Is protection against florivory consistent with the optimal defense hypothesis?

BACKGROUND: Plant defense traits require resources and energy that plants may otherwise use for growth and reproduction. In order to most efficiently protect plant tissues from herbivory, one widely accepted assumption of the optimal defense hypothesis states that plants protect tissues most relevant to fitness. Reproductive organs directly determining plant fitness, including flowers and immature fruit, as well as young, productive leaf tissue thus should be particularly well-defended. To test this hypothesis, we quantified the cyanogenic potential (HCNp)-a direct, chemical defense-systemically expressed in vegetative and reproductive organs in lima bean (Phaseolus lunatus), and we tested susceptibility of these organs in bioassays with a generalist insect herbivore, the Large Yellow Underwing (Noctuidae: Noctua pronuba). To determine the actual impact of either florivory (herbivory on flowers) or folivory on seed production as a measure of maternal fitness, we removed varying percentages of total flowers or young leaf tissue and quantified developing fruit, seeds, and seed viability. RESULTS: We found extremely low HCNp in flowers (8.66 ± 2.19 µmol CN(-) g(-1) FW in young, white flowers, 6.23 ± 1.25 µmol CN(-) g(-1) FW in mature, yellow flowers) and in pods (ranging from 32.05 ± 7.08 to 0.09 ± 0.08 µmol CN(-) g(-1) FW in young to mature pods, respectively) whereas young leaves showed high levels of defense (67.35 ± 3.15 µmol CN(-) g(-1) FW). Correspondingly, herbivores consumed more flowers than any other tissue, which, when taken alone, appears to contradict the optimal defense hypothesis. However, experimentally removing flowers did not significantly impact fitness, while leaf tissue removal significantly reduced production of viable seeds. CONCLUSIONS: Even though flowers were the least defended and most consumed, our results support the optimal defense hypothesis due to i) the lack of flower removal effects on fitness and ii) the high defense investment in young leaves, which have high consequences for fitness. These data highlight the importance of considering plant defense interactions from multiple angles; interpreting where empirical data fit within any plant defense hypothesis requires understanding the fitness consequences associated with the observed defense pattern.

Immediate Weight-bearing Through Walker or Crutches After Surgical Fixation of Clavicle Fractures in Patients With Lower Extremity Fractures: A Retrospective Cohort Study.

OBJECTIVES: To assess the safety of immediate upper extremity weight-bearing as tolerated (WBAT) rehabilitation protocol after clavicle fracture open reduction internal fixation (ORIF). DESIGN: Retrospective cohort study. SETTING: Three Level 1 trauma centers. PATIENTS SELECTION CRITERIA: Patients older than 18 years who had ORIF of mid-shaft clavicle fractures and lower extremity fractures who were allowed immediate WBAT on their affected upper extremity through use of a walker or crutches were included. All clavicles were fixed with either precontoured clavicular plates or locking compression plates. Included patients were those who had clinical/radiographic follow-up until fracture union, nonunion, or construct failure. OUTCOME MEASURES AND COMPARISONS: WBAT patients were matched in a one-to-one fashion to a cohort with isolated clavicle fractures who were treated non-weight-bearing (NWB) postoperatively on their affected upper extremity. Matching was done based on age, sex, and temporality of fixation. After matching, treatment and control groups were compared to determine differences in possible confounding variables that could influence the primary outcome, including patient demographics, fracture classification, cortices of fixation, and construct type. All patients were assessed to verify conformity with weight-bearing recommendation. Primary outcome was early hardware failure (HWF) with or without revision surgery. Secondary outcomes included postoperative infections and union of fracture. RESULTS: Thirty-nine patients were included in the WBAT cohort; there were no significant differences with the matched NWB cohort based on patient demographics. Both the WBAT and the NWB cohorts had 2.5% chance of acute HWF that required surgical intervention ( P = 1.0). Additionally, there was no difference in overall HWF ( P = 0.49). All patients despite weight-bearing status including those who required revision ORIF for acute HWF had union of their fracture ( P = 1.0). CONCLUSIONS: Our data would support that immediate weight-bearing after clavicle fracture fixation in patients with concomitant lower extremity trauma does not lead to an increase in HWF or impact ultimate union. This challenges the dogma of prolonged postoperative weight-bearing restrictions and allow for earlier rehabilitation. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Is the Iliac Cortical Density Similarly Positioned in the Developing Pediatric Pelvis?

OBJECTIVES: The iliac cortical density (ICD) is a critical fluoroscopic landmark for pelvic percutaneous screw placement. Our purpose was to evaluate the ICD as a landmark in pediatrics and quantify the diameter of osseous pathways for 3 screw trajectories: iliosacral (IS) at S1 and transiliac-transsacral (TSTI) at S1 and S2. METHODS: Two hundred sixty-seven consecutive pelvic CT scans in children 0-16 years of age were analyzed. ICD and S1 vertebral heights were measured at multiple regions along S1. Their height and corresponding ratios, as well as osseous screw corridor dimensions were compared between age groups and by the dysmorphic status. RESULTS: In the nondysmorphic pelvises, S1 height, ICD height, and the ICD to S1 height ratio increased across age groups for all locations (P < 0.001). All 3 screw pathway diameters increased with age (P < 0.001). In the dysmorphic group, there was no increase in ICD to S1 height ratio with age. Except for the age 0-2 group, the ICD to S1 height ratios were significantly larger in the nondysmorphic group. In the dysmorphic group, S1 TSTI pathway remained narrow with age, whereas IS at S1 and TSTI at S2 had a significant increased diameter with age (P < 0.001). CONCLUSION: The ICD is a useful fluoroscopic landmark for percutaneous screw placement in the pediatric pelvis. For nondysmorphic pelvises, the ICD to S1 height ratio, as well as osseous corridors for IS, TSTI at S1, and TSTI at S2 screw trajectories increase significantly with age. The margin for safe screw placement in S1 is smaller for younger and dysmorphic pelvises.