Biomass Allocation Research Articles

Soil Microbial Biomass and Bacterial Diversity Enhanced through Fallow Cover Cropping in Rice–Fish Coculture

Traditional rice production is often reliant on the unsustainable practice of utilizing intensive inputs in monoculture cropping systems. Alternatives fallow cover cropping and rice–fish coculture (RFC) offer promising solutions. However, the potential of fallow cover cropping in RFC remains underexplored, and its impact on soil microbes is poorly understood. In this study, assessments of soil–plant–microbe interactions were conducted across three cover cropping systems: Chinese milk vetch (Astragalus sinicus L.) single cropping (CM), Rapeseed (Brassica napus L.) single cropping (RP), and a combination of Chinese milk vetch and rapeseed intercropping (CM_RP). These systems were evaluated with and without nitrogen (N) addition, encompassing both the RFC and rice monoculture (RMC) systems. The findings indicate a notable increase in soil microbial biomass nitrogen (MBN) with CM. Soil microbial biomass carbon (MBC), influenced more by N-fertilizer than crop species, decreased with N addition. In the RFC system, the soil bacterial co-occurrence network exhibited more connections, yet negative links increased. CM_RP displayed similarities to CM without N but shifted closer to RP with N addition. N addition in intercropping significantly increased the root–shoot ratio (R/S) of A. sinicus, associated with decreased aboveground biomass and total root length. Compared to RMC, RFC with N addition reduced the relative abundance of Anaerolineaceae in CM while increasing Bacillus and Pontibacter across cover cropping systems. Overall, with N addition, both RFC and RMC showed decreased soil bacterial diversity indices. Changes in soil bacterial diversity correlated significantly with soil MBC, MBN, and plant R/S. Continuous fallow cover cropping altered soil microbial biomass and affected cover crop biomass distribution, impacting bacterial composition in paddy soil. These results shed light on how bacterial communities respond to N addition and fallow cover cropping in RFC and RMC systems, offering insights for sustainable nutrient management in paddy systems.

Growth and Morphophysiological Responses of Protium heptaphyllum Seedlings to Root Deformation and Light Availability

Abstract J-root deformation caused at the time of pricking out is highlighted in several forest nursery manuals, but there are few reports in the literature on the consequences of this type of root deformation on the physiology and growth of tree seedlings. Protium heptaphyllum is a tropical tree with potential for use in forest enrichment projects and agroforestry systems. This study aimed to evaluate the biomass allocation, root hydraulic conductivity and growth of P. heptaphyllum seedlings subjected to root deformation and three contrasting light levels (44%, 28%, and 2% of full sunlight) over a period of 155 days. Root deformation negatively affected the shoot to root dry mass ratio (S/R), the diameter to root volume ratio (D/RV), the height to root volume ratio (H/RV) and relative growth rate (RGR). Seedlings at 44% and 28% of full sunlight had lower S/R and higher hydraulic conductivity per unit of root volume (Kr/RV), net assimilation rate (NAR), and RGR when compared with seedlings at 2% of full sunlight. No significant interactions were observed between root deformation and light. Root deformation caused at the time of pricking out affects the quality of seedlings, decreasing growth rates and changing morphophysiological characteristics independently of light availability. Study Implications: Poor quality tree seedlings with J-root deformation is a problem frequently pointed out in forest nursery manuals. Despite this, there is scarce information in the literature on how errors in the pricking out process affect the morphology and physiology of tree seedlings. We demonstrated that this type of root deformation decreases the growth rate and changes important characteristics of Protium heptaphyllum seedlings regardless of light environment. We highlight important morphological and physiological effects of errors in the management of tree seedlings, which are frequently pointed out in forest nursery manuals but have not been demonstrated by experimental studies.

