Effects of Drought on Physiological Responses of 3 Month-old Rubber Trees

Abstract

To investigate the effects of drought on physiological responses of 3 month-old of rubber trees (clone RRIM 600), grown in 15 liter pots and placed in the nursery under natural conditions at Surat Thani Rubber Research Centre, during May to June 2008. Young rubber trees were subjected to two irrigation treatments: daily watered (control) and unirrigated  (drought). The drought during 17 days of unirrigated treatment significantly affected soil moisture content, growth and physiological performances. Girth increment and relative growth rate of control plants were significantly greater than those of unirrigated plants. In the unirrigated treatment, the drought decrease soil moisture content from 25 to 2% volume stomatal conductance from 476 to 20 Umol CO2/m2/s2, minimum leaf water potential from-0.7 to-2.7 MPa, relative water content from 91 to 21%, total chlorophyll content from 1.9 to 0.66 g/dm2 and specific leaf mass from 50 to 40 g/m2 before shedding. On the same time, the constant values of these parameters were found in the control treatment. Good positive relationships were found between leaf water potential and both stomatal conductance and relative water content. Good positive relationships were also found between soil moisture content; both relative water content and leaf water potential.