Morphoanatomical and physiological changes in Bauhinia variegata L. as indicators of herbicide diuron action.

The wide use of the herbicide diuron has compromised surrounding uncultivated areas, resulting in acute and/or chronic damage to non-target plants. Thus, the aim of this research was to evaluate physiological and morphoanatomical responses in Bauhinia variegata L. plants to different doses of diuron. Seedlings of 90-day-old B. variegata were transplanted into 10liter pots. After an acclimation period (about 30 days), treatments consisting of different diuron doses were applied: 0 (control), 400, 800, 1600, and 2400g ai ha-1. The experiment was conducted in a randomized block design in a 5×5 factorial scheme with five doses of diuron five evaluation times, and five replicates per treatment. Anatomical and physiological injuries were observed in leaves of Bauhina variegata 10h after diuron application. Disruption of waxes was observed on both sides of the leaves of plants exposed since the lowest dose. Plasmolysis in cells were observed in treated leaves; more severe damage was observed in plants exposed to higher doses, resulting in rupture of epidermis. The diuron herbicide also caused gradual reduction in the gas exchange and chlorophyll fluorescence variables. Among the morphoanatomical and physiological variables analyzed, the non-invasive ones (e.g., ETR, YII, and Fv/Fm) may be used as biomarkers of diuron action in association with visible symptoms. In addition, changes in leaf blade waxes and chlorophyll parenchyma damage may also be considered additional leaf biomarkers of diuron herbicide action.

Glands on the foliar surfaces of tribe Cercideae (Caesapiniodeae, Leguminosae): distribution and taxonomic significance.

Large elongated glands occur on Cercideae leaf surfaces. Leaves of Bauhinia (55 taxa, 53 species), Cercis (1 species), Phanera (1 species), Piliostigma (2 species), Schnella (19 species) and Tylosema (1 species) were observed to determine location and relative number of glands. They were only observed on the abaxial leaf surface of 42 Bauhinia taxa. The glands were analyzed by light stereomicroscope and scanning electron microscopy. They are large (up to 270 µm long and 115 µm wide) and multicellular, containing lipophilic substances, probably volatile oils. Presence or absence and density of the glands in species of Bauhinia may be useful to determine species delimitation or distinction among infraspecific taxa. Higher density of glands is more common in species from "cerrado" (a savanna ecosystem) and "caatinga" (a semiarid ecosystem from northeast Brazil) areas. Bauhinia species devoid of foliar glands are frequently from humid forests.