Integrated Ca, Mg, Cu, and Zn supply upregulates leaf anatomy and metabolic adjustments in Eucalyptus seedlings

Adaptive responses to abiotic stresses such as soil acidity in Eucalyptus—the most widely planted broad-leaf forest genus globally—are poorly understood. This is particularly evident in physiological and anatomical disorders that inhibit plant development and wood quality. We aimed to explore how the supply of Ca and Mg through liming (lime), combined with Cu and Zn fertilization (CZF), influences physiological and anatomical responses during Eucalyptus grandis seedlings growth in tropical acid soil. Therefore, related parameters of leaf area and leaf anatomy, stomatal size, leaf gas exchange, antioxidant system, nutrient partitioning, and biomass allocation responses were monitored. Liming alone in Eucalyptus increased specific leaf area, stomatal density on the abaxial leaf surface, and Ca and Mg content. Also, Eucalyptus exposed only to CZF increased Cu and Zn content. Lime and CZF increased leaf blade and adaxial epidermal thickness, and improved the structural organization of the spongy mesophyll, promoting increased net CO2 assimilation, and stomatal conductance. Fertilization with Ca, Mg, Cu, and Zn positively affects plant nutrition, light utilization, photosynthetic rate, and antioxidant performance, improving growth. Our results indicate that lime and CZF induce adaptive responses in the physiological and anatomical adjustments of Eucalyptus plantation, thereby promoting biomass accumulation.

The Role of Wood Density Variation and Biomass Allocation in Accurate Forest Carbon Stock Estimation of European Beech (Fagus sylvatica L.) Mountain Forests

The European beech (Fagus sylvatica L.) is one of the most common tree species in Romania, with importance both economically and environmentally. Accurate methods of biomass assessment at the tree compartment level (i.e., stump, stem, branches, and leaves) are necessary for carbon stock estimation. Wood density (WD) is an important factor in determining biomass and, ultimately, the tree’s carbon content. The average tree density was found to be 578.6 kg/m3. For this study, WD was evaluated by the weighting method related to tree volume. Also, to investigate a practical approach to determining the weighted wood density (WWDst), models were run using density at the base of the tree (WDBase), density at breast height level using discs (WDDBH), the wood core density (WDic), and the diameter at breast height (DBH) as predictors. The biomass assessment was conducted using different model evaluations for WWDst as well as allometric equations using the destructive method. From the results, it was noted that using the WWDst, the total biomass was underestimated by −0.7% compared to the biomass measured in the field. For allometric equations that included DBH and tree height as independent variables, the explained variability was around 99.3% for total aboveground biomass (AGBtotal), while it was 97.9% for allometric function using just the DBH. Overall, the distribution of biomass across different compartments was as follows: 73.5% in stems, 23.8% in branches, 1.9% in stumps, and 1.3% in leaves. The study findings offer valuable insights into WD, biomass distribution among different components, and biomass allometric quantification in natural beech forest environments in mountainous areas.

Biostimulants do not affect the performance of urban plant species grown under drought stress

Urban areas often have low soil water availability due to their impervious surfaces reducing rainfall infiltration. These water-limited conditions may be exacerbated by the projected increases in drought events caused by climate change. As a result, plants that grow in urban areas are vulnerable to drought stress. There are a range of practices that can be used to help mitigate drought stress, including the use of biostimulants. This study aimed to determine whether biostimulant application (1) improves plant performance and (2) mitigates the drought stress on urban plant species. To address these aims, we selected six woody and three graminoid plant species that are commonly planted in Australian urban areas and exposed them to different watering (drought-stressed, well-watered) and biostimulant (control, humic acid, protein hydrolysate, seaweed extract) treatments. We then measured their assimilation rate, growth metrics and biomass allocation. We found that drought stress reduced the assimilation rates and shoot growth of the study species. However, this did not translate into a biomass reduction because the drought-stressed plants reallocated resources towards root biomass. We found no evidence to suggest biostimulant application mitigated the impacts of drought stress on plant performance. Further, the only effect biostimulant application had on plant performance irrespective of the watering treatment was that the seaweed biostimulant increased the plant height growth of the woody species. These results show that the biostimulants used in this study will have a limited effect on the performance of plant species commonly planted in Australian urban areas.

