Growth and physiological response of selected clones of rubber grown under different water frequencies

Effects of water frequencies on growth and physiological response of different clones of rubber were investigated. Different clones of rubber were screened with different watering frequencies as everyday watering (EW), every 2 days (E2D), every 3 days (E3D), every 5 days (E5D), and every 7 days (E7D). The treatments EW and E2D were found to be suitable for all the five clones for increasing as shown in plant height. A similar result was also found for plant biomass after 4 and 8 months of treatments. Noticeably, watering had a pronounced positive effect on clone RRIM 3001 and greatly increased vigorous growth as shown in its highest height, largest girth circumference and relative growth rate after 8 months of different watering frequencies. This clone equally showed superior performance with a significantly higher total plant biomass after 4 and 8 months of watering frequencies compared to the other four clones. The result could be used in water management and the clone RRIM 3001 could be suitable for rubber production at the nursery stage and replanting exercise in rubber plantations.</jats:p

Stability of lipase immobilized on O-pentynyl dextran

O-Pentynyl dextran (PyD), an amphiphilic polysaccharide derivative with a degree of substitution (DS) of 0.43 was compared with ion exchange resins Lewatit VP OC 1600, Amberlite XAD 761 and Duolite A568 for immobilization of Lipase from Rhizopus arrhizus by adsorption method. The immobilized enzymes were employed for esterification of octanoic acid with geraniol in n-hexane as model reaction. PyD showed higher lipase adsorption and with 249 mu mol min(-1) g(-1) significant higher esterification activity than the other supports (67-83 mu mol min(-1) g(-1)). Biocatalysts from all types of supports except PyD became completely inactive within 8 weeks storing at -10 A degrees C while lipase immobilized on PyD retained its full esterification activity for at least 14 weeks. In repeated use, yield decreased rapidly after two cycles for all supports except for PyD. For this biopolymeric support, constantly 90% yield was achieved even after eight cycles, when the biocatalyst was washed with n-hexane and water and then freeze-dried. To achieve this yield, prolonged reaction times were required, partly on the account of an increasing delay period, probably to adapt active conformation, until the reaction starts.</p