Effect of Substrate Properties and Phosphorus-supply on the Rare Earth Element Facilitation in Mixed-culture Cropping Systems of Hordeum Vulgare, Lupinus Albus and Lupinus Angustifolius

This study presents how nutrient availability and intercropping may influence the migration of REE when cultivated under P-deficient conditions. In a replacement model, Hordeum vulgare was intercropped with 11% Lupinus albus cv. Feodora and 11% L. angustifolius cv. Sonate. They were cultivated on two substrates, A (pH = 7.8) and B (pH = 6.6). Two nutrient solutions were supplied, with N, K, Mg and high P-supply (P+), the other with N, K, Mg, and one-third of P-supply (P-, applied to L0 and Lan only). Simultaneously, a greenhouse experiment was conducted to quantify carboxylate release. There, one group of L. albus and L. angustifolius was supplied with 200 µM K2HPO4 (P+) together with the other nutrients while a second group received 20 µM P (P-). L. albus released higher carboxylates at low P-supply than L. angustifolius. Higher P-supply did not influence the P concentrations and contents of H. vulgare neither on substrate A nor on substrate B. However, addition of P decreased the concentrations of REEs, especially in plants cultivated on alkaline soil. Nutrient accumulation decreased in H. vulgare in intercropping with L. angustifolius when cultivated on the alkaline substrate A with high P-supply. In the same conditions, the accumulation of REE in H. vulgare significantly increased. Conversely, on the acidic substrate B intercropping with L. albus decreased REE contents and concentrations in H. vulgare. Intercropping with L. angustifolius opens an opportunity for enhanced phytomining and accumulation of REE. Furthermore, intercropping with L. albus on REE polluted soils may be utilized to restrict REE accumulation in crops used for food production.

Interactive Effects of Biochar, Nitrogen, and Phosphorous on the Symbiotic Performance, Growth, and Nutrient Uptake of Soybean (Glycine max L.)

Numerous studies reported the positive effect of soil amendment with biochar on plant development. However, little is known about biochar and its interrelation with nitrogen (N) and phosphorous (P) additions and their impact on plant growth. We carried out greenhouse experiments to understand the interactive effects of nitrogen and phosphorus supply, as well as biochar amendment, on the symbiotic performance of soybean (Glycine max L.) with Bradyrhizobium japonicum, and plant growth and nutrient uptake. The biochar was produced from maize by heating at 600 °C for 30 min and used for pot experiments at an application rate of 2%. Plants were fertilized with two different concentrations of P (KH2PO4) and N (NH4NO3). Biochar application significantly increased the dry weight of soybean root and shoot biomass, by 34% and 42%, under low nitrogen and low phosphorus supply, respectively. Bradyrhizobium japonicum inoculation enhanced the dry weight of shoot biomass significantly, by 41% and 67%, in soil without biochar and with biochar addition, respectively. The nodule number was 19% higher in plants grown under low N combined with low or high P, than in high N combinations, while biochar application increased nodule number in roots. Moreover, biochar application increased N uptake of plants in all soil treatments with N or P supply, compared with B. japonicum-inoculated and uninoculated plants. A statistical difference in P uptake of plants between biochar and nutrient levels was observed with low N and high P supply in the soil. Our results show that the interactions between nitrogen, phosphorus, and biochar affect soybean growth by improving the symbiotic performance of B. japonicum and the growth and nutrition of soybean. We observed strong positive correlations between plant shoot biomass, root biomass, and N and P uptake. These data indicated that the combined use of biochar and low N, P application can be an effective approach in improving soybean growth with minimum nutrient input.

