The physiological and psychological relaxing effects of viewing rose flowers in office workers

Background

In recent years, the physiological relaxing effect brought by nature is becoming clear; however, many workers find it difficult to be exposed to nature in their working environment. Exposure to fresh flowers represents an opportunity to incorporate nature into their working lives. In this study, we examined the effects of exposure to roses on physiological and psychological variables (heart rate variability, pulse rate, and subjective responses) in office workers.

Results

The experimental site was Mizuho Information & Research Institute, Inc., in the Tokyo metropolitan area. Thirty-one male office workers were included in the present study. The subjects were exposed to thirty unscented pink roses (Rosa, Dekora) arranged in a cylindrical glass vase for 4 min. In the control condition, the subjects were not exposed to flowers. After the experiments, the subjects completed a questionnaire. The order of exposure was counterbalanced among subjects. Among subjects exposed to roses, the high-frequency component of heart rate variability was significantly higher than in controls. Similarly, ''comfortable,’ ''relaxed’ and ''natural’ feelings were more common in subjects exposed to roses.

Conclusions

Data from this study support the presence of physiological and psychological relaxing effects of being exposed to flowers on office workers.     

Visual information without thermal energy may induce thermoregulatory-like cardiovascular responses

Background

Human core body temperature is kept quasi-constant regardless of varying thermal environments. It is well known that physiological thermoregulatory systems are under the control of central and peripheral sensory organs that are sensitive to thermal energy. If these systems wrongly respond to non-thermal stimuli, it may disturb human homeostasis.

Methods

Fifteen participants viewed video images evoking hot or cold impressions in a thermally constant environment. Cardiovascular indices were recorded during the experiments. Correlations between the ‘hot-cold’ impression scores and cardiovascular indices were calculated.

Results

The changes of heart rate, cardiac output, and total peripheral resistance were significantly correlated with the ‘hot-cold’ impression scores, and the tendencies were similar to those in actual thermal environments corresponding to the impressions.

Conclusions

The present results suggest that visual information without any thermal energy can affect physiological thermoregulatory systems at least superficially. To avoid such ‘virtual’ environments disturbing human homeostasis, further study and more attention are needed.     

Effects of Ginger and Expectations on Symptoms of Nausea in a Balanced Placebo Design

Objective

Ginger effects on (experimental) nausea have been described, but also strong placebo effects and sex differences when nausea is involved. The “balanced placebo design” has been proposed to allow better separation of drug and placebo effects.

Methods

Sixty-four healthy participants (32 women) were randomly assigned to receive an antiemetic ginger preparation or placebo, and half of each group was told to have received drug or placebo. They were exposed to 5×2 min body rotations to induce nausea. Subjective symptoms and behavioral (rotation tolerance, head movements) and physiological measures (electrogastrogram, cortisol) were recorded. Groups were balanced for sex of participants and experimenters.

Results

Ginger and the information given did not affect any outcome measure, and previous sex differences could not be confirmed. Adding the experimenters revealed a significant four-factorial interaction on behavioral but not on subjective or physiological measures Men who received placebo responded to placebo information when provided by the male experimenter, and to ginger information when provided by the female experimenter. This effect was not significant in women.

Conclusion

The effects of an antiemetic drug and provided information interact with psychosocial variables of participants and experimenters in reports of nausea.     

Analysis of physiological signals for recognition of boredom,pain, and surprise emotions

Background

The aim of the study was to examine the differences of boredom, pain, and surprise. In addition to that, it was conducted to propose approaches for emotion recognition based on physiological signals.

Methods

Three emotions, boredom, pain, and surprise, are induced through the presentation of emotional stimuli and electrocardiography (ECG), electrodermal activity (EDA), skin temperature (SKT), and photoplethysmography (PPG) as physiological signals are measured to collect a dataset from 217 participants when experiencing the emotions. Twenty-seven physiological features are extracted from the signals to classify the three emotions. The discriminant function analysis (DFA) as a statistical method, and five machine learning algorithms (linear discriminant analysis (LDA), classification and regression trees (CART), self-organizing map (SOM), Naïve Bayes algorithm, and support vector machine (SVM)) are used for classifying the emotions.

