| Abstrakt: |
Lignins are phenolic polymers of the cell wall and cinnamyl alcohol dehydrogenase (CAD) is the key enzyme involved in the synthesis of lignin monomers. A study was conducted in stems of 18 wild Hevea germplasm accessions and five popular clones to localize and correlate CAD activity and lignification at various stages of xylogenesis through tissue printing and in situ localization as well as quantitative image analysis techniques. Simultaneously, quantification of lignin produced was also done by classical histochemistry and gravimetric estimation. CAD activity was maximum during the early stages of stem development and minimum during the mature stage of xylogenesis whereas the pattern of lignification showed a reverse trend indicating that as xylogenesis increased, CAD activity decreased. The quantity of lignin produced was also increased in association with progress of secondary thickening. The percentage of lignin at different developmental stages of the stem was highly significant. The percentage of lignin ranged from 21.04-27.4 % in wild Hevea germplasm and 20.01-23.00 % in popular clones. Of the 18 wild accessions screened, nine showed significantly higher percentage of lignin over five popular clones. The present study revealed that CAD activity is involved in the lignification process in Hevea stem and its activity is restricted in the mature xylem. The CAD activity and lignification pattern in the juvenile growth phase can be used as reliable tools for the early detection of wood quality in Hevea brasiliensis. [ABSTRACT FROM AUTHOR] |
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