Effects of Biochar-Coated Nitrogen Fertilizer on the Yield and Quality of Bok Choy and on Soil Nutrients

This study was aimed at problems associated with low fertilizer using efficiency, excessive nitrate content of vegetables, and soil degradation in greenhouse vegetable production. A pot experiment was conducted to assess the effects of applying biochar-coated nitrogen fertilizer (BCNF) on the yield, quality, and nitrate content of bok choy (Brassica rapa subsp. Chinensis) as well as on soil nutrients in greenhouses. Four treatments were set up as follows: no nitrogen fertilizer application (BA), chemical nitrogen fertilizer application (CK), biochar-coated nitrogen fertilizer application (BCNF, the amount of nitrogen was equal to that of chemical fertilizer), and reduced biochar-coated nitrogen fertilizer application (D-BCNF, the amount of fertilizer was 80% of BCNF). Compared with the other treatments, BCNF treatment increased chlorophyll content, plant height, maximum leaf length, maximum leaf width, and other biological characters of bok choy. Compared with CK treatment, BCNF treatment increased the fresh weight of bok choy by 14.02%, while reducing the root–shoot ratio and nitrate content by 19.1% and 46%, respectively. It was further found that the application of BCNF could effectively increase the content of soil organic matter; reduce the leaching loss of nitrate nitrogen, exchangeable calcium and magnesium; and effectively improve nitrogen use efficiency. Therefore, the application of BCNF can not only reduce the loss of fertilizer nutrients, promote plant growth, and improve fertilizer utilization, but it can also improve soil nutrients, fix carbon, and reduce emissions. It is a new type of environmental protection fertilizer with application prospects.

Ecological stoichiometry and adaptations to drought and nitrogen in Hevea brasiliensis and Dalbergia odorifera in different planting patterns

Two tropical forest trees (Dalbergia odorifera T. Chen and Hevea brasiliensis Muell. Arg), cultivated both in pure or mixed planting systems under drought and nitrogen-applied conditions, were selected at seedling stages as experimental materials to investigate their eco-physiological responses, interactions with neighboring trees, and the stoichiometry of carbon (C), nitrogen (N), and phosphorus (P). The results highlighted significant differences in biomass allocation between D. odorifera, which allocates more to root growth, and H. brasiliensis, favoring stem growth. It demonstrates that mixed planting enhances tree growth under well-watered conditions, while nitrogen application promotes growth across different moisture levels, with species-specific responses. Water and nitrogen interaction notably affects H. brasiliensis growth but less so for D. odorifera, revealing complex effects on their biochemical responses to oxidative stress. The mixed planting benefits both species, influencing nutrient dynamics and stoichiometry in D. odorifera. The study also shows that nitrogen application under well-watered conditions alters nutrient ratios, particularly affecting nutrient availability and competition between species in mixed planting setups. In conclusion, this research emphasizes the complex interplay between planting patterns, water, and nitrogen, which significantly impacts tree growth, nutrient dynamics, and stress responses, suggesting that specific management strategies could optimize forestry practices.

Microbe‐induced plant resistance against insect pests depends on timing of inoculation but is consistent across climatic conditions

Abstract To cope with abiotic and biotic stressors, plants have developed mutualistic associations with beneficial soil microbes, but little is known about how extreme abiotic conditions impact on microbe‐induce resistance to insect herbivores. Extreme temperatures are often accompanied by extremes in plant water availability, which together reduce plant growth and change plant physiology. There are potential consequences for increasing plant susceptibility to biotic stresses, and this poses a real challenge for plant productivity. We evaluated how the effects of beneficial soil bacteria (Acidovorax radicis N35e) on barley plant growth and resultant resistance against aphid infestation (Sitobion avenae) were impacted by a single heatwave event across a plant water availability gradient. We also tested if timing of bacterial inoculation (before or after the temperature treatment) affected bacteria‐plant interactions on aphids. We found that heatwaves affected plant biomass allocation from above‐ground to below‐ground tissues. Inoculation with A. radicis led to reduction of aphid numbers, but depended on timing of inoculation, and led to stronger resistance when inoculations occurred closer to aphid infestation. Remarkably, microbe‐induced resistance against aphids was consistent across heatwave and water availability treatments. This study provides evidence that beneficial plant‐bacteria interactions may represent a potential solution for sustainable agricultural practices to enhance plant growth and response to insect pests under climate change. Future field trials should investigate the consistency of beneficial effects reported here for a better understanding of multispecies interactions in the context of global change. Read the free Plain Language Summary for this article on the Journal blog.

