Endogenous Hormone Activity Research Articles

Bisphenols and perfluoroalkyls alter human stem cells integrity: A possible link with infertility

Bisphenols and Perfluoroalkyls are chemical compounds widely used in industry known to be endocrine disruptors (EDs). Once ingested through contaminated aliments, they mimic the activity of endogenous hormones leading to a broad spectrum of diseases. Due to the extensive use of plastic in human life, particular attention should be paid to antenatal exposure to Bisphenols and Perfluoroalkyls since they cross the placental barrier and accumulates in developing embryo. Here we investigated the effects of Bisphenol-A (BPA), Bisphenol-S (BPS), perfluorooctane-sulfonate (PFOS) and perfluorooctanoic-acid (PFOA), alone or combined, on human-induced pluripotent stem cells (hiPSCs) that share several biological features with the stem cells of blastocysts. Our data show that these EDs affect hiPSC inducing a great mitotoxicity and dramatic changes in genes involved in the maintenance of pluripotency, germline specification, and epigenetic regulation. We also evidenced that these chemicals, when combined, may have additive, synergistic but also negative effects. All these data suggest that antenatal exposure to these EDs may affect the integrity of stem cells in the developing embryos, interfering with critical stages of early human development that might be determinant for fertility. The observation that the effects of exposure to a combination of these chemicals are not easily foreseeable further highlights the need for wider awareness of the complexity of the EDs effects on human health and of the social and economic burden attributable to these compounds.

Effects of plant age on antioxidant activity and endogenous hormones in Alpine Elymus sibiricus of the Tibetan Plateau.

Elymus sibiricus L. is a perennial forage species that has potential to serve as a forage source in livestock grazing systems. However, E. sibiricus has been shown to have a rapid and substantial reduction of aboveground biomass and seed yield after 3 or 4 years and an accelerated aging process. To determine possible aging mechanisms, we planted E. sibiricus seeds in triplicate blocks in 2012, 2015, and 2016, respectively, and harvested samples of leaves and roots at the jointing and heading stages in 2018 and 2019 to determine oxidative indices and endogenous hormones. The fresh aboveground biomass of 4- and 5-year old plants declined by 34.2% and 52.4% respectively compared with 3-year old plants, and the seed yield declined by 12.7% and 34.1%, respectively. The water content in leaves was 51.7%, 43.3%, and 35.6%, and net photosynthesis was 7.73, 6.35, and 2.08 µmol/m2·s in 3-, 4-, and 5-year old plants, respectively. The superoxide anion radical generation rate in leaves and roots did not show any aging pattern. There was a non-significant increase in malondialdehyde concentration with plant age, particularly in leaves and roots at the heading stage in 2019. The superoxide dismutase activity showed a declining trend with age of plant roots at the jointing stage in both 2018 and 2019. The peroxidase activity declined with plant age in both leaves and roots, for example, and the catalase activity in roots 4- and 7-year old plants declined by 13.8% and 0.85%, respectively, compared to 3-year old plants at the heading stage in 2018. Therefore, the reduced capacity of the antioxidant system may lead to oxidative stress during plant aging process. Overall, the concentrations of plant hormones, auxin (IAA), gibberellin (GA), zeatin (ZT), and abscisic acid (ABA) were significantly lower in roots than in leaves. The IAA concentration in leaves and roots exhibited different patterns with plant age. The ZT concentrations in leaves of 3-year old plants was 2.39- and 2.62-fold of those in 4- and 7-year old plants, respectively at the jointing stage, and in roots, the concentration declined with plant age. The changes in the GA concentration with plant age varied between the physiological stages and between years. The ABA concentrations appeared to increase with plant age, particularly in leaves. In conclusion, the aging process of E. sibiricus was apparently associated with an increase in oxidative stress, a decrease of ZT and an increase of ABA, particularly in roots. These findings highlight the effects of plant age on the antioxidant and endogenous hormone activity of E. sibiricus. However, these plant age-related trends showed variations between plant physiological stages and between harvest years that needs to be researched in the future to develop strategies to manage this forage species.

