Endogenous Hormone Levels Research Articles

Effects of brassinolide on the physiological characteristics of maize (Zea Mays L.) Cultivars Under salt stress.

Effects of brassinolide on the physiological characteristics of maize under salt stress were investigated. Effect of exogenous application of brassinolide on the antioxidant system, endogenous hormone levels, sodium and potassium ion contents of the plants were measured in a salt-tolerant maize cultivar, Xianyu 335, and a salt-sensitive maize cultivar, Dongnong 253. Brassinolide induced better alleviation of physiological damage in different salt-sensitive maize cultivars under salt stress treatment. Exogenous administration of brassinolide was found to increase the antioxidant enzyme activity, modulate the endogenous hormone levels, and promote potassium and sodium excretion by the plants. The effect was more significant in salt-sensitive maize cultivars. Bangladesh J. Bot. 52(2): 551-558, 2023 (June) Special

Effects of brassinolide on the physiological characteristics of maize (Zea Mays L.) Cultivars Under salt stress.

Effects of brassinolide on the physiological characteristics of maize under salt stress were investigated. Effect of exogenous application of brassinolide on the antioxidant system, endogenous hormone levels, sodium and potassium ion contents of the plants were measured in a salt-tolerant maize cultivar, Xianyu 335, and a salt-sensitive maize cultivar, Dongnong 253. Brassinolide induced better alleviation of physiological damage in different salt-sensitive maize cultivars under salt stress treatment. Exogenous administration of brassinolide was found to increase the antioxidant enzyme activity, modulate the endogenous hormone levels, and promote potassium and sodium excretion by the plants. The effect was more significant in salt-sensitive maize cultivars. Bangladesh J. Bot. 52(2): 551-558, 2023 (June) Special

Dynamic changes in the levels of metabolites and endogenous hormones during the germination of Zanthoxylum nitidum (Roxb.) DC. Seeds

ABSTRACT Accumulating experimental data have shown that endogenous hormones play important roles in regulating seed dormancy and germination. Zanthoxylum nitidum is a medicinal plant that propagates via seeds, which require a long dormancy period for normal germination, and complex changes in metabolites occur during the germination process. However, the regulatory network of endogenous hormones and metabolites during the germination of Z. nitidum seeds remains unclear. This study investigated the dynamic changes in the levels of metabolites and endogenous hormones during the germination of Z. nitidum seeds. The results revealed an increase in the levels of gibberellin 3 (GA3), 12-oxophytodienoic acid (OPDA), 1-aminocyclopropane-1-carboxylic acid (ACC) and trans-zeatin (TZ) and decrease in the levels of abscisic acid (ABA), jasmonic acid (JA), N-[(-)-jasmonoyl]-(S)-isoleucine (JA-Ile) and trans-zeatin riboside (TZR). Overall, 112 differential metabolites (DAMs) were screened from 3 seed samples (Sa, Sb and Sc), most of which are related to primary metabolism. A total of 16 DAMs (including 3 monosaccharides, 3 phosphate lipids, 3 carboxylic acids, 1 amino acid, 2 pyrimidines, and 4 nucleotides) were identified in the three sample comparison pairs (Sa vs Sb, Sa vs Sc, and Sb vs Sc); these DAMs were significantly enriched in purine metabolism; glycerophospholipid metabolism, citrate cycle (TCA cycle), alanine, aspartate and glutamate metabolism and pyruvate metabolism. OPDA, ACC and GAs were significantly positively correlated with upregulated metabolites, whereas ABA and JA were significantly positively correlated with downregulated metabolites. Finally, a hypothetical metabolic network of endogenous hormones that regulate seed germination was constructed. This study deepens our understanding of the importance of endogenous hormonal profiles that mediate seed germination.

