Seedling Traits Research Articles

Evaluation of Polyethylene Glycol (PEG-6000) Induced Drought Stress Tolerant Mungbean Genotypes by using Correlation, Principal Component, Hierarchical Clustering and Multi-Trait Genotype-Ideotypes Distance Index Analysis

Determining a plant's ultimate population under water stress requires seedling establishment and germination. The current study was aimed at identifying mungbean genotypes that were tolerant to drought stress. The treatments were: Factor A: polyethylene glycol 6000 (PEG-6000) inducing different levels of water potential (i.e., 0.0 (distilled water as a control), -0.7, -1, -2, and -4 bar) and Factor B: Thirty-three mungbean genotypes, collected from various national and international organizations. Each genotype's seeds were planted in a petri dish (9 cm diameter) containing sand bed and were moistened with appropriate amounts of water potential and left to develop into seedlings of all genotypes for up to 10 days. The findings showed that when PEG-6000 concentration was raised, germination, shoot and root length, and the associated fresh and dry weights decreased significantly. Among these tested genotypes, BMX-08010-2, BMX-08009-7, BMX-01015, BARI Mung-8, BARI Mung-2, and BU Mung-2 were found to be tolerant against drought stress based on their % germination and germination indices, as well as their seedling traits. Principal component analysis, multi-trait genotype-ideotype distance index (MGIDI), two-dimensional heat map, and hierarchical clustering analysis also revealed the same genotypes to be stable and capable of withstanding water deficiency stress. In response to water stress, the genotypes BARI Mung-1, BARI Mung-3, BU Mung-4, and BMX-05001 showed poor germination indices along with relatively poor seedling characteristics. The results of the present research provide criteria for the selection of drought-tolerant mungbean genotypes in future breeding programs.

Local adaptation and phenotypic plasticity drive leaf trait variation in the California endemic toyon (Heteromeles arbutifolia).

To survive climate change and habitat loss, plants must rely on phenotypic changes in response to the environment, local adaptation, or migration. Understanding the drivers of intraspecific variation is critical to anticipate how plant species will respond to climate change and to inform conservation decisions. Here we explored the extent of local adaptation and phenotypic plasticity in Heteromeles arbutifolia, toyon, a species endemic to the California Floristic Province. We collected leaves from 286 individuals across toyon's range and used seeds from 37 individuals to establish experimental gardens in the northern and southern parts of toyon's range. We measured leaf functional traits of the wild-collected leaves and functional and fitness traits of the offspring grown in the experimental gardens. We then investigated the relationships between traits and source environment. Most traits we investigated responded plastically to the environment, and some traits in young seedlings were influenced by maternal effects. We found strong evidence that variation in leaf margins is a result of local adaptation to variation in temperature and temperature range. However, the source environment was not related to fitness traits or survival in the experimental gardens. Our findings reiterate the adaptive role of toothed leaf margins in colder and more seasonally variable environments. Additionally, we provide evidence that fitness of toyon is not dependent on where they are sourced, and thus toyon can be sourced across its range for restoration purposes.

