Lenticel and water root development of swamp tupelo under various flooding conditions
Seedlings of swamp tupelo (Nyssa sylvatica var. biflora [Walt.] Sarg.) were grown in nonflooded soil or soil that was intermittently flooded, continuously flooded, or surface-saturated with moving or stagnant water. Lenticels on nonflooded seedlings were round, only slightly hypertrophied, and had few closing layers. Degree of hypertrophy and number of closing layers per lenticel increased with surface saturation and intermittent flooding, but closing layers were absent under continuous flooding. Flooded lenticels remained nearly round despite variations in hypertrophy. In all treatments, intercellular spaces were abundant in the complementary tissue and phellogen because of the spherical shape of these cells. Although the continuity of intercellular spaces was interrupted because the closing layers anastomosed, breaks within the closing layers prevented these spaces from being completely blocked. Water roots developed primarily under continuous flooding in moving water, some apparently originating beneath the phellogen of a lenticel and others within the phellogen or its derivatives.