Results

The result shows that the difference of physiological responses among emotions is significant in heart rate (HR), skin conductance level (SCL), skin conductance response (SCR), mean skin temperature (meanSKT), blood volume pulse (BVP), and pulse transit time (PTT), and the highest recognition accuracy of 84.7 % is obtained by using DFA.

Conclusions

This study demonstrates the differences of boredom, pain, and surprise and the best emotion recognizer for the classification of the three emotions by using physiological signals.     

Experimental defoliation affects male but not female reproductive performance of the tropical monoecious plant Croton suberosus (Euphorbiaceae)

Background and Aims

Monoecious plants have the capacity to allocate resources separately to male and female functions more easily than hermaphrodites. This can be advantageous against environmental stresses such as leaf herbivory. However, studies showing effects of herbivory on male and female functions and on the interaction with the plant''s pollinators are limited, particularly in tropical plants. Here, the effects of experimental defoliation were examined in the monoecious shrub Croton suberosus (Euphorbiaceae), a wasp-pollinated species from a Mexican tropical dry forest.

Methods

Three defoliation treatments were applied: 0 % (control), 25 % (low) or 75 % (high) of plant leaf area removed. Vegetative (production of new leaves) and reproductive (pistillate and staminate flower production, pollen viability, nectar production, fruit set, and seed set) performance variables, and the abundance and activity of floral visitors were examined.

Key Results

Defoliated plants overcompensated for tissue loss by producing more new leaves than control plants. Production of staminate flowers gradually decreased with increasing defoliation and the floral sex ratio (staminate : pistillate flowers) was drastically reduced in high-defoliation plants. In contrast, female reproductive performance (pistillate flower production, fruit set and seed set) and pollinator visitation and abundance were not impacted by defoliation.

Conclusions

The asymmetrical effects of defoliation on male and female traits of C. suberosus may be due to the temporal and spatial flexibility in the allocation of resources deployed by monoecious plants. We posit that this helps to maintain the plant''s pollination success in the face of leaf herbivory stress.     

Andromonoecy and developmental plasticity in Chaerophyllum bulbosum (Apiaceae–Apioideae)

Background and Aims

Andromonoecy, the presence of hermaphrodite and male flowers in the same individual, is genetically fixed or induced, e.g. by fruit set. Little is known about the forces triggering andromonoecy in the Apiaceae. In the present study, a natural population of the protandrous Chaerophyllum bulbosum was investigated to elucidate architectural constraints and effects of resource reallocation.

Methods

Three sets of plants (each n = 15) were treated by hand pollination, pollinator exclusion and removal of low-order inflorescences. Fifteen untreated plants were left as controls.

Key Results

Untreated plants produce umbels up to the third branch order, with increasing proportions of male flowers from 15 % (terminal umbel) to 100 % (third-order umbels). Fruit set correspondingly decreases from 70% (terminal umbel) to <10 % (second-order umbels). Insignificant differences from hand-pollinated plants do not reveal any sign of pollinator limitation at the study site. Bagged individuals show the same increase in male flowers with age as untreated plants, indicating that the presence of andromonoecy is not induced by fruit set. After umbel removal, individuals tend to present a higher number of hermaphrodite flowers and fruits in the umbels of second and third order. Three plants (25 %) produced an additional branch order composed of 100 % male umbels.

Conclusions

Inherited andromonoecy and the plastic response to environmental conditions are interpreted as a self-regulating system saving investment costs and optimizing fruit set at the same time.     

