Effect of plant density on yield and Quality of perilla sprouts

Morphophysiological and transcriptomic analyses during the development of microspores and megaspores in Orobanche coerulescens

Introduction

Orobanche coerulescens is a parasitic plant considered as a malignant weed due to its harmful effects on crops. However, its richness in high-value secondary metabolites makes it a significant medicinal resource. The development of microspores and megaspores is essential for sexual reproduction in plants but research on this aspect of O. coerulescens is lacking.

Methods

This study aimed to systematically observe the developmental processes of microspores and megaspores in O. coerulescens using microscopic techniques. We measured the levels of soluble sugar, starch, and phytohormones during different developmental stages. We also investigated the key regulatory genes in the metabolic pathways of phytohormones that are closely related to the development of microspores and megaspores using transcriptome sequencing technology.

Results and discussion

The findings revealed that the flower development process of O. coerulescens could be categorized into six stages. Mature pollen was tricellular, with downy ornamentation and pores on the outer wall. The embryo sac was the monosporangiate polygonum type, and the ovule was inverted. The megaspores developed and matured about 15 days later than the microspores. The soluble sugar level of the flower buds decreased initially and then increased during development, whereas the starch level showed an opposite trend. The levels of strigolactone, auxin, and gibberellins gradually increased throughout the development process. The key genes regulating phytohormone synthesis during the development of microspores and megaspores were identified as ALDHs (Aldehyde Dehydrogenases). In contrast, the key genes regulating phytohormone signaling included TIR1 (Transport Inhibitor Response 1) and IAA3 (Indole-3-acetic Acid Inducible 3), and the key TF was ARF5 (AUXIN RESPONSE FACTOR 5). The findings of this study enhanced the understanding of O. coerulescens biology, providing theoretical references for regulating its reproduction, implementing biological control measures, maintaining its population, and optimizing resource utilization.

Exploring the Influence of Planting Densities and Mulching Types on Photosynthetic Activity, Antioxidant Enzymes, and Chlorophyll Content and Their Relationship to Yield of Maize

High-density maize cultivation can enhance yield, but water scarcity on the Loess Plateau may limit this potential. Mulching is a sustainable practice that conserves soil moisture, yet limited studies exist on the combined effects of planting densities and mulching types on maize performance in this region. Over two years, an experiment investigated the effects of mulching (no mulching (NM), plastic film mulching (PM), and straw mulching (SM)) at various densities (60,000 to 90,000 plants ha-1). The results showed that mulching significantly improved grain yield and other metrics compared to NM. PM and SM enhanced yields notably at 75,000 plants ha-1, while NM was more favorable at 67,500 plants ha-1. Physiological responses varied with density, showing a decreased photosynthesis rate alongside an increased transpiration rate. PM exhibited a 32 and 13% increase in catalase and superoxide dismutase activities, while malondialdehyde content was reduced by 7% compared to NM. The average of both years indicates that PM significantly increased the grain yield, net photosynthesis rate, and chlorophyll content by 5.8, 26.8, and 26.9%, while SM showed a 3, 12, and 12% increase, respectively, compared to NM. In conclusion, the combination of mulching and optimized planting density could enhance maize cultivation in the Loess Plateau.

Endophytic Pseudomonas fluorescens promotes changes in the phenotype and secondary metabolite profile of Houttuynia cordata Thunb

The interactions between microbes and plants are governed by complex chemical signals, which can forcefully affect plant growth and development. Here, to understand how microbes influence Houttuynia cordata Thunb. plant growth and its secondary metabolite through chemical signals, we established the interaction between single bacteria and a plant. We inoculated H. cordata seedlings with bacteria isolated from their roots. The results showed that the total fresh weight, the total dry weight, and the number of lateral roots per seedling in the P. fluorescens-inoculated seedlings were 174%, 172% and 227% higher than in the control seedlings. Pseudomonas fluorescens had a significant promotional effect of the volatile contents compared to control, with β-myrcene increasing by 192%, 2-undecanone by 203%, decanol by 304%, β-caryophyllene by 197%, α-pinene by 281%, bornyl acetate by 157%, γ-terpinene by 239% and 3-tetradecane by 328% in P. fluorescens-inoculated H. cordata seedlings. the contents of chlorogenic acid, rutin, quercitin, and afzelin were 284%, 154%, 137%, and 213% higher than in control seedlings, respectively. Our study provided basic data to assess the linkages between endophytic bacteria, plant phenotype and metabolites of H. cordata to provide an insight into P. fluorescens use as biological fertilizer, promoting the synthesis of medicinal plant compounds.

