Nitrogen-improved photosynthesis quantum yield is driven by increased thylakoid density, enhancing green light absorption.

A nitrogen supply is necessary for all plants. The multifaceted reasons why this nutrient stimulates plant dry weight accumulation are assessed herein. We compared tomato plants grown in full sunlight and in low light environments under four N doses and evaluated plant growth, photosynthetic and calorimetric parameters, leaf anatomy, chloroplast transmission electron microscopy (TEM) and a high resolution profile of optical leaf properties. Increases in N supplies allow tomato plants to grow faster in low light environments (91.5% shading), displaying a robust light harvesting machinery and, consequently, improved light harvesting efficiency. Ultrastructurally, high N doses were associated to a high number of grana per chloroplast and greater thylakoid stacking, as well as high electrodensity by TEM. Robust photosynthetic machinery improves green light absorption, but not blue or red. In addition, low construction and dark respiration costs were related to improved total dry weight accumulation in shade conditions. By applying multivariate analyses, we conclude that improved green light absorbance, improved quantum yield and greater palisade parenchyma cell area are the primary components that drive increased plant growth under natural light-limited photosynthesis.

Multiple resistance to pirimiphos-methyl and bifenthrin in Tribolium castaneum involves the activity of lipases, esterases, and laccase2.

Several recent studies have elucidated the molecular mechanisms that confer insecticide resistance on insect pests. However, little is known about multiple resistance in red flour beetle (Tribolium castaneum) at molecular level. The multiple resistance is characterized as resistance to different classes of insecticides that have different target sites, and is mediated by several enzymatic systems. In this study, we investigated the biochemical and molecular mechanisms involved in multiple resistance of T. castaneum to bifenthrin (pyrethroid [Pyr]) and pirimiphos-methyl (organophosphate [Org]). We used artificial selection, biochemical and in silico approaches including structural computational biology. After five generations of artificial selection in the presence of bifenthrin (F5Pyr) or pirimiphos-methyl (F5Org), we found high levels of multiple resistance. The hierarchical enzymatic cluster revealed a pool of esterases (E), lipases (LIPs) and laccase2 (LAC2) potentially contributing to the resistance in different ways throughout development, after one or more generations in the presence of insecticides. The enzyme-insecticide interaction network indicated that E2, E3, LIP3, and LAC2 are enzymes potentially required for multiple resistance phenotype. Kinetic analysis of esterases from F5Pyr and F5Org showed that pirimiphos-methyl and specially bifenthrin promote enzyme inhibition, indicating that esterases mediate resistance by sequestering bifenthrin and pirimiphos-methyl. Our computational data were in accordance with kinetic results, indicating that bifenthrin has higher affinity at the active site of esterase than pirimiphos-methyl. We also report the capability of these insecticides to modify the development in T. castaneum. Our study provide insights into the biochemical mechanisms employed by T. castaneum to acquire multiple resistance.

Morpho-anatomical study of rhizome of Limonium brasiliense

AbstractLimonium brasiliense (Boiss.) Kuntze, Plumbaginaceae, is an herb popularly known as guaicuru, guaicurá or baicuru. The species inhabits salt marshes from the coastal region of southern Brazil, including Rio de Janeiro, to Uruguay and Argentina. Although widely used in folk medicine in the state of Rio Grande do Sul to treat genitourinary infections and to regulate menstrual periods, L. brasiliense has been little studied. The present morpho-anatomical study was undertaken to resolve some doubts in the literature as to the nature of the part of the plant that is used for medicinal purposes, a true rhizome or a root. The morpho-anatomical characteristics were analyzed with the aid of light and scanning electron microscopy. The botanical material was characterized as a rhizome with internodes that are evident in the younger but not the older portions. Microscopic analysis revealed the presence of a multilayered periderm with a cortex, ray parenchyma, and pith, formed by collenchyma tissue with abundant intercellular spaces in the outer portions of the cortex, responsible for the rigidity of the body, and with walls impregnated with phenolic compounds. The vascular bundles are collateral with elliptical to elongated cells, and with few conducting and sclerenchymal elements. Groups of sclereids are dispersed through the cortex and pith. These morpho-anatomical characteristics define the structure as a rhizome.