The Rewarding Aspects of Music Listening Are Related to Degree of Emotional Arousal

Background

Listening to music is amongst the most rewarding experiences for humans. Music has no functional resemblance to other rewarding stimuli, and has no demonstrated biological value, yet individuals continue listening to music for pleasure. It has been suggested that the pleasurable aspects of music listening are related to a change in emotional arousal, although this link has not been directly investigated. In this study, using methods of high temporal sensitivity we investigated whether there is a systematic relationship between dynamic increases in pleasure states and physiological indicators of emotional arousal, including changes in heart rate, respiration, electrodermal activity, body temperature, and blood volume pulse.

Methodology

Twenty-six participants listened to self-selected intensely pleasurable music and “neutral” music that was individually selected for them based on low pleasure ratings they provided on other participants'' music. The “chills” phenomenon was used to index intensely pleasurable responses to music. During music listening, continuous real-time recordings of subjective pleasure states and simultaneous recordings of sympathetic nervous system activity, an objective measure of emotional arousal, were obtained.

Principal Findings

Results revealed a strong positive correlation between ratings of pleasure and emotional arousal. Importantly, a dissociation was revealed as individuals who did not experience pleasure also showed no significant increases in emotional arousal.

Conclusions/Significance

These results have broader implications by demonstrating that strongly felt emotions could be rewarding in themselves in the absence of a physically tangible reward or a specific functional goal.     

Barriers and Facilitators of Participation in Sports: A Qualitative Study on Dutch Individuals with Lower Limb Amputation

Introduction

Although individuals with lower limb amputation may benefit from participation in sports, less than 40% do so.

Aim

To identify the barriers and facilitators that influence participation in sports for individuals with lower limb amputation.

Design

Qualitative study.

Participants

Twenty six individuals with lower limb amputation, all originating from the Dutch provinces of Groningen and Drenthe, of which 13 athletes.

Methods

Semi-structured interviews were used to gather information. Following thematic analysis, emerging themes were organized in three categories Technical, Social and Personal.

Results

Sport was perceived as enjoyable activity that would help participants to become and stay healthy, improve the number of social contacts, reduce phantom pain and decrease daily tension. Inadequate facilities, problematic transportation, trivialization from others, poor health and lack of motivation or the lack of a sports partner were barriers commonly mentioned by non-athletes. Remarkably, while all athletes were successful prosthetic users, the majority chose to participate in sports for which prosthesis was neither required nor needed.

Conclusions

Each individual with lower limb amputation needs to be counselled according to the barriers and facilitators he/she personally experiences. Athletes appeared to be more proactive in searching for a solution and also appeared less discouraged by failing.     

Standardized Handwriting to Assess Bradykinesia,Micrographia and Tremor in Parkinson's Disease

Objective

To assess whether standardized handwriting can provide quantitative measures to distinguish patients diagnosed with Parkinson''s disease from age- and gender-matched healthy control participants.

Design

Exploratory study. Pen tip trajectories were recorded during circle, spiral and line drawing and repeated character ‘elelelel’ and sentence writing, performed by Parkinson patients and healthy control participants. Parkinson patients were tested after overnight withdrawal of anti-Parkinsonian medication.

Setting

University Medical Center Groningen, tertiary care, the Netherlands.

Participants

Patients with Parkinson''s disease (n = 10; mean age 69.0 years; 6 male) and healthy controls (n = 10; mean age 68.1 years; 6 male).

Interventions

Not applicable.

Main Outcome Measures

Movement time and velocity to detect bradykinesia and the size of writing to detect micrographia. A rest recording to investigate the presence of a rest-tremor, by frequency analysis.

Results

Mean disease duration in the Parkinson group was 4.4 years and the patients were in modified Hoehn-Yahr stages 1–2.5. In general, Parkinson patients were slower than healthy control participants. Median time per repetition, median velocity and median acceleration of the sentence task and median velocity of the elel task differed significantly between Parkinson patients and healthy control participants (all p<0.0014). Parkinson patients also wrote smaller than healthy control participants and the width of the ‘e’ in the elel task was significantly smaller in Parkinson patients compared to healthy control participants (p<0.0014). A rest-tremor was detected in the three patients who were clinically assessed as having rest-tremor.

