Cadmium tolerance of Typha domingensis Pers. (Typhaceae) as related to growth and leaf morphophysiology

Typha domingensis (cattail) is a native macrophyte known by its capacity to tolerate several heavy metals effects and the potential use for phytoremediation. However, in despite that cadmium (Cd) is one of the most toxic pollutants; its effects in T. domingensis biology remain uninvestigated. Thus, the objective of this study was to study the tolerance of T. domingensis to cadmium contamination by evaluating its growth, Cd uptake, leaf anatomy and gas exchange. The experiment was designed using three cadmium concentrations (0, 10 and 50 µM) and ten replicates for 90 days. The cadmium uptake, growth, gas exchange, chlorophyll content and leaf anatomy were evaluated. Data was submitted to ANOVA and Scott-Knott test for P<0.05. Typha domingensis accumulates Cd proportionally to its concentration on the solution and the content of this metal was higher in roots as compared to shoots. Plants showed no significant modifications on growth parameters such as the biomass production, number of leaves, number of clones and the biomass allocation to organs. The photosynthesis, transpiration and chlorophyll content were not modified by Cd. Most anatomical traits evaluated were not modified by the metal but the stomatal density and the proportion of vascular tissues were reduced under 50 µM of Cd. In despite, the leaf anatomy showed no toxicity evidences for any Cd level. The absence of growth reduction and the stability of anatomical and physiological traits give insight about the Cd tolerance of this species. Therefore, T. domingensis is able to overcome Cd toxicity and shows potential for phytoremediation.

Anatomical traits related to stress in high density populations of Typha angustifolia L. (Typhaceae)

Some macrophytes species show a high growth potential, colonizing large areas on aquatic environments. Cattail (Typha angustifolia L.) uncontrolled growth causes several problems to human activities and local biodiversity, but this also may lead to competition and further problems for this species itself. Thus, the objective of this study was to investigate anatomical modifications on T. angustifolia plants from different population densities, once it can help to understand its biology. Roots and leaves were collected from natural populations growing under high and low densities. These plant materials were fixed and submitted to usual plant microtechnique procedures. Slides were observed and photographed under light microscopy and images were analyzed in the UTHSCSA-Imagetool software. The experimental design was completely randomized with two treatments and ten replicates, data were submitted to one-way ANOVA and Scott-Knott test at p<0.05. Leaves from low density populations showed higher stomatal density and index. These modifications on stomatal characteristics were more evident on the leaf abaxial surface. Plants from low density populations showed thicker mesophyll and higher proportion of aerenchymal area. Roots from low density populations showed a higher proportion of the vascular cylinder. Whereas, plants from higher density populations showed greater thickness of the endodermis, exodermis, phloem and root cortex. Higher density populations showed a higher proportion of aerenchymal gaps in the root cortex. Therefore, cattail plants from populations growing under high density population show anatomical traits typical of plants under stress, which promotes the development of less functional anatomical modifications to aquatic environments.

[The unreliability of neurologic examination in the diagnosis of neonatal periventricular-intraventricular hemorrhage]

OBJECTIVE: To evaluate the efficacy of the clinical neurologic examination, hematocrit and glycemia in the diagnosis of periventricular-intraventricular hemorrhage in the newborn weighing less than 2000g considering the neurosonography as the gold standard.METHODS: This is a cohort prospective study from May 18th, 1994 to May 17th, 1995 carried out at the Hospital das Clinicas da UFMG. The study group comprised 38 newborns with the ultrasound diagnosis of periventricular-intraventricular hemorrhage; the control group comprised 81 newborns who although submitted to the same evaluation protocol did not show any echographic signs of hemorrhage. The ultrasound examinations were all done by the same researcher who was not aware of the clinical history or the neurologic and laboratory examinations.RESULTS: Clinical neurologic alterations, mainly generalized hypotonia, were found to be associated with hemorrhage (p = 0.009), but there was a confounding effect due to the gestational age of the newborn. The predictive values of a positive or negative test were only 45% and 79%, respectively, which is clearly unreliable for the diagnosis of the hemorrhage. Hematocrit and glycemia were not clinically relevant either.CONCLUSIONS: The clinical neurologic examination is not reliable to indicate periventricular-intraventricular hemorrhage in the newborn. Newborns at risk should be routinely screened by neurosonography.

[Risk factors to periventricular-intraventricular hemorrhage in newborns weighing less than 2000g]

OBJECTIVE: To study the incidence and analyze risk factors to neonatal periventricular-intraventricular hemorrhage; to suggest a working protocol for diagnosis in newborns at risk.METHODS: This is a cohort prospective study including 120 out of 129 children weighing less than 2000g born from May 18 th, 1994 to May 17 th,1995 at the Hospital das Clínicas da UFMG. The study group comprised 39 newborns with the ultrasound diagnosis of periventricular-intraventricular hemorrhage; the control group comprised 81 newborns who although submitted to the same evaluation protocol did not show any echographic signs of hemorrhage. The ultrasound examinations were all done by the same researcher who was not aware of the clinical history or the neurologic and laboratory examinations. The hemorrhage was classified according to Papilés criteria: grade I (13%); grade II (7%); grade III (9%) and grade IV (3%).RESULTS: Low gestational age, low birth weight, masculine sex, vaginal delivery, and neonatal sepsis were significantly associated (p < 0.05) with periventricular-intraventricular hemorrhage in univariate analysis. Apgar score in the first or fifth minute and Battagliás and Lubchenkós classification for the weight in relation to gestational age were not predisposing factors to the hemorrhage. Low gestational age (p = 0.002), vaginal delivery (p = 0.037), and masculine sex (p = 0.016) kept statistical significance after multivariate adjustment. Birth weight may substitute for gestational age in the multivariate model because they are highly associated. The best cutoff point to screen for periventricular-intraventricular hemorrhage was 1750 g instead of the traditionally adopted point of 1500 g. CONCLUSIONS: The incidence of neonatal periventricular-intraventricular hemorrhage was similar to those reported by other studies. Low gestational age or low birth weight, vaginal delivery and masculine sex were the most important risk factors to the hemorrhage. The screening cutoff point of 1750 g seems to be more adequate than the commonly used birth weight of 1500 g.