Assessment of salt tolerance in eucalypts using chlorophyll fluorescence attributes

Chlorophyll fluorescence attributes were investigated for their potential as rapid, non-invasive indices of salt stress in eucalypts. After representative clones of E. camaldulensis and E. urophylla x grandis were subjected to salinity treatments, dark-adapted and quenching attributes did not show consistent responses to salinity stress. The light-adapted attribute F-ds, when measured in a controlled environment, did decline, often before physical symptoms of stress were visible. This value is required for the derivation of the effective quantum yield, and each measurement can be acquired and automatically recorded in a few seconds, permitting the rapid survey of large groups in a propagation facility. Monitoring of plants, that were treated with increasing concentrations of NaCl over time, permitted overall ranking of the responses of groups of clones and seedlings. Usually the data were heteroscedastic, so non-parametric methods of statistical analysis were used, and Pless than or equal to0.01 for ascribing significance to differences. Also, following the responses of individuals within clones and provenances showed the method should be useful for the early detection of particularly susceptible or resistant seedlings.