MtTGA1 Transcription Factor Enhances Salt Tolerance through Hormonal Regulation and Antioxidant Enzyme Activity in Medicago truncatula

The TGACG motif-binding factor1 (TGA1) transcription factor, in which belongs to the bZIP transcription factor family and has vast application potential in plant growth and development. Here, we cloned the gene of the MtTGA1 transcription factor from Medicago truncatula. The MtTGA1 promoter region contains a diverse range of photoregulatory and hormonal regulatory elements. The expression profile of MtTGA1 indicated its highest expression in the root. Additionally, the expression level of MtTGA1 was significantly upregulated after SA and BR treatments and showed a downward trend after GA and ABA treatments. To explore the potential function of MtTGA1, we treated the transgenic plants with salt treatment for 15 days, and the results showed that transgenic plants demonstrated significantly longer root lengths and heightened activities of antioxidant enzymes such as ascorbic acid catalase (APX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) in their roots and leaves. The levels of endogenous hormones, including ABA and BR were improved in transgenic plants, with a marked change in the morphology of their leaf cells. Transcriptome analysis identified a total of 193 differentially expressed genes, which were significantly enriched in the pathways of “Brassinosteroid biosynthesis”, “Ascorbate and aldarate metabolism”, and “Plant hormone signal transduction”. Furthermore, MtTGA1 was found to interact with the SPX domain-containing protein 1 (SPX1) in Medicago truncatula. In conclusion, these results are beneficial for further studies about the plant growth and development regulatory network mediated by the TGA1 transcription factor family.

Changes in root endogenous hormone levels and rhizosphere fungi diversity in alfalfa under drought stress

Changes in root endogenous hormone levels and rhizosphere fungi diversity in alfalfa under drought stress

The effect of nitrogen and water management on the yield and endogenous hormone levels of drip‐irrigated rice

AbstractImproving the management of water and fertilizers is an effective method for enhancing the seed‐setting performance of rice. This study aimed to explore the regulation of optimized water and nitrogen management on the root–leaf hormone balance and seed‐setting performance of drip‐irrigated rice. In a 2‐year field experiment, T‐43 (a drought‐resistant cultivar) and LX‐3 (a drought‐sensitive cultivar) were cultivated under two drip irrigation treatments (W1, limited, and W2, deficit) and three nitrogen fertilization treatments (N1, seedling:tillering:panicle:grain‐filling, 30%:50%:13%:7%; N2, 20%:40%:30%:10%; and N3, 10%:30%:40%:20%). Compared with other treatments, the W1N2 treatment increased the seed‐setting rate and grain biomass accumulation (2.7%–9.2% and 4.5%–69.8%) of the two cultivars on the basis of producing a higher effective panicle number, and T‐43 had a much higher seed‐setting rate and yield than LX‐3 (6.8%–14.6%). Increased fertilizer applications at the panicle and grain‐filling stages (N2) enhanced the root oxidation activity (ROA) and the zeatin+zeatin riboside (Z + ZR) and gibberellic acid (GA3) contents in the roots in the 0–10 cm layer and in the leaves from the heading stage to 20 days after heading. The grain biomass accumulation of T‐43 was significantly positively correlated with abscisic acid (ABA) and Z + ZR in the roots and leaves, while the grain biomass accumulation of LX‐3 was significantly positively correlated with auxin, ABA, Z + ZR/ABA, and GA3/ABA in the roots in the 10–20 cm layer. Overall, W1N2 promoted grain biomass accumulation by modulating the Z + ZR and ABA balance in roots and leaves, improved the root–shoot ratio, and enhanced ROA, thereby improving the seed‐setting performance of drip‐irrigated T‐43 rice.

The Roles of Hormone Signals Involved in Rhizosphere Pressure Response Induce Corm Expansion in Sagittaria trifolia.

