Divergence Of Photosynthetic Recovery Capacity Of Six Caragana Species Along Precipitation Gradient After Rehydration

Six species of Caragana korshinskii from arid region,Caragana intermedia and Caragana microphylla from a semi-arid region,Caragana boisi from semi-humid region,Caragana stipitata and Caragana sinica from humid region were used as plant materials for dehydration and rehydration experiments.This study revealed the divergence pattern of photosynthetic recovery after rehydration.The main conclusions are as follows:1.The hydraulic conductivity vulnerability of six Caragana species,namely the leaf water potential???that induces 50%loss of leaf hydraulic conductance(K_leafeaf P₅₀),increased linearly with increasing mean annual precipitation?MAP?,the result showed the ability of Caragana species from arid regions to withstand hydraulic conductivity vulnerability was significantly higher than that from the humid regions.2.After rehydration at-2.0,-4.0 and-6.0 MPa,leaf water potentials?LWP?of six Caragana species recovered within 1-2 days,but their photosynthetic rate and stomatal conductance recovered slowly.The time required for recovery of Caragana species from arid regions was significantly shorter than the species from humid regions.The time required for recovery was significantly and positively correlated with MAP.The lower K_leafeaf P₅₀,the shorter was the time required for the recovery of photosynthetic rate and stomatal conductance.3.After rehydration,the time required for the recovery of gas exchange was significantly and positively correlated with that of K_leaf,indicating that K_leaf is the main factor to limit the gas exchange recovery of Caragana species.when dehydrated,the foliar ABA level of Caragana korshinskii from arid region initially increased linearly but then declined,while Caragana sinica from humid region exhibited linear increase but then trended towards a stable level.Although the foliar ABA level of the both rapidly regained to unstressed level within 1 day after rehydration,indicated that the foliar ABA level did not limit the recovery of gas exchange.4.There was a positive correlationship between K_leafeaf P₅₀ and turgor loss point(?_tlp)in six Caragana species,indicated that turgor loss point effectively reduced K_leafeaf P₅₀.Caragana species from arid region has lower K_leafeaf P₅₀,which makes their water transport pathways slightly damaged at-2.0,-4.0 and-6.0 MPa,thus contributing to the recovery of photosynthetic capacity;leaf shrinkage and accumulation of osmotic adjustment substances have no influence on the recovery of photosynthetic capacity.