The hazardous threat of Bisphenol A: Toxicity, detection and remediation

Bisphenol A (or BPA) is a toxic endocrine disrupting chemical that is released into the environment through modern manufacturing practices. BPA can disrupt the production, function and activity of endogenous hormones causing irregularity in the hypothalamus-pituitary-gonadal glands and also the pituitary-adrenal function. BPA has immuno-suppression activity and can downregulate T cells and antioxidant genes. The genotoxicity and cytotoxicity of BPA is paramount and therefore, there is an immediate need to properly detect and remediate its influence. In this review, we discuss the toxic effects of BPA on different metabolic systems in the human body, followed by its mechanism of action. Various novel detection techniques (LC-MS, GC-MS, capillary electrophoresis, immunoassay and sensors) involving a pretreatment step (liquid-liquid microextraction and molecularly imprinted solid-phase extraction) have also been detailed. Mechanisms of various remediation strategies, including biodegradation using native enzymes, membrane separation processes, photocatalytic oxidation, use of nanosorbents and thermal degradation has been detailed. An overview of the global regulations pertaining to BPA has been presented. More investigations are required on the efficiency of integrated remediation technologies rather than standalone methods for BPA removal. The effect of processing operations on BPA in food matrices is also warranted to restrict its transport into food products.

2033-P: In Vitro Analysis of Bisphenol A Effects on Beta-TC-6 Cells Function

Bisphenol A (BPA) is an organic compound that is widely used in plastic products. It acts as an endocrine disruptor capable of mimicking or modifying the activity of endogenous hormones. Recent data have shown that exposure to BPA increases the risk of type 2 diabetes. The aim of this study was to examine the effects of BPA on beta-TC-6 mice cells. Cells were incubated with serial dilutions of BPA: control group, 0.002μM, 0.02μM, 0.1μM, and 0.2μM for 12, 24, 48 and 72 hours. Cell viability and proliferation levels were determined by measuring intracellular ATP levels. BPA effects on beta-TC-6 cells were investigated by studying gene expression regulated at the transcriptional RNA level by real time PCR technique (citrate synthase and ATP synthase 6) and protein concentrations regulated at the translational levels by western blot analysis. The aging rate of cells was studied using SenTraGor TM. Exposure of beta-TC-6 cells to all BPA concentrations resulted in significant decreases of intracellular ATP levels when compared with the control group (all p<0.05). Moreover, exposure of beta-TC-6 cells to 0,2μM BPA concentration for 24 and 48 hours resulted in significant increases in the relative gene expression levels and in increased expression of proteins involved in apoptosis. The percentage of aging cells was >20% of total number of cells 24 hours after incubation at the 2 higher concentrations of BPA and was significantly increased when compared with the control group and the lower concentration of BPA. BPA affects viability, function and aging of beta-TC-6 cells. BPA presumably increases apoptosis rate and induces mitochondrial dysfunction on beta-TC-6 cells in a dose-dependent manner. Disclosure I. Anastasiou: None. I. Eleftheriadou: None. A. Tentolouris: None. A. Angelopoulou: None. O. Kosta: None. I. Mourouzis: None. N. Tentolouris: None.

Dietary phytoestrogen intakes of adult women are not strongly related to fecundability in 2 preconception cohort studies