Soil is the base for conventional plant growth. The rhizosphere pressure generated from soil compaction shows a dual effect on plant growth in agricultural production. Compacted soil leads to root growth stagnation and causes bending or thickening, thus affecting the growth of aboveground parts of plants. In arrowhead (Sagittaria trifolia L.), the corms derived from the expanded tips of underground stolons are its storage organ. We found that the formation of corms was significantly delayed under hydroponic conditions without rhizosphere pressure originating from soil/sand. In the initial stage of corm expansion, the anatomic structure of arrowhead corm-forming parts harvested from hydroponics and sand culture was observed, and we found that the corm expansion was derived from cell enlargement and starch accumulation. Comparative transcriptome analysis indicated that the corm expansion was closely related to the change in endogenous hormone levels. Endogenous abscisic acid and salicylic acid concentrations were significantly increased in sand-cultured corms. Higher ethylene and jasmonic acid contents were also detected in all arrowhead samples, demonstrating that these hormones may play potential roles in the rhizosphere pressure response and corm expansion. The expression of genes participating in hormone signaling could explain the rising accumulation of certain hormones. Our current results draw an extensive model to reveal the potential regulation mechanism of arrowhead corm expansion promoted by rhizosphere pressure, which will provide important references for further studying the molecular mechanism of rhizosphere pressure modulating the development of underground storage organs in other plants.

Physiological and Biochemical Characteristics of Prunus sibirica during Flowering

Prunus sibirica, an ecologically and economically important early-flowering tree species, is susceptible to late frost damage, which can cause yield decline. Recognizing the mechanisms behind physiologic and biochemical processes changes during flowering in P. sibirica is important for regulating its flowering time. In this study, we examined the nutrient levels, reactive oxygen species levels, endogenous hormone levels, and antioxidant enzyme activity during flowering in two P. sibirica clones with different flowering times. We found that high indole-3-acetic acid (IAA) (88.05 μg/L) and low zeatin riboside (ZR) (8.26 μg/L) levels favoured P. sibirica flowering. Low gibberellic acid (GA) (472.17 pg/mL) levels; high abscisic acid (ABA) (325.23 μg/L), jasmonic acid (JA) (1116.62 pmol/L), fructose (11.70 mg/g), and sucrose (8.42 mg/g) levels; and high peroxidase (POD) (197.40 U/g), superoxide dismutase (SOD) (290.29 U/g), and catalase (CAT) (420.37 U/g) activities delayed flowering in P. sibirica. This study revealed the role of nutrients, reactive oxygen species, antioxidant enzymes, and endogenous hormones in P. sibirica flowering.

The determination of peanut (Arachis hypogaea L.) pod-sizes during the rapid-growth stage by phytohormones

BackgroundPod size is an important yield target trait for peanut breeding. However, the molecular mechanism underlying the determination of peanut pod size still remains unclear.ResultsIn this study, two peanut varieties with contrasting pod sizes were used for comparison of differences on the transcriptomic and endogenous hormonal levels. Developing peanut pods were sampled at 10, 15, 20, 25 and 30 days after pegging (DAP). Our results showed that the process of peanut pod-expansion could be divided into three stages: the gradual-growth stage, the rapid-growth stage and the slow-growth stage. Cytological analysis confirmed that the faster increase of cell-number during the rapid-growth stage was the main reason for the formation of larger pod size in Lps. Transcriptomic analyses showed that the expression of key genes related to the auxin, the cytokinin (CK) and the gibberellin (GA) were mostly up-regulated during the rapid-growth stage. Meanwhile, the cell division-related differentially expressed genes (DEGs) were mostly up-regulated at 10DAP which was consistent with the cytological-observation. Additionally, the absolute quantification of phytohormones were carried out by liquid-chromatography coupled with the tandem-mass-spectrometry (LC–MS/MS), and results supported the findings from comparative transcriptomic studies.ConclusionsIt was speculated that the differential expression levels of TAA1 and ARF (auxin-related), IPT and B-ARR (CK-related), KAO, GA20ox and GA3ox (GA-related), and certain cell division-related genes (gene-LOC112747313 and gene-LOC112754661) were important participating factors of the determination-mechanism of peanut pod sizes. These results were informative for the elucidation of the underlying regulatory network in peanut pod-growth and would facilitate further identification of valuable target genes.