Effects of Exogenous Ethylene and Cobalt Chloride on Root Growth of Chinese Fir Seedlings under Phosphorus-Deficient Conditions

Studying the effects of different concentrations of ethephon on morphological and physiological changes in the roots of Chinese fir (Cunninghamia lanceolata Lamb. Hook.) seedlings under P deficiency can reveal the internal adaptive mechanisms of these plants under nutrient stress. Herein, we investigated the effects of different ethephon and cobalt chloride concentrations under normal P supply and P deficiency. A significant effect (p < 0.05) of exogenous additive application was observed on the development of Chinese fir root length, surface area, and volume. These root development indices showed maximum values when the ethephon concentration was 0.01 g kg−1 under normal P supply and P deficiency, and they were significantly different from those under 0.04 g kg−1 ethephon treatment. Similarly, the indices showed maximum values when CoCl2 concentration was 0.01 g kg−1 under P deficiency and was significantly different (p < 0.01) from those under 0.2 g kg−1 CoCl2 treatment. Under normal P supply, an increase in ethephon concentration caused superoxide dismutase (SOD; E.C. 1.15.1.1) activity to decrease and peroxidase (POD; E.C. 1.11.1.X) activity to increase gradually. Conversely, CoCl2 addition (0.01 g kg−1) promoted SOD and POD activities under P deficiency. There were no significant differences (p > 0.05) in malondialdehyde content of seedlings among ethephon or CoCl2 treatments. In conclusion, ethylene plays a significant role in adaptative mechanisms underlying stress resistance in plants, prompting them to respond to P starvation and improving seedlings’ tolerance to P-deficient conditions.

Towards a history of Holocene P dynamics for the Northern Hemisphere using lake sediment geochemical records

Present-day lake water phosphorus (P) enrichment and accelerated P cycling are changes superimposed on a dynamic Holocene history of landscape development following glaciation, changes in climate, and long-term low-intensity human activity. Knowledge of the history of long-term P dynamics is essential for understanding present-day landscape P export and for managing both terrestrial and aquatic environments. This study is the first attempt to constrain the timing and magnitude of terrestrial changes in Holocene P dynamics across the Northern Hemisphere using lake sediment records. Here we reconstruct trajectories in terrestrial Holocene P dynamics for the Northern Hemisphere. We apply a simple process model to published lake sediment geochemical P records from 24 sites, producing records of landscape P yield and reconstructing lake water total phosphorus (TP) concentrations. Individual site trajectories of landscape P yield and lake water TP vary systematically, with differences attributable to local landscape development history. Three distinct traits are apparent. Mountain sites with minimal direct human impact show falling P supply and conform to conceptual models of natural soil development (Trait 1). Lowland sites where substantial (pre-)historic agriculture was present show progressively increasing P supply (Trait 2). Lowland sites may also show a rapid acceleration in P supply over the last few centuries, where high-intensity land use, including settlements and farming, is present (Trait 3). Where data availability permitted comparison, our reconstructed TP records agree well with monitored lake water TP data, and our sediment-inferred P yields are comparable to reported catchment export coefficients. Comparison with diatom-inferred TP reveals good agreement for recent records. Our reconstructions form the first systematic assessment of average terrestrial P export for the Northern Hemisphere over the Holocene and provide the empirical data needed for constraining long-term landscape P cycling models and values for terrestrial P export that could be used for ocean P cycling models. The long-term perspective provided by our sediment-inferred TP can be used to identify pre-disturbance baselines for lake water quality, information essential to target-driven lake management. We find the first detectable anthropogenic impacts on P cycling ca. 6000 BP, with more substantial impacts as early as 3000 BP. Consequently, to characterize pre-disturbance lake P conditions at Trait 2 and Trait 3 sites, it is necessary to consider time periods before the arrival of early farmers. Our use of trait classifications has a predictive power for sites without sediment records, allowing prediction of TP baselines and P trajectories based on regional landscape development history.

