GROWTH RESPONSE AND LEAF COMPOSITION OF SELECTED EUCALYPTUS SPECIES EXPOSED TO SALINE AND HYPOXIC STRESS

Abstract

A solution culture study on selected Eucalyptus species (E. occidentalis, E. tereticornis, E. camaldulensls-var. Silverton, and E. camaldulensis-Local) was conducted under saline and hypoxic conditions to determine the effect of treatments on growth and leaf composition. The treatments were non-saline, aerobic (control), saline aerobic (ISO mol m ! NaCl) and saline + hypoxic. Solutions in case of nonsaline aerobic and saline aerobic were aerated continuously while hypoxia was induced by surface sealing (oxygen concentration 2-3 ppm). Twenty five days after salinity I hypoxic stress, plants were harvested. Salinity negatively affected all the growth parameters (plant height, stem thickness, and root and shoot fresh weights) and the effect was further aggravated when it was associated with water logging. Among the species E. camaldulensis-Local and E. camaldulensis-var. Silverton were found better under saline conditions and E. camaldulensis-Local under saline hypoxic conditions. Young leaves of all the species had lower concentrations of Na and Cl as compared to old leaves, and concentrations of Na and Cl in the leaves of both categories were the highest under saline hypoxic conditions followed by saline treatment. Potassium:sodium ratio was better in the young leaves of alt the species compared to fully exposed old leaves, and the ratio was better also under favourable conditions. From amongst the species, E. camaldulensis-Local had low Na and better K:Na ratio in its leaves. Mean rate of growth measured as coefficient of shoot elongation (CSE) was the lowest in E. tereticornis whereas, all the other species had almost similar values of CSE. Nevertheless, the absolute mean shoot fresh weight was the highest and significantly superior to all the species in E. camaldulensis-Local.