Summary Plants respond to soil phosphorus (P) availability by adjusting leaf P among inorganic P (Pi) and organic P fractions (nucleic acids, phospholipids, small metabolites and a residual fraction). We tested whether phylogenetically divergent plants in a biodiversity hotspot similarly adjust leaf P allocation in response to P limitation by sampling along a 2 Myr chronosequence in southwestern Australia where nitrogen (N) limitation transitions to P limitation with increasing soil age. Total P and N, and P allocated to five chemical fractions were determined for photosynthetic organs from Melaleuca systena (Myrtaceae), Acacia rostellifera (Fabaceae) and Hakea prostrata (Proteaceae). Soil characteristics were also determined. Acacia rostellifera maintained phyllode total P and N concentrations at c. 0.5 and 16 mg g−1 DW, respectively, with a constant P‐allocation pattern along the chronosequence. H. prostrata leaves allocated less P to Pi, phospholipids and nucleic acids with increasing soil age, while leaf N concentration was constant. M. systena had the greatest variation in allocating leaf P, whereas leaf N concentration decreased 20% along the chronosequence. Variation in P‐allocation patterns was only partially conserved among species along the chronosequence. Such variation could have an impact on species distribution and contribute to species richness in P‐limited environments.
Aims Banksia attenuata is a resprouting species growing in deep sand, while B. sessilis is a fire-killed species occurring in shallow sand over laterite or limestone. We aimed to discover the ecophysiological basis for their different distributions by exploring their investment in deep non-cluster roots and shallow cluster roots, and their cluster-root functioning.Methods Deep-pot (1 m), shallow-pot (400 mm), hydroponic experiments and phosphorus (P)-extraction experiment were carried out. Biomass allocation, clusterroot exudation, plant P and leaf manganese (Mn) concentrations were measured.Results Banksia attenuata allocated more biomass to deep roots and less biomass to cluster roots than B. sessilis did in deep pots. The two Banksias released similar Revised version without track changes Click here to access/download;Revised version without track changes;Banksia manuscript 20190126 revision clean.docx carboxylates in all experiments, with similar carboxylate-exudation rates in hydroponics. The carboxylate amount per unit cluster root of B. sessilis grown in shallow pots was greater than that of B. attenuata, and B, sessilis acquired more P than B. attenuata did in limestone substrate. Conclusions Greater investment in deep roots for water uptake accounts for the presence of B. attenuata in deep sand, and vice versa for the absence of B. sessilis. A larger investment in cluster roots, which released greater amounts of carboxylates, likely accounts for B. sessilis occurring over limestone. Trade-offs in investment and cluster-root functioning support the species' distribution patterns and life histories.Leaf Mn concentration was a good proxy for the plant capacity to acquire P.
Panax ginseng C.A. Meyer is one of the most important medicinal plants in Northeast China, and ginsenosides are the main active ingredients found in medicinal ginseng. The biosynthesis of ginsenosides is regulated by environmental factors and the expression of key enzyme genes. Therefore, in this experiment, ginseng in the leaf opened stage, the green fruit stage, the red fruit stage, and the root growth stage was used as the test material, and nine individual ginsenosides and total saponins (the sum of the individual saponins) were detected by HPLC (High Performance Liquid Chromatography). There was a trend of synergistic increase and decrease, and saponin accumulation and transfer in different tissues. The expression of key enzyme genes in nine synthetic pathways was detected by real-time PCR, and the correlation between saponin content, gene expression, and ecological factors was analyzed. Correlation analysis showed that in root tissue, PAR (Photosynthetically Active Radiation) and soil water potential had a greater impact on ginsenoside accumulation, while in leaf tissue, temperature and relative humidity had a greater impact on ginsenoside accumulation. The results provide a theoretical basis for elucidating the relationship between ecological factors and genetic factors and their impact on the quality of medicinal materials. The results also have guiding significance for realizing the quality of medicinal materials.
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