing reduced terrestrial plant growth and low lake evaporation. According to the long-chain diol record, temperatures during these phases were relatively low, but experienced abrupt increases at the end of each period.

Impacts of global environmental change drivers on non‐structural carbohydrates in terrestrial plants

AbstractNon‐structural carbohydrates (NSCs, including soluble sugars and starch) are essential to support the growth and survival of terrestrial plants. Starch and sugars play different roles in multiple plant ecological functions such as drought tolerance, growth and plant defence, and several other processes which are being rapidly shaped by global environmental change. However, it is uncertain whether soluble sugars and starch show different responses across plant functional types, tissue types and treatment conditions (i.e. the intensity and duration of environmental variability) to global‐change drivers.Here based on a database of 275 plants (including 17 plant functional types), we conducted a meta‐analysis to examine the effects of elevated atmospheric CO2concentration (eCO2), nitrogen (N) addition, drought and warming on NSCs and its components.We found NSCs responses to global environmental change were mainly driven by (a) soluble sugar changes in response to N addition and drought, as well as (b) starch changes in response to eCO2and warming. The different responses between soluble sugars and starch were more evident under eCO2and drought, especially in herbs or leaves. Interactive effects of multiple environmental change drivers on soluble sugars and starch were mainly additive. The divergent main and interactive effects on soluble sugars and starch depend on experimental conditions. For example, the starch responses to eCO2and its interaction with N addition were the strongest in short‐term experiments.Overall, our study shows the divergent responses of soluble sugars and starch in terrestrial plants to different global environmental change drivers, suggesting a changed carbon sink–source balance in plants under future global changes. The findings also highlight that predicting plant functional changes into the future requires a mechanistic understanding of how NSCs and its components are linked to specific environmental change drivers.A freePlain Language Summarycan be found within the Supporting Information of this article.

Identifying microbial drivers promoting plant growth on soil amended with composted aquatic plant: insight into nutrient transfer from aquatic to terrestrial systems

Effects of applying composted aquatic plants on soil chemistry, soil microbes (fungi and bacteria), and the growth of cultivated plant were demonstrated. To identify drivers promoting cultivated plant growth on soil amended with composted aquatic plant, empirical data of pot experiments were incorporated into structural equation models by hypothesizing causal relationships between the application of composted aquatic plants, soil chemistry, soil microbes, and cultivated plant growth. Cultivated plant growth, total carbon content, and bacterial and fungal richness in soil increased on soil applied with composted aquatic plants, and the composition of bacterial and fungal assemblages in soil were significantly different among the application treatments. Structural equation models explicitly demonstrated the relative importance of bacterial assemblages compared to soil chemistry as a promoter of cultivated plant growth in response to the application of composted aquatic plants. The present study is the first to demonstrate that the positive effects of composted aquatic plants on terrestrial plant growth are mediated by soil microbial processes. Our results could provide basic insights into the transfer and cycling of nutrients from aquatic to terrestrial systems through human activities.

Variation in morphological and chemical traits of Mediterranean tree roots: linkage with leaf traits and soil conditions

AimsRoot functions are multiple and essential for the growth and survival of terrestrial plants. The aim of this work was to analyse the main trends in the variation of root traits, their coordination with leaf traits and their relationships with soil conditions.MethodsWe measured the variation of 27 fine root traits (five morphological, 20 chemical and two isotopic signatures) in trees of seven species of a mixed plantation in a metal-contaminated and remediated site of Southern Spain.ResultsWe found evidences supporting the existence of a root economics spectrum (RES). However, other dimensions were identified as being independent of the main RES: mainly the variation in the carbon concentration, the accumulation of trace elements associated with tolerance of metal-rich soils, and the fractionation of δ15N as a time-integrated trait of mycorrhizal-mediated nutrition. In general, roots and leaves were functionally coordinated, although most of the trace elements showed strong root-leaf discordance. The soil conditions interacted with the fine root traits in feedback processes. The ability of tree roots to accumulate trace elements and to reduce their translocation to leaves is a desirable trait for the phytoremediation of metal-contaminated soils.ConclusionsRoots are multifunctional. Understanding the variations in the root traits of trees will help us to predict both the responses of forests to global changes, including soil contamination, and the provision of soil-based ecosystem services.

Exploratory evaluation of the effects of Kelpak® seaweed extract on cultivated kelp Saccharina spp. exposed to sublethal and lethal temperatures

AbstractKelpak® is a seaweed extract from the phaeophyte, Ecklonia maxima, used to enhance growth and production of terrestrial plants. It is also beneficial for some red and green seaweeds. As such, we assessed if Kelpak® could enhance growth and thermal tolerance of the brown seaweeds, Saccharina latissima and S. angustissima. Juvenile sporophytes were dipped (30 or 60 min) in Kelpak® solutions of different concentrations (0.001, 0.005, 0.05, 1, and 5 ml L−1). These sporophytes were then cultivated in half‐strength PES at different temperatures (12, 16, 19, 23 and 25°C ± 1) for 20 days. The surviving sporophytes were then moved to 18 ± 1°C and cultivated for 14 additional days. Results show that temperature was the main factor driving survival and growth. Both species exposed to the temperatures of 23 and 25°C died during the first 7 days. Furthermore, no significant differences were observed in growth of sporophytes at the temperatures of 12 and 16°C. Results also show that treated sporophytes exposed to 18°C, the sublethal temperature, particularly of S. angustissima showed a higher survival and overall vigor than nontreated sporophytes. These results indicate that Kelpak® may enhance thermal tolerance and growth of S. latissima and S. angustissima exposed to sublethal temperatures.