Organ-specific responses during acclimation of mycorrhizal and non-mycorrhizal tomato plants to a mild water stress reveal differential local and systemic hormonal and nutritional adjustments

Main conclusionTomato plant acclimation to a mild water stress implied tissue-specific hormonal and nutrient adjustments, being the root one of the main modulators of this response.Phytohormones are key regulators of plant acclimation to water stress. However, it is not yet clear if these hormonal responses follow specific patterns depending on the plant tissue. In this study, we evaluated the organ-specific physiological and hormonal responses to a 14 day-long mild water stress in tomato plants (Solanum lycopersicum cv. Moneymaker) in the presence or absence of the arbuscular mycorrhizal fungus Rhizoglomus irregulare, a frequently used microorganism in agriculture. Several physiological, production, and nutritional parameters were evaluated throughout the experiments. Additionally, endogenous hormone levels in roots, leaves, and fruits at different developmental stages were quantified by ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). Water deficit drastically reduced shoot growth, while it did not affect fruit production. In contrast, fruit production was enhanced by mycorrhization regardless of the water treatment. The main tissue affected by water stress was the root system, where huge rearrangements in different nutrients and stress-related and growth hormones took place. Abscisic acid content increased in every tissue and fruit developmental stage, suggesting a systemic response to drought. On the other hand, jasmonate and cytokinin levels were generally reduced upon water stress, although this response was dependent on the tissue and the hormonal form. Finally, mycorrhization improved plant nutritional status content of certain macro and microelements, specially at the roots and ripe fruits, while it affected jasmonate response in the roots. Altogether, our results suggest a complex response to drought that consists in systemic and local combined hormonal and nutrient responses.

Methodological and physiological study of seed dormancy release in Tilia henryana

Tilia henryana is a rare tree of the Tilia family, found exclusively in China. Its seeds have severe dormancy features that limit its normal conditions of reproduction and renewal. Its seeds have severe dormant characteristics that limit its normal conditions of reproduction and renewal. The Dormancy in T. henryana seeds is a comprehensive dormancy (PY + PD) caused by mechanical and permeability barriers of seed coat and the presence of germination inhibitor in endosperm. L9 (34) orthogonal test was used to determine the best procedure for releasing the dormancy of T. henryana seeds, that is, first treating the seeds with H2SO4 for 15 min, followed by the application of 1 g L−1 GA3, stratification at 5 °C for 45 days, and finally germination at 20 °C, which can achieve a 98% seed germination rate. Large amounts of fat are consumed throughout the dormancy release process. As quantities of protein and starch marginally increase, soluble sugars are continuously decreased. Acid phosphatase and amylase activities increased rapidly, and the combined enzyme activities of G-6-PDH and 6-PGDH related to the PPP were also significantly increased. The levels of GA and ZR continued to increase, while the levels of ABA and IAA gradually decreased, among which GA and ABA changed most rapidly. The total amino acids content continued to decrease. Asp, Cys, Leu, Phe, His, Lys and Arg decreased with dormancy release, while Ser, Glu, Ala, Ile, Pro and Gaba showed an upward trend. The physical dormancy of T. henryana seeds is broken with H2SO4 in order to make the seed coat more permeable, which is a prerequisite for germination. As a result, the seeds can absorb water and engage in physiological metabolic activities, particularly the hydrolysis and metabolism of fat, which supply a significant amount of energy for dormancy release. In addition, rapid variations in the levels of different endogenous hormones and free amino acids, induced by cold stratification and GA3 application, are another important factor promoting the quick physiological activation of seeds and breaking the endosperm barrier.