Phytoestrogens are plant-derived hormonally active compounds found in soy, cruciferous vegetables, nuts, and seeds. Although phytoestrogens have been associated with altered endogenous hormonal activity, luteal phase deficiency, and reduced endometrial decidualization, the literature reporting examinations of phytoestrogen intake and fertility presents mixed findings. We sought to evaluate prospectively the association between dietary phytoestrogen intake (isoflavones, lignans, and coumestans) and fecundability, the per-cycle probability of conception, in 2 cohorts of women planning pregnancy. Pregnancy Study Online (PRESTO) and Snart Foraeldre (SF) are parallel web-based preconception cohort studies of women from North America and Denmark, respectively, who are trying to conceive. Participants complete an online baseline questionnaire on sociodemographic, lifestyle, and medical factors. We ascertained intake of individual phytoestrogens from validated FFQs. We measured fecundability using data on menstruation and pregnancy status from bimonthly follow-up questionnaires. We analyzed data from 4880 PRESTO and 2898 SF female study participants who had been attempting conception for ≤6 cycles at study entry. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% CIs. Phytoestrogen intake varied across cohorts, yet was associated with higher socioeconomic status and healthier behaviors in both cohorts. After adjustment for potential confounders, phytoestrogen intake was not substantially associated with fecundability in either cohort. We observed some evidence of improved fecundability with increasing isoflavone intake among women age ≥30 years in PRESTO (FR: 1.12; 95% CI: 0.94, 1.34, for comparison of ≥90th with <25th percentile intake) and SF (corresponding FR: 1.19; 95% CI: 0.92, 1.55). Lignan intake was associated with slightly increased fecundability in SF (FR for comparison of 75th to 90th with <25th percentile: 1.10; 95% CI: 0.96, 1.26), but decreased fecundability in PRESTO (FR for comparison of ≥90th with <25th percentile: 0.83; 95% CI: 0.72, 0.97). We did not observe strong associations between phytoestrogen intake and prospectively-measured fecundability among North American or Danish pregnancy planners.

Potential Developmental and Reproductive Impacts of Triclocarban: A Scoping Review.

Triclocarban (TCC) is an antimicrobial agent used in personal care products. Although frequently studied with another antimicrobial, triclosan, it is not as well researched, and there are very few reviews of the biological activity of TCC. TCC has been shown to be a possible endocrine disruptor, acting by enhancing the activity of endogenous hormones. TCC has been banned in the US for certain applications; however, many human populations, in and outside the US, exhibit exposure to TCC. Because of the concern of the health effects of TCC, we conducted a scoping review in order to map the current body of literature on the endocrine, reproductive, and developmental effects of TCC. The aim of this scoping review was to identify possible endpoints for future systematic review and to make recommendations for future research. A search of the literature until August 2017 yielded 32 relevant studies in humans, rodents, fish, invertebrates, and in vitro. Based on the robustness of the literature in all three evidence streams (human, animal, and in vitro), we identified three endpoints for possible systematic review: estrogenic activity, androgenic activity, and offspring growth. In this review, we describe the body of evidence and make recommendations for future research.

Potency matters: Thresholds govern endocrine activity

Whether thresholds exist for endocrine active substances and for endocrine disrupting effects of exogenous chemicals has been posed as a question for regulatory policy by the European Union. This question arises from a concern that the endocrine system is too complex to allow estimations of safe levels of exposure to any chemical with potential endocrine activity, and a belief that any such chemical can augment, retard, or disrupt the normal background activity of endogenous hormones. However, vital signaling functions of the endocrine system require it to continuously discriminate the biological information conveyed by potent endogenous hormones from a more concentrated background of structurally similar, endogenous molecules with low hormonal potential. This obligatory ability to discriminate important hormonal signals from background noise can be used to define thresholds for induction of hormonal effects, without which normal physiological functions would be impossible. From such thresholds, safe levels of exposure can be estimated. This brief review highlights how the fundamental principles governing hormonal effects – affinity, efficacy, potency, and mass action – dictate the existence of thresholds and why these principles also define the potential that exogenous chemicals might have to interfere with normal endocrine functioning.

Estrogenic activity of cadmium, copper and zinc in the yeast estrogen screen

Heavy metals are increasingly studied due to their apparent ability to disrupt signaling pathways of living organisms including humans. Among various mechanisms of action, metals are suspected of exerting estrogenic activity in human and wildlife. In this study, a wide range of concentration of cadmium, copper, lead, mercury and zinc (from 95.4 pM to 1 mM) alone or in combination with the natural estrogen, 17-β estradiol, has been tested using the yeast estrogen screen, an estrogen receptor dependent transcriptional expression assay. No direct trans-activation of the estrogen-responsive element could be measured with any of the concentration of the metals tested. Nevertheless, cadmium, copper and zinc were able to potentiate the estradiol-induced response in a dose-dependent manner. Significant stimulation was obtained from 10 nM cadmium, 100 nM copper and 2 nM zinc. Maximum response led to decrease of the estradiol EC50 by a factor 10. This study indicates that cadmium, copper and zinc can act as potential endocrine disrupters by modulating the estrogenic activity of endogenous hormones.