Conclusions

This study shows that standardized handwriting can provide objective measures for bradykinesia, tremor and micrographia to distinguish Parkinson patients from healthy control participants.     

Yohimbine-induced amygdala activation in pathological gamblers: a pilot study

Rationale and Objectives

There is evidence that drug addiction is associated with increased physiological and psychological responses to stress. In this pilot functional magnetic resonance imaging (fMRI) study we assessed whether a prototype behavioral addiction, pathological gambling (PG), is likewise associated with an enhanced response to stress.

Methods

We induced stress by injecting yohimbine (0.2–0.3 mg/kg, IV), an alpha-2 adrenoceptor antagonist that elicits stress-like physiological and psychological effects in humans and in laboratory animals, to four subjects with PG and to five non-gamblers mentally healthy control subjects. Their fMRI brain responses were assessed along with subjective stress and gambling urges ratings.

Results

Voxelwise analyses of data sets from individual subjects, utilizing generalized linear model approach, revealed significant left amygdala activation in response to yohimbine across all PG subjects. This amygdala effect was not observed in the five control individuals. Yohimbine elicited subjective stress ratings in both groups with greater (albeit not statically significantly) average response in the PG subjects. On the other hand, yohimbine did not induce urges to gamble.

Conclusions

The present data support the hypothesis of brain sensitization to pharmacologically-induced stress in PG.     

Guideline Compliance in Chronic Heart Failure Patients with Multiple Comorbid Diseases: Evaluation of an Individualised Multidisciplinary Model of Care

Objective

To assess the impact of individualised, reconciled evidence-based recommendations (IRERs) and multidisciplinary care in patients with chronic heart failure (CHF) on clinical guideline compliance for CHF and common comorbid conditions.

Design and setting

A retrospective hospital clinical audit conducted between 1^st July 2006 and February 2011.

Participants

A total of 255 patients with a diagnosis of CHF who attended the Multidisciplinary Ambulatory Consulting Services (MACS) clinics, at the Royal Adelaide Hospital, were included.

Main outcome measures

Compliance with Australian clinical guideline recommendations for CHF, atrial fibrillation, diabetes mellitus and ischaemic heart disease.

Results

Study participants had a median of eight medical conditions (IQR 6–10) and were on an average of 10 (±4) unique medications. Compliance with clinical guideline recommendations for pharmacological therapy for CHF, comorbid atrial fibrillation, diabetes or ischaemic heart disease was high, ranging from 86% for lipid lowering therapy to 98% anti-platelet agents. For all conditions, compliance with lifestyle recommendations was lower than pharmacological therapy, ranging from no podiatry reviews for CHF patients with comorbid diabetes to 75% for heart failure education. Concordance with many guideline recommendations was significantly associated if the patient had IRERs determined, a greater number of recommendations, more clinic visits or if patients participated in a heart failure program.

Conclusions

Despite the high number of comorbid conditions and resulting complexity of the management, high compliance to clinical guideline recommendations was associated with IRER determination in older patients with CHF. Importantly these recommendations need to be communicated to the patient’s general practitioner, regularly monitored and adjusted at clinic visits.     

Long-Term Effect of Bariatric Surgery on Liver Enzymes in the Swedish Obese Subjects (SOS) Study

Background and Aim

Obesity is associated with elevated serum transaminase levels and non-alcoholic fatty liver disease and weight loss is a recommended therapeutic strategy. Bariatric surgery is effective in obtaining and maintaining weight loss. Aim of the present study was to examine the long-term effects of bariatric surgery on transaminase levels in obese individuals.