Phosphorus-Use Efficiency Modified by Complementary Effects of P Supply Intensity With Limited Root Growth Space

Space availability and the maintenance of adequate phosphorus (P) supply in the root zone are essential for achieving high yield and P-use efficiency in maize production by manipulating the root morphology and arbuscular mycorrhizal (AM) fungi colonization. A major trade-off exists between root growth and AM colonization that is influenced by soil P supply intensity and space availability. However, how soil P manipulates the root morphological characteristics and AM colonization to compensate for the limitation of root-growth space induced by high-planting density is not clear. Therefore, pot experiments were conducted to investigate interactions between the root growth and AM fungi by optimizing soil P supply to compensate for limited root growth space induced by high-planting density. Similar shoot biomass and P uptake values were obtained in P200 (200 mg P kg−1 soil) under D = 40 (i.e., diameter of the pot is 40 cm) and P400 under D = 30, and similar values were obtained for root length, tap root length, root angle, lateral root density, and AM colonization. However, the improvement in P supply in the root zone, shoot biomass, and P uptake in P400 under D = 20 were lower than in P200 under D = 30, and there were no significant differences in the root parameters between P200 and P400 under D = 20; similarly, the root growth and AM colonization exhibited similar trends. These results suggest that optimizing P supply in the root zone to regulate the interaction between root morphological traits and AM colonization can compensate for limited root-growth space. Although P supply in the root zone increased after the root-growth space was compressed, it could not meet the P demand of maize; thus, to achieve the most efficient use of P under intensive high-density maize production, it is necessary to optimally coordinate root growth space and P supply in the root zone.

Effects of Phosphorus Supply on the Leaf Photosynthesis, and Biomass and Phosphorus Accumulation and Partitioning of Canola (Brassica napus L.) in Saline Environment

Salt stress is a major negative factor affecting the sustainable development of agriculture. Phosphorus (P) deficiency often occurs in saline soil, and their interaction inhibits plant growth and seed yield for canola (Brassica napus L.). P supply is considered an effective way to alleviate the damage of salt stress. However, the knowledge of how P supply can promote plant growth in saline environment was limited. A field experiment was conducted to explore the effects of P rate on accumulation, and partitioning, of biomass and P, leaf photosynthesis traits, and yield performance in saline soil in the coastal area of Yancheng City, Jiangsu Province, China, during the 2018–2019 and 2019–2020 growing seasons. P supply increased biomass and P accumulation in all organs, and root had the most increments among different organs. At flowering stage, P supply increased the biomass and P partitioning in root and leaf, but it decreased the partitioning in stem. At maturity stage, P supply facilitated the biomass and P partitioning in seed, but it decreased the partitioning in stem and shell, and it increased the reproductive-vegetative ratio, suggesting that P supply can improve the nutrients transporting from vegetative organs to reproductive organs. Besides, P supply improved the leaf area index and photosynthetic rate at the flowering stage. As a result, the seed yield and oil yield were increased. In conclusion, P supply can improve the canola plant growth and seed yield in a saline environment. P fertilizer at the rate of 120 kg P2O5 ha−1 was recommended in this saline soil.

Genome‑wide association study dissects the genetic control of plant height and branch number in response to low‑phosphorus stress in Brassica napus

Background and Aims Oilseed rape (Brassica napus) is one of the most important oil crops worldwide. Phosphorus (P) deficiency severely decreases the plant height (PH) and branch number (BN) of B. napus. However, the genetic bases controlling PH and BN in B. napus under P deficiency remain largely unknown. This study aims to mine candidate genes for PH and BN by genome-wide association study (GWAS) and determine low-P tolerance haplotypes. Methods An association panel of B. napus were grown in the field with a low P supply (P, 0 kg/ha) and a sufficient P supply (P, 40 kg/ha) across two years and PH and BN were investigated. More than five million single-nucleotide polymorphisms (SNPs) were used to conduct GWAS of PH and BN at two contrasting P supplies. Key Results A total of 2127 SNPs were strongly associated (P &lt; 6.25×10 −07) with PH and BN at two P supplies. There was significant correlation between phenotypic variation and the number of favorable alleles of associated loci on chromosomes A10 (chrA10_821671) and C08 (chrC08_27999846), which will contribute to breeding improvement by aggregating these SNPs. BnaA10g09290D and BnaC08g26640D were identified to be associated with the chrA10_821671 and chrC08_27999846, respectively. Candidate gene association analysis and haplotype analysis showed that the inbred lines carrying ATT at 'BnaA10g09290Hap1' and AAT at 'BnaC08g26640Hap1' had higher PH than lines carrying other haplotype alleles at low P supply. Conclusion Our results demonstrate the power of GWAS in identifying genes of interest in B. napus and provided insights into the genetic basis of PH and BN at low P supply in B. napus. Candidate genes and favorable haplotypes may facilitate marker-based breeding efforts aimed at improving P use efficiency in B. napus.

