Salinity Effects on Growth and Fine Structure of Atriplex Halimus 1

Atriplex halimus L. plants were grown in nutrient culture solutions of full-strength Hoagland's, and fullstrength Hoagland's supplemented with either 0.174 M NaCl or 0.345 M NaCl. Observations were made on growth habit, net growth, and leaf cell ultrastructure of plants from the various treatments. Plants grown under control conditions (full-strength Hoagland's with no supplemental salt) had an erect habit with no lateral branching, but had a reduced net growth in comparison to plants in either of the salt treatments. Plants in the 0.174 M NaCl treatment were relatively erect (some recumbency was noted) and exhibited much better growth than either the control treatment or the high-salt (0.345 M NaCl) treatment. This is an indication of the plant's need for sodium chloride in the medium as either a nutrient or an osmoticum, and leads to the classification of A. halimus as a halophyte. Plants grown in the high-salt treatment showed a marked recumbency and a reduction in growth, but nevertheless showed a better net growth than plants in the control treatment.

The fine structure of the leaf cells is correlated to salinity treatments. Plants grown in high-salt treatments showed swelling of organelles (chloroplasts and mitochondria) and other structural differences. The hair cells, which showed little ultrastructural response to high-salinity treatments, were characterized by unique ultrastructural features directly related to salinity tolerance.