INFLUENCE OF FLOODING ON GROWTH AND GAS-EXCHANGE OF MANGO ROOTSTOCKS (MANGIFERA-INDICA L.) AND PROPOSED SELECTION CRITERIA FOR FLOOD TOLERANCE

In a greenhouse experiment rooted cuttings of mango rootstock '13/1' w ere grown in containers filled with quartz sand. The temperature insid e the root containers was kept constantly at 22 degrees C. Containers were filled with stagnant water, whereby oxygen deficiency in the root zone was induced. Only plants with hypertrophied lenticells survived the treatment for more than 5 days. Flooding led to a decrease in leaf CO2 uptake. An enhanced stomatal resistance resulted in a reduced tra nspiration rate. Simultaneously root respiration and root growth decre ased during flooding conditions. Root respiration paths were discrimin ated, proving an alternative path as a residual respiration. From the present investigation two selection criteria for flood tolerance in ma ngo are deducted: 1. Development of hypertrophied lenticells, which en able mango trees to transport oxygen from the atmosphere into the root . 2. An alternative respiration path as well as residual respiration i s present in roots of the mango rootstock '13/1'. We assume, that non- cytochrome pathways might play an important role in energy charge of r oots under restricted soil oxygen.