Abstract
A study was conducted to examine the effects of various soil moisture conditions on endangered species star magnolia (Magnolia tomentosa) seedlings in a greenhouse. Four treatments representing a range of soil moisture conditions, from continuous flooding with or without stream to moderate drought, were imposed separately. A well-watered with well-drained treatment served as the control. Leaf phenology and water potential of 2-year-old seedlings were evaluated. Decreased number of leaves of shoots clearly demonstrated the sensitivity of seedlings to low oxygen conditions derived from flooding as well as to soil water deficit. Predawn leaf water potential was declined by drought treatment. Leaf water potentials at turgor loss were declined by flooding and drought treatments. Leaf osmotic potential at full turgor declined only by flooding treatment. These results imply leaf osmotic adjustment against flooding and leaf elastic adjustment against drought stress in M. tomentosa. Little differences in leaf phenology and in water relation were found between stream and control treatment. These results indicate swamps with spring or stream are indispensable for conservation of M. tomentosa.
