ON THE WATER RELATIONS PROBLEM OF FRUIT TREES IN GUANGDONG

The climate of Guangdong Province is of a humid subtropical type with distinctive both dry and wet seasons and frenquent alterations between droughts and waterloggings during the vegetative period.This situation coupled with the inferior structure of the predominent red soil often puts fruit trees in extremes of water regimes.The respouses of fruit trees to the local ecological conditions are the shallowness of root distribution and rapid built-up of internal water stress duriug dry spells.The disorders caused by uufavourable water regimes may be exemplified as excessive fruit-drop,uudersized fruits,wilting in a sudden clear day after a long spell of rains,fruit cracking,offseason leaf-drop and etc."An exuberant canopy supported by a shallow root system" characteristic of the local fruit tress is in sharp contrast to that "an exuberant canopy arises from a deep root system" in the temperate zone.Therefore,studies on the water relations of fruit trees in this areas are of no little significance.