Selection of M5 mutant lines of wheat (Triticum aestivum L.) for agronomic traits and biomass allocation under drought stress and non-stressed conditions.

In the face of climate changes and limited water availability for irrigated crop production, enhanced drought tolerance and adaptation is vital to improve wheat productivity. The objective of this study was to determine the responses of newly bred and advanced mutant lines of wheat based on agronomic traits and biomass allocation under drought-stressed and non-stressed environments for production and breeding. Fifty-three mutant lines, including the parental check and six check varieties, were evaluated under non-stressed (NS) and drought stressed (DS) conditions in the field and controlled environments using a 20 x 3 alpha lattice design with two replicates. The following agronomic data were collected: days to 50% heading (DTH), days to maturity (DTM), plant height (PH), number of productive tillers (PTN), shoot biomass (SB), root biomass (RB), total biomass (TB), root: shoot ratio (RSR), spike length (SL), thousand seeds weight (TSW) and grain yield (GY). Data were analyzed and summarized using various statistical procedures and drought tolerance indices were computed based on grain yield under NS and DS conditions. Significant (P < 0.05) differences were recorded among the mutant lines for most assessed traits under NS and DS conditions. Grain yield positively and significantly (p < 0.001) correlated with PTN (r = 0.85), RB (r = 0.75), SB (r = 0.80), SL (r =0.73), TB (r = 0.65), and TSW (r = 0.67) under DS condition. Principal component analysis revealed three components contributing to 78.55% and 77.21% of the total variability for the assessed agronomic traits under DS and NS conditions, respectively. The following traits: GY, RB, SB, and PTN explained most of the variation with high loading scores under DS condition. Geometric mean productivity (GMP), mean productivity (MP), harmonic mean (HM), and stress tolerance index (STI) were identified as the best drought tolerance indices for the identification of tolerant lines with positive correlations with GY under NS and DS conditions. Among the advanced lines tested, LMA16, LMA37, LMA47, LMA2, and LMA42 were selected as the superior lines with high performance and drought tolerance. The selected lines are recommended for multi-environment trails and release for production in water-limited environments in South Africa.

Prohexadione-Calcium Mitigates the Overgrowth of Corn Seedlings

In the temperate climate of South Korea, specific corn varieties are cultivated using plug trays. The cultivation process is initiated from February to March within greenhouse facilities, maintaining a temperature below 10 degrees Celsius. Following this, in April, seedlings are transplanted to enable an exceptionally early harvest for increased profitability. However, the subsequent elevation in indoor temperatures leads to seedling overgrowth. This study explores the effectiveness of three plant growth regulators—paclobutrazol, prohexadione-calcium, and diniconazole–on super sweet corn seedlings. Significantly, the application of prohexadione-calcium at 2 ppm during the first leaf stage substantially reduces seedling height and impedes the growth of both the first and second internodes. This impact extends to leaf-related traits, manifesting reductions in the area, length, and width of the third leaf. Furthermore, prohexadione-calcium induces a significant decrease in both fresh and dried shoot weight, while simultaneously augmenting root weight. This alteration results in a noteworthy shift in the root–shoot ratio, particularly at 2 ppm. Subsequent experiments have identified the optimal concentration of prohexadione-calcium at 15 ppm, effectively mitigating overgrowth in both hybrid and inbred corn varieties. These findings provide essential insights for practitioners seeking to efficiently manage corn seedling overgrowth. The study contributes to understanding the retardant effect of prohexadione-calcium on various morphological traits, offering practical applications for optimizing plant growth regulator concentrations in corn cultivation strategies.

