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Vein cavitation and stomatal behaviour of sunflower ( Helianthus annuus ) leaves under water limitation
Author(s) -
Trifilò Patrizia,
Nardini Andrea,
Lo Gullo Maria A.,
Salleo Sebastiano
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00154.x
Subject(s) - dehydration , turgor pressure , helianthus annuus , horticulture , sunflower , cavitation , transpiration , biology , botany , chemistry , photosynthesis , biochemistry , physics , mechanics
The impact of leaf vein cavitation and embolism on stomatal response and leaf hydraulic conductance was studied in potted plants of sunflower subjected to water limitation. Plant dehydration was achieved either by cutting well‐watered plants near their base and leaving them dehydrating in air or by depriving intact plants of irrigation. The vein cavitation threshold ( Ψ CAV ) was estimated in terms of ultrasound acoustic emissions (UAE) from the leaf blade versus leaf water potential ( Ψ L ). This was found to be the same ( Ψ CAV ≈ −0.6 MPa) for leaves of both cut and intact plants where stomata began to close in coincidence with starting vein cavitation. Vein embolism was detected by infiltrating leaves at different Ψ L with 0.7 m M fluorescein and measuring the percentage fluorescent area as percentage of total leaf surface area. A distinct loss of vein functionality (up to 50%) was found to occur in leaves at progressively decreasing Ψ L , starting when leaves reached Ψ CAV . A linear positive relationship with high statistical significance was found to exist between g L and percentage leaf fluorescent area, thus indicating that stomata were sensitive to vein embolism. The hydraulic conductance ( K L ) of the leaf was affected by leaf dehydration less than expected ( K L decreased by about 20% between near full turgor and Ψ L = −1.3 MPa). When the extravascular leaf compartment was excluded either by killing cells by immersing leaves in 70% ethanol or by cutting the main leaf venous system through to allow flow to bypass it, K L turned out to increase 5.5 times, thus suggesting that the high dominance of the hydraulic resistance of the extravascular leaf compartment over the total leaf resistance might buffer or mask possibly large local changes in K L inducing stomatal closure.