Effects of Different Donor Ages on the Growth of Cutting Seedlings Propagated from Ancient Platycladus orientalis

The effects of tree age on the growth of cutting seedlings propagated from ancient trees have been an important issue in plant breeding and cultivation. In order to understand seedling growth and stress resistance stability, phenotypic measurements, physiological assays, and high-throughput transcriptome sequencing were performed on sown seedlings propagated from 5-year-old donors and cutting seedlings propagated from 5-, 300-, and 700-year-old Platycladus orientalis donors. In this study, the growth of cutting seedlings propagated from ancient trees was significantly slower; the soluble sugar and chlorophyll contents gradually decreased with the increase in the age of donors, and the flavonoid and total phenolic contents of sown seedlings were higher than those of cutting seedlings. Enrichment analysis of differential genes showed that plant hormone signal transduction, the plant-pathogen interaction, and the flavone and flavonol biosynthesis pathways were significantly up-regulated with the increasing age of cutting seedlings propagated from 300- and 700-year-old donors. A total of 104,764 differentially expressed genes were calculated using weighted gene co-expression network analysis, and 8 gene modules were obtained. Further, 10 hub genes in the blue module were identified, which revealed that the expression levels of JAZ, FLS, RPM1/RPS3, CML, and RPS2 increased with the increase in tree age. The results demonstrated that the age of the donors seriously affected the growth of P. orientalis cutting seedlings and that cutting propagation can preserve the resistance of ancient trees. The results of this study provide important insights into the effects of age on asexually propagated seedlings, reveal potential molecular mechanisms, and contribute to an improvement in the level of breeding and conservation of ancient germplasm resources of P. orientalis trees.

Effects of Donor Ages and Propagation Methods on Seedling Growth of Platycladus orientalis (L.) Franco in Winter

To evaluate the effects of donor ages on growth and stress resistance of 6-year-old seedlings propagated from 5-, 2000-, and 3000-year-old Platycladus orientalis donors with grafting, cutting, and seed sowing, growth indicators and physiological and transcriptomic analyses were performed in 6-year-old seedlings in winter. Results showed that basal stem diameters and plant heights of seedlings of the three propagation methods decreased with the age of the donors, and the sown seedlings were the thickest and tallest. The contents of soluble sugar, chlorophyll, and free fatty acid in apical leaves of the three propagation methods were negatively correlated with donor ages in winter, while the opposite was true for flavonoid and total phenolic. The contents of flavonoid, total phenolic, and free fatty acid in cutting seedlings were highest in the seedlings propagated in the three methods in winter. KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis of differentially expressed genes showed phenylpropanoid biosynthesis and fatty acid metabolism pathways, and their expression levels were up-regulated in apical leaves from 6-year-old seedlings propagated from 3000-year-old P. orientalis donors. In addition, hub genes analysis presented that C4H, OMT1, CCR2, PAL, PRX52, ACP1, AtPDAT2, and FAD3 were up-regulated in cutting seedlings, and the gene expression levels decreased in seedlings propagated from 2000- and 3000-year-old donors. These findings demonstrate the resistance stability of cuttings of P. orientalis and provide insights into the regulatory mechanisms of seedlings of P. orientalis propagated from donors at different ages in different propagation methods against low-temperature stress.