Effects of Root Pruning and Size on Growth Traits of Hybrid Poplar Seedlings

Selecting seedlings of varying sizes and effectively managing root pruning are key challenges in transplantation. However, the effects of seedling size and root pruning on transplantation outcomes are not fully understood. This study classified one-year-old Populus ‘Beilinxiongzhu-01’ seedlings into three size categories based on height: large (308.75 ± 9.66 cm), medium (238.00 ± 7.71 cm), and small (138.92 ± 7.18 cm). In early March of the subsequent year, root pruning was applied with varying intensities based on root collar diameter: low (15 times), medium (7.5 times), and high (3.75 times). A control group without pruning was also included. Over the year, key phenological and morphological traits were monitored. The results showed that (1) root pruning significantly impacted the phenology of seedlings, accelerating root emergence, delaying early leaf phenology, increasing the dieback rate, and postponing end-of-season defoliation. Mortality and the rapid growth phase were not significantly affected. Larger seedlings exhibited earlier end-of-season defoliation and higher dieback rates early in the growing season, while smaller seedlings advanced in early leaf development. (2) Except under low or no pruning, root pruning reduced seedling height (H), diameter at breast height (DBH), and root collar diameter (RCD). However, across all treatments, these indicators remained higher in larger seedlings compared to smaller ones. Under medium- and high-intensity pruning, smaller seedlings exhibited higher relative growth rates and larger leaf areas than larger seedlings, with the reduction in these variables becoming more pronounced as seedlings increased in size. Notably, only larger seedlings demonstrated a reduction in maximum growth rate, suggesting greater vulnerability to root pruning. In summary, root pruning induced significant phenological and morphological differences across seedling sizes. While smaller seedlings showed some response to pruning, larger seedlings experienced more pronounced phenological disruptions and growth inhibition.

Copper mitigates salinity stress by regulating water status, photosynthetic pigments and ion homeostasis and increases the yield of Eggplant (Solanum melongena)

Eggplant (Solanum melongena) is moderately sensitive to salinity. Seed priming and exogenous supplementation are technique that enhances germination, growth, and crop yield by overcoming salt stress. Therefore, this study was designed to understand the role of seed priming and copper (Cu) supplementation in modulating salt tolerance in eggplant. When exposed to salt stress, eggplant seedlings showed significantly higher Na+ content, an increased Na/K ratio, prolonged mean germination time, higher relative water loss, more days to flower bud initiation and first flowering, along with decreased germination rate, growth factors, water content, photosynthetic pigments, ionic contents (K+, Ca2+, Mg2+), and yield. The results demonstrated that the germination rate, final germination percentage, germination index, germination energy, and seed vigor index significantly improved, while the mean germination time decreased in Cu-primed seeds. The results also revealed that Cu supplementations increased seedling traits, leaf water content, photosynthetic pigment contents, ionic contents (K+, Ca2+, and Mg2+), and yield while decreasing the contents of Na+, and Na/K ratio, mean germination time, relative water loss, days to flower bud initiation, and days to 1st flowering under salt stress. Germination of seeds, seedlings growth traits, plant water status, plant pigments, yield, and ionic contents with the NaCl and Cu treatments were found to substantially interact with each other according to both hierarchical clustering and PCA. Overall, Cu seed priming and exogenous supplementation emerged as a promising strategy to enhance salt tolerance and promote germination, growth, and yield by regulating water status, photosynthetic pigments, and ion homeostasis in eggplant seedlings under NaCl stress. These findings provide valuable insights into the mechanisms of Cu-mediated stress alleviation in eggplant, with implications for sustainable crop production in saline environments.

Effect of General Combining Ability for Different Seedling Traits in Mulberry (Morus spp.)

Effect of General Combining Ability for Different Seedling Traits in Mulberry (Morus spp.)

Genetic diversity, relationships among traits and selection of tropical maize inbred lines for low-P tolerance based on root and shoot traits at seedling stage.

The tropical maize breeding for low-P tolerance and good performance under low-P stress environments can be achieved through selection based on root morphology traits at seedling stage. Here, we assessed the genotypic variation and genetic diversity of a panel of 151 tropical maize inbred lines for root and shoot seedling traits, investigated the relationship among traits and selected a set of promising inbred lines for low-P tolerance and performance. We evaluated the inbred lines at seedling stage in a greenhouse experiment under two conditions: applied P (AP) and non-applied P (NAP). A mixed model approach was used to estimate variance components and predict the genotypic values of each inbred line. The genetic diversity among inbred lines based on root and shoot traits was assessed, and correlations were estimated between tested traits under AP and NAP. Our panel of inbred lines showed huge genetic variability for all traits and presented large genetic diversity under both P conditions. Variance components due to the inbred line × P condition interaction were also highly significant (P < 0.01) for all traits. Root dry weight (RDW) was positively associated with stalk dimeter (SD), shoot dry weight (SDW) and root length, volume, and area under both P conditions. Also, the SD and SDW were associated with most root traits under AP. Based on low-P tolerance and performance indices, we selected a set of top 20 inbred lines to be used in our maize breeding program. We therefore concluded that there is a significant genetic diversity in the tropical maize inbred lines which have the genetic potential to be use in association mapping studies and also to develop improved low-P tolerant and P-efficient hybrids and maize breeding populations for low-P stress environments.