Transcriptome Analysis Reveals the Role of Phytohormones in the Distant Hybridization of Peony Embryo Abortion

Peonies are significant ornamental plants that are primarily propagated through distant cross-breeding to create new varieties. However, hybrid failure is a critical issue that impedes the advancement of breeding. Numerous studies have demonstrated that endogenous hormones in the seed embryo constitute a significant factor in embryo failure. Nevertheless, it is still unknown how plant hormones control the development of peony embryos at the molecular level. In this study, we characterized the endogenous hormone levels in peony seeds of hybrid-aborted, hybrid-normal, and self-crossing normal after 26 days of pollination (DAP). Our findings show that the hybrid-aborted embryos had significantly higher amounts of ABA, IAA, and GA. In addition, the ratio of GA+IAA/ABA was lower than that of the hybrid-normal seeds and higher than that of the self-crossing normal seeds. To further investigate the mechanism of hormone control on peony embryo development, we conducted a transcriptome sequencing analysis of the three seed types. Results revealed that differentially expressed genes involved in phytohormone metabolism and signal transduction significantly enriched the aborted embryos. Furthermore, we examined the expression levels of six hormones in different seeds and used the Gene Common Expression Trend analysis to analyze genes highly correlated with phytohormone in the KEGG pathway. We used protein interaction networks to explore the interactions between proteins in the hormone pathway in aborted embryos. Then we identified key genes and transcription factors (TFs) such as Abscisic acid-insensitive 5 (ABI5), Auxin Response Factor 5 (ARF5), Gibberellin Insensitive Dwarf 1 (GID1), Arabidopsis Response Regulator4 (ARR4), Jasmonate-zim-domain protein 1 (JAZ1), Brassinazole-resistant 1 (BZR1), etc., whose functions require further investigation. Our findings establish a foundation for the metabolic regulation of peony hybrid embryo abortion via networks regulating phytohormone signaling. However, further research is needed to determine the exact mechanisms by which hormones regulate peony embryo development and to explore new methods for improving the success rate of hybridization.

Physiological Basis of High Nighttime Temperature-Induced Chalkiness Formation during Early Grain-Filling Stage in Rice (Oryza sativa L.)

Heat stress during the grain-filling stage seriously affects grain quality in rice. However, very limited information is available regarding the effects of short-term high nighttime temperature (HNT) on grain chalkiness formation in rice. In this paper, the effects of HNT at the early grain-filling stage (7 days after ear emergence) on rice chalkiness formation and the potential causes were investigated by using two rice varieties that differed in susceptibility to high temperature. Although the HNT treatment at night dramatically increased the grain chalkiness in Jiuxiangzhan (JXZ) and Huanghuazhan (HHZ), the increase was greater in JXZ compared to HHZ. The net photosynthetic rate and SPAD value were significantly reduced by HNT treatment in the flag leaves of JXZ, while no significant differences were observed in HHZ. Furthermore, HNT treatment reduced the antioxidant enzyme activity in the flag leaves of JXZ, while the opposite was observed in HHZ, exhibiting increased antioxidant enzyme activity. Moreover, HNT treatment altered the endogenous hormone levels, enhanced the enzymatic activities related to starch biosynthesis, and accelerated the filling rate in grains of JXZ when compared to HHZ. Scanning electron microscopy (SEM) observation exhibited that the starch granules in the endosperm of JXZ were loosely packed together and more starch granules with small pits were produced after HNT treatment. Based on these data, we inferred that HNT stress during the early stage of rice grain filling accelerated the grain-filling rate but shortened the grain-filling duration by changing the endogenous hormone levels and enhancing the enzymatic activities responsible for starch biosynthesis, resulting in significant changes in the morphological structure and arrangement of starch granules and eventually causing the occurrence of grain chalkiness.

Hormonal Balance, Photosynthesis, and Redox Reactions in the Leaves of Caragana korshinskii Kom. under Water Deficit.