Estudio de la variabilidad en el tiempo y espacio de la actividad antioxidante y composición bioquímica de Kappaphycus alvarezii en diferentes densidades de siembra

Kappaphycus alvarezii es una de las especies de algas más cultivadas en el mundo, debido a su alto contenido de compuestos bioactivos con reportes antioxidantes y bioestimulantes. El presente estudio evaluó el efecto de las densidades de plantación sobre la composición bioquímica y antioxidante de K. alvarezii cultivada en un sistema de línea larga durante las estaciones seca y húmeda, con el fin de proporcionar una base científica para una cosecha óptima. Se midieron el contenido de humedad, cenizas, grasa, fibra, auxinas, fenoles, flavonoides, DPPH y ABTS. Los datos se analizaron mediante pruebas t, Wilcoxon, Kruskal-Wallis y ANOVA unidireccional. Los resultados mostraron un mayor contenido de grasa (2,01 % P.s), fibra bruta (5,21% P.s), contenido total de fenoles (324,09 μg GAE/g P.s) y ABTS (9,32 μg GAE/g P.s) durante la estación seca. Con respecto a la densidad de plantación, se produjo un aumento significativo del contenido en cenizas, fenoles totales y ABTS con una densidad de 10 líneas.célula-1 al mismo tiempo. Los contenidos de flavonoides, DPPH y auxina mostraron una tendencia estacional opuesta, alcanzando los niveles máximos en la estación húmeda. Este estudio aporta nueva información sobre las condiciones ambientales que pueden provocar cambios en la actividad antioxidante y la composición bioquímica de esta especie con vistas al desarrollo de bioproductos para diferentes sectores industriales como el alimentario, el farmacéutico y el de los fertilizantes en Ecuador. Palabras claves: Alga roja; Fenoles; Flavonoides; Antioxidante; Composición bioquímica; Variación estacional; densidad de siembra.

Biochar combined with Bacillus subtilis SL-44 as an eco-friendly strategy to improve soil fertility, reduce Fusarium wilt, and promote radish growth

Bacillus subtilis as microbial fertilizers contribute to avoiding the harmful effects of traditional agricultural fertilizers and pesticides. However, there are many restrictions on the practical application of fertilizers. In this study, microbial biochar formulations (BCMs) were prepared by loading biochar with B. subtilis SL-44. Pot experiments were conducted to evaluate the effects of the BCMs on soil fertility, Fusarium wilt control, and radish plant growth. The application of BCMs dramatically improved soil properties and favored plant growth. Compared with SL-44 and biochar treatments, the BCMs treatments increased radish plant physical-chemical properties and activities of several enzymes in the soil. What's more, Fusarium wilt incidence had decreased by 59.88%. In addition, the BCMs treatments exhibited a significant increase in the abundance of bacterial genera in the rhizosphere soil of radish. Therefore, this study demonstrated that BCMs may be an eco-friendly strategy for improving soil fertility, reducing Fusarium wilt, and promoting radish plant growth.

A Seasonal Change of Active Ingredients and Mineral Elements in Root of Astragalus membranaceus in the Qinghai-Tibet Plateau

Astragalus membranaceus is an important traditional Chinese herb whose roots have been used for medicinal purposes for more than 2000 years. Because of excessive exploitation, the wild resources are currently almost exhausted, and therefore, artificial planting of Astragalus membranaceus has been increasingly important. But to date, few studies have focused on the active ingredients and mineral element of Astragalus membranaceus in the Qinghai-Tibet Plateau.In this study, five density gradients (M1: 10 cm × 25 cm, M2: 15 cm × 25 cm, M3: 20 cm × 25 cm, M4: 25 cm × 25 cm and M5: 30 cm × 25 cm) were assessed to evaluate the effects of various planting densities on the mineral element and secondary metabolite content of Astragalus membranaceus roots in different months. It was found that the content of calycosin-7-O-β-D-glucoside and astragaloside IV reached its highest in October. Ononin content increased month by month, while formononetin content decreased during months. Calycosin content did not show significant changes during seasons. Taken together, these results suggest that the optimal planting density is 15 cm × 25 cm (D2) and the optimal harvest period is October. According to the results, the Cu content in all samples did not exceed the limit (20 mg/kg). Principal component analysis (PCA) revealed that Na, P, K Al, Ba, Ca, Fe, Li, and Mn were selected as characteristic elements of Astragalus membranaceus. The results also showed a high correlation between elements and active ingredients. Ba and Co had extremely significant associations with astragaloside IV.