Silicon Mitigates the Attack of Pests and Diseases on Ipê-Roxo (Handroanthus impetiginosus) Seedlings

Abstract Background Silicon in plants is a structuring element that promotes water and saline stress tolerance and decreases transpiration. The silica accumulated in the cuticle establishes a physical barrier and helps fight against pests and diseases. The present study aimed to evaluate the development of ipê-roxo (Handroanthus impetiginosus) seedlings in different environments, and the application of potassium silicate and its efficiency in mitigating the attack of pests and diseases. Methods The experiment was carried out in an agricultural greenhouse and under full sun with silicic doses of 0 and 7.15 mg per plant in a completely randomized design arranged in a 2 × 2 factorial scheme, with 6 replications of 4 seedlings per plot. Plant height, chlorophyll, stem diameter, number of leaves, shoot dry matter, root dry matter, total dry matter, height-diameter ratio, root-shoot ratio, root-plant ratio, Dickson quality index, disease severity, and pest intensity were evaluated. Results Silicon application did not confer biometric qualities to the seedlings. The application of silicon conferred 24.6% higher protection against disease severity at a 90% probability level. The protected environment promoted 48.8% more protection against the attack of pests on the seedlings. The silicon application decreases the intensity of pests in the protected environment by 36.3%. Seedlings in a protected environment increase the production of chlorophyll but are 29.6% more susceptible to the severity of diseases. The full sun promoted greater diameters, phytomass, and Dickson quality index by 18%, 73%, and 195%, respectively. Conclusions The bestHandroanthus impetiginosusseedlings were obtained under full sun. Silicon mitigated the attack of pests and diseases onHandroanthus impetiginosusseedlings.

Pengaruh Pupuk Hayati Jamur Mikoriza Dan Pupuk Rock Phosphate Terhadap Serapan P, Pertumbuhan serta Hasil Tanaman Cabai Rawit (Capsicum frutescens L.)

Application of mycorrhizal fungi biological fertilizers and rock phosphate fertilizers can increase plant P uptake, growth and yield of cayenne pepper (Capsicum frutescens L.). The purpose of this study was to determine the effect of the interaction between mycorrhizal fungi biofertilizer and rock phosphate fertilizer on P uptake, growth and yield of cayenne pepper. The experimental design used was a completely randomized design (CRD) factorial with 2 factors and 3 replications. The first factor was the application of 0 gr (M0), 10 g (M1) and 20 g (M2) mycorrhizal fungal biofertilizers and the second factor was the application of 0 kg rock phosphate fertilizer or the equivalent of 0 g (R0), 150 kg or 1 g (R1) and 300 kg or 2.6 g (M2). The variables observed were plant height, number of fruit planted, fruit fresh weight, plant fresh weight, root volume, root infection, plant dry weight, root shoot ratio and P uptake. The observed data were tested using analysis of variance (ANOVA) and tested further. using Duncan multiple range test (DMRT) at 95% confidence level. The results showed that there was no interaction between the application of mycorrhizal fungi biofertilizers and rock phosphate fertilizers. Application of mycorrhizal fungal biofertilizer (M1) can increase the degree of root infection by 72.22%, the number of fruit planted, fruit fresh weight, plant fresh weight, plant dry weight, root volume, root infection, P uptake and root shoot ratio. Application of rock phosphate fertilizer can also increase the number of fruit plants, plant fresh weight, plant dry weight, root volume and P uptake.&#x0D;

Responses of plant biomass and biomass allocation to experimental drought: A global phylogenetic meta-analysis

