Wednesday, November 15, 2006 - 8:00 AM
295-1
Effects of Salinity and Flooding on Growth of Bald Cypress (Taxodium distichum (L.) Rich.).
The objective of this study was to discern the tolerances of bald cypress seedlings to various levels of flooding and salinity. Five flooding basins were set up using 185 × 152 × 23 cm plastic containers. There were five levels of salinity: 0, 2, 4, 6 and 8 ppt as sodium chloride (their EC values were 0.002, 3.5, 6.7, 10.5 and 13.8 dS m-1, respectively) and three levels of flooding: 0%, 50% (half the roots submerged in water) and 100% (plant roots completely submerged in water). The survival rates measured suggest that bald cypress seedlings can tolerate 100% flooding without salinity for at least 30 days, the length of the experiment. All seedlings were survived with 50% flooding with 2, 4, 6 or 8 ppt salinity, and also with 100 % flooding plus 2 ppt salinity. However, 25-75% of seedlings died under 100% flooding with 4, 6 and 8 ppt salinity. Plant analysis showed that potassium contents decreased more than calcium contents under salt stress with or without flooding. Under 100% flooding, potassium concentration in the tissues was as low as 15.7% (roots) of that without flooding. Sodium contents in plant tissues were 250.3% (roots) or 463.6% (stems) with 8 ppt salinity and 100% flooding higher than those of the control, while those with 8 ppt salinity but without flooding only 3.9% (stems) or 18.2% (leaves) higher than those of the control.
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