Study on Leaf Stomatal Conductance of Rubber

Abstract

The stomateal conductance (gs) parameter was used as an index in rubber breeding programme for evaluation of high growth and high yield clone under non-water limited condition. This experiment was conducted at Chachoengsao Rubber Research Centre, Chachoengsao province during August to October 2002. The objectives were to study (1) the genetic and diurnal variations of (gs) on three rubber parent clones namely, RRIM 600, RRII 105 and RRIT 251 and the relationships between (gs) and environmental factors (2) the frequency distribution of (gs) on these clones and (3) the frequency distribution of (gs) on their F1 progeny of RRIM 600 RRII 105 and RRIm 600 x RRIT 251. The results showed those wide variations in (gs) were observed among three rubber clones and diurnal times. Mean (gs of clone RRIM 60-2s--1) and RRII 105 (436mmolH2O m-2s--1). The diurnal variation of (gs) was also found. The maximum potentials of (gs) were exhibited during 09.30-11.30h due to the environmental effects. A strong correlation was found between (gs) and vapour pressure deficit, where as relationship between (gs) and temperature was excepted in RRIT 251. The frequency distribution of (gs) was the highest at 400 and 700 mmolH2O m-2s--1 for RRIM 600, while it was s--1 for RRIT 251. F1 progeny showed ) of some progenies were three times greater than that of their parents. Therefore, high (gs) might be used as a selection trait in rubber breeding programme for high growth and high yield in rubber grown under non-water limited condition