Divergent responses of plant biomass to drought were found across hundreds of manipulative experiments. While many researchers have explored the influences of plant functional types (PFTs) and climatic conditions, few focus on the importance of evolutionary history. Here we compiled a global dataset of the responses of plant biomass and biomass allocation to the experimental drought from 281 studies conducted on 329 wild species and conducted both traditional and phylogenetic meta-analyses to explore the potential role of evolutionary history in affecting the differences among PFTs and the regulation effects of environmental conditions. We found that there were no consistent differences in biomass responses to drought between gymnosperm and angiosperm woody plants when the traditional meta-analysis was applied. Taking the phylogenetic information (the proxy of evolutionary history) into account resulted in more sensitive responses in gymnosperms than angiosperms but with great uncertainty, probably due to the high hydraulic diversity in both groups. The observed higher drought sensitivity in evergreen gymnosperms than deciduous ones, and in C3 herbs than in C4 ones were mainly derived from the phylogenetic relatedness among species. The influences of drought intensity were prevalent in both traditional and phylogenetic meta-analyses. These results highlight the vital role of plant evolutionary history played in affecting plant responses to drought. Given the potentially complicated interactions of climatic change and evolutionary history, we call for experiments that aim to investigate the role of phylogenetic relatedness on plant and ecosystem functions in future studies.

Agroecological genetics of biomass allocation in wheat uncovers genotype interactions with canopy shade and plant size.

How plants distribute biomass among organs influences resource acquisition, reproduction and plant-plant interactions, and is essential in understanding plant ecology, evolution, and yield production in agriculture. However, the genetic mechanisms regulating allocation responses to the environment are largely unknown. We studied recombinant lines of wheat (Triticum spp.) grown as single plants under sunlight and simulated canopy shade to investigate genotype-by-environment interactions in biomass allocation to the leaves, stems, spikes, and grains. Size-corrected mass fractions and allometric slopes were employed to dissect allocation responses to light limitation and plant size. Size adjustments revealed light-responsive alleles associated with adaptation to the crop environment. Combined with an allometric approach, we demonstrated that polymorphism in the DELLA protein is associated with the response to shade and size. While a gibberellin-sensitive allelic effect on stem allocation was amplified when plants were shaded, size-dependent effects of this allele drive allocation to reproduction, suggesting that the ontogenetic trajectory of the plant affects the consequences of shade responses for allocation. Our approach provides a basis for exploring the genetic determinants underlying investment strategies in the face of different resource constraints and will be useful in predicting social behaviours of individuals in a crop community.

Trade‐offs in rooting strategy dimensions along an edaphic gradient in a grassland ecosystem

Abstract Roots are essential to the diversity and functioning of plant communities, but trade‐offs in rooting strategies are still poorly understood. We evaluated existing frameworks of rooting strategy trade‐offs and tested their underlying assumptions, guided by the hypothesis that community‐level rooting strategies are best described by a combination of variation in organ‐level traits, plant‐level root:shoot allocation and symbiosis‐level mycorrhizal dependency. We tested this hypothesis using data on plant community structure, above‐ and below‐ground biomass, eight root traits including mycorrhizal colonisation and soil properties from an edaphic gradient driven by elevation and water availability in sandhills prairie, Nebraska, USA. We found multidimensional trade‐offs in rooting strategies represented by a two‐way productivity‐durability trade‐off axis (captured by root length density and root dry matter content) and a three‐way resource acquisition trade‐off between specific root length, root:shoot mass ratio and mycorrhizal dependence. Variation in rooting strategies was driven to similar extents by interspecific differences and intraspecific responses to soil properties. Organ‐level traits alone were insufficient to capture community‐level trade‐offs in rooting strategies across the edaphic gradient. Instead, trait variation encompassing organ, plant and symbiosis levels revealed that consideration of whole‐plant phenotypic integration is essential to defining multidimensional trade‐offs shaping the functional variation of root systems. Read the free Plain Language Summary for this article on the Journal blog.

Variations in root architecture traits and their association with organ mass fraction of common annual ephemeral species in the desert of northern Xinjiang.

