EFFECT OF SALINE IRRIGATION WATER LEVELS ON THE GROWTH OF TWO ZINNIA ELEGANS L. CULTIVARS

The production and growth of ornamental plants are markedly affected by water deficiency. Therefore, enhancing their yield during the drought period has become the main goal in plant breeding. Two Zinnia elegans L. cultivars (Short Stuff and Profusion) were employed in this investigation to determine the effect of salinity and drought tolerance on plant growth for translation to a salinity and drought tolerance breeding program. Four irrigation treatments based on F.C. of medina used, (T1= 40, T2= 60, T3= 80, and T4= 100% (control) of field capacity) under five salinity levels (electrical conductivity (EC) of 0.63 dS m-1 (control)), EC1= 1.6, EC2= 3.1, EC3= 6.3, and EC4= 9.4 dS m-1) were imposed throughout a 120-day growing period using a drip irrigation system. The vegetative growth yield and the flowering characteristics were determined and gas exchange measurements were recorded. All flowering and vegetative characteristics decreased as the level of deficit irrigation water increased. Both cultivars treated with 40% under EC3= 6.3 and EC4= 9.4 dS m-1 did not flower. Nonetheless, significant differences were found between the two cultivars for all characteristics, indicating that they could be considered when adjusting for salinity and drought tolerance. Profusion cv. displayed better performance than Short Stuff cv., when grown under 80% and 100% irrigation treatments and the salinity levels, except for 40% with EC3 and EC4 which did not result in flower yield. Leaf chlorophylls content (chl. a, b, and total) reduced with the increase in the salinity level and with increasing deficit irrigation water treatments. Content of leaf minerals, such as Ca2+, Na+, and Cl-, was also determined. For both cultivars, Ca2+ content decreased as irrigation salinity increased, while Cl- and Na+ contents increased as salinity increased in the plant tissue following irrigation.