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To investigate the effects of drought and recovery on the transcript level of OePIP2.1 (a PIP2 aquaporin gene) in twigs, 2-year-old olive trees were subjected to a drought/rewatering treatment (the irrigation was suspended for a period of 4 weeks and restored for the following 4 weeks). Twig water potential, twig hydraulic resistance and incidence of embolisation in the twig were measured in parallel with gene expression under both drought stress and the following recovery. During drought, a decrease in twig water potential, an increase in twig hydraulic resistance and an increase in the extent of xylem vessel embolisation was observed in parallel with a decrease of aquaporin gene expression. Opposite trends were recorded during rewetting. A speculation on a possible contribution of OePIP2.1 aquaporin to modulate shoot embolism during drought and recovery is proposed. [ABSTRACT FROM AUTHOR]

Investigates modifications of vessel size and of shoot hydraulic conductivity induced by different water availability levels in container-grown grapevine plants. Measurement of xylem sap flow and leaf transpiration; Relationship between water stress, stomatal conductance, hydraulic conductivity and vessel stress; Formation of vessel embolisms in water-stressed plants.

Flavescence dorée ( FD) is among the major grapevine diseases causing high management costs; curative methods against FD are unavailable. In FD-infected plants, decrease in photosynthesis is usually recorded, but deregulation in stomatal control of leaf gas exchange during FD infection and recovery is unknown. We measured the seasonal time course of gas exchange rates in two cultivars ('Barbera' and 'Nebbiolo') during the term of 1 year when grapevines experienced a water stress and another with no drought, with difference in gas exchange rates in response to FD infection and recovery as assessed by symptom observation and phytoplasma detection through PCR analysis. Chlorophyll fluorescence was also evaluated at the time of maximum symptom severity in 'Barbera', the cultivar showing the most severe stress response to FD infection, causing the highest damage in vineyards of north-western Italy. In FD-infected plants, net photosynthesis and transpiration gradually decreased during the season, more during the no drought year than during drought. During recovery, healthy ( PCR negative) plants infected 2 years before, but not those infected an year before, regained the gas exchange performances to the level as measured before infection. The relationships between stomatal conductance and the residual leaf intercellular CO2 concentration ( ci) discriminated healthy versus FD-infected and recovered plants; at the same ci, FD-infected leaves had higher non-photochemical quenching than healthy ones. We conclude that metabolic, not stomatal, leaf gas exchange limitation in FD-infected and recovered grapevines is the basis of plant response to FD disease. In addition, we also suggest that such response is dependent upon water stress, by showing that water stress superimposes on FD infection in terms of stomatal and metabolic non-stomatal limitations to carbon assimilation. [ABSTRACT FROM AUTHOR]