Differential response of palmleaf morningglory (Ipomoea wrightii) and pitted morningglory (Ipomoea lacunosa) to flooding

Palmleaf morningglory (IPOWR) and pitted morningglory (IPOLA) were compared in field and greenhouse tears under simulated rice field conditions to quantify flood tolerance characteristics of the two species. IPOWR survived a 13-cm flood in the field if the flood was applied 12 days after planting (DAP) or later In contrast, IPOLA did not survive floods applied before 19 DAP. Only IPOWR survived a 5-cm flood applied 5 DAP in the field. In the greenhouse, both species were unable to emerge from under 1 cm of soil when flooded greater than I cm deep. Although both species emerged from water-saturated soil, IPOWR emerged earlier and produced more dry weight than did IPOLA. Emergence from the water surface of 2-cm-tall IPOWR was better than that of IPOLA when submerged in water up to 7 cm deep, and total dry weight (as a percent of a nonflooded control) was two to four times greater for IPOWR. Even a 5-cm flood reduced leaf area, height, dry weight, and photosynthesis of IPOLA more than that of IPOWR. At 20 C and low oxygen (1%), germination percentage of IPOWR was about four times higher than IPOLA. Germination, growth, and certain physiological processes of IPOWR are more tolerant than those of IPOLA to moderately deep hoods (and low soil oxygen levels). Thus, IPOWR is potentially a greater weed problem than IPOLA in rice fields. The fact that neither species was capable of emerging from soil under even shallow flood depths helps explain why morningglories are prevalent only in shallow or water-saturated areas on rice field levees.