Endophytic fungi stimulate the concentration of medicinal secondary metabolites in houttuynia cordata thunb

Endophytic fungi usually establish a symbiotic relationship with the host plant and affect its growth. In order to evaluate the impact of endophytic fungi on the Chinese herbal medicinal plant Houttuynia cordata Thunb., three endophytes isolated from the rhizomes of H. cordata, namely Ilyonectria liriodendra (IL), unidentified fungal sp. (UF), and Penicillium citrinum (PC), were co-cultured individually with H. cordata in sterile soil for 60 days. Analysis of the results showed that the endophytes stimulated the host plant in different ways: IL increased the growth of rhizomes and the accumulation of most of the phenolics and volatiles, UF promoted the accumulation of the medicinal compounds afzelin, decanal, 2-undecanone, and borneol without influencing host plant growth, and PC increased the fresh weight, total leaf area and height of the plants, as well as the growth of the rhizomes, but had only a small effect on the concentration of major secondary metabolites. Our results proved that the endophytic fungi had potential practical value in terms of the production of Chinese herbal medicines, having the ability to improve the yield and accumulation of medicinal metabolites.

Growing in Mixed Stands Increased Leaf Photosynthesis and Physiological Stress Resistance in Moso Bamboo and Mature Chinese Fir Plantations

Mixed-stand plantations are not always as beneficial for timber production and carbon sequestration as monoculture plantations. Systematic analyses of mixed-stand forests as potential ideal plantations must consider the physiological-ecological performance of these plantations. This study aimed to determine whether mixed moso bamboo (Phyllostachys pubescens (Pradelle) Mazel ex J. Houz.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands exhibited better physiological-ecological performance than monoculture plantations of these species. We analyzed leaf photosynthesis, chlorophyll fluorescence, antioxidant enzyme activities, chlorophyll content and leaf chemistry in a moso bamboo stand, a Chinese fir stand and a mixed stand with both species. The results showed that both species in the mixed stand exhibited significantly higher leaf net photosynthesis rate (Amax), instantaneous carboxylation efficiency (CUE), chlorophyll content, maximum quantum yield of photosynthesis (Fv/Fm), photochemical quenching coefficient (qP), PSII quantum yield [Y(II)], leaf nitrogen content, and antioxidant enzyme activities than those in the monoculture plantations. However, the non-photochemical quenching (NPQ) in Chinese fir and 2-year-old moso bamboo was significantly lower in the mixed stand than in the monocultures. In addition, the water use efficiency (WUE) of Chinese fir was significantly higher in the mixed stand. The results suggest that the increase in leaf net photosynthetic capacity and the improved growth in the mixed stand could be attributed primarily to the (i) more competitive strategies for soil water use, (ii) stronger antioxidant systems, and (iii) higher leaf total nitrogen and chlorophyll contents in the plants. These findings suggest that mixed growth has beneficial effects on the leaf photosynthesis capacity and physiological resistance of moso bamboo and Chinese fir.

Dividing the pie: A quantitative review on plant density responses

Plant population density is an important variable in agronomy and forestry and offers an experimental way to better understand plant-plant competition. We made a meta-analysis of responses of even-aged mono-specific stands to population density by quantifying for 3 stand and 33 individual plant variables in 334 experiments how much both plant biomass and phenotypic traits change with a doubling in density. Increasing density increases standing crop per area, but decreases the mean size of its individuals, mostly through reduced tillering and branching. Among the phenotypic traits, stem diameter is negatively affected, but plant height remains remarkably similar, partly due to an increased stem length-to-mass ratio and partly by increased allocation to stems. The reduction in biomass is caused by a lower photosynthetic rate, mainly due to shading of part of the foliage. Total seed mass per plant is also strongly reduced, marginally by lower mass per seed, but mainly because of lower seed numbers. Plants generally have fewer shoot-born roots, but their overall rooting depth seems hardly affected. The phenotypic plasticity responses to high densities correlate strongly with those to low light, and less with those to low nutrients, suggesting that at high density, shading affects plants more than nutrient depletion.