Methods

The Swedish Obese Subjects (SOS) study is a prospective controlled intervention study designed to compare the long-term effects of bariatric surgery and usual care in obese subjects. A total of 3,570 obese participants with no excess of alcohol consumption at baseline (1,795 and 1,775 in the control and surgery group, respectively) were included in the analyses. Changes in transaminase levels during follow-up were compared in the surgery and control groups.

Results

Compared to usual care, bariatric surgery was associated with lower serum ALT and AST levels at 2- and 10- year follow up. The reduction in ALT levels was proportional to the degree of weight loss. Both the incidence of and the remission from high transaminase levels were more favorable in the surgery group compared to the control group. Similarly, the prevalence of ALT/AST ratio <1 was lower in the surgery compared to the control group at both 2- and 10-year follow up.

Conclusions

Bariatric surgery results in a sustained reduction in transaminase levels and a long-term benefit in obese individuals.     

Asymptomatic Intracranial Arterial Stenosis and Metabolic Syndrome: The APAC Study

Purpose

The metabolic syndrome (MetS) is a major risk factor for cardiovascular diseases. We investigated potential associations between MetS and asymptomatic intracranial arterial stenosis (ICAS) in a general population.

Methods

The community-based “Asymptomatic Polyvascular Abnormalities in Community Study” examined asymptomatic polyvascular abnormalities in a Chinese population aged 40+ years without history of stroke and coronary heart disease. MetS was defined by the International Diabetes Federation criteria. Asymptomatic ICAS was diagnosed by transcranial color-coded Doppler sonography.

Results

Out of 5393 study participants, asymptomatic ICAS was detected in 713 (13.2%) participants, and MetS in 1323 (24.5%) individuals. Prevalence of asymptomatic ICAS increased significantly from 7.5% to 24.2% with increasing number of MetS components. After adjusting for age, gender, physical activity, body mass index, low-density lipoprotein cholesterol and high-sensitivity C-reactive protein, MetS was significantly associated with asymptomatic ICAS (OR: 1.50; 95%CI: 1.23,1.83). Compared with the subgroup without MetS, the ORs for asymptomatic ICAS increased (P<0.0001) for each of 5 components of MetS from 1.71 (95%CI: 1.27,2.30), to 2.20 (95%CI: 1.63,2.98), 2.79 (95CI: 2.01,3.88), 3.08 (95%CI: 2.11,4.51) and 4.27 (95%CI: 2.22,8.20).

Conclusions

In multivariate analysis, MetS was an independent and additional factor associated with asymptomatic ICAS. Study participants with 5 MetS components had a 4 times higher risk of asymptomatic ICAS than participants with no MetS component.     

Cognitive Control in Opioid Dependence and Methadone Maintenance Treatment

Background

Substance misuse is associated with cognitive dysfunction. We used a stop signal task to examine deficits in cognitive control in individuals with opioid dependence (OD). We examined how response inhibition and post-error slowing are compromised and whether methadone maintenance treatment (MMT), abstinence duration, and psychiatric comorbidity are related to these measures in individuals with OD.

Methods

Two-hundred-and-sixty-four men with OD who were incarcerated at a detention center and abstinent for up to 2 months (n = 108) or at a correctional facility and abstinent for approximately 6 months (n = 156), 65 OD men under MMT at a psychiatric clinic, and 64 age and education matched healthy control (HC) participants were assessed. We computed the stop signal reaction time (SSRT) to index the capacity of response inhibition and post-error slowing (PES) to represent error-related behavioral adjustment, as in our previous work. We examined group effects with analyses of variance and covariance analyses, followed by planned comparisons. Specifically, we compared OD and HC participants to examine the effects of opioid dependence and MMT and compared OD sub-groups to examine the effects of abstinence duration and psychiatric comorbidity.

Results

The SSRT was significantly prolonged in OD but not MMT individuals, as compared to HC. The extent of post-error slowing diminished in OD and MMT, as compared to HC (trend; p = 0.061), and there was no difference between the OD and MMT groups. Individuals in longer abstinence were no less impaired in these measures. Furthermore, these results remained when psychiatric comorbidities including misuse of other substances were accounted for.