To evaluate the physiological responses of Korshinsk peashrub (Caragana korshinskii Kom.) to water deficit, photosynthetic gas exchange, chlorophyll fluorescence, and the levels of superoxide anion (O2•-), hydrogen peroxide (H2O2), malondialdehyde (MDA), antioxidant enzymes, and endogenous hormones in its leaves were investigated under different irrigation strategies during the entire growth period. The results showed that leaf growth-promoting hormones were maintained at a higher level during the stages of leaf expansion and vigorous growth, and zeatin riboside (ZR) and gibberellic acid (GA) gradually decreased with an increase in water deficit. At the leaf-shedding stage, the concentration of abscisic acid (ABA) dramatically increased, and the ratio of ABA to growth-promoting hormones increased to a high level, which indicated that the rate of leaf senescence and shedding was accelerated. At the stages of leaf expansion and vigorous growth, the actual efficiency of photosystem II (PSII) (ΦPSii) was downregulated with an increment in non-photochemical quenching (NPQ) under moderate water deficit. Excess excitation energy was dissipated, and the maximal efficiency of PSII (Fv/Fm) was maintained. However, with progressive water stress, the photo-protective mechanism was inadequate to avoid photo-damage; Fv/Fm was decreased and photosynthesis was subject to non-stomatal inhibition under severe water deficit. At the leaf-shedding stage, non-stomatal factors became the major factors in limiting photosynthesis under moderate and severe water deficits. In addition, the generation of O2•- and H2O2 in the leaves of Caragana was accelerated under moderate and severe water deficits, which caused an enhancement of antioxidant enzyme activities to maintain the oxidation-reduction balance. However, when the protective enzymes were insufficient in eliminating excessive reactive oxygen species (ROS), the activity of catalase (CAT) was reduced at the leaf-shedding stage. Taken all together, Caragana has strong drought resistance at the leaf expansion and vigorous growth stages, but weak drought resistance at the leaf-shedding stage.

Estimated Ovulatory Years Prior to Menopause and Postmenopausal Endogenous Hormone Levels.

Lifetime ovulatory years (LOY) is estimated by the difference between ages at menopause and menarche subtracting time for events interrupting ovulation. We tested whether LOY influences sex hormone levels in postmenopausal women with at least one intact ovary not using hormones. Estradiol, estrone, estrone sulfate, total testosterone, dehydroepiandrostendione sulfate, prolactin, and sex hormone binding globulin were measured in 1,976 postmenopausal women from the Nurses' Health Study. Associations of age, body mass index (BMI), smoking, alcohol use, and other factors on hormones were assessed by t tests and ANOVA. Linear regression was used to assess multivariable adjusted associations between LOY and hormones and trends in hormone levels per 5-year increases in LOY were estimated. Women averaged 61.4 years old, 11.0 years since menopause, with BMI of 25.8 kg/m2. A total of 13.6% had irregular cycles, 17.5% hysterectomy, 6.4% unilateral oophorectomy, and 13.8% were current smokers. Variables associated with one or more hormone levels were included as covariates. Each 5-year increase in LOY was significantly associated with a 5.2% increase in testosterone in women with BMI < 25 kg/m2 and a 7.4% increase in testosterone and 7.3% increase in estradiol in women with above-average BMI. This is the first study to show that greater LOY is associated with higher testosterone in postmenopausal women and higher estradiol in those with elevated BMI, suggesting accumulation of functioning stromal and thecal cells from repeated ovulations and peripheral conversion of testosterone. A possible explanation for why greater LOY increases risk for breast, endometrial, and ovarian cancer is offered.

Abstract LB137: Ovulatory years prior to menopause and postmenopausal endogenous hormone levels

