VEGETATIVE GROWTH CYCLES AND COMPARISON O F CHLOROPHYLL AND PHENOL CONTENTS, GAS-EXCHANGE AND WATER REGIME FROM YOUNG TO OLD LEAVES IN MANGO

It is well known, that vegetative growth in mango and other tropical t ree species appears in flushes. In the present work a correlative inhi bition of shoot and root development was determined. Compared to the r emaining foliage the young leaves from terminal flushes show character istic differences in phenol and chlorophyll content, gas exchange and water regime. In leaves from exposed tree position an accumulation of phenols was measured, that supposed to be a protecting mechanism again st high radiation in the tropics. Compared to mature leaves chlorophyl l content in young leaves was 2 - 3 times less and also the rate of ph otosynthesis was low. Water potential in mature leaves decreased as a consequence of enhanced water vapour saturation deficit during daytime . However, leaf water potential in young leaves from terminal flushes showed scarcely any difference although turgid loss was visible. Hence a lack of osmotic adjustment in young leaves is postulated, that prov ides advantageous low transpiration rates. Sapflow showed a reduced ve locity at approximately 1 :00 p.m.. It is assumed that this phenomenon resulted from a decrease in stomata conductivity due to loss in turge scence.