The Effect Of Soil Treatment With Cow Manure Compost And Foliar Magnesium On Plant Growth Of Black Diyala Fig Ficus Carica L. Seedlings

The research was conducted at the research station affiliated with the Faculty of Agriculture / University of Kufa in the university city in the Najaf Governorate for the period from 1 March to 1 December 2023 to study the effect of organic fertilization with cow manure compost and foliar spraying with magnesium and their interactions on some vegetative traits of black Diyala fig seedlings. The foliar magnesium was used at four concentrations (0, 0.5, 1 or 1.5) gm L-1, and the ground addition of organic fertilizer (cow manure) was also applied at four levels (0, 5, 10 or 15) g pot-1, and their interactions. The results showed that black Diyala fig seedlings treated with cow manure compost recorded significant effect on the studied traits, as cow manure compost at 15 g pot-1 resulted in the highest increase of seedlings height 21.37 cm, stem diameter 2.07 mm, number of branches 3.30 seedling branch-1, number Leaves 10.03 leaf plant -1, and leaf area 2448.25 cm2 seedling-1. Spraying fig seedlings of the Black Diyala variety with magnesium at a concentration of 1.5 gm l-1 excelled in the amount of increase in seedling height 15.98 cm, stem diameter 1.82 mm, number of branches 3.23 seedling branch-1, and number of leaves. 10.36 plant leaves-1, average leaf area is 1899.50 cm2 seedling-1. However, best results were recorded in the interaction of foliar magnesium at 1.5 gm L-1 and organic fertilizer at 15 g pot-1 with significantly the highest increase in plant height 25.56 cm and stem diameter 2.28 mm, the number of branches is 5.28 branches, seedling-1, the number of leaves is 15.00 leaves-1, the average leaf area is 3030.00 cm2, seedling-1.

Variation in Seedling Quality Attributes of Lentil (Lens &amp;lt;i&amp;gt;culinaris&amp;lt;/i&amp;gt; Medik.) After Harvested Under Different Sowing Dates

Planting dates are the most important components for Lentil seedling growth and development. Seeds planted in diverse environmental situations lead to changes in various seedling development and the final output of the yield. The present study, aimed to assess the effect of different planting (sowing) dates harvested seeds on the physiological properties of nineteen (19) lentil genotypes. Lentil was growing during two consecutive planting days on average the normal (main) 17/08/2021 and lately 16/09/2021, then harvested seed extract after five months of storage, planted CRD with two factorial designs and three replications under laboratory condition within a white plastic container filled with autoclaved 3.0kg sand applying 100ml distilled water. The lentil was grown per standard, and the lentil&amp;apos;s postharvest physiological quality parameters were evaluated. Results indicated that the lowest speed of germination index was obtained during late planting time or stress situations on the genotype Adda (8.78) and ILL-1760 (8.94). Seedling length is the seedling vigor criterion and is statistically significantly different between planting dates at 1%. The effect of planting day on seedling fresh weight was significantly different (p &amp;lt; 0.01) on genotype Beredu (0.0022) on the main planting day. The seed viability on vigor index (II) as shown in was affected by planting date (p &amp;lt; 0.01) and genotypes (p &amp;lt; 0.01). The heritability value of shoot length, root length, and seedling fresh weight equal zero was the variation due to environmental it had no genetic effect after five months of storage both main and late planting. The seedling vigor index, fresh and dry weight traits maximum on the main planting day on the genotype Beredu indicates 0.0445, 0.00218, and 0.00045 respectively. Seeds from the main planting day had the best seedling traits performance and recorded minimal germination time compared to late planting seeds. Lentil seeds planted lately finally recorded lower seedling fresh and dry weight, vigor, and speed of germination index as compared to those harvested lentil seeds in main planting dates. As a result, when there is adequate rainfall necessary for lentil growth, development, and final output.