Abstract Background: Estimated lifetime ovulatory years (LOY) is the difference between ages at menopause and menarche subtracting time for events interrupting ovulation. We tested whether LOY influence sex-hormone levels in postmenopausal women not using hormone therapy. Methods: Hormones, including estradiol and testosterone, were measured in 1976 postmenopausal women from the Nurses’ Health Study in plasma collected in 1990. Effects of age, years since menopause, body mass index (BMI), smoking status, and hysterectomy on hormone levels were assessed by t-tests and ANOVA. Multivariable linear regression was used to assess associations between LOY and hormones adjusted for potential confounders and the trend in hormone levels per 5-year increases in LOY estimated. Results: Women in the sample averaged: 61.4 years old at blood draw, 11.0 years since menopause, with a BMI of 25.8 kg/m2. 17.5% had a hysterectomy and 13.8% were current smokers. These characteristics were associated with one or more hormone levels and included as adjustment variables. Each 5-year increase in LOY was associated with a 6.0% increase in testosterone (95% CI 3.3%, 8.7%) in all women. In women with above-average BMI, each 5-year increase in LOY was associated with a 7.3% (3.5%, 11.2%) increase in testosterone, a 6.9% (2.7%,11.3%) increase in estradiol, and a 6.9% (2.9%,10.9%) increase in estrone. Conclusion: Greater LOY is associated with higher testosterone in postmenopausal women as well as greater estradiol in those with above-average BMI. This may be due to an accumulation of functioning stromal and thecal cells from repeated ovulation and peripheral conversion of testosterone. Citation Format: Daniel W. Cramer, Allison F. Vitonis, Tianyi Huang, Amy L. Shafrir, Heather Eliassen, Robert L. Barbieri, Susan E. Hankinson. Ovulatory years prior to menopause and postmenopausal endogenous hormone levels [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB137.

Effects of the Most Appropriate Proportion of Phytohormones on Tree-Ring Growth in Clones of Hybrid Larch

The increase in the atmospheric carbon dioxide concentration promotes its accumulation in trees by regulating the synthesis and transportation genes for endogenous hormones, such as IAA and GA, which are key factors in regulating various life activities, including growth rings. To explore the impact of changes in endogenous hormone levels such as IAA and GA on the growth of tree rings, and to provide a basis for improving the management of hybrid larch clonal forests, we investigated the effects of exogenous indole-3-acetic acid (IAA), gibberellic acid 3 (GA3), and their combination on tree-ring growth in hybrid larch. IAA, GA3, and a combination treatment were sprayed on the leaves of one clone of a hybrid larch seedling every three days. Small blocks were collected at the base stems for sequential anatomical observations. The phytohormone type, instead of the concentration, had a more significant effect on wood formation. Specifically, IAA treatment at 300 mg L−1 significantly increased latewood (LW) layers until 90 days after treatment (DAT). The 500 mg L−1 treatment significantly increased the wall radial thickness (WRT) of latewood (LW) cells. GA3 treatment at 100 mg L−1 significantly decreased the layers and width of total wood (TW), LW, and earlywood (EW). The 300 mg L−1 treatment significantly increased the WRT of EW. The IAA 100 mg L−1 + GA3 100 mg L−1 combination treatment significantly increased the layers and width of TW and LW by inducing cambium activity and increasing the rate of wood cell development. The WRT and lumen radial diameter (LRD) of EW or LW in this treatment were similar to those observed with the corresponding single phytohormone treatment. These results indicate that combination treatment at 100 mg L−1 + 100 mg L−1 was a better way to promote tree-ring growth. Our study suggests that changes in phytohormone levels and ratios are important factors that affect tree-ring formation. Hormone levels and ratios should be regarded as important indicators to guide the improvement of management practices in hybrid larch clonal plantations.

Changes and transcriptome regulation of endogenous hormones during somatic embryogenesis in Ormosia henryi Prain.