TRANSACTIVATION AND REGULATION OF ESTROGEN RESPONSE ELEMENT BY FUNGAL-DERIVED COMPOUNDS IN TRANSFECTED HUMAN EMBRYONIC KIDNEY 293 CELLS.

Endocrine disrupting chemicals (EDCs) are synthetic or natural compounds that possess the ability to mimic or inhibit endogenous hormonal activity. A number of EDCs have been shown to possess estrogenic activity in mammalian systems. The objective of this study was to determine potential estrogenicity of several chemicals derived from fungi (alternariol, AOH; emodin; and hispidin) and the slime mold Dictyostelium (differentiation inducing factor 1 [DIF-1]) with structural similarity to known estrogen-like compounds. Human embryonic kidney (HEK) 293 cells were cotransfected with plasmids containing estrogen response element (ERE)-driven luciferase gene or human estrogen receptor alpha (ERα). Cells were treated with test chemical, 17β-estradiol (E2), and/or estrogen receptor antagonist ICI 182,780. Luciferase activity was determined as a marker for ERE transcriptional activation. The results demonstrated that increasing concentrations of DIF-1 inhibited ERE activity by almost 90% compared with vehicle control. AOH and emodin increased luciferase activity in a dose-dependent manner (up to 20-fold and 11-fold, respectively), and hispidin displayed weaker activation of the ERE (5-fold). ICI abolished the observed up-regulation of luciferase by AOH, emodin, and hispidin. E2 stimulation of AOH- and emodin-treated cells led to a concentration-dependent decrease in luciferase activity of up to 50%, whereas stimulation with E2 caused only a slight decrease in luciferase activity in hispidin-treated cells. The results provide evidence that DIF-1 antagonizes ERα-mediated transcriptional activity. The data further suggest that AOH and emodin, and to a lesser extent hispidin, act as ERα agonists, whereas AOH and emodin may also possess antiestrogenic properties. The findings of these studies implicate that fungi and other microfauna can be important contributors of estrogenic EDCs found in the environment.

Invited Commentary: Acne in Adolescence—Protecting the Heart but Damaging the Prostate Later in Life?

Cutaneous manifestations of diseases have long helped observant clinicians to establish a diagnosis (1), but can cutaneous clues or other physical characteristics predict the risk of mortality or incident disease far into the future? For some time, researchers have linked with mixed success various physical manifestations to the risk of developing diseases, such as coronary heart disease. Among these physical markers are earlobe crease (2), arcus senilis (3), baldness (4), early hair graying (5), and facial wrinkling (6). Good reasons exist for studying the associations between physical markers and disease endpoints, because physical characteristics may help not only to elucidate underlying pathogenetic processes for diseases but also to detect persons at increased risk who would benefit by early intervention. In this issue of the American Journal of Epidemiology, Galobardes et al. (7) add acne vulgaris to the list of physical characteristics that may serve as risk markers for the development of disease later in life. In a retrospective follow-up study of 11,232 men who attended Glasgow University between 1948 and 1968 and whose mortality was traced into 2004, the investigators found that participants who reported having acne during adolescence had a significantly lower risk of death from coronary heart disease and an increased, although statistically not significant, risk of death from prostate cancer. For the other causes of mortality (mortality from all causes, stroke, lung cancer, colon cancer, and external causes), no significant associations were found. This study provides an excellent example of how older epidemiologic studies can be creatively used to generate new hypotheses about the potential pathogenetic pathways of various conditions. Consistent with the longstanding hypothesis that endogenous sex hormones play important roles in the pathogenesis of prostate cancer and cardiovascular disease, the authors’ view of acne largely as a manifestation of endogenous hormonal activity, principally androgen activity, has precedent. Although there are many reasons to believe that androgen activity may increase the risk of prostate cancer, epidemiologic studies have produced inconsistent results in linking circulating concentrations of androgens to the risk of prostate cancer (8–10). In the current study, the hazard ratio of 1.67 for mortality from prostate cancer was based on only 37–43 such deaths, and the confidence interval was wide and overlapped 1.0 considerably. Surprisingly, the authors highlighted the findings pertaining to prostate cancer in the title of their article as well as in the body of the text. The cardiovascular findings are perhaps more interesting and noteworthy. The authors report hazard ratios of 0.74 for mortality from total cardiovascular disease and 0.67 for coronary heart disease mortality. In both instances, the confidence interval excluded unity. Adjustment for the various covariates considered by the authors had little effect on the hazard ratios. While a series of recent reviews seem to be cautiously converging on the view that androgens may exert a favorable effect on cardiovascular disease (11–13), the roles of androgens on the cardiovascular system are likely to be complex and may be sex specific. Among men, concentrations of testosterone have been inversely related to concentrations of insulin and insulin resistance (14–21), as

