Mechanisms of cadmium-stress avoidance by selenium in tomato plants.

Cadmium (Cd) is probably the most damaging metal to plant species; with a long biological half-life, it can be taken up by plants, disrupting the cell homeostasis and triggering several metabolic pathways. Selenium (Se) improves plant defence systems against stressful conditions, but the biochemical antioxidant responses to Cd stress in tomato plants is poorly understood. To further address the relationship of Cd-stress responses with Se mineral uptake, Cd and Se concentration, proline content, MDA and H2O2 production, and the activity of SOD, APX, CAT and GR enzymes were analyzed in Micro-Tom (MT) plants submitted to 0.5 mM Cd. The results revealed different responses according to Se combination and Cd application. For instance, roots and leaves of MT plants treated with Se exhibited an increase in dry mass and nutritional status, exhibited lower proline content and higher APX and GR activities when compared with plants with no Se application. Plants submitted to 0.5 mM Cd, irrespective of Se exposure, exhibited lower proline, MDA and H2O2 content and higher SOD, CAT and GR activities. Selenium may improve tolerance against Cd, which allowed MT plants exhibited less oxidative damage to the cell, even under elevated Cd accumulation in their tissues. The results suggest that Se application is an efficient management technique to alleviate the deleterious effects of Cd-stress, enhancing the nutritional value and activity of ROS-scavenging enzymes in tomato plants.

Impacts of warming and water deficit on antioxidant responses in Panicum maximum Jacq.

Agricultural activities are affected by many biotic and abiotic stresses associated with global climate change. Predicting the response of plants to abiotic stress under future climate scenarios requires an understanding of plant biochemical performance in simulated stress conditions. In this study, the antioxidant response of Panicum maximum Jacq. cv. Mombaça exposed to warming (+2°C above ambient temperature) (eT), water deficit (wS) and the combination eT + wS was analysed under field conditions using a temperature free-air-controlled enhancement facility. Warming was applied during the entire growth period. Data were collected at 13, 19 and 37 days after the start of the water deficit treatment (DAT) and at two sampling times (6:00 and 12:00 h). A significant decrease in chlorophyll was observed under the wS treatment, but an increment in total chlorophyll was observed in eT + wS, particularly at 19 DAT. Significant increase in H2 O2 content, malondialdehyde and protein oxidation was observed in the wS treatment at noon of the third sampling. In the combined wS + eT stress treatment, the activity of the enzymatic antioxidant system increased, particularly of superoxide dismutase (SOD; EC 1.15.1.1) and ascorbate peroxidase (APX; EC 1.11.1.11). The chlorophyll fluorescence images showed that the photochemical performance was not significantly affected by the treatments. In conclusion, under simulated future warming and water stress conditions, the photosystem II (PSII) activity of P. maximum acclimated to moderate warming and a water-stressed environment associated with a relatively favourable antioxidant response, particularly in the activity of APX and SOD.

An experimental model for the transplantation of fetal central nervous system cells to the injured spinal cord in rats.

INTRODUCTION: Traumatic spinal cord injury is one of the most disabling conditions occurring in man and thus stimulates a strong interest in its histopathological, biochemical, and functional changes, primarily as we search for preventive and therapeutic methods. PURPOSE: To develop an experimental model for transplantation of cells from the fetal rat central nervous system to the site of an injured spinal cord of an adult rat in which the transplanted cells survive and become integrated. This experimental model will facilitate investigations of factors that promote regeneration and functional recovery after spinal cord trauma. MATERIAL AND METHODS: Fifteen adult Wistar rats underwent laminectomy, and an spinal cord lesion was made with microdissection. Fetal spinal cord tissue was then transplanted to the site of the injury. The rats were monitored over a 48-hour period, and then their vertebral column was completely removed for histological analysis. RESULTS: In 60% of transplanted rats, the fetal tissue at the injured site remained viable in the site of the lesion.