Water Relations for Sun and Shade Leaves of Four Mediterranean Evergreen Sclerophylls

The water relations, stomatal conductance, size, chlorophylland proline content have been measured in sun and shade leavesof four evergreen sclerophyll species, throuthout the year.It was found that there were no major differences in water statusof the two leaf types. However, in young expanding shade leaves,higher stomatal conductance, turgor, chlorophyll and prolinecontent leves was significantly larger. Plastochron ratios ofthe two leaf types in the four species were similar, indicatinga synchronized gorwth rate related to seasonal rhythemicity.It is suggested that different mechanisms have been operatingin the response of the two leaf-types to microclimatic conditions:an avoidance by sun leaves and tolerance by shade leaves.