Abstract:
Shoot die-back condition has been observed in young-budded rubber plants especially under hot and dry weather
conditions. This is partly attributed failure of the root system. Therefore, it is imperative to find ways to improve
the root system while enhancing other growth attributes of polybagged rubber seedlings. Nitric oxide (NO) func tions as a signaling molecule as well as a phytohormone in numerous physiological processes in plants from seed
germination up to senescence. In the present study, the effect of sodium nitroprusside (SNP) as a NO donor on the
root architecture and growth characteristics of polybagged rubber seedlings were investigated. Seven days old
rubber seedlings were soaked in 200 µM and 500 µM solutions of SNP for 6 hours and 24 hours respectively prior
to transplanting in polybags. Mock treated seedlings were soaked in water. Pretreatment with SNP greatly im proved the root architecture of rubber seedlings by increasing the number and the length of lateral roots and the
dry weight of roots while enhancing other growth parameters viz., stem diameter, shoot height and dry weight,
leaf area and chlorophyll content in dose and time-dependant manner. Pretreatment with SNP at 500 μM for 6
hrs was found to be more effective for overall growth improvement in rubber seedlings. The improved growth
characteristics of rubber seedlings could be attributed to the beneficial effect of SNP as a NO donor in modifying
phytohormone signalling pathways, enhancing antioxidant enzyme activity, increase in nutrient uptake and effec tive allocation of photoassimilates.