The variation of plant traits is closely related to the trade-offs between resource acquisition and conservation, as well as the accumulation of biomass. However, there has been a lack of comprehensive insights into the variation patterns, phylogenetic conservatism, and covariation with biomass allocation of root system architecture in desert areas. We examined the root systems of 47 annual ephemeral species and evaluated their biomass allocation and six key root system architecture traits. Our results indicated that the variation in root traits mainly originated from interspecific variation (48.78%-99.76%), but intraspecific variation should not be ignored as to why the contribution rate of root tissue density (RTD) reached 51.22%. The six root traits were mainly loaded on the first and second axes of the principal component analysis (PCA), these traits mainly vary along two dimensions. The highest interspecific variation is in RTD (51.63%) and the lowest in topological index (TI; 5.92%). The intraspecific variation value and range of specific root length (SRL), specific root area (SRA), and RTD were significantly higher than TI (p < .05), and they are not limited by phylogenetic relationships (0< K < 1, p > .05). The SRA is positively correlated with SRL (r = .72, p < .001) and negatively correlated with RTD (r = -.57, p < .05). The LMF is positively correlated with SRL, and SRA demonstrated the coordination between water consumption and acquisition. The positive correlation between RMF and MRD indicated the coordination of root carbon investment with exploring soil vertical space. The multi-dimensional variation of root traits, divergence of RTDs, and convergence of TI are important ecological strategies for annual short-lived plants to adapt to heterogeneous desert habitats. Meanwhile, these plants achieve optimal access to scarce resources through the high plasticity of resource acquisition (e.g., SRL and SRA) and conservation traits (e.g., RTD), as well as the trade-offs between them and organ mass fraction.

Effects of light qualities on growth and physiological-biochemical traits of Scutellaria baicalensis.

Canopy spectral composition significantly affects growth and functional traits of understory plants. In this study, we explored the optimal light condition suitable for enhancing Scutellaria baicalensis's yield and quality, aiming to provide scientific reference for the exploitation and utilization of medicinal plant resources in the understory of forests. We measured the responses of growth, morphology, biomass allocation, physiological traits, and secon-dary metabolites of S. baicalensis to different light qualities. S. baicalensis was cultured under five LED-light treatments including full spectrum light (control), ultraviolet-A (UV-A) radiation, blue, green, and red light. Results showed that UV-A significantly reduced plant height, base diameter, leaf thickness, leaf area ratio, and biomass of each organ. Red light significantly reduced base diameter, biomass, effective quantum yield of photosystem Ⅱ (ФPSⅡ), and total flavonoid concentration. Under blue light, root length and total biomass of S. baicalensis significantly increased by 48.0% and 10.8%, respectively, while leaf number and chlorophyll content significantly decreased by 20.0% and 31.6%, respectively. The other physiological and biochemical traits were consistent with their responses in control. Our results suggested that blue light promoted photosynthesis, biomass accumulation, and secondary metabolite synthesis of S. baicalensis, while red light and UV-A radiation negatively affected physiological and biochemical metabolic processes. Therefore, the ratio of blue light could be appropriately increased to improve the yield and quality of S. baicalensis.

Combined Effect of Biochar and Plant Growth-Promoting Rhizbacteria on Physiological Responses of Canola (Brassica napus L.) Subjected to Drought Stress

Biochar (BC) and plant growth-promoting microbes (PGPR) could represent a suitable agronomical strategy to mitigate the impacts of drought in arid agro-environmental conditions. However, there is currently little understanding of the synergistic benefit of combining BC and PGPR to increase drought tolerance in oilseeds. In this study, the physiological response of two water-stressed canola (Brassica napus L.) plants subjected to the application of BC obtained from waste wood of Morus alba applied solely or in combination with PGPR strains (Pseudomonas sp.) was evaluated. The experiment consists of two genotypes and nine treatments [(C-Control, T1-15 days drought (15DD), T2-30 days drought (30DD), T3-15 days of drought + PG (15DD + PG), T4-30 days of drought + PG (30DD + PG), T5-15 days drought + biochar (15DD + BC), T6-30 days drought + biochar (30DD + BC), T7-15 days drought + biochar + PG (15DD + BC + PG), T8-30 days drought + biochar + PG (30DD + BC + PG)]. Drought stress decreased emergence energy (EE), leaf area index (LAI), leaf area ratio (LAR), root shoot ratio (RSR), moisture content of leaves (MCL), percent moisture content (%MC), moisture content of shoot (MCS) and moisture content of root (MCR), and relative water content (RWC) in both varieties of Brassica napus L., which in contrast, it is increased by the collective application of both biochar and PGPR. In both varieties, N, P, K, Mg, and Ca concentrations were highest in all the biochar and PGPRs separate and combined treatments, while lowest in 15 and 30 days drought treatments. Osmolyte contents like Glycine betaine (GB) and sugar remarkably increased in the stress condition and then reduced due to the synergistic application of biochar and PGPR. Drought stress has a repressive effect on the antioxidant enzymatic system like Peroxidase (POD), Superoxide dismutase (SOD), and glutathione reductase (GR) as well as total flavonoids, phenolics, and protein content. The antioxidant enzymes and phenolic compounds were dramatically increased by the combined action of biochar and PGPRs. A significant increase in EE, LAR, RSR, and RWC under 15 and 30 days drought conditions, evidently highlighting the synergistic effect of BC and PGPR. The results conclude a substantial and positive effect of the combined use of BC and PGPR strains on canola's response to induced drought stress, by regulating the physiological, biochemical, and agronomic traits of the plants.Graphical