Evaluation of Mung Bean Accessions for Salt Tolerance Based on Germination and Seedling Traits

Ten mung bean accessions collected from Bangladesh Agricultural Research Institute were exposed to two salinity levels (control and 8 dS m−1) to observe the sensitivity of their germination and early seedling traits. The observations were recorded on germination percentage, rate of germination, coefficient of germination, shoot length, root length and seedling dry weight. The accessions, salinity levels and their interaction exhibited significant differences for all the traits. The mean performance of all the traits reduced under salt stress as compared to control. Salt tolerant accessions showed less reduction in their germination and seedling traits under salinity than the other accessions tested. Considering salt tolerance index (STI) based on seedling dry weight, the order of tolerance was BD- 6882 &gt; BD-10022 &gt; BD-10024 &gt; BD-10026 &gt; BD-10023 &gt; BD-10027 &gt; BD-6885 &gt; BD-6887 &gt; BD- 6884 &gt; BD-6875. Based on relative total dry weight (RTDW), three accessions viz. BD-6882, BD- 10022 and BD-10024 were identified as salt tolerant and other seven as moderately salt tolerant. The identified salt tolerant accessions could be a useful stock for further breeding programs to develop salt tolerant mung bean genotype of considerable economic value. Bangladesh Agron. J. 2024, 26(2): 16-26

Improving Beneficial Traits in Bacillus cabrialesii subsp. cabrialesii TE3T through UV-Induced Genomic Changes.

It is essential to hunt for new technologies that promote sustainable practices for agroecosystems; thus, the bioprospecting of beneficial microorganisms complementing with mutation induction techniques to improve their genomic, metabolic, and functional traits is a promising strategy for the development of sustainable microbial inoculants. Bacillus cabrialesii subsp. cabrialesii strain TE3T, a previously recognized plant growth-promoting and biological control agent, was subjected to UV mutation induction to improve these agro-biotechnological traits. Dilutions were made which were spread on Petri dishes and placed under a 20 W UV lamp at 10-min intervals for 60 min. After the UV-induced mutation of this strain, 27 bacterial colonies showed morphological differences compared to the wild-type strain; however, only a strain named TE3T-UV25 showed an improvement in 53.6% of the biocontrol against Bipolaris sorokiniana vs. the wild-type strain, by competition of nutrient and space (only detected in the mutant strain), as well as diffusible metabolites. Furthermore, the ability to promote wheat growth was evaluated by carrying out experiments under specific greenhouse conditions, considering un-inoculated, strain TE3T, and strain TE3T-UV25 treatments. Thus, after 120 days, biometric traits in seedlings were quantified and statistical analyses were performed, which showed that strain TE3T-UV25 maintained its ability to promote wheat growth in comparison with the wild-type strain. On the other hand, using bioinformatics tools such as ANI, GGDC, and TYGS, the Overall Genome Relatedness Index (OGRI) and phylogenomic relationship of mutant strain TE3T-UV25 were performed, confirming that it changed its taxonomic affiliation from B. cabrialesii subsp. cabrialesii to Bacillus subtilis. In addition, genome analysis showed that the mutant, wild-type, and B. subtilis strains shared 3654 orthologous genes; however, a higher number of shared genes (3954) was found between the TE3T-UV25 mutant strain and B. subtilis 168, while the mutant strain shared 3703 genes with the wild-type strain. Genome mining was carried out using the AntiSMASH v7.0 web server and showed that mutant and wild-type strains shared six biosynthetic gene clusters associated with biocontrol but additionally, pulcherriminic acid cluster only was detected in the genome of the mutant strain and Rhizocticin A was exclusively detected in the genome of the wild-type strain. Finally, using the PlaBase tool, differences in the number of genes (17) associated with beneficial functions in agroecosystems were detected in the genome of the mutant vs. wild-type strain, such as biofertilization, bioremediation, colonizing plant system, competitive exclusion, phytohormone, plant immune response stimulation, putative functions, stress control, and biocontrol. Thus, the UV-induced mutation was a successful strategy to improve the bioactivity of B. cabrialesii subsp. cabrialesii TE3T related to the agro-biotecnology applications. The obtained mutant strain, B. subtilis TE3T-UV25, is a promising strain to be further studied as an active ingredient for the bioformulation of bacterial inoculants to migrate sustainable agriculture.