Conclusions

Methadone treatment appears to be associated with relatively intact cognitive control in opioid dependent individuals. MMT may facilitate public health by augmenting cognitive control and thereby mitigating risky behaviors in heroin addicts.     

Few Effects of Far Transfer of Working Memory Training in ADHD: A Randomized Controlled Trial

Objective

Studies have shown that children with ADHD profit from working memory training, although few studies have investigated transfer effects comprehensively. The current Randomized Controlled Trial analyzes transfer to other neuropsychological (NP) domains, academic performance and everyday functioning at home and school.

Method

Sixty-seven children with ADHD were randomized into a control group or a training group. The training group underwent Cogmed’s RoboMemo program. All participants were assessed pre-training, immediately after and eight months later with a battery of NP tests, measures of mathematical and reading skills, as well as rating scales filled out by parents and teachers.

Results

There was a significant training effect in psychomotor speed, but not to any other NP measures. Reading and mathematics were improved. There were no training induced changes in symptom rating scales either at home or at school. The increased reading scores remained significant eight months later.

Conclusion

The study is the most comprehensive study of transfer effects to date, and with mixed results compared to previous research. More research is needed regarding how to improve the training program and the conditions and thresholds for successful training.

Trial Registration

Controlled-Trials.com ISRCTN19133620     

HIV-1 Clade B pol Evolution following Primary Infection

Objective

Characterize intra-individual HIV-1 subtype B pol evolution in antiretroviral naive individuals.

Design

Longitudinal cohort study of individuals enrolled during primary infection.

Methods

Eligible individuals were antiretroviral naïve participants enrolled in the cohort from December 1997-December 2005 and having at least two blood samples available with the first one collected within a year of their estimated date of infection. Population-based pol sequences were generated from collected blood samples and analyzed for genetic divergence over time in respect to dual infection status, HLA, CD4 count and viral load.

Results

93 participants were observed for a median of 1.8 years (Mean = 2.2 years, SD = 1.9 years). All participants classified as mono-infected had less than 0.7% divergence between any two of their pol sequences using the Tamura-Nei model (TN93), while individuals with dual infection had up to 7.0% divergence. The global substitution rates (substitutions/nucleotide/year) for mono and dually infected individuals were significantly different (p<0.001); however, substitution rates were not associated with HLA haplotype, CD4 or viral load.

Conclusions

Even after a maximum of almost 9 years of follow-up, all mono-infected participants had less than 1% divergence between baseline and longitudinal sequences, while participants with dual infection had 10 times greater divergence. These data support the use of HIV-1 pol sequence data to evaluate transmission events, networks and HIV-1 dual infection.     

Are the Healthy Behaviors of US High-Deductible Health Plan Enrollees Driven by People Who Chose These Plans? Smoking as a Case Study

Purpose

To determine whether negative associations between enrollment in a high-deductible health plan (HDHP) and one exemplar unhealthy behavior – daily smoking – are found only among people who chose these plans.

Design

Cross-sectional analysis of nationally-representative data.

Setting

United States from 2007 to 2008.

Subjects

6,941 privately insured non-elderly adult participants in the 2007 Health Tracking Household Survey.

Measures

Self-reported smoking status.

Analysis

We classified subjects as HDHP or traditional health plan enrollees with employer-sponsored insurance (ESI) and no choice of plans, ESI with a choice of plans, or coverage through the non-group market. We used multivariate logistic regression to measure associations between HDHP enrollment and daily smoking within each of the 3 coverage source groups while controlling for potential confounders.