Cyclic Cushing's Syndrome: An Overview

Cyclic Cushing's syndrome (CS) involves rhythmic fluctuations in ACTH secretion resulting in a cyclic variation of adrenal steroid production. In the majority of cases, cyclic CS is caused by an ACTH-secreting pituitary adenoma, but it can also be due to ectopic ACTH production or an adrenal adenoma. This condition should be strongly suspected in patients with symptoms or signs of hypercortisolism but normal cortisol levels and paradoxical responses to the dexamethasone test, that may reflect an increasing or decreasing endogenous hormone activity. Dynamic tests are best interpreted if they are performed during a sustained period of hypercortisolism. Sometimes, it is necessary to confirm the diagnosis over lengthy periods of observation. Responses to treatment must be closely monitored, interpreted and evaluated with caution because of the potential variations in steroidogenesis. An original case report of a cyclic Cushing's syndrome is presented in this review.

The Endocrine and Reproductive System: Adverse Effects of Hormonally Active Substances?

Chemicals that have the intrinsic property to modulate or even disrupt the endocrine system are present in the human environment. Because it is the potency of such chemicals that determines the toxicologic relevance, assessment of the risk to human health must consider both the endocrine disrupting potential and the potency. Usually in vitro assays are applied to detect the potential of a hormone-like effect, and such data are considered useful to set priorities for additional testing and for mechanistic studies. However, such data allow only determination of relative potency of a chemical as compared with other xenobiotics, natural compounds, or endogenous hormones. Relevant information on the endocrine-disrupting potency can be taken only from in vivo assays, eg, the Hershberger (male reproductive organs) and uterotrophic (female reproductive organs) assays, the updated versions of the 28- and 90-day toxicity studies in rodents, and the 2-generation studies in rodents. With the use of this information and the concentration of these chemicals in humans, the potency of the effect as compared with endogenous hormone activity can be estimated. So far, the relative potencies of chemicals tested in in vitro systems as compared with estradiol are several orders of magnitude smaller, whereas potency of the phytoestrogen, eg, isoflavones such as genistein or daidzein, can even exceed that of estradiol, especially in infants who are fed soy-based formula as a sole source of nutrition. Although there are still open questions regarding in utero or early postnatal exposure, the low potencies and concentrations of manmade chemicals as compared with the endogenous hormones in humans make it unlikely that adverse effects occur at common exposure.

