The understanding of acclimation strategies to low temperature and water availability is decisive to ensure coffee crop sustainability, since these environmental conditions determine the suitability of cultivation areas. In this context, the impacts of single and combined exposure to drought and cold were evaluated in three genotypes of the two major cropped species, Coffea arabica cv. Icatu, Coffea canephora cv. Apoatã, and the hybrid Obatã. Crucial traits of plant resilience to environmental stresses have been examined: photosynthesis, lipoperoxidation and the antioxidant response. Drought and/or cold promoted leaf dehydration, which was accompanied by stomatal and mesophyll limitations that impaired leaf C-assimilation in all genotypes. However, Icatu showed a lower impact upon stress exposure and a faster and complete photosynthetic recovery. Although lipoperoxidation was increased by drought (Icatu) and cold (all genotypes), it was greatly reduced by stress interaction, especially in Icatu. In fact, although the antioxidative system was reinforced under single drought and cold exposure (e.g., activity of enzymes as Cu,Zn-superoxide dismutase, ascorbate peroxidase, APX, glutathione reductase and catalase, CAT), the stronger increases were observed upon the simultaneous exposure to both stresses, which was accompanied with a transcriptional response of some genes, namely related to APX. Complementary, non-enzyme antioxidant molecules were promoted mostly by cold and the stress interaction, including α-tocopherol (in C. arabica plants), ascorbate (ASC), zeaxanthin, and phenolic compounds (all genotypes). In general, drought promoted antioxidant enzymes activity, whereas cold enhanced the synthesis of both enzyme and non-enzyme antioxidants, the latter likely related to a higher need of antioxidative capability when enzyme reactions were probably quite repressed by low temperature. Icatu showed the wider antioxidative capability, with the triggering of all studied antioxidative molecules by drought (except CAT), cold, and, particularly, stress interaction (except ASC), revealing a clear stress cross-tolerance. This justified the lower impacts on membrane lipoperoxidation and photosynthetic capacity under stress interaction conditions, related to a better ROS control. These findings are also relevant to coffee water management, showing that watering in the cold season should be largely avoided

ABSTRACT In the northeastern region of Brazil, saline soils are constraints to banana production, becoming necessary to understand the mechanisms of salt tolerance. Two bananas genotypes, Tap Maeo, tolerant, and Berlin, sensitive, were subjected to treatment with 50 mol m-3 NaCl or without salt. This study evaluated the effects of salt on the following physiological aspects: leaf area, content and distribution of Na+, membrane integrity, proton AT Pase activity. Besides, a search for differentially expressed genes was performed using the Differential Display technique. Tap Maeo genotype showed the smallest reduction in leaf area, smaller accumulation of Na+ and malondialdehyde (MDA), and higher activity of proton AT Pase activity. Two sequences differentially expressed in the tolerant genotype, (Musa 07, Musa 23), shared a high degree of identity with the amino acid sequences of the genes SOS1 and SOS2, respectively. The clone Musa 10 was highly similar to amino acid sequence of the ascorbate peroxidase gene, and Musa 26, encodes the enzyme betaine aldehyde dehydrogenase. These significant biological markers indicate that salinity tolerance in banana involves at least two simultaneous mechanisms: the activation of the SOS pathway, increasing the extrusion of Na+, and the activation of antioxidative system, increasing the synthesis of APX and betaine aldehyde dehydrogenase enzyme.

Abstract: The objective in this work was to investigate the effect of nitric oxide (NO) like protective agent in sesame seeds submitted to different osmotic potentials. The treatments, in total of eight, were water (control), water plus sodium nitroprusside (SNP) and the other treatments with PEG 6000 and PEG 6000 plus SNP: - 0.1 MPa, -0.1MPa +200 µM of SNP, 0.2 MPa, -0.2 MPa +200 µM of SNP, -0.3 MPa and -0.3 MPa, +200 µM of SNP. Were done the following determinations: germination, first count of germination, speed germination index, hypocotyl length, radicle length, dry mass of hypocotyl and radicle. It was quantified the activity of the antioxidative enzymes, superoxide dismutase, catalase, ascorbate peroxidase and total peroxidase. The experimental design was completely randomized with five replications. The water restriction reduced the germination of sesame seeds, however, the presence of nitric oxide (NO) due to the application of SNP, was beneficial, promoting increase in germination, vigor and seedlings. There was an increase of antioxidative enzymes activity in the period of 0 to 24 hours, demonstrating organization of antioxidative system in all long the time. The association of PEG 6000 to SNP, increased the activity of antioxidative enzymes, evidencing an efficient system of elimination of ROS formed during the exposition to water deficit.