Anatomical traits explain drought response of seedlings from wet tropical forests.

Water availability regulates plant community dynamics but the drought response of seedlings remains poorly known, despite their vulnerability, especially for the Asian tropics. In particular, discerning how functional traits of seedlings mediate drought response can aid generalizable predictions of tree responses to global environmental change. We assessed interspecific variation in drought response explained by above- and below-ground seedling traits. We conducted a dry-down experiment in the greenhouse using 16 tree species from the humid forests of Western Ghats in southern India, chosen to represent differences in affinity to conditions of high and low seasonal drought (seasonality affiliation). We compared survival, growth, and photosynthetic performance under drought and well-watered conditions and assessed the extent to which species' responses were explained by seasonality affiliation and 12 traits of root, stem and leaf. We found that the species from seasonally dry forest reduced photosynthetic rate in drought compared with well-watered conditions, but seasonality affiliation did not explain differences in growth and survival. Performance in drought vs well-watered conditions were best explained by anatomical traits of xylem, veins and stomata. Species with larger xylem reduced their growth and photosynthesis to tolerate desiccation. In drought, species with smaller stomata correlated with lower survival even though photosynthetic activity decreased by a larger extent with larger stomata. Overall, anatomical traits of xylem and stomata, directly related to water transport and gas-exchange, played a more prominent role than commonly used traits (e.g., specific leaf area, leaf dry matter content) in explaining species response to drought, and may offer a good proxy for physiological traits related to drought tolerance of seedlings.

Genetic and Physiological Insights into Salt Resistance in Rice through Analysis of Germination, Seedling Traits, and QTL Identification.

Understanding the genetic basis of salt resistance in crops is crucial for agricultural productivity. This study investigates the phenotypic and genetic basis of salt stress response in rice (Oryza sativa L.), focusing on germination and seedling traits. Under salt stress conditions, significant differences were observed in seed germination and seedling traits between parental LH99 (Indica rice LuHui 99) and SN265 (japonica rice ShenNong 265). Transgressive segregation was evident within the RIL population, indicating complex genetic interactions. Nine QTLs were detected at germination and seedling stages under salt stress, namely qSGE5 and qSGE7 for seed germination energy (SGE); qSGP7 for seed germination percentage (SGP); qSSH7, qSSH9-1, and qSSH9-2 for seeding height (SSH); qSRN6 for root number (SRN); and qSDW6 and qSDW9 for dry weight (SDW). Among them, qSSH9-1 and qSDW9 were localized in the same interval, derived from the salt-resistant parent SN265. PCA revealed distinct trait patterns under salt stress, captured by six PCs explaining 81.12% of the total variance. PC composite scores were used to localize a QTL associated with early salt resistance in rice qESC9, which was located in the same interval as qSSH9-1 and qSDW9, and was subsequently unified under the name qESC9, an important QTL for early-growth salt tolerance in rice. Correlation analysis also confirmed a relationship between alleles of qESC9 and the resistance to salt, underscoring the critical role this locus plays in the determination of overall salt tolerance in rice. Physiological analyses of extreme phenotype lines highlighted the importance of ion exclusion mechanisms in salt-resistant lines, while salt-susceptible lines exhibited elevated oxidative stress and impaired antioxidant defense, contributing to cellular damage. This comprehensive analysis sheds light on the genetic and physiological mechanisms underlying salt stress response in rice, providing valuable insights for breeding programs aimed at enhancing salt resistance in rice.