The Highs and Lows of P Supply in Medical Cannabis: Effects on Cannabinoids, the Ionome, and Morpho-Physiology

Environmental conditions, including the availability of mineral nutrients, affect secondary metabolism in plants. Therefore, growing conditions have significant pharmaceutical and economic importance for Cannabis sativa. Phosphorous is an essential macronutrient that affects central biosynthesis pathways. In this study, we evaluated the hypothesis that P uptake, distribution and availability in the plant affect the biosynthesis of cannabinoids. Two genotypes of medical “drug-type” cannabis plants were grown under five P concentrations of 5, 15, 30, 60, and 90 mg L–1 (ppm) in controlled environmental conditions. The results reveal several dose-dependent effects of P nutrition on the cannabinoid profile of both genotypes, as well as on the ionome and plant functional physiology, thus supporting the hypothesis: (i) P concentrations ≤15 mg L–1 were insufficient to support optimal plant function and reduced photosynthesis, transpiration, stomatal conductance and growth; (ii) 30–90 mg L–1 P was within the optimal range for plant development and function, and 30 mg L–1 P was sufficient for producing 80% of the maximum yield; (iii) Ionome: about 80% of the plant P accumulated in the unfertilized inflorescences; (iv) Cannabinoids: P supply higher than 5 mg L–1 reduced Δ9-tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA) concentrations in the inflorescences by up to 25%. Cannabinoid concentrations decreased linearly with increasing yield, consistent with a yield dilution effect, but the total cannabinoid content per plant increased with increasing P supply. These results reveal contrasting trends for effects of P supply on cannabinoid concentrations that were highest under &lt;30 mg L–1 P, vs. inflorescence biomass that was highest under 30–90 mg L–1 P. Thus, the P regime should be adjusted to reflect production goals. The results demonstrate the potential of mineral nutrition to regulate cannabinoid metabolism and optimize pharmacological quality.

Mixed Growth with Weeds Promotes Mycorrhizal Colonization and Increases the Plant-Availability of Phosphorus under Maize (Zea mays L.)

(1) Background: Weed control decreases the competition for nutrients, but also the potential of increased phosphorus (P) mobilization in soils caused by higher plant diversity. (2) Methods: Impacts of weed species under maize on mycorrhizal colonization and plant-availability of P were investigated in two pot experiments. Plant traits and P mobilization were tested in weed-free maize and in mixed growth with six annual weed species. (3) Results: Growth of maize decreased in treatments with weeds, while P concentrations in its shoots increased in mixed growth with C. album, E. crus-galli and P. convolvulus. Mycorrhizal colonization of maize without weeds was low (<20% of root length), but increased in mixed growth with C. album, E. crus-galli and V. arvensis up to 40%. The activities of Pmobilizing hydrolytic enzymes (phosphatases, ß-glucosidase) and plant-availability of P were occasionally higher under mixed growth with weeds. The dimension of weed impacts on P cycling under maize differed significantly between both experiments. (4) Conclusions: Weeds potentially promote P mobilization and mycorrhizal colonization under maize, but this impact is not guaranteed. The weed-based improved P supply of maize should be defined under field conditions to allow a controlled weed tolerance in maize cropping systems.