Experimental Investigation of Water Infiltration Law in Loess with Black Locust (Robinia pseudoacacia) Roots

Physical model experiments are increasingly applied in the study of the water infiltration law in loess with roots. In the past, due to differences in study objects and the limitations of measuring techniques, the infiltration law in loess with roots is rarely evaluated by using appropriate indoor physical model experimental data. In order to investigate the law of water infiltration in loess with roots, we designed a new soil column experimental device that can automatically collect data and images. By comparing the soil column experiment data of loess, we analyzed variables in root contents (the ratio of root mass to dry soil mass) and root types. Roots with diameters of 0–2 mm, 2–5 mm, and 5–10 mm are defined as type I, type II, and type III, respectively. It was found that the water infiltration rate, water-holding capacity, and saturated permeability coefficient increase with the increase in root content. In loess containing different root types, the root types were found to improve the rate of water infiltration, water-holding capacity, and saturated permeability coefficient in the soil. The root types were ranked in descending order in terms of their impact: root type II had the highest improvement, followed by root type III, and then root type I. The phenomenon of circumferential flow existed when water infiltrated loess with roots. Root content and root type would affect the radius of circumferential flow, infiltration path, and cross-section. When calculating the saturated permeability coefficient of loess with roots, ignoring the effect of circumferential flow would lead to a higher result.

Morphological and physiological response of amphibious Rotala rotundifolia from emergent to submerged form.

Rotala rotundifolia is an amphibious aquatic plant that can live in submerged and emergent forms. It is superior in nitrogen and phosphorus removal. To elucidate its adaptation strategies from emergent to submerged conditions, phenotypic and physiological responses of R. rotundifolia were investigated during three months of submergence, at water levels of 0cm (CK), 50cm (W50), and 90cm (W90). Results showed that submergence stress reduced the relative growth rate of plant height, fresh weight, and biomass accumulation, leading to root degradation and a significant decline in the root-shoot ratio. The amounts of soluble protein (SP), soluble sugar (SS), and starch in the aerial leaves of W50 and W90 decreased during the early stages of submergence compared to CK, whereas the total chlorophyll and proline contents, and activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased. The contents of endogenous hormones, including abscisic acid (ABA), gibberellin (GA), and indole-3-acetic acid (IAA), decreased during the change in leaf shape; the decline in ABA was more obvious. The leaf primordium generated transition leaves and submerged leaves to resolve the "carbon starvation" of plants. The maximum values of non-structural carbohydrates (NSC) in the leaves of W50 and W90 occurred at day 30, reaching 14.0 mg g- 1and 10.5 mg g- 1, respectively. The contents of SP and starch, activities of SOD and CAT of the roots in submerged treatments increased, while SS and proline content decreased at day 7. These results demonstrated that developing heterophyllous leaves, increasing chlorophyll content, and regulating plant carbon allocation and consumption were important mechanisms of R. rotundifolia to adapt to underwater habitats.