Copper oxide nanoparticles mitigate cadmium toxicity in rice seedlings through multiple physiological mechanisms.

Heavy metal pollution poses a serious threat to crops growth and yield. Recently, nanoparticles (NPs) have emerged as a promising strategy to mitigate the negative effect of heavy metal on crop growth. This study investigated the beneficial effects of copper oxide nanoparticles (CuO NPs) on the morphological and physiological-biochemical traits of rice seedlings (Oryza sativa L.) under cadmium (Cd) stress. The results demonstrated that the application of CuO NPs increased the contents of nutrition elements in shoots and roots as well as photosynthetic pigments, consequently improving the growth of rice seedlings under Cd stress, especially at low level of Cd stress. Meanwhile, CuO NPs obviously decreased the Cd accumulation in the rice seedlings and immobilized Cd in less toxic chemical forms and subcellular compartments. Moreover, CuO NPs modulated the antioxidant system, ameliorating oxidative damage and membrane injury caused by Cd. Multivariate analysis established correlations between physio-biochemical parameters and further revealed the mitigation of Cd damage to rice seedlings by CuO NPs was associated with inhibition Cd accumulation, altering Cd chemical form and subcellular distribution, increasing the contents of mineral nutrients, photosynthetic pigments and secondary metabolites and antioxidant enzyme activities, and reducing oxidative damage. Overall, the present study indicated that CuO NPs could effectively reduce the Cd toxicity to rice seedlings, demonstrating their potential application in agricultural production.

Multi‐cohort survival of northern red oak seedlings at a northern hardwood forest transition

AbstractGlobal change has created less stable forest systems and given urgency to understanding limitations to the establishment of tree seedlings beyond current range boundaries. We quantified trends in 13 years of annual northern red oak (QURU) seedling survival data for 1733 marked individuals at a local species distribution boundary within the northern hardwood forest in New Hampshire, USA. Over the study period, the median distance of seedlings into the valley did not change, although there was a net gain of 89 plots (5 m2) occupied. For a subset of seedlings that were marked in their year of birth (N = 937), we examined relationships among terrain, vegetation community, and initial individual seedling traits, and evaluated their effects on time to seedling mortality using a parametric accelerated failure time model. The year of seedling germination had the largest effect on survival with increasing mortality rates for seedlings from more recent cohorts. Seedlings had longer survival times where oak seedling densities were lower, shrub cover was higher, and when the acorn remained attached. Additionally, survival time was increased in higher elevation plots, which were also located further into the valley. Interannual seedling survival (N = 1580) was strongly impacted by seedling condition in the previous year, particularly leaf number and amount of leaf damage. Most seedling deaths occurred over winter, and seedlings failed to break bud the following spring. Interannual variation in seasonal climate, particularly deep, heavy snowpack in 2019 followed by drought conditions in 2020, coincided with recent elevated mortality. Overall, the median survival time of 3–4 years and the rapid turnover of the oak seedling population currently limit ability for expansion, although the net gain of occupied plots and increase in survival at higher elevation plots with lower QURU densities present some mechanisms that could promote expansion if the current suboptimal understory conditions shift to favor QURU.

