Sayan Sdoodee, Naree Wongwongaree, and Vichanee Ormzubsin

pp. 9 - 17

Abstract

The water use of two species of tropical fruit trees: rambutan (Nephelium lappaceum) and longkong
(Aglaia dookkoo Griff.) were investigated by heat-pulse method. The sapflow rate of both species were determined during phenological development. An experiment was established at Prince of Songkla University,
Songkhla Province. Characteristics of sapwood in each species and optimum depth for probe implanting on
the trunk were investigated. During the measurement period, diurnal changes of photon flux density, leaf
water potential and stomatal conductance were recorded. It was found that sapwood of rambutan and
longkong were homogeneous. An appropriate probe depth to implant on the trunk was 25 mm from bark.
It was found that diurnal changes of sapflow rates of each species varied with the changes of radiation, leaf
water potential and stomata conductance. The results of measurement showed that water use decreased at pre-flowering stage, and fruit maturity stage. In rambutan, water use increased during vegetative growth
stage followed by flowering stage. The marked increase of water use in rambutan was during fruit development. In longkong, water use increased at the flowering stage followed by vegetative growth stage, and the
peak of water use was during fruit development.