Aktivitas Hormon Endogen dalam Buah Anggur Muscat OfAlexandria Muda tanpa Biji Hasill Induksi Antibiotika

The experiment was conducted to determine the activity of endogenous hormones in young seedless berry of Muscat of Alexandria (MOA) grapes induced by streptomycin (SM) and spectinomycin (SE). Young berries dipped in 200 ppm M or 200 ppm SE at 3 days before full-bloom and untreated berries were analyzed for the activity of . endogenous auxin, cytokinin. gibberellin and abscisic acid (ABA). The experiment was conducted at the Laboratory of ! Pomology, Faculty of Agriculture, Okayama University, Japan, from February 1999 to August 1999. Both SM and SE treatments did not affect ABA activities of young berries. Cytokinin activity were slightly decreased by SM and SE treatments at 6 days after treatment (DAT) and became more severe at J 0 and J 3 DAT The response of berry auxin activity to antibiotic treatment was similar but stronger than cytokinins. Antibiotic treatments significantly decreased the activity ofGA at 6 and 10 DAT 1 Keywords,' Antibiotics, Endogenous hormones, Spectinomycin, Streptomycin

Principles of immunomodulation

Abstract Investigation into hormone antibody interactions have demonstrated that antibodies can inhibit or potentiate both exogenous and endogenous hormone activity, raising the possibility that the immune system can be used to improve animal production efficiency. This paper reviews the physiology of antibody-manipulated hormone activity in growth regulation, particularly in relation to hormone enhancement; possible mechanisms for such a phenomenon are discussed. Lastly, it is now clear that potentiation and inhibition of peptide hormones may occur in vivo and this is reviewed in terms of growth factor bioavailability. Parallels are made between this natural means of regulation with antibody-mediated regulation.

Hormonal Contraception and Breast Cancer: Accounting for Age at Diagnosis

Background: Breast cancer risk is altered by endogenous hormonal activity and there is evidence of a link with hormonal contraception. This paper evaluates existing evidence on the association between hormonal contraceptive use and the risk of breast cancer with respect to age at the time of diagnosis.Methods: A search was conducted for studies which provided estimates of the relative risk (RR) of breast cancer among hormonal contraceptive users compared with non-users by age at the time of diagnosis. Ten studies reported on oral contraceptive use and three studies on depo-medroxy progesterone acetate (DMPA) use. The relationship between the RR of breast cancer in users and age at the time of diagnosis was estimated by means of weighted least squares regression and with the use of procedures to estimate typical odds ratios.Results: The RR and 95 percent confidence interval (95%CI) of breast cancer among oral contraceptive users compared with non-users was 1.60 (1.35–1.90) (p <0.0001) in studies involving 1,680 cancer patients less than 35 years of age at the time of breast cancer diagnosis, and 0.89 (0.82–0.97) (p = 0.007) in studies involving 4,156 cancer patients aged 45 to 54 years. The RR (95%CI) of breast cancer among DMPA users compared with non-users was 1.91 (1.38–2.63) (p = 0.0001) in studies involving 257 cancer patients aged less than 35 years at the time of breast cancer diagnosis, and 0.94 (0.26–1.17) (p = 0.31) in studies involving 2,000 cancer patients aged 35 or more years. An association with longer duration of use was found in only three studies.Conclusions: Recent studies of hormonal contraception and breast cancer suggest that the increased risk of breast cancer among hormonal contraceptive users is confined to women who experience breast cancer at a young age. The risk of breast cancer among older women who have used hormonal contraceptives is either unchanged or slightly reduced.

THE ENVIRONMENT UNDER WHICH THE STOCK PLANT IS GROWN INFLUENCES EXPLANT PERFORMANCE IN VITRO

Environmental factors under which the stock (mother, donor) plant has been grown, including temperature; light duration, quality, and intensity; mineral nutrition; and ambient gases can have significant impact on explant responses in vitro. Bulblet production in hyacinth has been influenced by mother bulb storage temperature. Shoot proliferation and rootability of microshoots of rhododendron have been modified by light intensity and light quality. Photoperiod has been demonstrated to affect tuber and callus formation on potato and dahlia. Furthermore, plant growth regulator treatments of the stock plant can strongly influence in vitro responses of explants taken from such plants. Implications of these latter responses will be discussed with regard to possible endogenous hormonal activity.