Ormosia henryi is a rare and endangered plant growing in southern China. Somatic embryo culture is an effective measure for the rapid propagation of O. henryi. It has not been reported how regulatory genes induce somatic embryogenesis by regulating endogenous hormone changes during the process of somatic embryogenesis in O. henryi. In this study, we analysed the endogenous hormone levels and transcriptome data of nonembryogenic callus (NEC), embryogenic callus (EC), globular embryo (GE) and cotyledon embryo (CE) in O. henryi. The results showed that the indole-3-acetic acid (IAA) content was higher and the cytokinins (CKs) content was lower in EC than in NEC, and the gibberellins (GAs) and abscisic acid (ABA) contents were significantly higher in NEC than in EC. The contents of IAA, CKs, GAs and ABA increased significantly with EC development. The expression patterns of differentially expressed genes (DEGs) involved in the biosynthesis and signal transduction of auxin (AUX) (YUCCA and SAUR), CKs (B-ARR), GAs (GA3ox, GA20ox, GID1 and DELLA) and ABA (ZEP, ABA2, AAO3, CYP97A3, PYL and ABF) were consistent with the levels of endogenous hormones during somatic embryogenesis (SE). In this study, 316 different transcription factors (TFs) regulating phytohormones were detected during SE. AUX/IAA were downregulated in the process of EC formation and GE differentiation into CE, but other TFs were upregulated and downregulated. Therefore, we believe that relatively high IAA content and low CKs, GAs and ABA contents contribute to EC formation. The differential expression of AUX, CKs, GAs and ABA biosynthesis and signal transduction genes affected the endogenous hormone levels at different stages of SE in O. henryi. The downregulated expression of AUX/IAA inhibited NEC induction, promoted EC formation and GE differentiation into CE.

Exogenous hormone application regulates dwarf mutant plant height in Sophora davidii (Franch.) Skeels by changing endogenous hormone levels

Dwarf mutants are valuable materials for investigating plant gene function and developing new crop varieties. In the present study, dwarf mutant (D-CK) and wild-type (W-CK) Sophora davidii (Franch.) Skeels plants foliarly sprayed with distilled water were used as controls, and dwarf mutants were treated with different concentrations of gibberellin A3 (GA3; 20, 40 and 60 mg L-1), brassinosteroid (BR; 12.5, 25 and 50 mg L-1); and auxin indole-3-acetic acid (IAA; 12.5, 25 and 50 mg L-1) to study the changes in plant height at 20, 40 and 60 d after exogenous hormone spraying. The changes in endogenous contents of IAA, GA3, BR, abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) and IAA:ABA ratio in the dwarf mutant plants were also measured at 20, 40 and 60 d after exogenous hormone application. The dwarf mutants reverted to the W-CK height phenotype after 60 d of exogenous spraying with different concentrations of GA3 and BR (except 50 mg·L-1), but after exogenous spraying with IAA, dwarf mutants did not revert to the W-CK height phenotype. Compared with D-CK plants, endogenous GA3, BR and IAA contents in dwarf mutant plants increased to some extent with exogenous spraying of GA3, BR and IAA. The results indicated that exogenous spraying of different concentrations of GA3 and BR regulated S. davidii plant height by promoting the secretion of endogenous GA3, BR, IAA and SA and inhibiting endogenous ABA secretion in dwarf mutant. The height of mutants was sensitive to exogenous GA3 and BR but not to exogenous IAA.

Aboveground Biomass and Endogenous Hormones in Sub-Tropical Forest Fragments

Associated endogenous hormones were affected by forest fragmentation and significantly correlated with aboveground biomass storage. Forest fragmentation threatens aboveground biomass (AGB) and affects biodiversity and ecosystem functioning in multiple ways. We ask whether and how forest fragmentation influences AGB in forest fragments. We investigated differences in AGB between forest edges and interiors, and how plant community characteristics and endogenous hormones influenced AGB. In six 40 m × 40 m plots spread across three forest fragments, AGB was significantly higher in plots in the forest interior than in those at the edge of forests. The proportion of individuals with a large diameter at breast height (DBH &gt; 40 cm) in the forest edges is higher than that in the forest interiors. Further, trees within a 15–40 cm DBH range had the highest contribution to AGB in all plots. Trees in interior plots had higher abscisic acid (ABA) and lower indole-3-acetic acid (IAA) concentrations than those in edge plots. In addition, AGB was significantly positively and negatively correlated with ABA and IAA concentrations at the community scale. In this study, we provide an account of endogenous hormones’ role as an integrator of environmental signals and, in particular, we highlight the correlation of these endogenous hormone levels with vegetation patterns. Edge effects strongly influenced AGB. In the future, more endogenous hormones and complex interactions should be better explored and understood to support consistent forest conservation and management actions.