Interactions of cadmium and zinc in high zinc tolerant native species Andropogon gayanus cultivated in hydroponics: growth endpoints, metal bioaccumulation, and ultrastructural analysis.

Cadmium (Cd) and zinc (Zn) toxicity causes physiological disorders and harms plants, interfering with the rehabilitation of areas affected by mining activities. This study evaluated how the exposure to Zn and/or Cd affects the growth of native andropogon grass (Andropogon gayanus Kunth) plants originally found in areas contaminated with Cd and/or Zn due to zinc mining activities. Plants were cultivated for 7 weeks in a nutrient solution treated with Zn (142.3-854.0 µM) or Cd (0.9-13.3 µM) separately or combined with a molar ratio of 64:1 (Zn:Cd). A control treatment was grown in a complete Hoagland and Arnon solution (without Cd). Plant height, stem diameter, internode length, dry weight, Cd and Zn concentration, and accumulation in shoots/roots, as well as ultrastructure of roots and leaves were analyzed at the end of the experiment. The root dry weight was not significantly affected by the addition of the metals. Moreover, Zn provided higher shoot dry weight (up to 160%) relative to control. Andropogon grass tolerated both metals better separately than when applied together. Transmission electron microscopy analyses showed modifications such as vesiculation and vacuolation in the ultrastructure of andropogon tissues by Cd and/or Zn. The andropogon grass was tolerant to the doses tested, evidencing that it has potential for recovering areas contaminated with Zn and/or Cd.

Do parasitoid density and host age affect the parasitism of Palmistichus elaeisis (Hymenoptera: Eulophidae)? / Densidade de parasitoides e idade do hospedeiro afetam o parasitismo de Palmistichus elaeisis (Hymenoptera: Eulophidae)?

The incidence of lepidopteran defoliants is one of the environmental factors that regulate the productivity of cultivated forests. The parasitoid Palmistichus elaeisis (Hymenoptera: Eulophidae) has significant importance for its efficiency in the parasitism of pupae of these Lepidoptera. The objective of this study was to evaluate the development and reproduction of P. elaeisis in different densities of pupae of Spodoptera frugiperda (Lepidoptera: Noctuidae) at different ages. Pupae of 24, 48, 72 and 96 hours were exposed at densities of 1:1, 4:1, 10:1, 19:1, 31:1 and 46:1 parasitoids/host, respectively. The parasitoids remained in contact with the pupae for 72 hours in 500 mL plastic pots, conditioned in an air-conditioned room, with temperature of 25 ± 2°C, relative humidity of 70 ± 10% and photoperiod of 12 hours. It was concluded that the density of 10:1 presented great results of parasitism, and further increase of density was not needed. Pupae of 24 and 48 hours had a higher percentage of emergence. Biological variables were affected neither by parasitoid densities nor by host age.(AU)

A incidência de lepidópteros desfolhadores é um dos fatores ambientais que regulam a produtividade das florestas plantadas. O endoparasitoide Palmistichus elaeisis (Hymenoptera: Eulophidae) destaca-se pela eficiência no parasitismo e pode ser promissor no controle de Lepidoptera pragas em diversas culturas com importância econômica. Assim, avaliaram-se o desenvolvimento e a reprodução de P. elaeisis em pupas de Spodoptera ­frugiperda (Lepidoptera: Noctuidae) com idades distintas submetidas a diferentes densidades do parasitoide. Pupas de 24, 48, 72 e 96 horas foram expostas às densidades de 1:1, 4:1, 10:1, 19:1, 31:1 e 46:1 parasitoides/hospedeiro. Os parasitoides permaneceram em contato com as pupas por 72 horas em potes plásticos de 500 mL, acondicionados em sala climatizada com temperatura 25 ± 2°C, umidade relativa de 70 ± 10°C e fotoperíodo de 12 horas. A densidade 10:1 apresentou resultados adequados de parasitismo. Pupas de 24 e 48 horas de idade apresentaram maior porcentagem de emergência. O ciclo de vida, o número de indivíduos emergidos, a razão sexual, a longevidade das fêmeas e o comprimento da cápsula cefálica e da tíbia de P. elaeisis não foram afetados pelas densidades do parasitoide nem pela idade do hospedeiro.(AU)