Association study of yield and its component traits in sugarcane seedlings

An experiment was carried out to investigate the relationship between specific quantitative characters and sugarcane yield at the Sugarcane Research Institute, Pusa, Bihar, in February 2022. Thirty sugarcane seedlings obtained from three different crosses along with check were subjected to estimation trait association by correlation and path analyses. Cane yield showed strong positive and highly significant correlation with single cane weight, number of millable canes per clump and brix percent at 12th month. There was also positive significant correlation of number of shoots per clump with cane yield. Path analysis revealed the highest positive direct effect of brix percent at 12th month on cane yield followed by brix percent at 10th month and cane diameter. However, number of shoots per clump had considerable negative direct effects and indirect positive effects through single cane weight and number of millable canes per clump on cane yield. The traits that provide considerable positive correlation and positive direct effects to cane yield could be used as selection indices for yield improvement in for further clonal generations.

Using machine learning algorithms to cluster and classify stone pine (Pinus pinea L.) populations based on seed and seedling characteristics

AbstractThe phenotype of a woody plant represents its unique morphological properties. Population discrimination and individual classification are crucial for breeding populations and conserving genetic diversity. Machine Learning (ML) algorithms are gaining traction as powerful tools for predicting phenotypes. The present study is focused on classifying and clustering the seeds and seedlings in terms of morphological characteristics using ML algorithms. In addition, the k-means algorithm is used to determine the ideal number of clusters. The results obtained from the k-means algorithm were then compared with reality. The best classification performance achieved by the Random Forest algorithm was an accuracy of 0.648 and an F1-Score of 0.658 for the seed traits. Also, the best classification performance for stone pine seedlings was observed for the k-Nearest Neighbors algorithm (k = 18), for which the accuracy and F1-Score were 0.571 and 0.582, respectively. The best clustering performance was achieved with k = 2 for the seed (average Silhouette index = 0.48) and seedling (average Silhouette Index = 0.51) traits. According to the principal component analysis, two dimensions accounted for 97% and 63% of the traits of seeds and seedlings, respectively. The most important features between the seed and seedling traits were cone weight and bud set, respectively. This study will provide a foundation and motivation for future efforts in forest management practices, particularly regarding reforestation, yield optimization, and breeding programs.

Contrasting light capture strategies between shade-tolerant and -intolerant tree seedlings responding to solar canopy spectral composition

Forest regeneration is a crucial ecological process for promote self-reproduction and restoration, which is essential for maintaining complex community structure and preserving biological resources. Although sunlight have been considered as the main driver of forest regeneration, how light quality shapes functional traits of seedlings is poorly understood in the forest understorey, where spectral compositions of solar radiation change dramatically. We investigated the responses of 15 typical functional traits of Pinus koraiensis and Quercus mongolica to five filter treatments that differed in the spectral transmittance: (a) 95 % of solar radiation was transmitted (280–700 nm); (b) ultraviolet (UV)-B radiation was attenuated (>315 nm); (c) all UV radiation was attenuated (>400 nm); (d) all UV radiation and blue light was attenuated (>500 nm); (e) all UV radiation, blue-green light was attenuated (>580 nm). Our results showed that functional traits responded to UV-B radiation (contrasting treatment [a] vs. [b]) with species-dependence, but consistently showed a positive response to blue light (contrasting treatment [c] vs. [d]). UV-B radiation decreased the relative growth rate (RGR) and leaf area ratio (LAR) of P. koraiensis seedlings by 48 % and 42 %, respectively; however, it increased seedling height, total leaf area (TLA), and above-ground biomass of Q. mongolica. Blue light consistently increased LAR and RGR of two species. Furthermore, Q. mongolica was more plastic in morphological traits (including plant height and TLA) and root/shoot ratio than P. koraiensis to the single spectral region (UV-B, UV-A, blue, and green light), but opposite in physiological and biochemical traits (such as chlorophyll and anthocyanidin). These suggest that two studied species have evolved different light capture strategies in the understorey: Q. mongolica seedlings tended to adjust morphology and biomass allocation to enhance light interception capacity, while P. koraiensis seedlings preferred to adjust physiological and biochemical traits to enhance light utilization efficiency. A better understanding how canopy spectral compositions affect seedling regeneration may provide a new insight for future forest management (i.e. the appropriate gap creation or tree species combination).

