Date of Award:

1991

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Lynn M. Dudley

Abstract

Two greenhouse experiments were conducted to determine the amelioration effect of Ca salts (CaS04 and CaC12 ) on the growth of snapbeans (Phaseolus vulgaris L.) under sodium stress and to determine the effect of ion speciation on the uptake of Ca, Na, S04, and Cl by snapbeans.

In Experiment 1, the seeds were grown in styrofoam pots, with a growing medium of sand and vermiculite at a volume ratio of 3:1. The treatment solutions were 0 (Hoagland's solution), 20, 40, 60, and 80 mmolc/L NaCl or Na2S04.

Statistical analysis (ANOVA) showed that NaCl treatments depressed the growth of snapbeans more than corresponding Na 2S04 treatments. Also NaCl treatments increased the uptake of Na and Ca as compared to Na2S04treatments. Sodium uptake appeared to be related to the concentrations of complex species rather than to free Na ion, whereas Ca uptake strongly correlated with free Ca2+ concentration.

In Experiment 2, the seeds were grown in a sand growing medium. The treatment solutions were 0 (Hoagland's solution), 15, 30, 45, and 60 mmolc/L NaCl or Na2S04 , combined with CaSO4 • 2H20 or CaCl2 • 2H20 at concentrations of 15 or 30 mmolc/L . In addition, one replicate was planted in PVC cells (with electrodes) in order to monitor the electrical conductivity of the media using the four probe.

The results showed that addition of CaS04 to NaCl or Na2S04 was associated with a better amelioration of Na stress than CaCl2 • Also the presence of CaS04 , with NaCl or Na2S04 , decreased the uptake of Ca and Na ions relative to CaCl2 treatment. Ion speciation data suggested that Na complexation was more important than free ion concentration in affecting Na uptake by the plant, whereas Ca, S04 , and Cl uptake were correlated to free ion concentrations.

With respect to EC, determinations, the four probe was used to monitor salinity during the whole experiment period. Ion speciation data showed that Na2S04 treatments had a lower EC than NaCl at the same molar concentration levels. Also, CaS04 treatments, regardless of the Na salt, had lower EC values than CaCl2 treatments of equal concentration.

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