TY  - BOOK
AU  - Gunasekara H K L K
AU  - De Costa W AJ M
AU  - Nugawela E A
TI  - Genotypic variation in canopy photosynthesis, leaf has exchange characteristics and their response to tapping in rubber (Hevea brasiliensis)
PY  - 2007///
PB  - Experimental Agriculture
KW  - Genotypic variation
KW  - LEaf gas exchange
KW  - Tapping
N2  - The main objective of this study was to quantify the genotypic variation of photosynthetic and gas exchange parameters of Hevea and to examine their relationships to dry rubber yield and its components. Canopy photosynthesis (Pc) of the genotype RRISL 211 was 20;greater than that of RRIC 121. This was primarily due to RRISL 211s greater light-saturated leaf photosynthetic rates and a greater leaf area index in the top canopy stratum. Tapping significantly increased Pc in RRISL 211, but not in RRIC 121. The genotypic variation in photosynthetic capacity was not reflected in the overall dry rubber yield, which did not differ between the two genotypes. However, analysis of yield components showed that while RRISL 211 may have preferentially partioned a greater proportion of its additional assimilates to increasing the latex volume and extending the root system, RRIC 121 partioned more assimilates to increasing its dry rubber con tent through greater biosynthesis of rubber. The higher plugging index and the greater post-tapping girth increment of RRIC 121 were probably responsible for observed increases in its dark respiration following tapping. Although RRISL 211 had a greater transpiration efficiency, this did not provide a yield advantage as the trees were growing in an environment with adequate rainfall throughtout the year
ER  -