Climate legacy in seed and seedling traits of European beech populations.

Tree species' ability to persist within their current distribution ranges is determined by seed germination and seedling growth. Exploring variation in these traits in relation to climatic conditions helps to understand and predict tree population dynamics, and to support species management and conservation under future climate. We analyzed seeds and seedlings of 26 European beech populations from the northeastern boundary of the species range to test whether: 1) adaptation to climatic conditions is reflected in depth of dormancy and germination of seeds; 2) climatic characteristics of origin predictably affect seedling traits. The variation in seed dormancy and germination in a laboratory test, and seedling growth and morphology traits in a nursery common-garden test was examined. Populations originating from warmer and drier sites (mostly from the northern region), compared to those from the opposite end of climatic gradient, germinated later, with a lower success, and produced seedlings with shorter and tougher roots. They had deeper dormancy and poorer seed germination capacity, and are likely more vulnerable to environmental changes. The climatic conditions at the origin shape the intraspecific variation of seed germination and seedling traits, and may limit regeneration from seed and affect adaptation potential of beech to increasing temperatures and decreasing precipitation.

Interspecific selection in a diverse mycorrhizal symbiosis.

Coevolution describes evolutionary change in which two or more interacting species reciprocally drive each other's evolution, potentially resulting in trait diversification and ecological speciation. Much progress has been made in analysis of its dynamics and consequences, but relatively little is understood about how coevolution works in multispecies interactions, i.e., those with diverse suites of species on one or both sides of an interaction. Interactions among plant hosts and their mutualistic ectomycorrhizal fungi (ECM) may provide an ecologically unique arena to examine the nature of selection in multispecies interactions. Using native genotypes of Monterey pine (Pinus radiata), we performed a common garden experiment at a field site that contains native stands to investigate selection from ECM fungi on pine traits. We planted seedlings from all five native populations, as well as inter-population crosses to represent intermediate phenotypes/genotypes, and measured seedling traits and ECM fungal traits to evaluate the potential for evolution in the symbiosis. We then combined field estimates of selection gradients with estimates of heritability and genetic variance-covariance matrices for multiple traits of the mutualism to determine which fungal traits drive plant fitness variation. We found evidence that certain fungal operational taxonomic units, families and species-level morphological traits by which ECM fungi acquire and transport nutrients exert selection on plant traits related to growth and allocation patterns. This work represents the first field-based, community-level study measuring multispecific coevolutionary selection in nutritional symbioses.

Nursery cultural practices influence morphological and physiological aspen seedling traits: implications for post-fire restoration

Aspen forests are threatened by the impacts of a changing climate and are showing large-scale mortality with meager natural regeneration to restore these loses. Therefore, there is an increasing demand for high-quality aspen seedlings to assist with forest restoration efforts. Nursery cultural practices can be used to alter aspen seedling traits to improve adaptability to dry planting conditions. In this study, the effects of container size (SC10 and D30; 158 and 490 mL, respectively) and nursery irrigation treatment (high and low irrigation; 90% and 70% container capacity, respectively) on seedling growth and a suite of morphological and physiological traits were investigated. The combination of large container size and low irrigation treatment resulted in seedlings with lowest height-to-diameter ratio and specific leaf area, which are desired traits for seedling performance on dry sites. Additionally, seedlings exposed to low irrigation conditions at the nursery stage had a lower (more negative) osmotic potential at full turgor, suggesting a higher likelihood of drought tolerance. Overall results from this study provide insight into utilizing nursery cultural practices to produce seedlings with target characteristics that may ultimately lead to establishment on harsh, dry planting sites in large-scale reforestation projects.