Plants that store nonstructural carbohydrates (NSC) may rely on carbon reserves to survive carbon‐limiting stress, assuming that reserves can be mobilized. We asked whether carbon reserves decrease in resource stressed seedlings, and if NSC allocation is related to species' relative stress tolerances. We tested the effects of stress (shade, drought, and defoliation) on NSC in seedlings of five temperate tree species (Acer rubrum
Marsh., Betula papyrifera
Marsh., Fraxinus americana
L
., Quercus rubra
L., and Quercus velutina
Lam.). In a greenhouse experiment, seedlings were subjected to combinations of shade, drought, and defoliation. We harvested seedlings over 32–97 days and measured biomass and NSC concentrations in stems and roots to estimate depletion rates. For all species and treatments, except for defoliation, seedling growth and NSC accumulation ceased. Shade and drought combined caused total NSC decreases in all species. For shade or drought alone, only some species experienced decreases. Starch followed similar patterns as total NSC, but soluble sugars increased under drought for drought‐tolerant species. These results provide evidence that species deplete stored carbon in response to carbon limiting stress and that species differences in NSC response may be important for understanding carbon depletion as a buffer against shade‐ and drought‐induced mortality.
BACKGROUND: Dental workers including dental health students experience a high incidence of neck/shoulder symptoms. However, research into interventions has been scarce and largely focused on tools and technological modifications. OBJECTIVE: This study investigates the feasibility and benefits of a neck/shoulder exercise intervention on work posture and local symptoms in dental health students. METHODS: Twenty-three students participated in a 10-week resistance exercise program for 2 minutes daily, 5 days per week. Work posture (evaluated with the Rapid Upper Limb Assessment tool, RULA), muscle strength measures, self-rated symptom severity and function were collected. Feasibility of the intervention was determined with six items scored on a 5-point Likert scale. RESULTS: The exercise intervention improved: work posture score by 1.88 (95% CI 1.05–2.70, p < 0.01) points on the RULA; isometric maximal strength of neck flexor and extensor muscles by 17.2% (95% CI 6.9–27.6%, p < 0.01) and 23.2% (95% CI 10.2–36.3%, p < 0.01) respectively; and clinical performance (77%). Isometric strength of the shoulder muscles, and symptom severity at the neck/shoulder showed no improvement. Adherence to training was 77%. CONCLUSION: Ten weeks of exercise was feasible for dental health students, and likely beneficial with improvements in work posture and neck muscle strength.
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