The influence of temperature on germination of Quercus ilex acorns in Phytophthora infested soils was quantified for the first time. Radicle damage and mortality of Q. ilex seeds germinating at 17, 20, 23 and 26°C in Phytophthora cinnamomi, P. gonapodyides, P. quercina and P. psychrophila infested soils were assessed and related to in vitro mycelium growth of the same isolates of the pathogens. The optimum growth temperatures of isolates of P. cinnamomi, P. gonapodyides, P. quercina and P. psychrophila were 20-23, 23-26, 20-23 and 20°C, respectively. At 17 and 20°C, all four Phytophthora species caused 100% acorn mortality, whereas at 26°C, acorn mortality was 100, 10, 25 and 0% in P. cinnamomi, P. gonapodyides, P. quercina and P. psychrophila infested soils, respectively. At 23°C, P. cinnamomi and P. gonapodyides reduced acorn radicle length more than P. quercina and P. psychrophila, whereas at 26°C, only P. cinnamomi caused further reduction in radicle length. The higher susceptibility of germinating acorns in comparison to seedlings reported in the literature indicates age-related susceptibility of Q. ilex to Phytophthora. The seedling/pathogen growth ratio was inversely related to the reduction in radicle length at different temperatures (R 2 adj = 0.84, p < 0.0001), suggesting that rapid germination may allow seedlings to escape from infection. Increasing temperatures had different effects on damage to acorns depending on the pathogen present in the soil, indicating that Phytophthora species 9 temperature interactions determined Q. ilex germination. The effects of temperature on the impacts of Phytophthora species based on climate change predictions for Mediterranean countries are discussed.

Exogenous supply of nitric oxide (NO) increases drought tolerance in sugarcane plants. However, little is known about the role of NO produced by plants under water deficit. The aim of this study was to test the hypothesis that drought-tolerance in sugarcane is associated with NO production and metabolism, with the more drought-tolerant genotype presenting higher NO accumulation in plant tissues. The sugarcane genotypes IACSP95-5000 (drought-tolerant) and IACSP97-7065 (drought-sensitive) were submitted to water deficit by adding polyethylene glycol (PEG-8000) in nutrient solution to reduce the osmotic potential to -0.4 MPa. To evaluate short-time responses to water deficit, leaf and root samples were taken after 24 h under water deficit. The drought-tolerant genotype presented higher root extracellular NO content, which was accompanied by higher root nitrate reductase (NR) activity as compared to the drought-sensitive genotype under water deficit. In addition, the drought-tolerant genotype had higher leaf intracellular NO content than the drought-sensitive one. IACSP95-5000 exhibited decreases in root S-nitrosoglutathione reductase (GSNOR) activity under water deficit, suggesting that S-nitrosoglutathione (GSNO) is less degraded and that the drought-tolerant genotype has a higher natural reservoir of NO than the drought-sensitive one. Those differences in intracellular and extracellular NO contents and enzymatic activities were associated with higher leaf hydration in the drought-tolerant genotype as compared to the sensitive one under water deficit.

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