10 The implantation window

The implantation window is defined as that period when the uterus is receptive for implantation of the free-lying blastocyst. This period of receptivity is short and results from the programmed sequence of the action of oestrogen and progesterone on the endometrium. Implantation itself is a process that commences with apposition, continues through attachment to trophoblast outgrowth and decidualization. For maximal effectiveness of assisted reproductive technologies in women, it is important to know the optimal time for embryo transfer which implies a need to predict the period of uterine receptivity. At present there are no good markers of, or for prediction of, uterine receptivity. In cycles where endogenous hormonal activity is suppressed or absent, the optimal time for embryo transfer can be easily defined and lies between luteal days +3 to +5, where luteal day +1 is the first day of exogenous progesterone treatment. In the human, it is suggested that blastocyst apposition begins about LH day +6 and is complete by LH +10. Human embryos survive in vitro manipulation well, and the stage of development at which they are placed in the uterus seems less critical than in other species, provided they are at an earlier stage of development than that of the endometrium.

ACTIVE IMMUNIZATION WITH A SYNTHETIC PEPTIDE REGION OF GROWTH HORMONE: INCREASED LEAN TISSUE GROWTH

The effects of active immunization against a specific peptide region of GH (sequence 134-154) were examined in a species relevant for animal production in vivo. Peptide-immunized lambs exhibited significant increases in carcass protein and water contents and consequently increased carcass weight. The comparatively smaller increases in carcass water and protein contents which occurred in GH-treated lambs were offset by decreased fat accretion. Thus, even though peptide immunization improved lean tissue growth, it did not simply enhance all actions of GH or mimic exogenous hormone administration. This is the first definitive demonstration that endogenously produced antibody may enhance endogenous hormone activity and performance in animals.

EFFECTS OF BENZYLADENINE AND GIBBERELLIC ACID ON THE RESPONSES OF TOMATO PLANTS TO ANAEROBIC ROOT ENVIRONMENTS AND TO ETHYLENE

SummaryBenzyladenine (BA) and gibberellic acid (GA) were applied together as a foliar spray to young tomato plants growing in pots of well drained soil, waterlogged soil or in nutrient solution supplied with air (aerobic), nitrogen gas (anaerobic), or ethylene (20 or 100 ul 1−1 in air) for up to 6 days.BA and GA (10 fig ml−1) lessened the inhibitory effects of waterlogging on stem elongation, transpiration and the increase of fresh and dry wt of the shoots. In absolute terms the promotion of shoot growth by BA and GA was greater in plants growing in non‐waterlogged than in waterlogged soil. Root growth was inhibited by BA and GA. The effect of waterlogging in promoting adventitious rooting at the base of the stem was reduced by BA and GA.Epinastic curvature by petioles was promoted by growing plants in waterlogged soil or anaerobic solution culture in association with an increase in the production of ethylene by the petioles. Applications of BA and of GA inhibited this epinastic growth but they did not lower the rate of ethylene production. However BA and GA diminished the effectiveness of ethylene as a stimulator of epinastic curvature.The application of ethylene to the roots inhibited the accumulation of dry wt by the root system and decreased slightly the growth promoting effects of BA and GA in the shoots.The inhibiting effect of waterlogging the root system on stem elongation could be offset if adventitious roots maintained in well aerated conditions were previously induced on the main stem above the primary roots. Epinastic curvature and ethylene production were not decreased by the presence of an adventitious root system. The extent to which applications of BA and GA may reflect the activity of endogenous hormones produced by aerobic roots is discussed.

Physiological Characteristics of Sugar Maple and Implications for Successful Planting

Investigations of the physiology of sugar maple seedlings have partially defined the phenological patterns associated with (1) root growth, (2) dormancy and budbreak, (3) changes in carbohydrate reserves and (4) the activity of endogenous hormones. Results are interpreted and discussed in relation to the problem of establishment of sugar maple seedlings on openfield sites in southern Ontario. The need to produce seedlings with the physiological characteristics, and in the developmental stage, most favorable to growth of a vigorous root system at time of planting is stressed. Future research is suggested.