Respiration Rate and a Two-component Model of Growth and Maintenance Respiration in Leaves of Rubber (Hevea brasiliensis Muell. Arg.)

Abstract

The future information of leaf selection for studies on respiration rate and leaf greenness, and position variations of different rubber clones was investigated. Respiration rate and greenness were nonsignificantly different between leaf position (leaf No. 1, 2 and 3) and leaflet position (left, middle and right), but they were significantly different among clones. During leaf expansion, respiration rate per unit leaf area declined with leaf age, but the differences were not obviously detected among clones. Leaf expansion rate was sigmoid shaped curves, and increased with leaf age. Relative growth rate on an area basis (RGRarea) of leaf declined with age. At fully expanded leaf of PB 235, RRIM 600, PB 260 and GT 1 clones, the greatest leaf area was found in PB 235, and the least in GT 1. For crop growth model development and environmental response studies, a two- component model of growth and maintenance respiration was used in leaves of rubber. Growth respiration coefficients were non-significantly different (ranging from 4.928 x 10⁵ to 5.678 x 10⁵ µmolCO₂ m^-2) among 4 rubber clones. While, the greatest maintenance coefficients were in RRIM 600, PB 60, GT 1, the least was in PB 235. In particular, strong positive correlation between respiration rate and RGRarea was found for all clones. Maintenance respiration was weakly related with leaf temperature, but growth respiration was not significantly related with leaf temperature.