Results

HDHP enrollment was associated with lower odds of smoking among individuals with ESI and a choice of plans (AOR 0.55, 95% CI 0.33–0.90) and those with non-group coverage (AOR 0.64, 95% CI 0.34–1.22), though the latter association was not statistically significant. HDHP enrollment was not associated with lower odds of smoking among individuals with ESI and no choice of plans (AOR 1.04, 95% CI 0.69–1.56).

Conclusions

HDHP enrollment is associated with lower odds of smoking only among individuals who chose to enroll in an HDHP. Lower rates of unhealthy behaviors among HDHP enrollees may be a reflection of individuals who choose these plans.     

Marcescent corollas as functional structures: effects on the fecundity of two insect-pollinated plants

Background and aims

Persistence of withered corollas after anthesis (‘corolla marcescence’) is widespread in angiosperms, yet its functional significance does not seem to have been explored for any species. This note reports the results of experiments assessing the fecundity effects of marcescent corollas in two southern Spanish insect-pollinated plants, Lavandula latifolia (Lamiaceae) and Viola cazorlensis (Violaceae).

Methods

The effect of marcescent corollas on seed production was evaluated experimentally on wild-growing plants. Newly open flowers were randomly assigned to either control or treatment groups in experimental plants. After anthesis, withered corollas of treatment flowers were removed and those in control flowers were left in place. Fruits produced by treatment and control flowers were collected shortly before dehiscence and the number of seeds counted.

Key Results

In V. cazorlensis, removal of withered corollas had no effect on percentage of fruit set, but mean seeds per fruit increased from 9·5 to 11·4. In L. latifolia, corolla removal had no effect on the number of seeds per fruit, but reduced the proportion of flowers ripening fruit from 60 % to 40 %. The detrimental effect of corolla removal on L. latifolia fecundity resulted from the drastic increase in fruit infestation by seed-predatory cecidomyiid larvae, which occurred in 4 % and 34 % of control and treatment fruits, respectively.

Conclusions

Because of their potential effects on plant fecundity, marcescent corollas should not be dismissed a priori as biologically irrelevant leftovers from past floral functions. The simplicity of the experimental layout required to test for short-term fecundity effects of corolla marcescence should help to achieve a better understanding of the ecological and evolutionary correlates of this widespread but poorly understood trait.     

Size-dependent gender modification in Lilium apertum (Liliaceae): does this species exhibit gender diphasy?

Background and Aims

Variation in the relative female and male reproductive success of flowering plants is widespread, despite the fundamental hermaphroditic condition of the majority of species. In many hermaphroditic populations, environmental conditions and their influence on development and size can influence the gender expression of individuals through the formation of hermaphroditic and unisexual flowers. This study investigates the hypothesis that the bulbous, animal-pollinated, perennial Lilium apertum (Liliaceae) exhibits a form of size-dependent gender modification known as gender diphasy, in which the sexual expression of individuals depends on their size, with plants often changing sex between seasons.

Methods

Variation in floral traits was examined in relation to their size using marked individuals in natural populations, and also under glasshouse conditions. Measurements were taken of the height, flower number, floral sex expression, flower size, flower biomass and pollen production of individuals over consecutive years between 2009 and 2012 in seven populations in south-west China.

Key Results

Flowers of L. apertum are either perfect (hermaphroditic) or staminate (male) and, in any given season, plants exhibit one of three sex phenotypes: only hermaphrodite flowers, a mixture of hermaphroditic and male flowers, or only male flowers. Transitions between each of these sex phenotypes were observed over consecutive years and were commonly size-dependent, particularly transitions from small plants bearing only male flowers to those that were taller with hermaphroditic flowers. Hermaphroditic flowers were significantly larger, heavier and produced more pollen than male flowers.

Conclusions

The results for L. apertum are consistent with the ‘size advantage hypothesis’ developed for animal species with sex change. The theory predicts that when individuals are small they should exhibit the sex for which the costs of reproduction are less, and this usually involves the male phase. L. apertum provides an example of gender diphasy, a rare sexual system in flowering plants.