Drivers of vegetative dormancy across herbaceous perennial plant species.

Vegetative dormancy, that is the temporary absence of aboveground growth for ≥ 1 year, is paradoxical, because plants cannot photosynthesise or flower during dormant periods. We test ecological and evolutionary hypotheses for its widespread persistence. We show that dormancy has evolved numerous times. Most species displaying dormancy exhibit life-history costs of sprouting, and of dormancy. Short-lived and mycoheterotrophic species have higher proportions of dormant plants than long-lived species and species with other nutritional modes. Foliage loss is associated with higher future dormancy levels, suggesting that carbon limitation promotes dormancy. Maximum dormancy duration is shorter under higher precipitation and at higher latitudes, the latter suggesting an important role for competition or herbivory. Study length affects estimates of some demographic parameters. Our results identify life historical and environmental drivers of dormancy. We also highlight the evolutionary importance of the little understood costs of sprouting and growth, latitudinal stress gradients and mixed nutritional modes.

Falls and Orthostatic Hypotension in Older Adults: Re-examining Limits.

Background: Orthostatic hypotension (OH) is defined using substantial thresholds of blood pressure (BP) drops with standing, which may be insufficient for identifying falls risk. Objective: To assess associations between falls risk and (1) consensus-defined OH (cOH), (2) standing BP levels, (3) BP changes with standing, (4) combined standing BP levels and BP changes with standing. Design: Observational study of normative aging. Setting: Baltimore Longitudinal Study of Aging. Participants: Participants ≥65 years with first visits evaluating OH and self-reported falls (2004-2010). Measurements: BP was measured supine and 3 minutes after standing. A drop in systolic BP (SBP) ≥20mmHg or a drop in diastolic BP (DBP) ≥10mmHg upon standing defined cOH. Participants self-reported the number of falls experienced in the previous 12 months. Results: Among 400 participants (45% women; 30% black; mean age 74.8 years), 113 (28%) reported ≥1 fall; 19 (4.8%) had cOH. In adjusted models, cOH (OR=2.77, 95% CI: 1.00-7.71 p=0.051) and continuous SBP-drops per 5mmHg (OR=1.21, 1.00-1.47 p=0.046) were associated with having any fall and multiple falls (cOH: OR=3.94, 1.04-14.96 p=0.044; SBP 5mmHg drops: OR=1.34, 1.00-2.15 p=0.020). Attained SBP with standing was not associated with falls either alone (OR=1.01, 0.99-1.02 p=0.369) or in combination with SBP-drops (interaction OR=1.03, 0.96-1.09 p=0.414). Limitations: Cross-sectional design, prohibiting conclusions about causal relationships. Conclusions: Findings suggest that postural SBP-drops that are much lower than current OH definition thresholds indicate increased falls risk in older adults, regardless of absolute SBP level. This has implications for standard clinical falls risk assessment and communication of falls risk to patients.

Recovery from bud disappearance explains prolonged dormancy in Cleistes bifaria (Orchidaceae).

PREMISE OF THE STUDY: Virtually nothing is known about what actually happens during prolonged dormancy, the period during which significant proportions of geophyte populations do not sprout after seasonal dormancy but remain alive underground, to emerge again 1 or more years later. This study investigated the fate of perennating buds on plants of the orchid Cleistes bifaria during prolonged dormancy, as well as effects of bud removal on dormancy and future sprouting. METHODS: Fates of healthy perennating buds were observed by examining underground plant structures over an annual cycle (fall, spring, fall). Effects of bud loss were assessed by removal of mature buds from one group of plants, followed by comparison with a control group a year later. KEY RESULTS: Of the 142 perennating buds under observation, 38% did not emerge in the spring, and all these were missing the buds that were present and healthy the previous fall. Removal of perennating buds in the fall did not affect whether a plant emerged in the spring; however, it reduced the number and size of perennating buds produced for the following year. CONCLUSIONS: For C. bifaria in West Virginia, prolonged dormancy appears to be the time period during which plants are recovering from the disappearance of perennating buds. Although the cause of bud loss remains unknown, research can now be focused on whether other species fail to emerge for the same reason, what causes buds to disappear, and why removal had no effect on spring emergence but negatively affected future sprouting.

Laryngeal involvement in two severe cases of childhood tuberculosis.

Laryngeal tuberculosis in children is seldom reported in the literature. We present 2 children from Cape Town, South Africa who had disseminated tuberculosis involving the cervical lymph nodes and the larynx. The cases emphasize the pathophysiology, the clinical picture, the bronchoscopic appearance, and the response to therapy in laryngeal tuberculosis.