Document: MON-3-35-14

A comparison of the effects of salinity levels and light levels on the growth of Helianthus paradoxus and Helianthus annuus.

MENDEZ, M.O.* and O.W.VAN AUKEN

The University of Texas at San Antonio, San Antonio, TX, 78249. ¹

Abstract:
Due to direct or indirect anthropogenic effects, Helianthus paradoxus Heiser (the puzzle sunflower, Asteraceae) has been recently designated a threatened species. Helianthus paradoxus is found only in western Texas and several locations in New Mexico. It is a hybrid of Helianthus annuus L. (common sunflower) and H. petiolaris Nutt. (plains sunflower). Helianthus paradoxus seems to be a halophyte. Yet, H. annuus, one of its parents, is a known glycophyte. The purpose of this study was to determine the individual effect of salinity and its interaction with light intensity on the growth of H. paradoxus and H. annuus. In a greenhouse study, the growth of H. paradoxus and H. annuus was examined in 0, 5, 10, 20, and 30 ppt of NaCl, Na₂SO₄, and polyethylene glycol. In a field study, the growth of H. paradoxus and H. annuus was examined in 0, 5, 10, 20, and 30 ppt of one osmotic agent under 100%, 75%, 50%, 25%, and 12.5% sunlight. All treatments contained five pots with five individual plants per pot. Parameters measured were basal diameter, number of leaves, height, root and shoot biomass, and growth rate. The growth of H. paradoxus was inhibited by high concentrations of NaCl and Na₂SO₄ but NaCl was more inhibiting. The growth of H. annuus was inhibited more than H. paradoxus. Inhibition of growth in high concentrations of the osmotic agents was increased at lower light levels.

Keywords: Helianthus paradoxus, Helianthus annuus, salinity tolerance, light requirements, NaCl, Na₂SO₄, polyethylene glycol.

This abstract is being presented at: 10:30 AM in session:
Poster Session #1: Light Relations.